The original systems were made of odd size tubing 1 3/8" – 1 5/8" etc. This size tubing is still available at a cost. I have proven that by going up to the next size 1 1/2" – 1 3/4" there is a small gain in power plus there is a greater variety of mufflers and resonators in these common sizes.
The following is a table of pipe size to engine size:
| For road use | |
|---|---|
| 1200cc | 1 1/2" pipe |
| 1300cc | 1 3/4" pipe |
| 1500cc | 1 1/2" pipe |
| For racing purposes | |
|---|---|
| 1200cc | 1 3/4" pipe |
| 1300cc | 2" pipe |
| 1500cc | 2" pipe |
For best results bring the pipe out the side inline with the back of the door (race only).
The above information is for single pipe systems only. For the twin pipe system which is very popular overseas, the following applies:
| For racing purposes | |
|---|---|
| 1200cc | 1 1/2" into twin 1" |
| 1300cc | 1 3/4" into twin 1 1/2" |
| 1500cc | 1 3/4" into twin 1 1/2" |
Depending on how loud you want the note to be you use resonators or sports mufflers. For the single pipe system I use a long resonator up the front and a short resonator at the rear. It is effective with no rattles and a magnificent sound.