Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: cloggy on September 24, 2007, 07:12:21 PM
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Has anyone else done any tuning on these motors, or knows of any source material?
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Hi, I bought a GN400 lump( v.cheap) with the intention of dropping it into a Morini frame. As they only kick out 27 HP from new I decided to investigate a bit and see what could be done. There is what appears to be some sort of dam in the inlet throat, possibly to limit power for various markets, so out with the dremel and it soon disappeared! The state of the inlet and exhaust ports can best be described as 'rough as a badgers a***' so a bit of smoothing out would help. I was then going to put a 38mm dellorto on it and blend in the inlet, but a DR750 bargain (ha ha ha) came along so thats as far as I got so the 750's going into the Morini instead and the GN is in a box under the bench. Standard compression is quite low so there's room for improvement there, did think of resleeving the barrel out to 90 or 91 but I doubt if you could go much bigger as you would break into the cam-chain tunnel , try Wiseco or Omega for pistons and Joy engineering for cams. A mate sent me a picture of a racer with DR500 head (4-valve), bore is the same but longer stroke, best of luck,
cheers Jez
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It's a Suzuki dirtbike lump so there should be heaps of stuff for it. Keep in mind, though, that the starter gear will not be happy with any significant increase in compression.
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They stopped selling them in the very early 80s. There's precisely nothing available of the shelf.
Phil Joy does a very nice Protec copy road and track cam grind, you have to use aftermarket springs and keepers. I use Protec keepers and kent clubmans springs for the 1600 cortina lump. This cam eliminates a hole in mid range
MegaCycle do a couple of cams and springs. With the exchange rate that's peanuts at present. One does indeed grind off the inlet weir, to very little detriment straight off idle. They bored them out to 420cc max. Any more than that and apparently the drive train gives problems. The piston was a high comp Wiseco. I've not managed to source one. Possibly a big bore XT 500 piston might fit. The clutch plates don't last long even on a mildly tuned bike. White Bros did a Mikuni carb kit but I've lost the spec and they've packed. It was a 36. Since the standard is 33 and an elongated shape at that I would imagine much bigger than that the bike will lose power. The stock 33 carb does not respond well to tuning though replacing it with the SP 370 needle/needle jet may work as the 370 32mm carb works great. You have to jet down on the needle and main once it's tuned, which is not what one expects. The 34 Amal Mark 2 doesn't seem to have a slide that works, though apart from a slight hesitation off idle it runs fine with a KN. 27bhp is what Suzuki claim so that's pony power. Real horsepower is around 23. The 370 was faster with the same gearing. I always thoght it was due to changing from points to primitive electronic advance/retard but the staggering difference in the carbs have caused me to rethink. I'm running two sets of wheels with my road gearing, the same as the GN 400, using a locally made Supertrapp and pipe, the Protec cam and gubbins, cleaned up head and modified airbox. The standard airbox , like the standard exhaust, is incredably restrictive.
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I have a sp400 with the 370 slide carb on it, k&n and a openish pipe. Its still gutless...
I used to have another motor with the exact same combo on it, and it would pull 90 on the speedo with that lump in, but a camchain tensioner slide snapped, and I left it at a shop to have the engine swapped for a spare gn400 one and it mysteriously was stolen out the storage area before I had chance to crack open and see what had been done to it. By I suspect someone who wanted to know what was done to the innards too...
Since then she went to another shop to be rebuilt in the engine dept, and fitted with a new 1mm oversize piston and stuff, and is still completely gutless...
I have plans afoot for a higher comp ratio, some porting and perhaps a bigger piston to see what can be done to the old girl to warm her back up. I have a spare head, and barrel to play with, and a handy assortment of machinery to perform the deed when I get around tuit, but currently Im off playing with a turbo bike and my xt motard amongst other things...
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It's a Suzuki dirtbike lump so there should be heaps of stuff for it. Keep in mind, though, that the starter gear will not be happy with any significant increase in compression.
Your thinking of the drz there ;)
SP/DR400, poxy 6v electrical system, kickstart only ;)
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Dead easy and cheap to convert to 12v lights
I've got my engine set up as a trail engine. If I wanted it to produce more power further up the range I'd play with the aftermarket 36mm mikuni and get a race cam. 4 valve head sounds intereesting but as far as I know the DR/SP500 never got across the english channel
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I turned down a whole DR500 in a sorry state about a year back on the basis that they were so rare and I had enough projects already. We were sizing up the motor to go into my sp as the original frame had snapped, and its physically taller and wouldn't go. The whole engine had a completely different appearance so I would be unsure the head would fit straight onto the sp bottom end. Thats the only one Ive ever seen in the metal, and until I got to measuring that one up I thought it was just a overbored sp400. I didnt even realize it had a 4valve head to be honest.
I have a 6v solid state regulator/rectifier from paul goff and a 6v 60W halogen bulb in the headlight + led taillight, it all seems to work fine so I dont think Ill create more work converting it yet. I didnt want to risk converting it to 12v and the electronic ignition circuit suddenly get robbed of power by the extra load (nicking the magnetic flux, deprived of webers, theres a joke there somewhere). Ive seen other bikes with electronic ignition magnetos have weird effects when the lighting circuit was converted to 12v.
I have a spare xt500 carb that I can use, since i used a 38mm del-orto on the XT (it has a 600 kit). If (when) I get carried away, Ill probably put a cam in it too. Im trying desperately not to convert my sp into yet another winter project right now, theres already 5 on the go in the shed :)
I read it as phil joy did your cam. Whats special about the protec keepers and why are they needed with the cam?
Im not after amazing power out of my sp, Ive just had the old girl so long I feel like she should be improving as time goes by, so I try to keep doing bits and bobs, but Ive sort of run out of things round the outside to tackle so maybe its time for internal surgery.
Id love to know what was inside that other motor. That still rankles me 14 years on...
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The stock 400 has a bore size of 88mm. This is probably to try and reduce it's height, being a wet sump motor. XT500 is 87mm. TBM has not only got the details wrong for the DR400 [they state it's got 4 valves etc], they've also got the year of manufacture several years out!
The standard cam is pretty mild and has a hole in the power just where they probably did the noise test.
The Phil Joy Protec copy has slightly more lift and a lot more duration. The extra duration causes the valve to be slammed shut quicker than standard and thus standard springs allow valve float, ie the valve stem rocker briefly loses contact with the face of the cam, which doesn't do perfomance or the cam much good.
The Protec springs were wider and thus needed different seats and keepers. Fortunately, though the Protec springs were made of knicker elastic and never made it to 7000 miles without sacking, the Kent Custom springs fit the Protec keepers, never seem to wear out [on this engine at least] and used to be dead cheap. They also have the same spring rate
Megacycle do two cams and recomend their own springs on both
The Protec keepers aren't just wider, they are also made of aluminium. I'd be worried about this but I must have done something close to a 100000 miles on them so....
The stock SP370/DR400 carbs don't have the sophistication of the XT carb, but seem to work fine with a stock airbox, whatever is done to the inlet weir and exhaust. However once one 'derestricts' the airbox only the SP370 carb is close in terms of jetting. You can play around with needle position and mainjet forever, and not get the 33mm DR400 carb quite right. Quite apart from the annoying jetting glitches the engine is just plain sharper and much faster with the 32mm SP carb. Of course it's possible that the DR float height was off but it was ok on my standard engine.
I haven't tried swapping the needle jet and needle over as the SP carb was only one needle notch and one mainjet size off as stock. The DR carb didn't idle as reliably either. I suspect that when Suzuki did the original developement work they jetted the carb and then restricted the inlet and exhuast as a matched pair till they'd got it quiet . I think they used those restrictions as a starting point when they put together the 400 so the carb doesn't respond so well to the restrictions being subsequently removed; but it's only a theory and I'm no more than a back street butcher.
The GN and SP400 varients use a vacuum 36mm carb. After I got a watchmaker to drill out the mainjet mine ran fine with a no airbox and a K&N filter. You just don't get the initial whoomph of a slide carb.
Mead and Tompkinson, 24 hour endurance racers, got hold of a 370 engine and I think sleeved it down to 350 for the new endurance rules. If I remember right they used a 32mm Amal mark 2. The rules were then changed before the new season so they never raced it. They had loads of experince with the BSA B50 unit motor so I bet that little Suzuki engine went like stink.
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Ah so the keepers are just different because theyre lighter (aluminium) and hence raise the rev limit a bit, and are a different size. Bit of 7475 grade aluminium alloy should do the same job...
You wouldnt happen to know what kents part # for those springs are? or the spring rate/dimensions ?
Ill have a peek at how much the cams are now, it may indeed get done this winter...
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I think they are called clubman spec springs and they are for the 1600 crossflow ford cortina lump. They are shorter than the 2000cc pinto lump springs. I can find out exactly but don't want to bother the engineer until he's found my parts of 14 years ago....
Quite frankly the dollar is so low at present that I'm tempted to get my next cam and springs from megacycle. I'd get the milder of the two grinds. I doubt there's much difference between that and what I already have. They have an excellent online catalogue but no apparent way of accessing via internet
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Hi there,
I am quite interested in tuning a SP370 as I recently bought an old Hejira SP370.Only had a brief ride during practice and ran into brake problems.Still it felt perky enough but could do with a wee bit more top end.I have raced a couple of singles over the years had a Yamda(TZR125RR yamaha with a XBR 500 motor) built it myself and finished second in the championship that year,a couple of years ago had a Honda Tigcraft with a Dominator motor was fine till it went bang.anyway back to the Suzuki been surfing the interweb but not much information to be had.Was looking through an old mag from 1980 and found an article about the Hagon SP370 Racebikes.Found out that Hagon would take the motor out to 480ish by stroking the crank,spacing the barrel 9mm and boring it out and welding up the crankcases to strenghen them,a wee bit too serious for me.I have got a couple of motors and could make 1 good one out of the 2.Any info would be much appreciated.
cheers the noo Brian #88
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Ah you bought that recently advertised bike?
Mead and Tompkins in Hereford built an SP up for the world endurance series, then the rules were changed. They used an Amal 32 mark 2. I found the 34 had a flat spot straight off idle whatever parts I used.
Dirt Bike reported that quite a few tuners had attempted to tune the DR400 only to have problems if they went much above a high comp 420cc. White Bros did a Wiseco high comp 420 kit but that's long gone {standard liner]. They also had a 36mm round slide carb kit which may be better for a revver. I've got the body but I've lost the carb specs. It's possible if you contacted Tom White directly he might still have the jet specs [he sold the firm].
I've got a bunch of clutch plates with bugger all wear that started slipping. It's possible that all I ever needed were new springs. The standard ones sack pretty quickly with a lightly tuned motor.
The XR 400 has a slightly weak clutch and thus it's advisable NOT to use synthetic as apparently this causes clutch slip, something to think about.
I'd go to Megacycle for the cam, springs and keepers. They do a high reving cam profile.
All my tuned 400 motors have the intake weir ground off. It doesn't seem to have much of a detrimental effect straight of idle, doesn't bugger the jetting and breathes better. I don't know if the weir was on the 370.
In the USA the DR was only around for a year so they are rare as hens teeth and there seems to be no tuning info available. You could approach Wiseco directly and ask if they have any old stock.
The 400 motor was beefed up, I think in the gears, kick start and crankpin; whether the cases are the same I don't know.
Interestingly the 370 seemed peppier than the 400.
I've wondered if overbored XT500 pistons might fit, but not found any info.
Good luck!
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PS I've got a feeling M and T were going for a capacity of 350cc
The motor mught be better suited for that class if you had it relined and matched up a smaller piston.
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Hi there
the class that I run in is up to 500cc(Junior Forgotten Era),our class goes out with Classics and earlystocks so I get a race with somebody.Over the winter I have changed the front end for an Aprilia RS 125 with 17" wheel and put a NSR125 rear wheel with disc,its a wavey disc from a pitbike bought on Ebay along with a 2 pot caliper/hose and master cylinder for £35 all brand new.As far as I know the motor was tuned by Stan Stevens?? its got one of his stickers on the old fairing,an Amal carb and a reverse cone mega.Like yourself Cloggy I have been looking at XT500 pistons think Wossner do one,had a couple of cams done in the past by David Newman he does a good job at a resonable price and can repair worn rockers.I have a heavy duty clutch/springs to go in,whats the best oil to put in a quality 10/40 or a semi 10/40?
cheers the noo Brian #88
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Well for XRs with similarly weak clutches they say go for the best 10/40 mineral. But don't ask me. I'm not at your level. Joy did my cam 20 years ago. He may have a spec for a full on race cam.
Let me know if you ever discover an oversize piston match. My motor's all midrange. great for B roads, which is pretty much all that exist here [W Herefordshire].
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Oh yeh
Powroll [the Honda singles engine people]did a whole bunch of tests on aircooled stuff and found better wear rates with mineral oils. It's all on their website http://www.powroll.com/tech_specs_OIL.htm
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Happy New Year
made a start to the spare motor,stripped the spare 370 motor right down doesn't look too bad for a 20 odd year old lump,cleaned up the crankcases and painted them,going to replace the main bearings then check the gearbox and rebuild the bottom end.fit a heavy duty clutch then some porting of the head then a cheecky valve job and try and find a piston for the job.still trying to find a piston if I go 91mm using the 400 barrel that makes it 424cc.
cheers the noo Brian #88
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many years ago a mate of mine managed to get his SP370 out to approx 490cc running a big carb, using what piston I dont know but it was quite lively.
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Hi there,
I'm Hans from Munich (so please pardon my english ::)) and join the forum to get some info for my GN400-classic-racer project. Of course I let take part everyone here to (nearly..) all of my knowledge.. ;)
I do some hobby-racing with a slightly modified XT500 (http://www.nefo.med.uni-muenchen.de/~hiha/bilder/Rijeka_07/SANY0069.JPG) with the Grab the Flag (http://www.grabtheflag.de/index.html), where "no japanese four-valves" are allowed. The GN is for my brother in law, who won't ever sit on a Yamaha...
First I try to build up a reliable engine with 400ccm, and later perhaps will downbore it to 350ccm, or upstroke/-bore it a bit, to be competitive in the 500-class.
I found out, the GN-engine is very nice made, many things are solved much more elegant than in the yamaha XT/SR500 engines. Advantages for racing are the close gear ratios and the lower weigth.
Also the valve-gear seems to be less sensible. I ordered stage2 megacycle cam, and after having calculated the valve spring force, I will choose the right ones from Schrick, (http://www.drschrick.de) as I made good experiences with his products, unlike with R&D-springs.
For the first trials I will use a Mikuni TM36(I've got a spare one) and later an old 38mm Mik. flat slide out of a DR600. Exhaust will be a megaphone with reverse cone (mostly no noise limit).
Info: XT/SR500-Pistons have a 2,5mm lower compression heigth, equal pin diameter, but exhaust valve pocket is not in symmetry axis and must be reworked. There are many aftermarket pistons with different compression ratios from woessner(athena), wiseco, J.E. and others.
I don't know much about the british racing scene, except what I read on the http://www.bmzrc.org.uk/
Cheers,
Hans
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hi
sounds like interesting projects are afoot!
Hans, what were your problems with R&D??
Anyone got a preferance?
andy
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Hi andy,
SR500 with hi-lift (more than 13mm) cams make lots of problems with broken R&D-springs.
Best would be, to change them after each racing weekend. Schrick springs last several seasons.
Cheers
Hans
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Hi Hans
If you find a piston suitible for the 400 could you let me know,I was looking for a 91mm piston which should be around 420cc's
cheers the noo Brian #88
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Hi Brian,
I only could find a forged Athena-piston with 90mm, for XT500, which is ~2-3mm lower in compression heigth.
Cheers
Hans
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seen www.kedo.com for XT and associated pistons??
dunno if its any use....
a
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You are right, KEDO has 91mm-Pistons, but not for XT500. With original sleeve 90mm maximum bore.
They offer 91mm pistons for the TRX850. I don't know any measures of it.
There are very modern 91mm pistons for KTM 450 in the wiseco-list I would like to try, but they are very short.
Please compare a XT500-Piston with one of a Honda CRF450:
http://www.nefo.med.uni-muenchen.de/~hiha/bilder/kolben_alt_modern/kolben1.jpg
Weigth difference is 150g...
Cheers
Hans
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Not sure if this has already been mentioned, but.....
The GN400 Yahoo user group had a posting a year or so back about a chap who raced GN400's. He extensively modified the bike (chassis and engine) and, if memory serves me correctly, was talking about speeds of around 120mph!!!
Photo,s too- so I guess he was genuine (certainly sounded like he knew what he was talking about).
stu
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Thanks for the tip, I think I will join that group.
Cheers
Hans
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Evening all
was up the shed at the weekend and got the spare head ported including tapering the inlet valve guide.Cleaned the valves up on the lathe and carried out a wee bit machining of the valves.Head is ready to be skimmed once a piston is sourced,measured the liner and think it would be safer to go 90mm which would leave some meat on the liner.Was also up at my local bike tuners YPE who is Scotlands leading engine tuner,recently over the last few years Stuart the owner has been building motors for top moto x teams and showed him the piston out the SP he laughed and said the last time he saw a piston like that was in a Jaguar.He is going to try and match something up ,possibly a Rotax or KTM.Will keep you all posted.
cheers the noo Brian
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Hi there
Had a wee bit bother with the the rear wheel/chain line up,the wheel has to go.Got another wheel from a TZR 125 to try.The front brakes all bled up and feels great.There is a couple of photos of my bike under members current projects.Its at the top with #88 on it,the numbers are offset for a reason so when I race with another club/circuit all I do is put a 1 or a 2 infront of 88.My spare engine is coming on new mains,SP 400 gearbox and a SP 400 clutch.removed all the kickstart gears shafts as I bump start the bike and was told that you can get bother with the gears and they cause damage to the crankcases,so I'll make a plug for the casing on the lathe.
cheers the noo Brian #88
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Hey Brian
Looking good... Who do you race with?? And whats your front end-
I've got a KR1S 41mm front end on my supermono project, but I dont know if it'll be up to much... Lets get it running first!
andy
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Hi Brian,
really looking good.
For the class I want to race USD-Forks, multi-piston-brakes, slicks and 17"-wheels are not allowed, so the GN will look a bit more like a "classic"-racer.
What engine-mods will you do? Only bigbore, ore stroking too?
Cheers,
Hans
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Hi Andy the front end is of an aprillia RS 125,I used the steering stem/inserts fron the original Hejira
yokes,RS 125 front wheel and disc and a Fireblade Caliper with CBR600 master cylinder.I race at East Fortune In East Lothian,about 20miles east of Edinburgh with the Melville club.I race it in the Junior Forgotten Era class.Hans for the first couple of meetings I will run the 370 motor that I got with the bike but when I get the 400 motor built will use that,hopefully will find out soon what piston I am going to use,may need to change the liner,will get a cam. reground aswell.Dont think I'll be stroking the motor unless I get a wealthy sponsor ;).Away up the shed to see if I can get a smart wee race can to fit as the old mega is a bit too noisy.
cheers the noo Brian #88
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Evening all
got a rear wheel from ebay from a TZR 125r fits a treat and the chain lines up perfectly.Hans hows the bike coming on?any joy with a piston yet?decided to go for a 90mm as it leaves a bit meat on the liner.Andy do you still live in the weege or have you moved doon south.hows the bike coming on?Waiting on a rear disc from ebay then get the bike up an running a hopefully ready for practice on the 16th of March.
cheers the noo Brian #88
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Hi #88
I found some modern 90mm-pistons on the Woessner-pages: KLX400 '03-'07, 20mm pin, and DR-Z400 '00-'07, both are also available as "Hi-Compression"-types. But no idea about heigth and other measures. Maybe you have to use a stroked crank or a longer Rod. I would like to try one of them, if I only could find somenone making the crank-weldings for me...
There are also 90mm-ATV-Pistons. As I could see, they are mostly a bit longer, but also no measures.
http://www.woessner-kolben.de
I'm still waiting for the Megacycle-cams, it will need time until middle of March.
Most cahssis-modifications belong to my brother in law, and he has a to do lots of work in the moment. I'm only the motor-guy ..
Cheers,
Hans
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Andy do you still live in the weege or have you moved doon south.hows the bike coming on?Waiting on a rear disc from ebay then get the bike up an running a hopefully ready for practice on the 16th of March.
cheers the noo Brian #88
Hi Brian,
Nope, I ran away to London about 6 years ago now... Its ok, but starting to do my nut a bit, thinking about reloacation at *some* point...
The bike's coming on slowly, am getting some help from a club member Rog to make up some shims to go under the valve springs to give correct installed height... I have a feeleing maybe the head's been machined for different srings at some point?? A pain, but should be ok. There are a few pics here-->
www.team-thumper.blogspot.com
The motors now out the chassis again, head off to get it built up and then once its down the combustion chamber is (hopefully) not going to see daylight for a while...
cheers
a
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Got the bike fired up for the first time this year,sounds fruity.Going to use last years 370 motor
but in the middle of building a 400.Hans I may have found a piston that might just do the job,its
from a tractor(Harley),if you go on the Wiseco site and go on the Harley catalogue it is the big bore kit for the 883 to take it out to 1200.They do a piston that is just shy of 90mm and is a high comp.
I have measured the pistons as my friend has bought a kit for his bike and I measured them.The gudgeon pin is 20mm and the crown height(pin to crown) is just over 21mm which is roughly the same as the suzuki one.I will go down next week and compare both pistons and let you know how I get on.I have put a couple of pictures in the Gallery section,the bike now has a tz fairing and the word Tattie on the fairing.
Cheers the noo Brian #88
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Have been looking for piston as well. Try googling 'Pistal' they do pistons for 2 valve bevel Ducati's, 90mm bore 20mm gudgeon pin, not sure whether the pin to crown height would be ok but might be worth a look.They also do a 92mm version. There is also a Guzzi with a 90mm bore but they use a 22mm pin.
Jez
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Aye Brian#88,
The Tattie 's looking good and I hope you have a good season at East Fortune. Maybe down for some of the meetings and will be trying to get down for the Bob Mac as usual. Just hope the precipitation leaves us alone this year. Last years Bob Mac was not much different from what we have now, except it was rain for 36 hours instead of the white stuff!
My regards, Bill.
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@#88
Hi Brian,
I would search for a more modern piston, especially one with low crown and very low heigth. The Pistals look like what I'm looking for :o Thanks to Jez F ;D
Next thing: I will do some crank-welding research for stroking the original crankshaft. Here in Germany I couldn't find anybody who did such, and would tell me something about that. (350ccm-conversion is dead momentarily)
Brian, your Tattie looks really nice. But for the class I am racing, such brakes are prohibitet :'(
Nice frame, did you write something about it?
Only thing I wonder is the tiny diameter and extreme length of the ext.pipe. Have wou been on the dyno with it already?
Last week I tried the fit of the head-carb combo in the GN-frame. For your info: I'll use the 38mm Mikuni flatslide out of a DR600 with a 24mm spacer between head and carb-socket(?). It fits great, I'm really eased about that.
Gruss
Hans
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Hi Hans
Not had the bike on a dyno yet still got a couple of things to finish off,found that the fuel taps
where leaking so will have to source new ones.Will probably do the first meeting at East Fortune in April and if all goes well will get it on the dyno.Bill hope you get down to East Fortune sometime this year come over for a bleather,if you are going to the Bob Mac I'll be there as I help with the scruitineering.
cheers the noo Brian #88
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A couple of possible piston alternatives that I'm looking into, Ducati Monster 900, 92mm dia, getting to the limit on the liner according to a mate who has built a few racing engines in his time and modern Triumph twin, 90mm dia but a 4 valver, might be worth a thought.
Cheers Jez
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Since piston materials are matched to their use, putting a piston in that's designed for a watercooled engine may pose problems for an air cooled motor.
At the very least one would have to run greater clearences, and with a very short slipper piston you could end up with piston rattle before you'd even run the thing in, not that I'm an authority.
Air cooled trail bike engines recommended piston clearances are greater than equivalent road motors [though I don't think Suzuki bothered with different clearances for the GN motors] due to fording streams and having the barrel shrink onto the piston.
The Yam XT 600 piston has a much shorter skirt than the Suzy
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Since the standard Suzuki rod is nothing special anyone know a better replacement?
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Hi there,
there is no need for a different rod. The only advantage would be a replaceable small end bushing.
Japanese rods are made of very good steels, and if nobody had polished them without shot peening, they will last nearly forever.
@cloggy
you are right, clearings in air cooled cylinders with very short slippers could be a big problem. And I know what can happen, if a worn short piston hast to much clearance:
http://www.nefo.med.uni-muenchen.de/~hiha/bilder/schrott/kolbenschrott-001.jpg
http://www.nefo.med.uni-muenchen.de/~hiha/bilder/schrott/kolbenschrott-003.jpg
Gruss
Hans
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AAAAaaww! :( Crivins an' hap ma bob!! They is grim :'(
Did you grab the clutch in time?
Keep boppin', Bill.
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It was a friends' Rotax KTM, the piston was a Wiseco. It happened on the road at full speed. He survived...
Wiseco recommends to change Pistons every 50hours..
P.S. My english isn't good enough for understanding your first sentence. For me it sounds like "Monty Pythons flying Circus" or "Billy Elliot, I will dance" in original tone. ;-)
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It's alright I didn't understand it either.
Some XT500 tuners recommend fitting a better rod if overboring the motor
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Standard Yamaha rods in the 600 engines tends to stretch at high revs. A Carrillo rod will allow the engine to rev much further into the red for longer without doing to much damage.
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Good evening Hans,
I have used Google to translate what I wrote and I hope it reads correctly. My Norfolk, Scots, English pronounciation and jumble of colloquialisms, causes problems over here ???. I apologies for confusing you. A bit like a Hanovarian trying to understand Bavarian dialect! ;)
Ein Eid blasphemischen oft geäußert und westlich von Schottland.
Auch ein Umgangssprachausdruck, die von einem berühmten Comic-Familie namens "The Broons" Sonntag in einer Zeitung, hier in Schottland.
"Sie ist düster", die eine Beobachtung der Zustand der beiden verbleibenden Klumpen Metall.
My regards, Bill.
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@Bill
thanks for the translation. The translationmachine ist quite bad, but I understand the meaning now. ;)
I AM Bavarian ;D
@steveH and cloggy
The reason for this failure was NOT a broken rod. (A Carrillo was mounted, AFAIK)
I don't agree with you that yamaha-rods(or other japanese) make problems. I have seen more broken carrillos than yamaha-rods.
The piston turned upside down without loosing connection to the rod !
My XT500 in the first version with 600ccm (95mm J.E.) reved easily into 9500/min, and could be kept for a longer distance above 9000/min without problems. When the reglement changed, and max500ccm where allowed in that class,I transplanted it into my all-day-XT, (with a chang in cam-timing) where it just absolved successfully the 30000km-long time test, also without problems.
By the way:
When I made a two day trip in the Alps last weekend, I had so extremely much fun with it, winding up to Jaufenpass (http://www.mtbc-wehrheim.de/Bilder/Sonstige/Oetztaler%20Radmarathon/Strecke_2.jpg), singing loud under my helmet...
Gruss
Hans
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I don't agree with you that yamaha-rods(or other japanese) make problems. I have seen more broken carrillos than yamaha-rods.
I didnt say they caused problems I just said they stretched.
Could it be the case that engines with Carillos are ridden/revved harder (because they have a Carillo), which results in other components failing.
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Ah, I see.
Therefore squishband-clearings for original rods in XT500/600-engines should have a minimum of 1,2mm. Maybe with Carrillo it can be closer? I won't try ;D
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Have a look at ebay uk there's a classic racer
sp370/400 bored and stroked to just under 500cc
Reading between the lines it may be using a modded SP400 piston and rod. Mostly it was stroked.
l
Look under "sp370" "parts and vehicles" or paste this
http://cgi.ebay.co.uk/Vic-Camp-Suzuki-500cc-Classic-Racer-SP-370-based_W0QQitemZ280219477468QQihZ018QQcategoryZ9808QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
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Evening all just back from a weekend racing at East Fortune.It was the first time out on the Hejira,practice on Saturday went reasonble,the riding position is a bit cramped(just need to lift the fairing so I can raise the handlebars on put them out wider),swap to a road change set up rather than race(made a couple of bad gear changes going down the gears instead of up),the bike is also a bit under geared and the tacho has a mind of its own,Qualified not quite last(2nd last row) its been a long time since I've been that far back.1st race got a terrible start didn't see the lights go out had a couple of dices with bigger bikes on the bends but lost out on the straights finishing last in class but had some earlystocks behind so was not dead last.Saturdays other race was cancelled due to lack of time due to a couple of nasty crashes in other races and riders requiring hospital treatment nasty.Sunday got Saturdays race which was canelled,got a terrible start not my fault this time the bloke in front bogged down his Manx so I thought I would nip by the outside of him but his bike picked up and I had to nip in behind him loosing time,had a good race with a novice on a CBR600 who had been moved into my class as he was too slow for his own class.I would pass him round the twisty stuff and he would blast me on the straights,I passed him 3 times coming out of the snake(a corner flat in 4th)on the outside as I had good corner speed but on the 4th occasion as I was lining him up and about to pounce and he ran wide causing me to sit up to avoid hitting him and I ran off the track and onto the field which had freshly grow crops so if I crashed it wouldn't be too bad,dont know what speed I was doing but I think that the old SP engine was at home :) as the bike eventually came to a stop,when I rejoined the track I kept of the racing line to clean my tyres.Finished last again but no damage,when I got back to the pits the bike was covered in mud,the
Tattie looked at home.2nd race got a blinder of a start going fron the 6th row up to about the 3rd before the lights went out(oops) got into the first corner mid pack then down the back straight it was like I was in reverse,halfway through the race I had been concetrating that much that the left hand clip on was nearly into the fairing/tank,should I pull in or finish the race bugger it Race,down the staights i pushed the bar straight then after a lap it would creep in,I eventually finished 9th out of 11.I missed my last race because I noticed fuel dripping from the carb,never mind the bike goes, stops and handles well and I knocked 7 seconds of my lap time over the weekend.Will fettle the Tattie before Knockhill in June.
cheers the noo Brian #88
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@#88
Nice to read. :-)
@cloggy
I read the article the seller posted to the yahoo-GN400-forum. The piston is original GN400, also the rod is,
but he stroked the crank by welding and reboring it +7,5mm for a stroke of +15mm..
Cheers,
Hans
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Hi there
waiting on some parts for the hejira,was wondering if anyone knows what tacho would work on the SP motor as the one that is fitted on it has a mind of its own,I would like to keep it cable driven.
cheers the noo Brian #88
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going back a few years, one of the most fun bikes i ever had was a honda xl125 frame with a suzuki gn400 engine in it. it handled ok, and was light, but the best thing was, it went like stink, a propper flyer. id done a bit of tidying up the ports in it and had fitted a home made copper head gasket, (mainly because i had it apart so often). the only signioficnt changes to the stock spec were a nice fre flowing exhaust pipe, and a huge klr 650 cv carb the carb enabled it to really fly, whilst still being a grunty mud plugger. alas, i got fed up of the local scrotes trying to nick it every time i parked it up at home, so i flogged it.
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Oooops! :o
R
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Hans I was wondering if you have had any joy finding a suitable piston for your bike?
Or if anybody else has found a suitable one.
cheers the noo Brian #88
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@#88
No, the main problem with a very low single-ring-Piston will be the valve pockets, which will reach through to the upper ring groove. I think I will take a SR500-Piston from Wiseco, (they are easiest to get here,) and maybe try to get a 3mm excentric wrist-pin (because SR-pistons have about 2-3mm lower compression heigth) That won't bring me much displacement, but it is a reliable, and comparatively cheap solution. Finace is the next major problem momentarily...
Cheers,
Hans
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Hi Hans in the same boat as you lack of funds for developing the bike,all I have done before my next outing at Knockhill is a new road pattern gearchange and a new rear sprocket and an oil change.Oh aye and I put a couple of coats of paint on it,my old race colours,I've put a couple of pictures on the photo section under projects it blue and yellow nos. 88.
cheers the noo Brian #88
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http://www.eurospares.com/tt500.htm
Have a look at this re stretching rods