Insurance

[DEANSFASTWAY]

Looking for a little valve clearance on a YZF 250motor . the kid is dropping valves on a regular basis and everything is definitely correct in the top end . He is always on the rev limiter good local A mx rider . Thinking of trying the Wiseco high comp piston and running thicker base gasket to get some extra room this might also advance the cams a bit Just looking for a little degree of durability .I realize 20 or 30 thousandths might not make much difference when those valves start floating but??? Anybody else got any ideas . weve been telling the kid to stop the revving so much So far hes had a couple of rods snap in the middle and take out cases and valves etc a couple times on like 2 different bikes . We suggested a 250 2 stroke as theres less parts to replace but guess what pops just bough :clue: t an 04 YZF 250. Any ideas .At least now hes got parts bikes.

 

[Rich Rohrich]

Try running the Kibblewhite spring kit with the stock valves. It should give you a bit of extra float insurance. What are you currently setting the valve to piston clearance at, and where are you checking it in the rotation?

FYI, Carillo is making rods for most of the new japanese singles, and so is Falicon.

 

[DEANSFASTWAY]

Rich everything so far has been all stock with this fellow so far . maybe ill trey the KW springs . ill let you know more later .Thanks DEAN

 

[SFO]

What has been the exact order of failures?
There is some issue of tangled valves causing premature rod failure if the rod is not replaced when the top end is replaced due to valves dropping or touching the piston.
Rich has also seen some signs of main brg funkiness that would eat a hole in your V to P clearance.
Push comes to shove after a full rebuild add a ignition with a lower rev ceiling and hope for better results.
Or just show him the dyno curve and explain there is no real power up on the rev limiter, he might as well be on the idle jet... :flame:

 

[Rich Rohrich]

Or just show him the dyno curve and explain there is no real power up on the rev limiter, he might as well be on the idle jet... :flame:

That's probably the best advice of all. :thumb:

 

[bclapham]

talking of fast riders, 4-stokes and possible bad things, can you run a 04crf450 with the Hi Comp wiseco piston on regular pump gas?

 

[Rich Rohrich]

talking of fast riders, 4-stokes and possible bad things, can you run a 04crf450 with the Hi Comp wiseco piston on regular pump gas?

I haven't seen any cases of knocking problems with US premium pump gas and the 13:1 Wiseco pistons in the CRFs, but they have only been out for a short while.

 

[bclapham]

LOL, i was hoping you wasnt going to say that Rich! Let me know if you hear anything, i will let him know that in principle he should be OK.

 

[Rich Rohrich]

LOL, i was hoping you wasnt going to say that Rich! Let me know if you hear anything, i will let him know that in principle he should be OK.

The only way I could see him running into trouble is if he is running the OEM cam too far advanced. The higher trapped CR from advancing the cam timing might push it a bit on a hot day.

Instead just tell the cheap gitt to buy some decent fuel. :laugh:

 

[bclapham]

Instead just tell the cheap gitt to buy some decent fuel. :laugh:

He's a CPA! :thumb: :laugh:

 

[Rich Rohrich]

He's a CPA! :thumb: :laugh:

Cheap Paininthe A :moon:

 

[bclapham]

but very fast!

 

[DEANSFASTWAY]

Only time Ive seen CRFs melt down Other than the usual valve issue is when the hot start pulls out or unscrews from the carb and they run real lean suck dirt or whatever. Ive been putting the 04 Honda piston in the older bikes and in some of the quads . SFO it seems this kid needs a 2 stroke with a new top end every week , he does run up front though, hes had various calamities with YZFs , the latest wiped the exhaust cam on the RF bucket & lobe It seems maybe the bucket wasnt spinning in its bore and kinda wore the center out, hes had his share of welded cases and snappered rods . I told him get a regular 2st YZ250 but he just got 04 YZF. go figure.