Smog Pump Removal Does Stop Backfiring

While finishing up dual sporting my bike for CO with light switch, break switch, and horn, the YZ throttle stop finally came in. (The stock stop was missing from the bike.)

So, while removing the smog pump to replace the stop, I temporarily plugged all the inserts with vacuum hose caps and the stock clamps as a test. I was still undecided about permanently removing it using Lowedog's kit, but the thing is just plain in the way. I was able to ride this weekend. After fine tuning the Zip-Tye fuel screw as I normally do, the bike did not backfire or pop once. I thought that my previous backfires were due to lean jetting because of cold air and a FMF T-4 pipe with the quiet core that is less restrictive than stock. The popping must have been due to the pump because the jetting and pipe were not changed.

So it's true. That valve injecting fresh air into the exhaust causes the unburnt fuel to explode in the muffler, making it pop? I thought it only diluted the exhaust. I guess that the unburnt fuel comes in spurts so explosion in the muffler rather than a controlled burn is an accurate description. The bike runs fine without it so it will be left off permanently. So lame, in the way when working, exploding mufflers, thanks but no thanks California. Go back to vacuuming your lawns. :)

Guess it will be soon time to order that kit.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now