Motorcycle Club » Star 650 Classic & Custom

No More Backfire!

12 posts from 5 voices
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  1. KSPILOT245

    Finally got my gas tank off and drilled out the brass plugs on the carburator,
    turned the PMS scews out 3 1/2 turns(were at 2) put everything back together and went for a ride..NO MORE BACKFIRE!YEAH....
    This was Mikeys diagnosis..and just got around to it..
    Thanx Mikey!
    By the way I have V&H Cruzer pipes but it backfired with the stock pipes with the baffles drilled too.

  2. MigejCojode

    Glad it worked for ya. Get some seafoam in the tank too. Just did a little research and KS is spear heading adding more ethanol to blended fuels. The seafoam will help with what ethanol does to your jets

  3. rwrrunner

    I have a 2002 650 Classic with 12,750 miles I bought about 2 months ago. I've driven it about another 1000 miles and it backfires and pops like crazy under all decelleration conditions. I have to sneak out of my neighborhood at 6:30 am or will be run out permanently because it is so loud. As best as I can tell the bike is all stock except it definitely has after market pipes and they are pretty loud (but sound great).

    I've read on this board about this bike being tuned pretty lean and expect that is my problem. I will pull the tank and check to see if the carbs are still stock with the brass plugs and will drill and adjust if they are. My only concern is that whoever put the pipes on may have changed the jetting and I have no way of telling without tearing the carbs apart. Bike gets solid 53mpg and runs great except for this problem.

    Your thoughts would be greatly appreciated.

  4. zbungj

    I had the same thing .... with the after market pipes the AIS is your problem, you can either bypass or do a removal

    here is the removal
    and the bypass, easier way

  5. KSPILOT245

    I did the ais removal and it still backfired and popped,it drove me crazy,like I said the enrichment of the carbs did the trick.

  6. rwrrunner

    Thanks much for this info. I'll be doing this today and can't wait to see if it works.

    As a side note:

    I rode 200 miles yesterday with a group of around 20 bikes. My 650 was the smallest and almost the oldest bike. Most were new Victories, a Kaw 900 and a single HD RoadKing. These guys like to go fast and the road had lots of hills and turns. The 650 had no problem keeping up and accelerating out of the turns. Only time I noticed I was running with the big boys was when we would be doing 70 mph and they would open it up on a straight. I just didn't have the power to make that fast acceleration from that speed. I've been worried if I had made a mistake buying the 650 but now I am all grins. Especially since I paid $3.5k for mine and they paid in the double digits for theirs!! I even had a guy say he wants to buy it when I move up (if I do). The 650 even sounds a bad as their bikes with the pipes I have installed.

  7. rwrrunner

    Just finished the AIS disable mod and it appears to have really worked. Taking it out for a longer ride this evening to make sure.

    Really appreciate the help.

  8. rwrrunner

    I have a new bike, at least that is what it feels like after doing the AIS disable mod. Took my lady for an evening ride yesterday and I could actually go through town without sounding like a shootout in Tombstone. It still pops a little but nothing like it did before. This really made riding this bike even more pleasurable.

    Thanks again.

  9. c5padmopile

    So you have to take the tank off to get to the PMS screws?

  10. rwrrunner

    I didn't touch the carbs at all. I did the alternate AIS disable approach shown in the link from the post from zbungj ("easier way").

    I took the air breather off, reconfigured the rubber hoses as shown then plugged the small hose going to the AIS valve.

    It definitely cleared up 95% of my problem. Now I have aftermarket pipes on my bike so not sure if this works as well on stock pipes.

  11. c5padmopile

    I have straight pipes. No baffles and an aftermarket intake so Im thinking the pms screws may need to be adjusted.

  12. rwrrunner

    I should correct my last post, I plugged both the small hoses going to the intake and the AIS valve. I did this by removing the connection fitting that allowed free flow of vacuum and replaced it (not with a golf tee) with a solid piece of metal the same size as the fitting. This made it look as it did before without open hoses hanging out in clear view.


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