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Annoyed. Backfiring

Discussion in 'The Garage' started by Yamaha77, Aug 9, 2016.

  1. So when I got my bike 5 days ago it sounded like this:


    Left it at the mechanic to get a few things done like swapping handlebars. When he gave me the bike back he said it was "running rich" and adjusted the screws right in front of me. Now the damn thing is backfiring all over the place. It sounds like fireworks when I ride and I pissed because, as you can see from the link above, the bike was running good. Ugh.

    Do I just adjust the mixture via the screws to remedy this, or must more be done. Also, I should note, there is no baffler in the exhaust header, if that makes sense.

    The shop manual is on the way to me in the mail. If I had it maybe I could figure this out.
    Last edited: Aug 9, 2016
  2. Well, no one else has answered so I will. Are you running stock exhaust and airboxes? Read the McKay carb guide (just google it), particular the section on syncing carbs and the fuel/air mixture
    You report that he changed your fuel mixture screws in front of you, did he say what he did? It sounds like he has leaned the mixture too far. Back the screws out 1/8 turn at a time until the popping/backfiring stops. The carb guide will tell you the right setting for your carbs.
  3. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi 77,
    that'll teach you to change your own effin' handlebars rather than pay money to someone who more than likely knows less about your bike than you do, eh?
    scott s likes this.
  4. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    Show us with a photo or carb part identification where he adjusted the carbs, and we'll be able to get it back to where you had it... There are only a few possibilities....
    Or ask him to re-adjust it back to where it was.
  5. scott s

    scott s XS650 Junkie

    Take it back to the mechanic. You paid him to install bars and then the lights stopped working.....make him fix it. He adjusted the carbs and now it runs worse....make him fix it. Unless you like paying people to screw up your stuff. ;)

    And as Fred says.....sometimes it's better to do it yourself, even if you have to learn how,
  6. scott s

    scott s XS650 Junkie

    BUT....if you want to try it yourself, he probably adjusted the mixture screws, (You can snap a pic and show us what he adjusted...that would be helpful). You can adjust those yourself.

    (Thanks, 5Twins, for the picture)

    The mixture screw on those carbs is on the engine side, which means it controls fuel. A good rule of thumb is that if the screw is on the intake, or air box side, it controls air flow. If it's on the engine side, it controls fuel.
    If he thought it was running rich, he probably screwed it in, in an attempt to cut off the fuel flow a little bit. But who knows what he really did. If he DID screw it in and lessen the fuel flow, it's possible that it's now lean.....hence the popping and backfiring.
    Stock, baseline setting for your carbs is 1.5 turns out from lightly seated. Can you gently screw one in until it bottoms out and count the turns? Tell us where the screws are set?

    Here's a good guide to carbs. You have a "D" model bike.....XS650D.

    Last edited: Aug 11, 2016
  7. Thanks so much for this. Will take a look over the weekend. Im very short on free time these days.
  8. 650Skull

    650Skull Dinosaur Lives Top Contributor

    Blue headers...................Running lean...............Hole in the piston.

    golden colour...............About right. or running rich.

    A mechanic who doesn't know this........................................

    You were warned the jetting was lean, and you have been riding it all over the place. Need to do a complete, new to you, bike inspection using the threads in the "Tech Menu" under the "Maintenance and general Troubleshooting" section. This will familiarize you with the bike. Reading in conjunction with answers is the only way to learn.
  9. Thanks for your thoughtful response!
  10. 5twins

    5twins XS650 Guru Top Contributor

    Yes, I'd have your "mechanic" fix what he broke. Then I'd be inclined to find a new mechanic, a real one, lol. Or at least one familiar with this bike. It may appear to be a simple old vertical twin but it has many little unique attributes. Not knowing about them can get a mechanic in trouble quite quickly. What may be the norm for most other bikes sometimes doesn't apply to these.
  11. To be honest, in my frustration, I may have been unfair to my mechanic. Hes great and he has done a great job on my bikes and the bikes of others. He may not have messed it up at all. Just talked to the seller and he informed me of a few things about the bike that may be causing the backfires. Ive learned a lesson in not accusing ppl. My mechanic is great.
  12. scott s

    scott s XS650 Junkie

    I'd still make him fix what he messed up.
  13. . I was too quick to judge and I dont know that he did anything wrong at all.

    In any case, the bike will be made to run properly and whoever needs to make that happen, will.
  14. 650Skull

    650Skull Dinosaur Lives Top Contributor

    Fair enough...................Being new to bikes, what 3-5 months. Have a lot to learn squirrel.

    Unless a mechanic is versed with these bikes, or works mainly on classic bikes, then the chances are he will be learning at your expense. If he was that good then the earth to the other switch block would have been checked and made good. A simple test after the completion of the job would have picked up the problem. Standard procedure for a tradesman.

    The truth it is you who needs to make that happen, by understanding the basics at least.
  15. Thanks for your comments!
  16. Brassneck

    Brassneck XS650 Guru

    Carb adjustments are super easy... getting familiar with it is almost mandatory so you can adjust things as needed. Which will happen more often than you think. When you get your manual, read up on the process. Then jump in and fix it yourself...you'll be happy you did. One thing at a time and soon you'll know a lot more about the various components of your bike, and won't need a mechanic for the most basic things. Saving you $, but more importantly, making you more confident in all things XS. (I also heard it grows hair on your chest and women flock to you!) Ha ha.
  17. Im married to a model and have two little boys. And Im a faithful man!!!

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