Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: guest668 on September 18, 2011, 06:00:13 PM
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hi i have just been putting cylinder head onto srx but have encountered a problem wiht the cam chain sprocket alignment marks.. After putting tension onto the camchain by putting finger through cam chain hole the alignment marks on the cam sprocket are meant to line up above the top of the cylinder head. However one side seems slightly raised to the other by about a mil...we have tried to correct this several times but it always ends up with one of the marks slightly raised higher than the other . I was wondering if anyone else has had same problem how critical is it ..could it be due to wear in the chain? i was looking in a xt600 manual i have and they say it must be aligned but then they show a photo in which there marks are also tilted and not at an equal distance above top of cylinder head? hope this makes sense any advice will be greatfully recieved.
ps all the other alignment marks line up ok just the horizontal marks on cam sproket that dont?
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Having done a fair bit of work on a 250RSA which sounds virtually the same design I would suspect a little cam-chain wear plus manufacturing engineering tolerances.
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thanks for the reply so should i not worry to much about it and go for near as level as possible?
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also just to check it is the dot on the cam shaft timingsprocket i should be checking against the mark on the crabkcase and not the T for top dead centre isnt it? the manual says the dot so ive been going with that but thought id better check just in case...thanks
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heres a photo to illustrate problem
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It doesnt look far out, but I would have expected a stretched chain to move the timing in the opposite direction. Have you tried fitting the camchain tensioner and rotating the engine a few times, it maybe that the load exerted by just pushing the tensioner is insufficient.
Also did you use a Yamaha head gasket or a copy ?. If a thicker head gasket were used then the timing would move in the direction it has.
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we have tried adjusting it several times and it either sits like this or the same difference but on the opposite side i used genuine yamaha parts. Shoutl i set it up to er more towards intake side then? many thanks steve
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also can anyone tell me if i should be setting the timing using the t mark on the crank or the dot...the manual says dot but i would have thought it would be the t?
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oh and another thing do i need to readjust the cam tensioner before refitting it and how do i do this....is it just a case of loosening the nut on the tensioner
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oh and another thing do i need to readjust the cam tensioner before refitting it and how do i do this....is it just a case of loosening the nut on the tensioner
I would use a wooden rod or similar down the spark plug hole to determine TDC. I think the manual mentions the spot because in general, when building an engine, the flywheel and cover will not be fitted at this point of assembly.
In order to fit the tensioner, I would
- Remove the cap retaining the spring
- De-adjust the tensioner by releasing the ratchet
- Refit the tensioner body without the spring and cap
- Refit the spring and cap, this will tension the chain
- Rotate the engine several revolutions
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thanks steve tried your suggestions and it looks like a stretched chain still...what is the procedure for changine the chain is it just a case of removing the alternator rotor or is it more involved...and where can i get a puuler from does it have to be the yamaha one?
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On bikes I've had, T was for Time and the mark is for top. Yours may be different. The cam chain can be replaced without disturbing the bottom. Get a new one with split link, pop the old one with a chain splitter and attach it to the new one, pull on the old one until the new one comes up. Bob's yer proverbial. Takes half an hour.
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The alternator can be difficult to remove. I usually use an air hammer on the nut, you can use any puller which uses the three tapped holes in the flywheel (I think a mini flywheel puller works but dont quote me). I would also recommend leaving the camchain fitted whilst removing the alternator as its easy to damage casting that the camchain tensioner locates in.
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thanks for the advice wil have a go at the alternator next week...my sons got a mini flywheel puller so will let you know how we get on....dont like the idea of split links on a camchain though !! will see how we get on.
THanks for all the advice
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It is possible that the cam chain sprocket on the crankshaft has moved.... as it is fitted using the hot/cold process, and there is no keyway for exact location.... never happened to me, but just a thought.
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its a thought steve how do i go about checking it ? or am i asking a stupid question lol
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ok taken casing off to get at alternator is there a good method of holding the alternator while undoing the nut without having to shell out for the yamaha special tool!! also is it a stright forward process to remove and replace the bottom camchain sprocket ...because if i replace the chain im presuming its good form to change sprockets to...again many thanks for everyones help
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Aye beezer
When removing the flywheel nut etc I use one of these: 'BOA' rubber strap wrench (http://www.amazon.co.uk/BOA-BOASTD-Standard-Strap-Wrench/dp/B00096JDKS/ref=sr_1_4?ie=UTF8&qid=1317251888&sr=8-4). If you don't wish to purchase corporately, then just stick 'Boa' strap wrench in Google and browse. There are now lots of imitations out there and I don't know how strong they are. However, the 'BOA' works and takes the 'stick' ! ;)
Never needed to replace the sprocket, so can't give any advice. I can only think that something pretty brutal has been going on, to cause the timing chain and sprockets to wear that badly. New chain and sort out the tensioner with a new OE gasket and maybe a tension spring if it has lost its compression strength, plus blades if they are badly worn. A lack of lube and tensioning sounds likely, if its flapping about like w..... knicker elastic! :-X :-X
Others may not agree with my last paragraph, but I hope the 'BOA' suggestion helps.
My regards, Bill.
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hi bought a boa strap but still no joy the flywheel nut is stuck solid so i think i might have to take the engine to the local garage and get them to remove it...im only contemplating rplacing the cam chain because the timing marks diont line up so presuming chain has stretched and since i have had rebore etc done though it would be good to replace cam chain too. hope its easiser to put the flywheel back on lol....
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Aye beezer,
Airgun wrench, no sweat, just wheel the bike round if its nae far.
All the best, Bill.
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Aye beezer,
Airgun wrench, no sweat, just wheel the bike round if its nae far.
All the best, Bill.
I like the idea of those airgun wrenches but how do 'built-up' cranks get on bearing in mind that they're usually aligned with the help of copper mallets and not subjected to very heavy blows at that. If the crank is roller bearing it probably wouldn't take too much torque at the shaft extremes to introduce a degree of 'twist' would it ?
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Aye Dick,
You'r not trying to twist the two halves of the crank, only applying torque to one half of the crank, whilst it remains rigidly held between the crankcases.
You are applying a torque to the nut, which has forced the taper surface of the crank end and the inside taper of the alternator flywheel together. It is a friction join. The woodruff key which lies between the surfaces is nothing more than an acurate locater, it does not take any mechanical strain if the rotor is correctly installed. Hence the dynamic balancing of the flywheel, before installation, as its position on the crank is a known constant.
By using the 'BOA' on the alternator circumference and then applying the torque to the nut you are only resisting the turning of the left hand side of the crank. Providing the taper has been correctly assembled, it shouldn't move, until you apply the pulling force to the end of the crank, using the BMC Mini flywheel puller or similar.
The wheeze to ensure a good fit of the taper is to clean it scrupulously, then breath on it and bring the two halves together. The dampness of the breath creating a slight oxidisation of the two tapers, which makes them bind. If you are unlucky, a 'bright spark' will have applied a metal 'glue' i.e. 'Studlock', to the taper and then you may have to destroy the bottom end!!!!!!!!! 'Nutlock' is a different kettle of fish and I have used that to hold an abused Ducati single crank taper and alternator together and be able to seperate the two items, using a conventional puller.
As for adjusting the alignment of the whole crankshaft, with a soft metal mallet, it is indeed a delicate touch and patience in abundance that is required. However, having had to put 30 tonnes pressure onto the end of the crankpin of a Ducati single, before it would separate from the flywheel, and it being a different component part of the same assembly I think that the air wrench is unlikely to cause problems. I am happy to eat humble pie, if others with different experiences know otherwise.
My regards, Bill.
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Thanks Thermoudie for a comprehensive and thoroughly logical answer. I questioned this 'air-wrench' usage after hearing reports of miss-alignment in some Laverda triple crankshafts allegedly put down to these devices which in retrospect I realise was more likely the responsibility of some clown who shouldn't be allowed to get anywhere near to a toolbox.
Kindest regards...........Dick S.
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As Steve L indicates, the camchain sprocket on the crank is a press fit and is not located with a woodruf key. If the crank has been rebuilt at some point, then since there are no obvious alignment marks, it is quite possible the sprocket was fitted incorrectly. This happened to me some time ago and I had to send the crank back to the muppets to get them to do it correctly.
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im taking engine to my local garage on monday and their going to try their air gun on it so crossing fingers lol if the lower sprocketr has no obvious alignment marks how would i know if its lined up properly if i have to replace it?? is it necessary to replace the sprockets with the chain or is that just being over cautious...many thanks again for all the helpful advice....
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Based on the parts list the crankshaft camchain sprocket is part of the crankshaft assembly. The sprockets are made of a pretty tough material and I would be surprised if they are worn
From memory there is a dot on the spocket which needs to be aligned to the centre of the woodruff keyway.
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Are these photos of any use?Taken of an SRX 400 engine partly dismantled I have here.
HTH
Ian
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Aye beezer,
Sally now has 78,000km + on the clock and so far as I am aware is still running the original sprockets and cam chain. The only apparent wear is to the timing chain guides and that is marginal. The other thing to keep an eye on, is ensuring that the tensioner plunger doesn't bind. There doesn't appear to be obvious wear to the cam drive sprockets. I haven't taken my crank apart and can't remember from the last time of stripping out the motor if there were marks on the sprocket to enable alignment with the woodruff key keyway.
However, in the Clymer, Yamaha, XT600 & TT600 1983-89 Maintanence Handbook (ISBN 0-89287-546-1), on page 161, Image 57, Paragraph 11. reads "Inspect the camshaft drive chain sprocket . Check the sprocket for worn or damaged gear teeth. Also check the teeth for cracking or rounding, replace if necessary." "NOTE If the camshaft drive sprocket is worn, also check the camshaft sprocket, drive chain, chain guides and chain tensioner.". Page 198, Image 89 and again on page 199, Image 93 the 'dot' mark on the lower chain drive sprocket, referred to by SteveH, can clearly be seen aligned with the centre of the crank woodruff key keyway. The only guidance given as to whether the timing chain and the two sprockets might be worn is to "If the camshaft chain is worn, the sprockets (upper and lower) as well as the camshaft chain guides are probably worn also. Inspect all parts closely. Running the engine with new and used parts will cause rapid wear to the new parts. Always replace these parts as a set." GRAND! But how long is a worn cam chain compared with a new one, before you've ordered the new one to measure it against??? >:( >:(
Finally, did you when checking the two timing marks on the upper cam chain sprocket "Pull up on the FRONT section of the drive chain until all slack is removed from the drive chain. At this point the following timing marks must align. a/The timing mark on the crankshaft must still be aligned with the timing mark pointer on the crankcase. b/The upper position mark on the cam sprocket must be at the top. c/The two horizontal timing marks on the cam sprocket must be aligned along the top surface of the cylinder head."? If "No" this might be your problem. This is before the installation of the alternator rotor, or the cam drivechain tensioner components.
I hope this helps.
My regards, Bill.
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Aye beezer,
Ian's 1st image clearly shows the alignment of the dot on the sprocket with the centre of the woodruff keyway and in the other two images, the pointer cast in the case, which must align with the 'dot' in the sprocket, when aligning the upper sprockets horizontal timing marks. Digital images, where would we be without them?
Regards, Bill.
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Looking at Ians pictures, the sprocket dot seems to be slightly offset from the centre of the woodruff key
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SteveH is quite correct, there is a dot on the camchain drive sprocket which should align with the key slot.
However, I do have a 'workround' (as microsoft term repairs to their hopeless operating systems)
a cam sprocket with slotted holes (rather than the usual round ones), I bought this when i was playing around with different cams and timing, and allows shifting of the cam in relation to the crankshaft, you could use this to take out the mis-alignment, far less hassle than splitting the engine and taking the crankshaft to an engineer who can do the 'sweat off/on' job.
it is relatively new, only used on an engine i used for track days, you are welcome to try it, if it does the job i'm sure we can come to an amicable arrangement.
cheers
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thanks steve will let you know if i need it
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have got rotor off !!!!!!!!! air gun and mini puller did the job thanks for all the advice everyone. The chain is looking a bit stretched the crankshaft sprocket looks fine...will it be ok to just replace the chain and maybe top sprocket rather than all sprockets anyone done this i cant see how that bottom sprocket could be replaced without mega hassle. Interestingly the dot that lines up with woodruff key isnt perfectly centred on mine either and im sure this engine has never been tampered with before.
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steve thanks for offer of the slotted cam sent you message but havent recieved reply yet think it would be a good option would it be possible to send via post? whereabouts did you get hold of it ?
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Yeah... big probs with my email at the mo... all 3 accounts seem to be playing up.... the most reliable one is .. pightlefarm@lineone.net
i got the sprocket from the guy in the states who does thumper stuff... he's listed on here somewhere (or maybe it was on steveH's site)
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Aye beezer,
This maybe the site SteveL refers to: THUMPER_STUFF (http://www.thumperstuff.com/SRX.html#top)
However, I've had a looksee and can't see a slotted sprocket at present. Drop him a line, just in case.
I hope this helps, Bill.
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you're right Bill, no sign of it.... worth dropping him a line though.
another thing worth remembering if you order any piston/barrel/gasket components is that their (usa) 'standard' srx600 bore size is different to the european 'standard', european (and home market) srx600 are 607cc and the usa is 595cc..
cheers
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well we hecked the timing again today with a tdc tool and timing mark on sproket at top are 1mm outwhen all set up...is it worth worrying about will it make that much difference. I suppose while engine is out and alternator off might aswell replace the chain and maybe top sprocket but dont think i will bother with bottom one it sounds like way too much bother ...thing is tension on chain is good sprockets look ok it just seemes to have stretched a bit.
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well, a good test is to use the valve opening angle, with a 'degree' disk on the crankshaft make sure the valves open at the correct point (valve opening data is in the workshop manual)... if the valves open correctly (with the gaps set up properly, i use 3 thou inlet, 6 thou exhaust) then you don't have a problem.
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thanks steve will check that out
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just a thought on the valve opening angle option will the valve opening data in the srx600 manual be right for the srx400 are the cam shafts the same etc...if not does anyone know the aprropriate data i need ...again many thanks
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Aye beezer,
This should be the site of reference for the SRX400! SRX400_Tech_Info (http://www.srx400.co.uk/tinfo.shtml)
However, at present they are exceeding their permitted bandwidth and consequently, you can't view a thing! ??? I am not sure how to deal with this, but SteveH or SteveL may do.
All the best with the continuing assembly.
My regards, Bill.
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The only thing I can think to do is
1 - Fit the original cam chain sprocket
2 - Measure the valve timing when the cam chain sprocket marks are aligned with the head gasket face.
3 - Fit the adjustable sprocket
4 - When the crank is timed in correctly check the valve timing
5 - Adjust the timing to suit and repeat ad infinitum
If it was me I would just fit and forget that the timing is slightly out.
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The only thing I can think to do is
1 - Fit the original cam chain sprocket
2 - Measure the valve timing when the cam chain sprocket marks are aligned with the head gasket face.
3 - Fit the adjustable sprocket
4 - When the crank is timed in correctly check the valve timing
5 - Adjust the timing to suit and repeat ad infinitum
If it was me I would just fit and forget that the timing is slightly out.
I agree with the final sentence. ;) Bill.
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me too
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thanks guys for your help ...im starting to think i might just forget about timing been out slightly so will probably take your advice...have just checked out price of cam chains!!!!!!!!!!!!!!!!!!!!!
it was probably running slightly out befire anyway
again many thanks