Jump to content
Sign in to follow this  

Intake Valve Goop

Recommended Posts

I'm into the top end of my 04 CRF450 and found the right side intake valve to have deposits below the valvestem. Left side looked great..

http://img.photobucket.com/albums/v490/datasponge/Picture021.jpg

Picture020.jpg

What would cause this? Bad valvestem seal? Bad guides? :)

I'm doing the top end right... new piston, rings, pin, bearing, vavles, springs, keepers and seals along with getting the seats cut.... but if I need guides I better get'em ordered.

The piston had some blow-by on the front right side corner... which happened to line up with the oil scraper ring gap? Interesting... The cylinder still has the cross hatch marks and everything else looks new inside...

Thanks,

Share this post


Link to post
Share on other sites

Both times I've replaced the intake valves on my '04, the left (one that went to 0) looked like that. I went with the Ferrea SS valves and springs from RHC, had the seats redone and the intake and exhaust ports cleaned up. If your valve(s) went to 0 I'd have the seats redone and matched to the new valves. My guides were ok. I also went with the JE 12.5:1 piston. I love it on the '04. It makes more bottom end and smoothed out the power delivery. Feels like the '03 but with more power.

Share this post


Link to post
Share on other sites

Id be looking at the guide on the one with the deposits. But Ive take motors apart with PC seals on them that had the same deposits. Most of that crap comes out of the fuel believe it or not. Why it stuck to one valve and not the other is something I dont have an answer for. :)

Share this post


Link to post
Share on other sites
Looks to me like fuel coked on the valve. Crappy gas and heat are generally the cause of coking.

Why one intake and not the other? Valve getting too hot due to to tight of tolerances on the stem/guide?

Thanks,

Share this post


Link to post
Share on other sites
Id be looking at the guide on the one with the deposits. But Ive take motors apart with PC seals on them that had the same deposits. Most of that crap comes out of the fuel believe it or not. Why it stuck to one valve and not the other is something I dont have an answer for. :)

Thanks... I'll be checking the valve stem tolerances tonight.. .the head is at a shop getting the seats cut and the guides checked (I dont have the correct tools to check the guide tolerances).... Hopefully we will have some insight tomorrow...

Thanks,

Share this post


Link to post
Share on other sites
Why one intake and not the other? Valve getting too hot due to to tight of tolerances on the stem/guide?

Thanks,

With the carb offset to the left side of the motor I'll bet most or all of the accel pump squirt goes towards the right valve. Raw unvaporized fuel on hot a valve could certainly coke. Are you prone to grabbing big handfulls of throttle? Gee, I wish I could do that without falling off......

Share this post


Link to post
Share on other sites
I'll bet most or all of the accel pump squirt goes towards the right valve.

Hmmmmm. Interesting idea. Hadn't thought of that.

Share this post


Link to post
Share on other sites
With the carb offset to the left side of the motor I'll bet most or all of the accel pump squirt goes towards the right valve. Raw unvaporized fuel on hot a valve could certainly coke. Are you prone to grabbing big handfulls of throttle? Gee, I wish I could do that without falling off......

Never thought of that... yep... since I XC race its either on the gas or on the brakes...

Got the info from the shop... Valve guides were in spec.. the old valves were still in spec, but were cupped so they go in the trash... the springs were trashed.. no were near tolerance. Under close inspection the valve seal on the valve with goop had some "assembly" marks / scratches the others did not (we were curious so we took the extra time to look at the various parts under magnify glass / microscope)

So I'm going with the theory of bad seal. But the coke from hot gas from the pumper carb is going in my log book... Next inspection will see whats up.

The heads all back together with all new parts, fresh cut seats... should be putting the bike back together tomorrow and get some ride time between the down pouring rain storms!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×