TC 88-95-106 Upgrade # 2, Starting, Idiling, Popping Issues

Discussion in 'Engine, Fuel and Exhaust' started by Mixer08, Aug 22, 2010.

  1. Mixer08

    Mixer08 Member

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    Well after my second upgrade I'm up to a 106 with a S & S stroker crank and some major starting, idiling, and a pop/backfire issues. Please Help! I recently put my engine back together after the lower end rebuild and some new pistions. On my initial I had some trouble getting it started but finally got the carb some gas, after it finally started I had some trouble starting it and getting it to idle. It seems the front cylinder is not running so good, it is popping and slightly backfiring through all throttle positions. And I had to keep the throttle cracked to keep it running. So far I have tried swapping the spark plugs and re gapping them, no luck, also I thought I might be sucking in air at the intake seal, so I shot some break free in the area but the engine pitch did not change. Next I pulled the carb and intake but the seals looked fine, so I reinstalled them and again, no luck. FYI, I have a S&S Super G and TwinTec ignition.
     
  2. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    What carb is it?

    TQ
     
  3. Mixer08

    Mixer08 Member

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    S&S Super G Shorty
     
  4. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    OK. I am guessing that you will need to tune the carb some based on the larger displacement. Your symptoms are those of being too lean, and with all that added displacement/volume, you will need more fuel. Try the next size up in the low speed jet, and high speed jet. Tweak the fuel/air idle mixture screw with the bike running about 1200 rpm to peak rpm, then back off 1/4 turn.

    See if that helps. If it is better but still has some problems, you know what to do!!

    TQ
     
  5. Mixer08

    Mixer08 Member

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    Thanks!! Will try the mixture first as I'm in the UK and getting parts can be a long waiting game. Sure mis the good ol' USA!!!!
     
  6. Mixer08

    Mixer08 Member

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    TQ,
    What are your thoughts on it only seeming to be effecting the front cylinder, even thought the whole engine is not wanting to idle.
    Thanks!!
     
  7. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Eliminating the possibility of an intake leak. I know you checked for one above, but double and even tripple check.

    You are gonna need more fuel, and that will affect the front cylinder more. Additionally, you may want to play with the ignition curves that are probably built into the TwinTec ignition. If they have some info on those curves in the documentation that came with it, see what the curves do. If you don't have any info, check below for the module/system you have. Then experiment to see what works best for your riding style. I would do this AFTER tweaking up the fuel with larger jets - intermediate and high. There is no low speed jet on that carb. Low speed is adjusted with the low speed idle mixture screw setting.

    http://www.nightrider.com/biketech/download/ssmanuals/super_e_g.pdf

    Daytona Twin Tec LLC - Tech FAQ Download Page

    TQ
     
  8. Mixer08

    Mixer08 Member

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    Looks like there are no intake leaks and I was having a bit of a problem with getting fuel, but it is getting a bit better. I fine tuned the jet settings on my Super G carb but just can't get it just right. As of now I have it cranking and running, but have to keep it idled up to stay running. The backfiring has toned down to just a thump or somewhat from the front cylinder in the exhaust. I'm starting to think I may be needing to upgrade my intermediate jet to one size up, thinking the 106 may need a bit more fuel. Another question is are the jets in a S&S carb standard in HD CV carbs or do I have to go straight to S&S?

    Thanks again for all the info, and here is my latest update. I changed the intermediatte jet out from a .0295 to a .031 and the nike runs great about 15 mph and on up through the speeds. But I cannot get it to idle. I have adjusted and readjusted but it will not run unless I have the idle screw turned in or the throttle twisted to keep it running. I'm wondering if anyone has ever had this be caused by a faulty or clogged petcock, when I pulled the bike apart I had to get a crazy amount of vacuum to get the gas to flow. So I'm wondering if that could be causing my idle problems. It just seems like I'm not getting gas unless I'm wrenching on the throttle.
     
    Last edited by a moderator: Sep 8, 2010
  9. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    If your petcock was an issue, your lack of fuel would happen in the upper rpm range and not in the lower ones. When the rpm's are higher the bowl would be empty of fuel. Since that is not happening, I say the petcock is delivering enough fuel. Having said that, make sure you dont have a vacuum leak.

    Bodeen
     
  10. Jack Klarich

    Jack Klarich Expert Member

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    I suspect something in the ignition trigger, is this single fire?