valve sticking?

[underpowered]

alright, i keep sticking a valve in my 400ex. i never had a problem for 3 years. tore down last summer, put back together and rod it for about 3 times. while cranking an exhaust vavle stuck. tore down, replaced both exhaust valves, and it is been fine for about 7 months now. well riding this weekend, whil actually riding this time i stuck another valve, the other exhaust valve. why?? i am gettin oil to the top end, the valves were new and it was fine for 7 months, since last october. i cannot afford the downtime to keep tearing it down all the time. no other damage was caused either time, valves not bent or anything. just stuck. removed them this time, oiled them up, put them back in and it is fine. why would it keep this up?

[Sparky_20]

I would try replacing the valve guides and seals to start. I have seen this on automotive applications. How do you figure that they are sticking? are you just not getting compression?

[underpowered]

well seals are new, and guides were reamed before valves were re-installed after the P&P.


and i figure the valves are sticking by process of elimination. the first time, it did the exact thing the first time and when i pulled it apart the right side exaust vavle was hung open. i have not torn down yet, but due to no clunking like a broken rod, no noised like a broke piston, no oil like a blown gasket, so it MUST be a valve again.

if it is the same vavle, i will change guides, but right now i have an HD spring kit on order and am gonna try changing the oil i use and see what happens from there.

[Sparky_20]

good start. Let us know what happens! Any motor work done that could affect oiling?

[underpowered]

well i did not start until after a complete re build last summer. but whenever i tear it down there is always plenty of oil getting to the top end. as far as i know there is no oiling problem, as the head always has oil getting to it. but i am gonna switch oils anyway to see what happens. i will let you know what i find out. gonna tear it down as soon as i have a chance.

[400exrider707]

What oil are you using now just out of curiosity? This is a very odd problem and is the first I've ever heard of such a thing happening on these motors.

[underpowered]

i am currently using rotella T 15w-40. the mechanic at the shop i work at has never heard of a problem like this either.

[underpowered]

well i tore it apart today, hopin for an easy fix. turns out the cam is junk.


the dowel that holds the bearing on came out and let the cam slid around. and it just chewed itself up and then without the bearing it tilted sideways adn held a valve open. so i rush ordered a stage 3 cam, and am gonna try to get it all back together friday morning so i can race it saturday at the sparta GNCC. i will get pics of the cam tomorrow.


luckily the head was not damaged, but the rocker arms may be. no time to fixe them now though. i will tear back down after the race saturday and replace it all.

[Sparky_20]

wow that is odd. Glad you found it tho. Is it a hot cam?

[underpowered]

yes it was an old stage 2 hotcam. it is destroyed. the dowels are gettin a dab of permatex on them this time to be srue they hold in. can't have this happen again.