Exhaust Fabrication Tutorials

Could you make a pattern for them out of plastic pipe? (In UK) I would first try domestic waste and overflow pipe in PVC or ABS, it might have to be a bit up or down on OD compared with the real thing. That's assuming you're not putting nice curves in it!

Hi Mike,

"Could you make a pattern for them out of plastic pipe? (In UK) I would first try domestic waste and overflow pipe in PVC or ABS, it might have to be a bit up or down on OD compared with the real thing. That's assuming you're not putting nice curves in it!"

I have the Rotax supplied straight pipe, donuts, spring loops and flanges.

I need to do this because the existing pipe (one of four) does not "curve" quite enough to clear the engine frame (striking during stop & possibly start) - so yes this is a curved pipe, that must fit within existing head to muffler dimensions.

I will research plastic plumbing pipe/fittings and if I can find one that is a fairly close approximation, this may just be the answer I am looking for.

Suggestion from another Forum:

To improve/increase clearance, the exhaust pipe could be dented/deformed, for a short distance, down one side, in the "offending" area.

The dent would need to be a minimum of 10mm deep (at deepest point) to allow for bad engine stop and  potential for engine mounts to "soften" over time giving increased movement.

The idea has appeal -  no need to make new pipe - no worries about fitting - quick & easy/minimal down time - no additional cost.

I am assured, that the change in cross sectional shape, will have minimal impact on gas flow (cross section area remains the same).

How to do ? - I have access to oxyacetylene, so could heat pipe to plasticity, then press or tap (ball peen) to achieve the required shape.

Questions:

# Will a 10mm deep flattening, of one side of the exhaust pipe, have any negative effects on engine performance/gas flow?

# What, if any effect, will heating a section of the pipe, to the plastic stage, have on its durability?

# Other????

Check out this automotive experiment, in denting an exhaust system & its apparently minimal effect on performance.

https://www.facebook.com/watch/?v=152724102049876

Your comments are eagerly awaited

If you don't want hammer marks left behind, heat the tube to plastic and press on it with a large diameter object (big socket with a hefty screwdriver through it for a handle?).  That should produce a smoother transition at the pinch point than hammering.

If you don't have access to an oxy-acetylene rig, a MAPP gas torch (yellow bottle) from the local hardware store will produce similar results.