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tradrockrat
10-31-2004, 05:07 AM
So I got this roll of Thermo Tech Exhaust wrap for my "little bike" cause I'm plnning on tearing it down to a bare, basic bike. I love the look, but I would really appreciate some pro advice on this stuff.
It claims to retard the expansion of exhaust gases by keeping a more even heat throughout the pipe. I thought that gases were supposed to expand? Isn't the back pressure of expanding gases, well... important to the running of an engine? The bike is an air cooled single cylender 500 CC bike. The pipe can and has turned cherry red from heat once while working on it with the engine running (my Pop did that, not me). Would this wrap make this more or less likely to happen again?
Also, I should have asked these questions BEFORE I wrapped the pipe, but I didn't. I took it for a good ride (about 40 minutes) and the bike backfired when I shut it off. This bike has never backfired once in 26 years! What is the cure for this? Any ideas?

Thanks in advance, fellas.

P.S. I know the site is about Harleys, but if this works out, I plan on "minimalizing" my sportster and wrapping the pipes as well. Remember, Less is More!

TexasFatBoy
10-31-2004, 07:40 PM
If the pipe was turning red, I'd be more concerned with combustion/air-fuel mix. No bike should be running that hot. BTW, what is the bike? I know a bunch of guys that specialize in old Jap iron and I could get some info from them for ya.

tradrockrat
10-31-2004, 08:15 PM
Tha Pipe got red hot a long time ago (years). It was just sitting and running while he was putzing with the carb. The pipe had a rather extreme bend comming out of the head and it caught a lot of heat. This bike does run hot. It was dual walled too! Shortly after I got the bike, the innerwall actually melted and collapsed inside the pipe. I went nuts trying to figure that one out, even rebuilt the head. Now I have a pipe made by some guys up the street. It has a much smoother bend on it and is single walled, but I've been running it with no problems for about nine months now. I put the Wrap on it and right away I got this back fire when I shut it off.

The bike is a 1978 Yamaha SR 500, though this particular model has OHC on its side panels rather than SR. There's an older pic of it in my photo album.

Oh yeah, other than cosmetics, the only changes to this bike are its exhaust pipe and muffler which shaved about fifteen pounds from the bike and boosted its power considerably. Everything else is stock.

tradrockrat
11-02-2004, 12:07 AM
quick update,
The bike backfired on both trips -- to and from work -- today. the ride is only about 15 minutes long.

Any ideas at all?
Thank you fellas

P.S. I've hit 300 posts!!!

wreckerman
11-02-2004, 12:20 AM
try cheaking the carbrators out , and make sure they are closeing the butterfly all the way shut usaly a back fire on turning any motor off means gas is still flowing into the cilenders

tradrockrat
11-02-2004, 12:29 AM
I'll check that now, thanks.

wreckerman
11-02-2004, 12:33 AM
my pleasure