I’ve put about 130 miles on the 1978 Puch Maxi Luxe I was given earlier this year.
On level ground it had no problem running 30-31 MPH (GPS).
It started with a ¼ kick and would sit and idle at about 1,350 RPM (set with a General Technologies Corp TA100 Smartach+) as long as I needed it to.
I suspect the bike was originally a 1.5 HP model but has been modified prior to it being given to me.
I do know that the bike as given to me had:
A 349.1.16.000.2 Silencer cover
A 16 tooth counter sprocket
A 12mm Bing (1/12/304) - I looked at the main jet when I was cleaning the carb but didn't bother recording its size. Needle clip was and is third position from bottom.
A 349.1.15.070.0 air cleaner assembly.
I recently had access to a new Bing 14mm carb and against my better judgement I swapped the 12mm Bing for it.
I’ve got some jets coming this week and also the Uni 20mm air filter that several vendors sell.
I suspect the original exhaust was modified somewhat (as well as other things) to get that 30-31 MPH speed.
Here’s how it is now.
The inner exhaust pipe is approximately 14 ½” long with an ID of approximately .770”.
There are three vertical drill thru holes in this inner exhaust pipe.
The holes are approximately 2 3/8”, 3 7/8”, and 10 ½” from the asbestos seal.
The first two drill thru holes are approximately .360” and the last one is approximately .390”.
There is a 6mm rod welded to the end of the inner exhaust pipe and bent down to allow the “Dampening Insert” to be attached inside the “Silencer Cover”.
When attached the front of the “Dampening Insert” is about 1” from the rear end of the inner exhaust pipe.
There are 10 approximately 8mm (approximately .320”) holes in the “Dampening Insert”.
The front end of the "Dampening Insert" has a 6mm hole allowing it to be put over the 6mm rod that is welded to the end of the inner exhaust pipe.
The rear end has an approximately 10 mm hole.
A short piece of 10mm tube with an inner diameter of approximately .370” with two approximately 8mm drill thru holes is inserted into the “Dampening Insert” and stops on an inner ledge with about ½” protruding from the end of the “Dampening Insert”.
When assembled an extruded washer goes into the endo of this tube forcing all exhaust gas to exit around the 6mm rod and through the two 8mm holes.
It would seem to me that asking those two 8mm holes (with a 6mm rod through the tube) to get rid of all the exhaust is pushing it, especially with the new 14mm Bing and Uni filter.
I really don’t want to go with a custom pipe with stock cylinder, etc. and I have absolutely no desire to “kit” the bike.
Has anyone had any experience (positive or negative) with adding additional holes in the rear faces of the “Dampening Insert”.
This would allow more exhaust gas to exit.
I’m aware that there is a need of some “echo” waves to push the fresh charge back into the transfer port and into the combustion chamber.
And experiences with modifying this stock Puch system that proved favorable would be greatly appreciated.