valve shim help!!

my next shim is goin to be 1.35 does this mean i need new valves?? i dont know too much about this stuff, what is the process do my valve seats need to be machined?

I think you can go all the way to a 1.20, but it sounds like you have shimmed more than once. Once the stock valves start moving they don't seem to stop, so a valve job is in your future. You will need to have the seats cut otherwise your life of you new valves will be drastically shortened.

If your riding still does not include constantly bouncing off the rev limiter, I suggest you look into stainless steel valves.

My expirence is not with the Honda motor however I feel this type of thinking will work well with any late model four stroke. If I have to change shims more then once within ten hours of riding, I replace the valves. We generally do not have the valve seats cut. However if we do we use local automotive machine shop. I usually have them inspect the head to determine if there is damage. By replacing the valves before the outer coating is completely gone you generally will not damage the head. So the rule of thumb is a big change in valve shim size in a short amount of time.

yeh i only just bought the bike so i dont know what has previously been done to the valves, but im assuming they have been shimmed several times. also are the exhaust valves stainless from factory? they haven't moved at all still reading .011"

Yep the exhaust valves are stainless.

There are lots of options but I would definitely consider stainless intakes. You can buy a new head with ss valves ready to bolt on for around $550 from somewhere like Bigborethumper.com or crfsonly.com. You can send your head off to an engine builder like AS racing or RHC. Or you can buy a valve kit from eBay and find someone that is familiar with CRFs that can grind seats. Some people just replace the intakes to save a little money. There is tons of info on this site about valve jobs. Good luck.

My expirence is not with the Honda motor however I feel this type of thinking will work well with any late model four stroke. If I have to change shims more then once within ten hours of riding, I replace the valves. We generally do not have the valve seats cut. However if we do we use local automotive machine shop. I usually have them inspect the head to determine if there is damage. By replacing the valves before the outer coating is completely gone you generally will not damage the head. So the rule of thumb is a big change in valve shim size in a short amount of time.

I agree with your theory on shimming multiple times within 10 hours being a good time to replace. Now for not cutting the seats, that is a bad idea, I know people that don't cut the seats and it will work, but it will without a doubt shorten the life of your new valves. Most places charge around $75 to cut the seats or throw the seating cutting in if they are replacing the valves for you.

For the OP, if you want the shortest amount of downtime order a head from bigborethumpers. If you can handle not having your bike for a week and a half, check into Ron Hamp Cycle or Mxtime. I just got my head back from MXtime a few weeks ago and was very pleased with the work, cost, and customer support I received.

I agree with your theory on shimming multiple times within 10 hours being a good time to replace. Now for not cutting the seats, that is a bad idea, I know people that don't cut the seats and it will work, but it will without a doubt shorten the life of your new valves. Most places charge around $75 to cut the seats or throw the seating cutting in if they are replacing the valves for you.

You can often get away with just a valve swap if you do it as soon as you discover a tight valve. If you shim a tight valve, the irregular surface of the worn valve will pound out the seat, which will then require seat cutting for the new valve. Unfortunately, most people take the easy way out and just shim them, which ruins the seat, creating a bigger job 10-20 hours later.

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