Friday, July 30, 2010

MLM Performance Exhaust

I made a post earlier about MLM performance expansion chamber exhausts, and another about how they work. I just got mine back from the welder last night (our welder apparently does pretty good work even after 12 beers) and bolted it up. My variator is opening way too soon for the bike to hit the pipe's power band and it feels like I am running a bit rich. I will either drill out the variator weights I have, or get some lighter ones so that the variator will open at more like thirty or thirty-five miles an hour and not fifteen or twenty like it is now. Nonetheless, I can feel the pipe wanting to hit the power band; it just doesn't have the rpm's. I have more pictures of the details such as the header flange I fabricated and the rear hanger, but in the meantime, here are some pictures of the basic process:
Pieces of laser-cut 18 gauge steel ready to be rolled into the cones of the "Cali" and "RevRun" pipes.

Devin can usually get about fifty cones out of a single sheet of steel. When we get the stacks of oddly shaped steel back we take them to various conical jigs made of either maple or steel, depending on the curvature and tightness of the cone, and basically beat them into shape with rubber mallets. It took me about a week to finally begin to understand how the metal would react to the impact and where exactly to direct the force of the blow.

The rolled cones ready for welding.

 After the cones are rolled we send them off to the welder who welds the ends together. Then we take them back to the jigs and true them up to fit together perfectly and then tack-weld them together creating the basic form of the exhaust. At this point they are nothing more than five variously shaped cones tacked together.

What happens if your hit your hand and not the sheet metal when rolling the cones...

 Then it is back off to the welder for the whole pipe to be welded up. When we get it back we then mock it up to a bike (in this case a Honda Hobbit) making sure that the header clears the center-stand and provides a clear flow of gases from the cylinder through the chamber. We also tack the hanger and perforated tube in the appropriate position. Then it goes back to the welder again.

 Here is the pipe getting the rear hanger, header flange, and silencer  welded in place.

 Jim, the welder TIG welding my pipe while smoking a cigar after a twelve pack of Mich Lite. 

He warned me that his welding might not be up to par, but I told him I had complete faith in his abilities (which I do) and he didn't let me down.

Here is my old stock exhaust. It is the little box down there under the magneto.

 And here is the bike with the new pipe...
I have yet to see how and where the pipe hits the power band, but the sound of the pipe is amazing. It is surprisingly quiet; barely louder at idle than the super-silent stock exhaust, but when you open it up it really sounds good, with a wonderful purr when you let off the gas. The bike is already going a bit faster than stock, even without hitting the power band. The pipe should clear the side cover once I work with it a bit. More updates to follow...