SRX/XT 600 engine rebuild, cam chain, guides & sprockets sources.

[LoCo]

Hi, Currently getting toward finishing my a rebore and rebuild of my srx 600 engine (1mm overbore)
Inspecting the cam chain guides the black (plastic coating?) has worn through a bit the pivot on the rear guide stopper has a bit of play, but sprockets & chain seem good.
Obviously replacing everything is the best option to stop accelerated wear on the parts.
Yamaha don't list the sprockets anymore and the guides are ~£50 & £70 each.
What I'm wondering is:
How much wear is acceptable on the guides?
Does anyone know of any sources for replacement new sprockets?

Any other suggestions would be gratefully accepted too on rebuild tips for the engine.
Thanks.

[Steve Lake]

rebuilt & partially rebuilt several of these .... never had cause to replace cam chain or sprockets, and my #1 srx which I've owned for 15 years and rebuilt twice is still on the same cam chain & sprockets at 50k kilometres. So don't be too hasty in changing that stuff. one thing I ALWAYS change, expensive though it may be (£100 ish), is the oil pump... any slight wear in the pump (which isn't the finest pump in the world anyway) will compromise the oil distribution and can (in my case , did) result in surface failure between piston & barrel at the rear left quadrant... the hot spot adjacent to the cam chain tunnel/adjuster.,

also, 4th & 5th gear parts, known problem area, though touch wood I have not had gear box problems myself.

good luck with the rebuild, it's a stonking & pretty bomb proof lump

I change oil & filter & plug, every 2000 miles , wildly overserviced I know... but may account for me not having gearbox problems.

[LoCo]

Hi Steve,
thanks,
have you changed the cam chain guides at rebuild time? The sprockets and chain look good.
I've already got a new oil pump as the old one was scored and the engine was originally stripped by the previous owner due to scoring on the rear of the barrel.

[Steve Lake]

no, I havn't replace the cam chain guides, they have always looked ok to me when I've stripped my engines. not sure if you can get them now?.... xt600 ones should do the trick...
but do make sure the cam chain auto tensioner (well, I say auto, it's just a ratchet and pawl one way jobbie, spring loaded) is free to tension the chain and the ratchet teeth are in good shape and the pawl can hold the tensioner bar well.

make sure the head/barrel mating surfaces are immaculate, and a good gasket, preferably a Yamaha one (I've had aftermarket ones fail on several occasions).

the allen bolt that is under the head steady bracket (the one that appears to be (and sometimes is) nearly impossible to remove, one of the many that hold the rocker cover on.....  use a new stainless bolt with a liberal coating of 'copperslip' or similar, then, when it's all tightened up ok, put a load of grease over the bolt head and surrounding area. that 'well' where the bolt sits is a magnet for water and crud. as is the spark plug 'well' ... but not much you can do about that one, although, as the coil sits just above it, I have resorted to shaping a bit of clear Perspex to  fit in front to divert the worst of the weather, but you have to be careful not to reduce the (already limited) airflow over the head.

keep up the good work

[LoCo]

Excellent cheers, shall swap the gasket for a Yam. one, barrel, head & rock cover have been vapour blasted so need a re finish anyway.

Will check the tensioner as it's on the bench but not been inspected yet.

Going off on a slight tangent, I have a second engine (& a half) out of a grizzly that will eventually be rebuilt as a higher performance one, what's your opinion on maxbore size for these engines? This would be in conjunction with new a new conrod, cams etc too, or have you heard of anyone turboing an xt lump?!

[Steve Lake]

never heard  of one of these lumps being turbo'd, but as they say 'if you can imagine it, then it's probably been done'.

I'm not sure what the absolute maximum bore these lumps will go out to, I remember chatting about this to the guys at (now sadly no more) Denver Motorcycles, they had done some extraordinary things with xt/srx engines, and they had taken one out to 690cc, it involved a special liner and ended up lifting the barrel off the crankcase during a race, this due to the fact that on these engines the barrel is bolted to the crankcase at the base and due to the rebore was extremely thin in that area.... unlike good old brit iron, where the whole kit & caboodle is bolted through from the head downwards.

I'm guessing that any decision on bore size will be down to piston availability in the correct format ... I'm running my #1 srx at 640cc, with a wiseco piston and carillo rod... works well, (#1 featured in a head to head with a sorted XBR in Practical Sportsbikes a couple of years ago, and came out very well.)

[mthee]

(#1 featured in a head to head with a sorted XBR in Practical Sportsbikes a couple of years ago, and came out very well.)

Any chance of the issue no. to allow me to order a copy? 

[Steve Lake]

I 'think' it was Feb 2013 issue #28 ...

[Steve Lake]

this looks like it .. http://www.themagazineman.co.uk/images/Practical_Sportsbikes_28.jpg

[themoudie]

Aye LoCo,

I have had problems with big bore pistons in SRX600 motors and reverted to standard bore liners and pistons, as SteveL and I have chewed the fat on here before. Use the 'Search' box in the top right of the screen to search for the posts using "big bore", it brings up plenty of reading. 

As for your interest in "turbo's and superchargers" it has been done with mixed results; cranckcase pressure blowing the oil out of the crankcase breather being one of the messy problems. A relatively weak little end and SteveL's "hotspot" in the rear left of the SRX barrel, make it a not so good canidate for the "treatment"! However, this link should fuel your interest and there are many more if you 'Google' "Yamaha XT turbo or supercharger".

XT660_supercharging

I know that somebody in Kent added a supercharger to an XT660 and had it well sorted, but cannot for the life of me remeber "Who?", I'll sleep on it and maybe post the answer this coming week.

Good health, Bill

[mthee]

this looks like it .. http://www.themagazineman.co.uk/images/Practical_Sportsbikes_28.jpg

Appreciate that 

[Steve Lake]

if you can't get hold of the mag, i'll scan in the relevant pages and post them if you like, can't see there'd be a copyright problem, seeing as the miserable sod who blagged my bike for a week while they did the article didn't have the decency to send me a copy  (promised, and I reminded him twice)... or i'll post the mag to you....

[mthee]

Thanks for the offer, Steve, but I've already ordered. Pretty rough, not sending you a copy. Did you get anything at all? How did it come about then?

[Steve Lake]

the guy who did the article put a request up on here (TC), for a tidy SRX and XBR to do an item on, as they are part of EMAP based in Peterborough and I work on Wisbech 15 miles away, it made sense for them to use my bike, so I rode it into work, they collected, and brought it back to my house the following week.

[mthee]

So did the XBR belong to someone on here? I read Timbo's has been tuned? I'm really looking forward to receiving my copy of that issue