Check your little rubber caps. I went to go take out the shock and replace the spring today, and discovered they were all rotted and not making a seal at all.

I didn't notice any performance issues.

 

I Noticed that with the one on my carb. I used a small one put RTV on top then a second larger cap on top.

 

Yes a cracked rubber vacuum plug will cause backfiring and some power loss.

 

Hmm I figured it was my jetting. Only occurred on deceleration. Popping, bubbling...etc.

Thanks.

 

I had the same problem a while back. The bike was running so badly, I thought I broke something. I smeared another cap with gasket silicone and it's been ok, but I want to find something that works better.

 

can i ask, what is the smog vacuum hole, i think it the hole on the air manafold on the head, what does it do, it never came out on the ones here in oz, but i imported a head from usa which had a new hole on the manifold which i just caped off.

 

The one i had trouble was on the carb. The one on the head manifold has cracked for me too though. Bill blue, (and also another company), make a cover that you replace that whole manifold outlet with. You cold make your own too. I think Bill's is like $8.

 

Same thing happened to me last year. Bike all of a sudden started running wierd, it was the small cap on the carb had a tiny crack in it. If you buy one of those packs of assorted sizes that come in the "Help" section at some auto parts places beware the rubber is of inferior quality. I just used a piece of good vacuum hose with a bolt in the end to cure mine.

 

+1. Just put a screw in the hose. Auto part houses sell utter crap when it comes to miscellaneous housebrand stuff.