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Q: I just bought an older bike and the last owner ran an ultra rich premix mixture ratio that really carbonized up the exhaust system. How do I clean it out?

A: There are a lot of ways to clean exhaust systems, some involve caustic solutions and torches, I've used them all and I wouldn't recommend most of them. Probably one of the best (and safest) ways is to use a solution of 75 % used DOT 3 brake fluid and 25% water. Pour this in the pipe and tape the ends with duct tape to seal it. Move the pipe around so that all the carbon deposits are coated by the brake fluid, which will loosen it. Let this sit overnight.

Get a length of small woven steel cable (an old car speedometer cable is perfect) that is long enough to reach just past the center of the pipe. Fray one end (the more the better) and chuck this in a 1/4 inch drill that has a variable speed so it won't turn too fast. Use the cable to scrub the inside of the pipe from both ends which will take out the carbon loosened by the brake fluid. Be very careful while doing this and wear protective goggles, gloves and clothing and don't pull the cable out while it is turning as it will flail around. The ends of the pipe can be cleaned with an abrasive flap wheel (60 grit) obtained from a hardware store. The pipe can then be flushed out with solvent or brake cleaner.

Run a full synthetic premix oil at 80 or 100 to one and this will keep the system clean.
Professional tuner and 'Trials Competition' writer Jon Stoodley has very kindly stepped up to the plate to answer your questions. If you're having problems, or need some advice just send an email to Jon. If it's something that could be useful to others, we'll post it on the site.
This article originally appeared in 'Trials Competition', and was reproduced with permission.
Home. Back. ..... The Gas Gas Guru. Technical Information.