Author Topic: srx cam chain sprocket timing marks alignment query  (Read 4641 times)

guest668

  • Guest
Re: srx cam chain sprocket timing marks alignment query
« Reply #15 on: September 26, 2011, 08:06:14 PM »
its a thought steve how do i go about checking it ? or am i asking a stupid question lol

guest668

  • Guest
Re: srx cam chain sprocket timing marks alignment query
« Reply #16 on: September 28, 2011, 08:23:06 PM »
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

themoudie

  • Full Member
  • ***
  • Posts: 4645
Re: srx cam chain sprocket timing marks alignment query
« Reply #17 on: September 28, 2011, 11:32:24 PM »
Aye beezer

When removing the flywheel nut etc I use one of these: 'BOA' rubber strap wrench. 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.

guest668

  • Guest
Re: srx cam chain sprocket timing marks alignment query
« Reply #18 on: October 03, 2011, 08:17:13 PM »
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....

themoudie

  • Full Member
  • ***
  • Posts: 4645
Re: srx cam chain sprocket timing marks alignment query
« Reply #19 on: October 03, 2011, 09:01:48 PM »
Aye beezer,

Airgun wrench, no sweat, just wheel the bike round if its nae far.

All the best, Bill.

Dick Scratcher

  • Full Member
  • ***
  • Posts: 246
Re: srx cam chain sprocket timing marks alignment query
« Reply #20 on: October 04, 2011, 09:47:40 AM »
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 ?

themoudie

  • Full Member
  • ***
  • Posts: 4645
Re: srx cam chain sprocket timing marks alignment query
« Reply #21 on: October 04, 2011, 07:53:47 PM »
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.

Dick Scratcher

  • Full Member
  • ***
  • Posts: 246
Re: srx cam chain sprocket timing marks alignment query
« Reply #22 on: October 04, 2011, 08:07:51 PM »
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.

Steve H

  • Posts: 1845
Re: srx cam chain sprocket timing marks alignment query
« Reply #23 on: October 04, 2011, 08:15:53 PM »
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.

guest668

  • Guest
Re: srx cam chain sprocket timing marks alignment query
« Reply #24 on: October 05, 2011, 04:42:03 PM »
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....

Steve H

  • Posts: 1845
Re: srx cam chain sprocket timing marks alignment query
« Reply #25 on: October 05, 2011, 06:17:15 PM »
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.

Ian

  • Full Member
  • ***
  • Posts: 1870
Re: srx cam chain sprocket timing marks alignment query
« Reply #26 on: October 05, 2011, 10:28:03 PM »
Are these photos of any use?Taken of an SRX 400 engine partly dismantled I have here.

HTH
Ian

[attachment deleted by admin]
« Last Edit: October 05, 2011, 10:31:08 PM by ian650 »
1 SRX 1 C400X -2 thumpers

themoudie

  • Full Member
  • ***
  • Posts: 4645
Re: srx cam chain sprocket timing marks alignment query
« Reply #27 on: October 05, 2011, 11:33:17 PM »
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.

themoudie

  • Full Member
  • ***
  • Posts: 4645
Re: srx cam chain sprocket timing marks alignment query
« Reply #28 on: October 05, 2011, 11:40:47 PM »
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.

Steve H

  • Posts: 1845
Re: srx cam chain sprocket timing marks alignment query
« Reply #29 on: October 06, 2011, 07:54:03 AM »
Looking at Ians pictures, the sprocket dot seems to be slightly offset from the centre of the woodruff key