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Buying a bike (but it backfires)

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by bonkerrs, May 22, 2011.

  1. I am looking to buy a 2011 Triumph Thruxton, it is a nice bike and I want to make an offer except it has a backfire when shifting down gears and when you release the throttle (coasting).



    The bike has a 2 year warranty and the guy said the fuel mix is "probably" too rich (or something like that). He said they need to get the mechanic to adjust it.

    I wanted to know if backfiring can cause long term damage to the motor. I read here (on a different thread) about it but didn't get a definitive yes or no. Should I not worry about the bike because of it?
     
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  2. long term yes, because it's running too rich.
    needs to be tuned. probably backfiring because an aftermarket system or muffler is fitted.
    if so, will be expensive to sort it , assuming 2011 model is fuel injected.
    ask him for the original system/can.
     
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  3. Thanks for the advice. Yep, they put on a Staintune exhaust.

    So you say long term 'yes'. Is it bad... I mean what kind of long term damage?
     
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  4. Think you will find the backfire comes standard with most of the twin Trumpets. Specially if they have the shorty pipes on them.
    Tell them you don't want to lay cash down till they have it fixed or come up with one that doesn't fart on closed throttle.
    Or get them to throw a PC and dyno in on the deal.
     
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  5. or could be bike was tuned to suit aftermarket system and fuel/air induction.
    then the old system was just re-fitted for the sale of bike.
    anyway, nfi really, nice bikes though, chicks dig em, you could do worse. at least it's not a Harley
     
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  6. spark plugs are cheap, but burn out the valves maybe
     
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  7. Backfiring on deceleration is a very common problem and not one that will wreck your motor.
    It is easily (EASILY!) fixed.

    It happens when your mixture is running too LEAN not too rich (that guy doesn't know his own bike!).

    Running lean means that there is too much air for the amount of fuel.

    This will be fixed INSTANTLY at your first service.

    Worse case scenario (eg the pipes and the intakes were changed from the stock ones ad a service can't balance them out) you only need to buy a fuel management system (not expensive or involved to install) and you're good to go.

    If it's a 2011 and the guy is that clueless, then it's possible it hasn't even finished been run in. It still has a couple more major services to go before it settles down. :)

    Don't let that put you off at all!!!
     
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  8. pc if there is one for it avail (would assume so), plus dyno tune, maybe a few other bits and pieces, around a grand total, should be able to eliminate it. might still do it occasionally
     
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  9. i think phoenix is right actually, too lean
     
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  10. I would say they have just stuck the staintunes on without a tune. They usually cause a bike to run a little rich on idle but lean elsewhere. Would sound nice though. And yup a nice bike.
    Backfiring is not great Most bikes with EFI don't actually backfire:
    The popping you are hearing is not back-firing. It is a popping resonating sound generated by a lean condition on decel. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit of the EFI. However, momentum of the bike is actually "driving" the engine in a sense, and that engine is still spinning at rpm that needs far more gas than the closed throttle can provide. The engine is still spinning but the incoming fuel rate is very low, until just enough builds up in the combustion chamber to "fire" on the exhaust stroke of the engine.
     
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  11. Righto. From replies the message is go ahead and make an offer but have them fix the problem first.

    BTW, it's only done around 750km.
     
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  12. Mate of mine's dad has a carbed Thruxton, he (dad) turned it over for me once. Beautiful looking bike and beautiful sound. If you do end up buying it then enjoy and you MUST post pics.
     
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  13. All proper bikes frap and bang on the overrun :D.
     
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  14. Think I will make an offer. It sounds so good with the Staintune on! They fired up a standard exhaust too and the Staintune sounded so much better. I'll be posting pictures EVERYWHERE if/when I get this bike.

    EFI came in after the 2008 models. But they kept the carby housing for the authentic look!
     
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  15. Go for it. They are a great looking bike with heaps of character. If you feel the weight of the std pipes against the Staintunes you will notice how much lighter the Staintunes are. All the weight of the std ones is the packing to stop them doing exactly what you are talking about.
    But I would haggle on the backfire bit on the sale and get them to tune it as best they can anyway.
     
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  16. NO WAY!!

    I googled the Staintune. Apparently 2kg less then standard exhaust.
     
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  17. 2kg per pipe. That's a family sized chook before you roast it.
    The carbons I have coming for my Viffer are about ten KG less than the std set up. Hoping it will help with the weight and slowness when flipping side to side on it.
     
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  18. Here is the new member to the family! She's so much fun to ride... and the excitement every time I start her up or dial the throttle. The Staintune exhaust on this bike sounds beautiful awesome.

    IMAG0330_small.
    IMAG0331_small.
     
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  19. Niiiiiiiiiice.
    I want one in the shed too. Good luck with it. Love it.
    The pipes look factory too. Very good. Get some 3m clear sheets to stop the front of the forks chipping from stones.
     
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  20. backfire caused by air injection the silver tube next to spark plug pull it out and block off nissan blue bird sump plug and rubber grommet on intake manifold ahd plug in air box mt bike bar end
     
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