Jump to content

what causes a ring to catch a port?

Recommended Posts

a buddy rebuilt his bike.  2 stroke dirtbike. theyre all the same... pretty generic question.

 

what causes a ring to catch a port??  what was done wrong?  got 5 engine hours out of it.

Share this post


Link to post
Share on other sites

Was it a ring end, or from the center section of the ring? 

Is the bore wore out in the middle? All cyls wear more in the center then in the ends, but it can be dramatic on some 2ts. If the bore is worn far out of spec in the area of the ports, the ring will expand as it goes through that area, and possibly expand enough to not be fully supported in the ringland. Combine that with the piston likely being cocked as it travels through the  worn area and it's easy to picture how a ring can snag and break.

  • Like 2

Share this post


Link to post
Share on other sites
1 minute ago, ohiodrz400sm said:

What he said^
Also, not allowing the engine to warm up, not having the ring gap placed correctly, and not enough chamfer on the port edges.

Not enough chamfer was my first thought.  I've seen it happen.

Share this post


Link to post
Share on other sites
19 minutes ago, cjjeepercreeper said:

Not enough chamfer was my first thought.  I've seen it happen.

Yes, because the chamfer disappears with cyl wall wear.

Share this post


Link to post
Share on other sites

How can you tell chamfer and if it's good or not? Can you add chamfer to them if needed? I'll get some pics for you guys. Curious to know what happened and learned from this so it doesn't happen again.

Share this post


Link to post
Share on other sites

On sleds, sometimes the pin will come out of the ring groove.

If you slide the ring in without the pin locking the ring in place, the ring will spin on the piston and catch the exhaust port. 

 

 

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:


×