Odd hole in exhaust pipes

hal0tw0 · Posted: August 1, 2008, 8:35 am Post subject: Odd hole in exhaust pipes

Ive been trying to track my exhaust backfire issue by the simple things first. I was looking for leaks by touch and noticed my aftermarket pipes have a small 4/5 mm hole near the beginning of the pipe where it connects to the headpipes. Could this be for water drainage or maybe for tuning purposes.

I will later crack the carbs open see what jets are in there because of the pod filters/exhaust mods, hopefully they are larger jets.

BTW only the left side pipe backfires. Shocked

Shannon60 · Posted: August 1, 2008, 11:32 am Post subject: Re: Odd hole in exhaust pipes

Plug the holes and try it, the back fire is often caused by air getting into the exhaust, another reason is a lean pilot circuit often caused by dirty carbs or improperly adjusted mixture screws

bluebikerblan · Posted: August 1, 2008, 12:11 pm Post subject: Re: Odd hole in exhaust pipes

Vent holes.... two on each set of the "pipe within a pipe" stock headpipes. Exhaust does not flow through these holes which are only in the outer pipe of the two. My guess is that it was to keep the outer pipe from bluing from heat. Down side is the concept results in a restrictively small inner pipe diameter and adds a lot of weight...........IMHO

hal0tw0 · Posted: August 1, 2008, 12:55 pm Post subject: Re: Odd hole in exhaust pipes

These holes are on the muffler system after the stock headpipes. Ill do some more investigation after work today Wink

hal0tw0 · Posted: August 1, 2008, 7:12 pm Post subject: Re: Odd hole in exhaust pipes

Well all I can assume is that they are weep holes for condensation....I found my backfire issue....unhooked vacuum petcock on left Cool

gs1327 · 650Rider Supporter Joined: Feb 20, 2007 Posts: 170

You're right they are weep holes for condensation, you'll see these on lots of bike mufflers.

What Happened to 650rider.com?

Yamaha xs650