exhaust system question:

[BubbaZanetti]

my 84 r100 came to me a bit of a "rat bike" and that is the way i have chosen to ride it for this summer. among the numerous little "issues" with the bike is the fact that the crossover pipe has been cut off and the ends (about 2" sticking inward from each pipe) have been capped. is this bad in terms of flow or engine performance? should i hack off the caped ends and fit an appropriately sized piece of tubing or just leave it? also can this be clamped on or does it have to be welded?

[Cosmoline52]

Exhaust crossovers act to assist gas scavenging. With bigger twins the pipe allows a "push" from the active opposite exhaust pulse to keep the gases moving and ready for the next exhaust stroke. Without a continuous flow, stagnant exhaust in the system can resist the incoming of new exhaust pulses and hamper performance. That's why multi's work best with one pipe, all the feeder headers dump into one exhaust where gas flow helps empty each tube in ready for the next exhaust charge.

Twins don't have that advantage since the cycles between exhaust pulses are longer and less frequent, so a connecter pipe from the opposite side helps keep things moving. Without it, the burble from the back may sound cooler, but at real-riding speeds the performance can be hampered.

That crossover pipe isn't cheap but IMO is necessary.

[rocketman]

to answer part two, yes it can be clamped, in fact the original has clamps (built in).

RM

[BubbaZanetti]

any ideas on a good source for the crossover piece?

[lorazepam]

If you can get an accurate measurement of the pipe ends after cutting, see if you can find someone that sells stainless tubing in your yellow pages. I would get a piece that is long, so if you need to try again, you have it available.

[dlearl476]

Originally posted by BubbaZanetti
any ideas on a good source for the crossover piece?

The pipe is available at any dealer, and frequently for sale on ebay. If you're interested in a PROPER good sounding set up, a two into one from Dennis Kirk or Mac is the way to go. And you could probably finance a good portion of it sellin your stock exhaust on ebay, provided it's in good shape (other than the crossover pipe).