Try Me

Member
May 1, 2006
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Well, i bought this bike from a friend of mine who rode 250a with it like 3-4 races and some practice for the last two seasons. Very well maintained bike, and after riding a 2000 yzf 426 for the last couple years im loving this bikes lighter feel, better handling, super brakes, and smooth power. I was also looking forward to the easier starting (i really had gotten good at starting the 426 though) but about 2 weekends after having the bike i all of a sudden had major problems starting it. this is where the fun begins :)

After a ton of reading online I immediatly went out and pulled it down and checked the valves. imagine that, the intake valves are tight. since i also ride hard everytime i ride/race, i opted to go the stainless valve route. ive ordered my kibblewhite intake valves, kibblewhite spring kit, and ordered the hotcams shim kit. ok enough :blah: Now for questions :)

For anyone who has been down this road, did you have to reshim after installing the new valves? I obviously will check clearances and shim accordingly, just curious about others experience.

Also, i have talked to people who told me the stock head gasket is reusable at least a couple times as long as you dont kink it up or anything. I have had great luck with using the copper spray gasket on multi layer steel head gaskets on my honda cars and was able to reuse the head gasket 2-3 times on a car that was 10-1 compression with a turbo pushing 12-15lbs of boost without any leaks. Is it a bad idea to reuse the gasket? Since i just spent the money on the vales and springs i was hoping to save a couple dollars here but im also used to having to spend big money on head gaskets on my turbo toys in the garage.

Thanks in advance! !

Tom Joy
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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The head gasket is NOT reusable. If you want the new stainless valves to be reliable you'll need to have the valve seats machined to ensure a proper seal with the new parts.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
Try Me said:
So can the stainless valves just be lapped in or would it actually have to be machined?

The seats have to be machined.
Even if the seat wear is minimal, lapping the seats won't give you a proper sealing surface for a new valve, and you won't be able to get the seat narrow enough for good airflow. It's a very narrow seat that you need to have machined to bring it back into spec. Valves and seats that don't seal properly bleed off pressure and really kill performance at high rpm , and seats that are too wide really hurt airflow which can cause all kinds of weird performance issues with intake reversion near TDC.

It's pretty rare to see a CRF that doesn't need the valve seats recut to get a proper seal even on a BRAND NEW HEAD. Lots of folks try lapping the new valves in to get a good seal, but that doesn't do it. Even if you do the other work yourself I would strongly suggest taking the head to a performance machine shop and getting the valve seats recut to ensure you have a concentric seat. Have them measure the exhaust valve guide clearance as well. The intake guides don't wear much but the exhaust guides need to be checked each time you change valves.

You also have to set the spring installed heights for all 4 valves to ensure you have the correct seating pressure. A height micrometer or a height standard guage is used to measure the distance between the base washer and upper retainer (the installed height) . This distance is changed with precision ground shims that fit under the base washers. The shims are available at any speed shop or performance machine shop. Other than that it's not really much different than changing OEM parts.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
The cylinder head nuts should be torqued to 43 foot lbs.
 

Try Me

Member
May 1, 2006
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well ive had the bike back together for 3 races and a fair amount of practice and have been super pleased. motor runs great! starts easy too, but not too easy which brings me to my next question. when i put it all back together i had to use new shims on the valves. Since i dont have a service manual handy, i didnt know the spec for the compression release and didnt adjust it. when i first put it back together it was obviously loose and the bike kicked pretty hard but would fire up and run. i took the bike apart and tightened the adjustment on the compression release but i think i made it too tight. the bike kicks and starts super easy when cold, but once its hot it almost kicks too easy and is difficult to start unless i kick it real fast. so...

can someone please tell me the correct clearance for the compression release adjustment?

THANKS!
 
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