Hole in new pipe

[2strokd]

I got my "new" pipe from GMI the other day. The pipe was a little used though i think. It was already discolored at the cylinder mounting point. The pipe was in great condition, and would turn color anyway so i put it on. After starting my cpi i noticed smoke coming from the bottom of the pipe as well as out the silencer. I checked it out, and there is a hole at the most bottom point, right before the expansion chamber. The thing i dont understand is why it is there? It was built this way, its not there from damage. Anybody no why a pipe would have a hole in the most bottom point? Im gonna call GMI today as soon as they open. Keep in mind, this is not a high-end performance exhaust, just the cheapest "new" pipe i could find...Guess you get what you pay for.

[90GTVert]

The only thing I can think of being the bottom-most point of the pipe would be a drain. I don't see why you would need a drain though. Water shouldn't be getting in there and you would have to be grossly over-injecting oil to need a drain. I would think it is a manufacturing flaw if you don't believe it's damage. Letting exhaust escape there would probably be A)illegal and B)counter-productive, especially being an expansion chamber design. Regardless, if they won't replace the pipe for you I would just weld the hole shut.

[scosgt]

Hmmm
The Benelli has a hose from someplace that connects to the exhaust system for the cat converter. If it falls off, you gets all kinds of smoke. I wonder it this could be related.

[90GTVert]

That may be it, but it should be a nipple/port and not just a hole if that's the case.

[2strokd]

Well i cant get ahold of GMI until tomm. I dought the hole is for a cat converter, its very small, about 8th inch maybe.Im not sure they sell a performance 2 stroke pipe with emissions? I ran my scoot with the hole and it didnt run very well, so i welded it shut. It runs good now, with a 5mph average gain. I wish i would have spent the extra $ and got a good pipe. This one seems restrictive, better than before, but still a little to restricted to be called a performance pipe. I took my silencer off, and the thing wasnt any louder...weird huh?

[90GTVert]

I agree. I don't think you'll find too many tuned pipes intended for use with catalytic converters... at least not good ones. I'm not familiar with emissions systems on 2 strokes. None of the 2 strokes I've worked on have ever had any special emissions equipment. I'm also used to catalytic converters being inline and not connected via a small hose etc...

Here's a quote from an SAE site :

"The two-stroke engine, by its nature is very dependent on the unsteady gas dynamics within an exhaust system. This is demonstrated by the tuning effects on two-stroke engines, which have been well documented. In consideration of current emissions legislation, a two-stroke engine can be fitted w markets. The catalytic substrate represents a major obstruction to the flow of exhaust gas, which hinders the progression of the main exhausted pulse, and in turn effects the scavenging of the cylinder and ultimately the performance of the engine."

[dude]

I bought a KeyWay Fact Pipe. Looks like a perf. pipe. It has a air tube running in next to the head. I cut it open it has a few baffles and some thing that looks like a Catalytic Converter.
Wish i could show you all pics.
One day Ill put it back to gather and see what happens.

[scosgt]

According to my manual, it has a "catalytic exhaust", whatever that means.
It is a 2 stroke that is CARB approved.

[2strokd]

Well this restrictive pipe wasnt doin the job anymore with the 70cc Polini sport kit. GMI claims it is a performance pipe, i know its not so i just cut it half to see how bad the restriction was and it was bad! There was 2 plugs in the biggest part of the expansion chamber with small(about 1inch) pipes running though, and through which totally defeats the purpose of an exhaust with an expansion chamber. If any of you have seem a car muffler cut in half, thats what was in the "performance" pipe. I cut all of the unnecessary metal out and welded it back together. Sorry no pics, and thinking back i really wish i would have taken some and learned to post here, so nobody makes the same mistake i did and buys the same pipe under the performance assumption. If you were just looking for a little more flow than stock with the look of a performance pipe, this is the one for you. I will be able to test it out tomorrow.