350X Valve Carnage

[manbearpig]

Went racing with CALVMX last weekend and after the first moto, dad pulled into the pits with a loud metal-on-metal 'ticking' coming from the head of his 350X

HairyJR was there with his XR500/350X and was gracious enough to lend it to dad to run the 2nd moto and gain his points.

Just got the motor pulled apart this morning and heres what i found:













Top of the valve broke off at the keepers, valve dropped down and piston punched it

Bike still ran.
DUH... its a HONDA

[jb2wheels]

Amazing!

Is that a Honda valve?

[El Camexican]

It's just a little bent Looks like you got lucky, could have been a lot worse.

[atc007]

Hmmm, They usually do that with the left ex valve.. I never saw one drop the intake. Nice clean engine

[6speedthumper]

Ouch!! So... What's the game plan? Big bore? Wink, wink lol

[manbearpig]

from what i can tell, its an OEM honda valve.

Plan of action is already under way. New OEM guides + seals, OEM valve, OEM keepers, and a top end gasket kit have already been purchased. Taking the head to Keith Lynas (Owner of OSSA and Weixeldorfer's mechanic while riding for Nicholson/Holiday Honda) for a valve job. should be back together by next weekend

[350for350]

Even though it doesn't look like a lot of damage, it might not hurt to pull the piston and inspect it closely. There could be a crack on it somewhere. It's probably not real likely, but it's still a possibility.

[HairyJR]

Glad we where able to trouble shoot your Dad's engine noise before other major damage may have occurred from the dropped intake valve keepers. I think the valve finally dropped down and hit the piston when we listening after checking valve lash clearance the first time.

If I can help give me a call.....have to ask does Dad now want big bore and head mod?

"HJ"

[shortline10]

I pulled a 400ex motor apart yesterday with the same issue , left side intake valve snapped at the keepers .
I would replace the valve guide and would be surprised if its not damaged .

[atc007]

It's funny. Out of all of these I saw come through here. 250X,300EX were the only ones that ever had broken/visibly damaged guides. I think this 350X head may be in good hands ,,lmao I would at least Wiseco it while in there if the rules permit?? But that's just me

[BOB MARLIN]

What would cause the keepers to fall out ?

[shortline10]

Its not that the keepers fall out , the valve snaps off were its machined down to hold the keepers , just a weak spot .

What would cause the keepers to fall out ?

[HairyJR]

Sorry my mistake in saying keepers fill out, should have read all posts and viewed pics..... wrote my post from memory at what it looked like at the races during our limited inspection. MJB is it big bore time? .....bb......bb.....

[manbearpig]

Sorry my mistake in saying keepers fill out, should have read all posts and viewed pics..... wrote my post from memory at what it looked like at the races during our limited inspection. MBP is it big bore time? .....bb......bb.....

We researched some parts to do the conversion and already have a couple useable heads, but ultimately the 350X is just getting its head redone and being put back together. We have 2 XR500 trikes with mildly modified motors (cams, porting) and building the 350X to be just as powerful isnt on the agenda. For pops its not about how much power the motor can make, its about how much power can he hold onto for 5 laps without falling off. Thats one of the reasons he races the 350X instead of the Nicholson 500. Lots of torque, but not so much that it wants to rip your arms out of the sockets. He (and I) loved the overall power your 420X has and there was some serious conversation about who and how to do the conversion, but getting the stock head redone and back in our hands next week would ensure the 350 can be ready for the next race.

[manbearpig]

Its not that the keepers fall out , the valve snaps off were its machined down to hold the keepers , just a weak spot .

yuup. what really concerned me though.. i didnt find the broken off piece of the valve. found a small sliver of metal that might indicate that the valve didnt break, but slipped past the keepers when the groove they sit in was damaged. ill know more this week.