DEANSFASTWAY

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May 16, 2002
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We all know that Ti Valves are the lightest quickest reacting valves used but what happens when you mix & match Ie: Stainless intakes on CRFs and Ti exhausyts on YZfs? the rasons I ask this are Ive been doing alot of changeovers recently like 450 cams in 429s but now Im doing this 444(originally98 YZ400) with steel valves and want to install a 450 decomp cam. Both exh cams lift is near the same @ .315 in or 7.88mms but the ramp on the 450 cam is just so much more radical Im really svcared that the steel valves wont follow the cam and dont want to chunk up this motor.I just set and cut the valves but am not sure whether I sould buy HD springs or shim up stock springs or buy new Ti exh valves from 426(actually I have some but reserved for another job). Has anyone ever installed 450 cams in 400s w steel valves and had good results? You know the springs look the same but I havent yet checked part #s or seat pressure at installed heights . Just kind of hoping someone here has already done the homework so to speak . Oh yeah and its not like you can really boost seat pressure by shimming up the springs, on the CRF the stock spring starts to coil bind at like .018 under the spring seat and at like .024 the cam stops turning because of coil bind . Ive been installing the stainless Back Diamonds in the CRFs but dont really see the need for new Exh springs . It would be kinda cool if we could buy the stainless intakes with a matching stiffer spring sold together. Actually Ive installed quite a few of them (CRF intakes)with stock springs no spring shimming at all in bikes but both these motors( CRF and YZF 444) are in quads and those guys somethimes really rev the crap out of these motors Their tires are only like 20" tall overall and they shift like three or four gears down a normal straightaway and always on the rev limiter,maybe I should cut the valve reliefs deeper in the pistons for more space. What do you guys think?
 

john stu

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Jan 7, 2002
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i thought you couldn't run ti valves with the same seats that were run with stainless valves do to the different metals you need to change the seats also
 

DEANSFASTWAY

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May 16, 2002
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Johnstu Really not supposed to but almost everytime I change valves on 400s Ive been installing TI 426 valves cutting the seats and checking the seat margin with dye, and still using 400 stock springs which I think are a bit stiffer than 426 springs . Weve been cutting the Ti valves on CRFs and YZfs Where Honda and Yam always reccomend replacement , you gotta cut the valves slowly . We always reshim under the spring plate @ same amount as taken off valve & seat to keep spring pressure correct. Theyve been running for a good 2 years now. The Ti valves are expensive though.
 
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