Posted by William A. Boylan on September 29, 2002 at 05:43:42:
In Reply to: Drilling holes in Exhaust . . What do you guys think ? posted by Uni-Killer on August 22, 2002 at 21:51:09:
Sorry I am a bit late in replying to your request. Vacation has kept me away from the computer for quite a while.
I am writing from memory so I will not try to quote figures, but some time ago I bought a nearly new, used stock muffler from e-bay. While installing the new muffler, I made some measurements of the outlet pipe at the head vers. the outlet of the muffler and was quite surprised at the difference.
The outlet of the muffler was only about 1/2 that of the head pipe. I did the math and found that by drilling about 8 ea. 3/8" holes around the outlet hole in the muffler, I could almost exactly duplicate the area of the head pipe. The exact number of holes I drilled, escapes me just now, and the bike is out in the shop, but I wrote about this, in detail, on this forum some months back. You might want to look it up.
Did it help? I dunno. Unfortuatly I also made some changes to the carberator at the same time, so I am not sure what the effect of drilling the holes had on the performance. But I do know that the bike sounds MUCH MUCH beter, and the combination of the muffler changes and the carb repairs made the bike run much stronger.
I have about 1/4 mile of gravel driveway, and I have found that now, it is not a good idea to "honk" on it in the first two gears. Not in the gravel.
The bike is an 87 with low miles. Still has the "white spacer".