Jump to content

cause of bike shooting a valve

Recommended Posts

Just curious what exactly happens when you r bike" shoots a valve", and what causes it to happen and thing you can do to prevent it from happening :applause:

Share this post


Link to post
Share on other sites

Never heard the term before. So valve broke free from the rocker? Material defect. Worn due to lots of high rpm. Ran out of spec for clearance.

Sent from my Nexus 6P using ThumperTalk mobile app

  • Like 1

Share this post


Link to post
Share on other sites
4 hours ago, CDNSXV said:

Whut? 

Maybe the proper term is drop a valve. its when the valve falls into the engine.

  • Like 1

Share this post


Link to post
Share on other sites
Never heard the term before. So valve broke free from the rocker? Material defect. Worn due to lots of high rpm. Ran out of spec for clearance.

Sent from my Nexus 6P using ThumperTalk mobile app



"Valve broke free from rocker" is a term I don't understand.... I have a feeling if a valve is stuck to a rocker, you are in trouble! Mx bikes have dual overhead cam, bucket/shim style heads, honda has a rocker arm for exhaust but still uses shims on them. Dropping a valve happens when either you are on the revlimiter and get coil bind on valve spring which pops keepers out and valve interferes, or the keepers weren't installed properly and it just drops on in. Most every single case of "dropped" valves in mx comes from slow guys who stay on the limiter in neutral or in the air to sound cool and get coil bind.....usually they are idiots and I would never suggest working on their bikes because they are dumb and if you fix the head, they ride it and the tire falls off they will blame you because you worked on the head which made the tire fall off. Revlimiter means shift. If you are hitting the limit in neutral or in the air, save yourself some money and find a different sport.

Sent from my SM-N920V using ThumperTalk mobile app

  • Like 4

Share this post


Link to post
Share on other sites

I have seen where "people" have worked on engines themselves who have not installed the shims/caps correctly have the shims jump onto the spring, pushing the valve in further and hitting on the piston.

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:


×