Effect of a leaky pipe on cylinder wear ?

Hi guys,

Quick question for those with a very good understanding of 2 strokes. 

I have a pipe that is bent in a way that the pipe doesn't seal great with the cylinder. I don't see any smoke coming out, it doesn't make a different noise than it should, but I can see quite a bit of spooge exiting the cylinder/pipe connection. Also visually you can tell the pipe throat isn't quite aligned with the exhaust flange. 

Considering all this I would be tempted to run it like that as exhaust should let anything in due to exhaust pressure I guess. But then I remembered that the whole point of 2 stroke pipe is that it pushes exhaust air back in (I simplify). So the question is, could it affect negatively my cylinder by letting some dust back in it, or the flow is 99% out and no significant amount of dirt could make it into my cylinder this way ?

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sandman768
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Saratoga Springs, NY, USA
3/31/2025 5:32am

Over thinking it, just buy a new pipe….

1
3/31/2025 5:43am

... or repair the old one!

1
Nairb#70
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Ivoryton, CT, USA
3/31/2025 5:47am

Any good pipe reair shop can return that pipe to it's original shape.

3/31/2025 6:24am

The current one is new, one of KTM pipe that used to be stuffed with a cat (for a 125 exc). I got it from someone who cut it open, removed the cat material and closed it back. Visually it is in perfect condition but the angle of the pipe throat is slightly off. I'd rather not have to buy a brand new pipe, second hand is very hard to come by since it is a 2004 which have a longer stinger than any year after, and a massive cooling jacket meaning the pipe needs a dent at a precise location to fit around the cylinder jacket. I don't really want to throw 300€ at it considering the age of the bike, unless it can definitely kill the bike faster.

The Shop

Factor E
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9/22/2011
Location
So Cal, CA, USA
3/31/2025 11:03am Edited Date/Time 3/31/2025 11:03am

 

Make a copper washer/shim to fill void so it will seal better

j368
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Location
Tulsa, OK, USA
3/31/2025 5:57pm
Factor E wrote:

 

Make a copper washer/shim to fill void so it will seal better

What he said. The Honda CR125’s used a copper crush washer. 

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