Flamethrower exhaust mods

[JPark]

When I got my 100B+ running I was surprised by the amount of racket it generated. I don't mind so much, but wife and neighbors opinions may be more negative.

Looking at the end baffle, it seems like the -is it two?- holes in the final peashooter would be incapable of doing anything. With a pipe that short, more perforations wouldn't have much of a chance anyway, to my understanding. I haven't tried running without it, but it would seem like the final opening size is mostly what it's doing.

The spark arrestor swirl can probably does most of the work, but for road use is there a design which can be subbed in to reduce the racket, preferably not involving repacking maintenance? I have a few ideas, but there's no point in reinventing the wheel if it's been done before.

[matt glascock]

I had a flame thrower exhaust on my Combat Wombat where the flame thrower end and all the internals were thrashed. It was hack sawed off and replaced with a bolt-on FMF Turbinecore II silencer which really quieted it down. It would be helpful if you could remove all of the internals and post a picture so we can see directly what you're working with.

[JPark]

I'll get some pics up tomorrow - going out soon. Mine seems to be stock original. It came with so much original carbon that it took me about an hour to get it apart.

[viclioce]

After you disassemble the pipe, build a fire and place the pipe on the fire to burn out the excess carbon inside. Remove all chrome and painted parts. After the BBQ, you can clean & repaint then pipe! Victor

[JPark]

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[JPark]

[Al Harpster]

What you show is the complete package.

Mine came with the back end hack sawed off of the spark arrestor.

Took me years to find the complete spark arrestor.

You MAY get just a bit more muffle if you drill more holes in the necked down diameter of the "end piece".

And perhaps wrap that necked down length with steel wool after you've drilled it.

But it won't be much.

It's a loud pipe.

My two cents, you got the real deal as-is.

[matt glascock]

Yep, that's the real deal. The B+ pipe is a great pipe and its not like there are thousands lying around so taking a hack saw to it would not be too cool. It is louder than its predecessors, but is a better performing pipe. The FMF Turbinecore II is a great silencer with the added benefit of being a spark arrestor. Easy to retrofit. With some luck, you might be able to find a trashed B+ pipe for short money with a good header and chamber and go from there.

[JPark]

I just reread Gordon Jennings treatise on two stroke tuning and applied some of his findings to this design. It's almost as if he'd been there. He came up with the first inverted stinger design which has the stinger going inside the pipe rather than hanging off the back. The Flamethrower has the same, which leaves room for the swirl can spark arrestor which may have some added noise abatement. The final baffle is mostly decorative and answers any baffling questions.

According to Jennings, putting the stinger internal has no effect upon power output but does reduce the noise factor considerably. I'd like to make a new baffle pipe which would have pretty much the same general measurements but use the aft bulge as a muffler rather than an arrestor.

It's interesting to note that the intake goes through a 20mm hole and the output comes out of a 13mm. When you don't have an exhaust valve, some back pressure is a good thing. I seem to recall running a J&R pipe on my Ace100 back in the day and had a glass pack can on the end; had to go up a jet or so but had better top end but no better midrange and probably worse mileage and definitely more 'authoritative' sound.

Link to Jennings:

http://www.amrca.com/tech/tuners.pdf

[Bruce Young]

Might suggest something lots of 2 stroke riders did back in the day to cut noise, old VW tail pipe, its chrome probably close to same size needed and it can be shortened to work just as well, has a internal screen and baffle built in Take a look at this. other way is to find a FMF short silencer and make it fit to your pipe, those are also a little hard to find but they work.

[JPark]

Yes, I'm more than familiar with the old VW end pipes. A bit like a gun silencer and rather like what I'm planning on doing in the space where the arrestor currently resides. On a 4 stroke bike the VW snout had a sort of fweep fweep sound which wasn't charming plus enough restriction to spoil the fun, but it might be just about right for a Hodaka all right. Might be a good replacement for the final end baffle.

Thanks for the suggestion. There's a VW graveyard a mile from here; should be one that hasn't been run over yet in their yard.