Those of you who have fitted after-market pipes and rejetted carbs, could you tell me the header length(including the bit in the silencer), and what the improvements were at what revs/roadspeed ?

thanks a lot

Clive W  

I'm using a RAASK with about 1 foot cut off and the baffle in the HD-FXD muffler would be about the end of the original RAASK. When I tried a HH Drag Pipe for a couple days, I lost about 8 mph on where I could run in 5th gear. 43 up from 35. High end was probably better. With the set up I have I'm back to 35-37 in 5th as minimum where it will pull cleanly to cruising. I'm hoping this company will develop a suitable high torque/ high HP muffler, http://www.performance-design.net/index2.htm.  They have designed one that provides both torque and HP results. Years ago I had a book with a formula in it for max torque length of intake and exhaust tract or conversely max HP at RPM. In the early 70's I had a Honda SL-125 I modified and used for observed trials and commuting. I had lightened it to 200 lbs, had high back pegs, CT90 seat cut down, Preston Petty fenders (rear with light), removable headlight, and a Powroll stroker kit with a hand made exhaust from bits and pieces with a round flat muffler, forerunner to Supertrap I think, exdusher?? Had amazing torque for 150cc about 1600 - 2500 RPM. Did well in amatuer trials of the time with it. I have looked in vain for the book and/or formula since. It must have been loaned and not returned or lost in moves over the years.  

Thanks very much for your info guys.

Clive W  

Maybe some kind of fishtail tip on the end of the Raask?

I was going to machine an exhaust insert to help silence KLX (carb area - needle area = silencer outlet area) but not reduce power.
Anyway it was below zero in the garage so I didn't.

Clive W  

Exhaust insert is done and fitted, haven't been out yet but it is quieter and should be big enough not to loose power.
The std. outlet is 20mm the one I've made is 40.4mm, just over 4 times the area.

Clive W