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Hey everyone so I am in the process or rebuilding the motor in my '03 kdx200 while I was taking off the head studs with vice grips I managed to let the vice grips shoot open and they hit the top of the right sub-valve and broke the top off of it! So the first thing I did was go inside and order a used one off ebay... well I seemed to forget that there is a right and a left sub-valve... so that was a waste of $50 lol. I was considering putting it in the bike any way but I heard that there will be a severe power loss so my question is can I run the broken sub-valve in the bike? the gears and the bottom piece is fine its just the tip that rests in the cylinder head I will include a picture.

I think where your is broken off you could still run it with very little risk. There is a journal that fits over the valve center pin so it should work just fine. Obviously you need to replace it, but IIWM I'd reassemble it and run it until the new part came.

2 nuts on the threads locked together to get the studs out next time. i know hindsight is 20/20, but maybe help someone else.

Ok thanks for the info

bufftester wrote:I think where your is broken off you could still run it with very little risk. There is a journal that fits over the valve center pin so it should work just fine. Obviously you need to replace it, but IIWM I'd reassemble it and run it until the new part came.

Alright I will see what I am going to do

I would have to say go ahead and replace it. Stabilized on two ends is part of the design. It wasn't just an extra portion.

Jason wrote:I would have to say go ahead and replace it. Stabilized on two ends is part of the design. It wasn't just an extra portion.

Ok thanks for the advice I would rather be safe then sorry

Ok, I completely agree that it needs replaced and I wouldn't run my bike like that.

BUT...

hypothetically speaking... I think it could be ok? The little bushing that slides into the head will keep the valve rotating along its axis properly. And, once you put the head on, the head will capture that bushing, which also captures the valve and keeps it from moving up and down. The majority of the stress on the valve is going to be on the nub on the bottom of it, and the shaft portion that is inside of the bushing. The portion was broken off, I bet, sees a very low amount of stress, compared to the rest of the valve. I dunno, just my 2 cents. Feel free to disagree!

KDX Rippa #36 wrote:I was taking off the head studs with vice grips

There was your first mistake, vice grips are a last resort