Re shimming

Hi guys I have a 99 model yz400f when I bought it it had no compression and didn't start so I assumed it was rings or some thing like that so I or new rings in checked barrel etc and found my valves were stuck open so I had all my valves re seated........rebuilt bike and still no compression and wont start so I had a really ex race mechanic take a look and he said it just needs re shimming as when he losened the cam covers I got most of my compression back as there wasn't as much pressure on the valves ......... but now I'm really struggling to find some one to do it as yamaha want 50quid an hour to do it is there anywhere in the west midlands preferably that can do it. Please help

its verry easy. look around on here there are countless threads on shimming valves. pick up a service manual for your bike and you should be able to do it for verry little money on your own.

Id rather have it done properly tho ive heard no end of stories about unless you have the correct shims you cam be there all week as everytime you try a new shim you have to bolt up the cams and chain and a big pain in the arse so I don't mind paying I would just like to get it abit cheaper than 50 quid an hour

your gunna half to find a backyard mechanic like me. but more in your area... you will be lucky to find a good one for cheep

watch some vids on youtube, buy a feeler gauge set and be done with it. its very simple to do. the service manual tells you step by step and what shim to replace with. I have done this on my bike and a couple friends bikes now and every time I do I get faster and it gets easier.  I like the art of self reliance, and the local shop wants 100$ an hour just for labor.

I used vids on You tube

Well I managed to get them done and now the bike has tons of compression and starts but it backfires alot and doesnt idle now n to be fair these bikes seem rubbish I wish I hadnt bothered its 1 thing after another and is costing me too much money to keep repairing thanks for your advice tho guys

If it backfires and won't idle, it could simply be that your pilot circuit isn't adjusted right, or that the jet needs to be cleaned out.


The bikes are far from being rubbish.  People turn them into that by how they take care of them.

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