22lyons Posted June 29, 2011 Share #1 Posted June 29, 2011 Got my new to me 2000 with 31k last fall and am needing to check valves and a carb sync (anyone in the area that may be able to help with the sync). Do you think these things could help with the little bit of popping I have on downshift. I also have been getting 32-35mpg no matter how i drive. I am one who likes speed but even when i have tried to drive easy 35mpg is all. Would there be more of a carb issue than the sync, etc. Thanks for your thoughts, Larry Link to comment Share on other sites More sharing options...
V7Goose Posted June 29, 2011 Share #2 Posted June 29, 2011 Your problem is quite common - LOTS of discussion of this in many older threads. Most common causes include dirty carbs, bad carb sync, vacuum leak, and exhaust leaks. I'd bet your carbs are both dity and out of sync, AND that you have a vacuum leak. Goose Link to comment Share on other sites More sharing options...
22lyons Posted June 30, 2011 Author Share #3 Posted June 30, 2011 thanks so much. will different mufflers make a difference? i don't know what the po put on it but they are louder. will they casue some popping with carbs in good order with no air leaks? Link to comment Share on other sites More sharing options...
V7Goose Posted June 30, 2011 Share #4 Posted June 30, 2011 Mufflers generally will not affect this problem unless they are essentially straight pipes which allow free back flow of fresh air into the header. Goose Link to comment Share on other sites More sharing options...
22lyons Posted June 30, 2011 Author Share #5 Posted June 30, 2011 Mufflers generally will not affect this problem unless they are essentially straight pipes which allow free back flow of fresh air into the header. Goose good to know. I know they are not straight pipes. They appear to have something in them. After reading some older posts i guess i will try to start with a carb synch and check the two rubber caps for leaks. Link to comment Share on other sites More sharing options...
mnelson Posted June 30, 2011 Share #6 Posted June 30, 2011 I had these same problems with my 2001. I found that my idle flow was actually a little lean...once I adjusted that the backfire went away. I too am still looking for a boost in mileage - getting about the same as you. Link to comment Share on other sites More sharing options...
Squidley Posted June 30, 2011 Share #7 Posted June 30, 2011 Check the other 2 vacuum lines on the intake manifold of #2 and #3 cylinders. These go to the AIS system and if they are disconnected or have leaks in them you will get popping Link to comment Share on other sites More sharing options...
midnightventure Posted June 30, 2011 Share #8 Posted June 30, 2011 I had the carb backfire when my bike was brand new. After I bought my synch tool and did the job it has never back fired again. It has 89000 miles on it now. Link to comment Share on other sites More sharing options...
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