heavier valve springs on big bore

[2001 trx400ex]

I am getting my 416 done right now and i was wondering if i have to get hiever valve springs or can i get away with stock? and how will a heavier valve spring compare to a stock one with a 416 in it.

[modracer5]

if you change cams i would suggest that you change the valve springs... i would personally change them anyway...valve springs are cheap as compared to a head and piston if a weak spring causes the valves to float and break. also i would suggest that you have your valves backcut to lighten them to help control valve float....

[nastynotchback1]

modracer5 i see you deal with quinn motorsports.i just had him zps my rear shock and he done an great job and was cheap as dirt.do you ride at anoina any.i ride there just about every weekend.

[modracer5]

yea been there a few times...i mostly come during the gpg races tho. do you run any of the gpg races? i may try to make the next ride out there..

[nastynotchback1]

no.i just play around on the weekend.a freind that rides with me runs some gncc races and wants me to race at durham town this sunday but i got tranny problems.he said i could ride his raptor but i dont think so LOL

[2001 trx400ex]

whats backcutting the valves worth as compared to heavier vavle springs.

[modracer5]

i am not sure as to what your last question was asking...if you could refrase your question i will try to answer to the best of my ability.

[2001 trx400ex]

what is getting your vavle back cut and how much does it cost? Where can this get done? Also is undershaving the piston a good idea for more vavle clearance.

[modracer5]

back cutting is when you take the valve and turn it in a lathe and trim material from the back side of the valve all the way to and up the stem a little. this does a few things...it allows more air to flow in and out of the head because of a lesser amount of valve in the way...it also lightens the valve enableing it to keep in better contact with the rocker arm and put less strain on the springs.i think i payed a little more than a 100.00 for this process. my motor guy does this for me. i personally run titanium valves in my motor at a little over 100.00 each. they are not for everybody. as far a shaving the piston you should not have to do this unless you were running an extremely high compression piston or your cam has high lift or a combination. at any rate you should not be performing these tasks by yourself. and any qualified motor guy could get you lined up with what you need for your type of riding.

[2001 trx400ex]

i got a hotcam stage 1 and a 11-1 piston i shouldnt have a problem should I.

[modracer5]

so long as your head or cylinder has not been cut you should have no problems with clearance.

[2001 trx400ex]

I also have an unlimited rev rev kit, will that affect it any

[modracer5]

i am not familar with that rev kit but they dont affect any of your motor mods.