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the pistons can be installed from the bottom of the cylinder where there should be a chamfer ( use a ring compressor here makes the job easier--on the bench)
once you have the piston in the cylinder then install the assembly into the block taking care to ensure that the piston is at the top of the cylinder so that the big end doesn't damage the crank journal as you slide the cylinder down into the block I take it that the engine is a diesel ( wet sleeves) so check the liner to block face height before fitting because if the cylinder lip is too low , it will blow head gaskets
make sure that the piston is orientated correctly , the same as the others
Bummer. Usually you need to drop the oil pan, pull the rod and piston out, replace the sleeve, and use a ring comprssor to get the piston back into the cylinder and then put it all back together EXACTLY how it came apart including position on the sleeves, rods and bearings. I have not done this on a VW but I do not see this being much different than any other car that I have worked on. No matter what it will be a huge pain in the ***.
Honestly - it's just as cost effective to just buy a new cylinder complete from Yamaha - unless you have a lot of porting done to your cylinder. The cylinders are plated and you typically don't bore them - you have them re-sleeved.
I have raced semi-pro for many, many years (AMA District 13, A-class). When I raced 125s (1998-2002) I would usually go through 6 to 8 cylinders per season and I would rebuild the engine after every race (every week). I never bothered getting the worn cylinders resleeved because the sleeves cost almost as much as a new cylinder from Yamaha.
Price out a new cylinder then price out the re-sleeve. You'll see there's only a slight difference. I recall the new cylinders being about $245 and a sleeve was around $225.
Once you get it rebuilt, keep the ring fresh and make sure you run at least 28:1 mix. I raced at 26:1 to get the engines to last. They are single ringers and the piston ring just doesn't last. Yamaha recommends changing the ring every 2.2 hours for maximum output. I couldn't get 2 hours on a motor running 32:1, so I switched to 26:1 for more lubrication and better sealing of the ring. Long story.
There should be no play up and down. Any play is coming from a worn out needle bearing on the crank. A bit side to side is okay and normal. The crank will need to come out then it gets pressed apart and fitted with a new bearing. Price out the difference in cost of fixing the crank verses getting a new $170 crank assembly.What probably happened is a broken piston ring extended into a cylinder port and the piston against the ring is what gouged the cylinder and head.
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Replace the sleeve is the only option - I think there would not be enough cylinder wall left if you rebored it as it is a sleeved cylinder it relys on the sleeve for extra wall thickness and strength you can rehone the sleeve if it is not too badly scratched you can get honing tools around $80 ish? they fit into cordless drill
Yes, that is a plated cylinder so if it galls, or wears out, it cannot be bored out you have to put a new sleeve in it. The new sleeve will be able to be bored out so it will last for a long time. The resleeving is best left to a cycle shop or machine shop with the propper equipment, as it is an interfearence fit and the cylinder must be bored perfectly, then heated in an oven to be able to install the new sleeve.
If you say it is definately sleeved it should be possible to bore it, you normally get one or two oversizes before it needs resleeving. If you are able to buy an over size piston from kawa or wiseco, chances are it can be bored.
if it is piston slap,you will need pull the top off again and measure with a feeler gauge between the piston skirt and the sleeve, should only be a couple of thou
If your going to the trouble of replacing the cylinder - wouldn it make sense to replace it with a quality part ? You really should do new piston & rings while your at it..
If not - you might be doing it again allot sooner than you would like..
Your local bike shop should be able to get one for you..
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