Barrels off

yellowdog

yellowdog

yellowdog
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Ok ,got the cylinder head and barrels off today ,all looks to be in good condition apart from the piston crowns and valves being heavily coated with carbon.
What should i renew as a matter of course ?
Can I use the piston rings or should they be replaced ?
The only problem I can see is the cam chain tensioner at the rear,the rubber bush that the pushrod pushes against is cracked and from what I have learnt this part on a 72 is unobtainable now .all suggestions welcome ,
Thanks
 
When you take a top end apart, you need to take measurements of pistons/cylinders/rings/valve guides/valve seats, etc. Then you compare those measurements with the Yamaha specs that are in the Yamaha Service Manual. That will tell you what needs replacement and/or machining. Read the manual carefully.

www.biker.net

Always replace the front camchain guide and the camchain if the engine has high miles/kms. New gaskets and oil seals must be used.

Its normal to have a lot of carbon, so just clean it all off.
 
Yup, like the gentleman suggests. You might want to take the head and barrels to a machinest to give them a once over.
 
Thanks will do .The rubber cushion is compressed with a few cracks in it ,It might be ok as it doesnt make contact wiyh anything apart from the pushrod.
 
A close uo of the cam chain tensioner ,it may be repairable but if not what are the options ? It is a 72 xs-2
 

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On your 72 the rear cam chain guide and tensioner is a two part system. the lower part bolts into the case and the upper part that bolts to the cylinders. Your upper part has a small gear wheel that rides on the chain.
The later 74 up engines uses a one piece system. The lower case part gets replaced by a unit with a long bar that presses on the chain. It bolts in p[lace of your lower part and replaces the gear wheel. The part the gear wheel was mounted to just holds the adjuster and push rod. I think you can just replace the entire system from the later into your early cases.
Should be able to find the parts to do the swap on Ebay. Or maybe someone on here may have the parts to do the swap.
Leo
 

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