Running rough and sputtering from too much air

[AnthonyZ]

Okay, I know I am likely to get a dressing down for my lack of understanding of internal combustion engines, but I have to tell my story. A couple months after buying my shadow this summer, I put in some new iridium plugs, new fuel filter, new K & M air filter, and a new gas tank (because the old one had lots of rust inside and I dropped it while lining the tank).

After all that, the bike didn't seem to run quite as well. I kept fiddling, looking for loose hoses, etc. It wasn't until this week when I took off the air breather housing again that I noticed the duct connecting the filter housing to the engine wasn't fitting tightly. It had slipped out of its groove and was letting too much air into the engine. I took it off and put it back together and put some silicone gasket maker around the fitting to ensure it was a tight seal. WOW, it is like a whole new bike. I have great acceleration, nice smooth idle, almost no pops on decel, etc.

I always thought more air was better, but I guess it's too much of a good thing.

[justinmahn]

You're correct. More air is only good with the proper mix of more fuel. The fuel to air mixture has to be just right, or you have lots of problems.

Oh, and ROCK ON for finding the Gremlin!

[gat803]

Engines are tuned to run well under a certain set of circumstances. Having all of the pieces in place and functional is a biggie. It is possible to make them run well without those pieces in place, but you must retune for it. You just learned that lesson.