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valve replacement questions

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ok i have a lot of hrs on my bike. like 2 prety hard seasons, its starting to be hard to start. kick it like maybe 5 times, then it will pop once, and start right up usually. bike is all taken apart motor is ready to go to a guy for valves. i have never messed with a 4stroke motor so i am having this guy do it, but what would i need to replace? so far this guy is telling me prob new valves, needs some shims, cam chain, and rings if pistons still looking good. he also said something about nickle plating the cylinder or head to make it last longer, whats that about? but i was just wondering if there was anything else i should have done to make my motor last another season or two. like he said dont need valve springs or anything and that just sounds a little half ass to me.. please let me know anything else that you might need to do with a common valve job i would really apreciate it guys... thanks :bonk:

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Most modern cylinders are plated with an alloy called Nikasil, they can be replated if they are damaged or just worn beyond spec.

Who is this guy you speak of? Is he some hack garage mechanic?

I had Ron Hamp (famous eng tuner and member of this site) do my head and valve work...06 CRF250X @ 120 hrs. His recommendation for head work follows: valves, springs and keepers, re-cut/replace valve seats, check intake guides and seals, replace exhaust guides seals.

If you are doing valves I would not cheap out on a couple of springs.

If your cam chain is worn I would also replace the cam chain guides as well.

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no dude is good. he has rebuilt a lot of bikes, he does this out of his grage yes, but he does it for a living he works on all kind of motorcycles from harleys to scooters... he is good, he has rebuilt my buddys 06 cr450f and my buddy loves him and will go back to him... but i guess i should have told u a little more detail on my bike. its an 08kx450f not sure how many hrs it has but the motor was fully rebuilt right b4 i got it, if rode it some racing for 2 seasons now. i was hurt for about 4 months so i guess not really even 2 full seasons on it but i def rode the hell outa it.. idk if this helps with what parts i would for sure needs to replace. but from what i understand i for sure need valves. but that helps alot i wrote it all down and i am gonna ask him about all this and tell him i heard from thumpertalk to do all they above.. so will see how it goes. he said he is gonna open upthe motor and show me what all needs to be done and will go from there.

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no i have never done it, but from what i hear/read it just gonna buy me a few more weeks.. forget that, i am trying to make my bike last at least another full hard season of racing and riding. thats a lot of rides, i try to practice twice a week and if a make the full race season ill be riding at least twice a week, one of them being a race.. so thats the whole point of this work is to make my bike last as long as posible... i was originaly shooting to buy a 2012 kawi 450, but times are really tight so not gonna happen so this is my only other option... i love working on my bike. but when it comes to motor or suspention work, id rather get it done by someone who knows what they are doing.. i would love to learn these things but i have enough going on with a kid, work, GF!, and trying to stay in shape to ride/race.. but if just doing shims would buy me this kinda time i would be more then willing to give it a try because i dont have a lot of cash to pay ppl to work on my stuff...

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prolly just needs shimmed..

see above convo... :bonk: ^^^^

doesnt shim just buy you a little more time? i need another season! dont wanna work on it half way into the race season...

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Not necessarily.....

Dude u could go out and get a full head job and they could tighten right up in the first 5 hours if ur unlucky enough.. then they will need shimmed again!

The problem is you dont wana learn to shim it... If you did that you could def make it through another season, might need shimmed once and thats it. Ive seen people with kx450s that needed a valve shim in the first 20 hours then the valves didnt budge for another 100 hours..

I got a KX450F that has WAYYY more than 2 hard seasons on it, and it needed its first shim this past winter, at the same time I did my first top-end on it too. Take it to your guy and have him do a piston (it needs it, regardless of how it looks) and when he does the piston have him shim the valves to get it in spec. Dont pay more that $100 or so for this service or youre gettin ripped off. Thats $100 for shim and top-end install plus price of piston/gasket kit.

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