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Misfire at low rpm

Old 03-17-2005, 10:31 PM
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Misfire at low rpm

I'm new to this group and my Super Hawk is new to me so forgive me if this has been discussed at length.

From what I've read it's a misfire when going from the idle to the pilots at about 3k rpm, just cracking open the throttle. Other than this anoying 'ding' the bike runs great. Around town though it's right in the middle of my range.

It has Erion pipes and jetting. Previous owner had the bike tuned at a local shop and they concluded the jetting was 'excelent'. Dyno run was at 105.9 hp. It's loud and backfires and I love it.

Should I 1) mess with the fuel; 2) start looking for a spark issue; or 3) live with it?

Thanks for the help. Tons of great information here.
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Old 03-18-2005, 06:35 AM
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Re: Misfire at low rpm

I guess that's what happens when you tune a bike on the dyno where it's only run at full throttle.

This sounds like a problem some of us have had and disucssed here. Probably you need to adjust the needle jets. Read the "hesitation after installing dyno-jet kit" thread in this same section. Good news is it's doesn't cost a thing or require expensive parts; just your time.
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Old 03-18-2005, 07:48 AM
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I've never been able to fully get rid of it but some careful tuning (of a Factory jet kit) limits it to a minor irritation between 3000 and 3200 rpm.
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Old 03-18-2005, 07:07 PM
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Re: Misfire at low rpm

Thanks for the help! I'll definintely be taking the needles up. The bike is new to me so I have no idea what kit is installed. I tested it on the way to work this morning and running slightly choked eliminates the problem.

This is my first twin so I'm excited about the 'what-the-f' factor since I've been taking apart my Bandit for a years.


I hope to learn quite a bit from the knowledge here. Thanks again.
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Old 01-03-2006, 09:58 AM
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Re: Misfire at low rpm

wow - my bike does the annoying "blipping" between 3000 and 3200 as well. the bike is new to me so i am not positive about carb work and jetting. it does have two brothers carbon fiber slip ons, but i am not sure about jetting and honestly have not much carb work in my mechanical life.

are you saying that it is adjusted where it needs to be or that something can and should be done about it. just wondering if this is part of the "SuperHawk character".

thanks guys!
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Old 01-03-2006, 11:07 AM
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Yeah, the Factory jet kit is the same way. The needle has 6 notches and you put it on notch "4" for this kind of setup and notch "5" for this kind of setup. I put mine on the fifth notch, knowing it would run a little rich, and jetted accordingly. The powerband is now as smooth as silk and I had major problems in the 0-3000 range before the change.

The problem originates from the exhaust pipes and Two Brothers and others really should just start adding $20 to their exhausts to throw in a jet kit, because you're gonna have to do it.

3000-3200 is still within the idle jet/low jet range, so its a matter of drilling the carb slides when you change the needles. (I feel like this topic is in 3 different places... :S ) Once that's done, you may have to tinker with that circlip(s) like RC996 was saying, which is easy once you manage to get the needles out of the carbs!

I agree with Superbling that the Dyno testing will have very little pertinent information for your early RPM issues being as how its done at full throttle.
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Old 01-03-2006, 06:35 PM
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Re: Misfire at low rpm

ATLSHawk98, I think it depends on what you are talking about, whether your problem is a 'stumble' or worse. Some people have said they never really get rid of the stumble, although only those in tune with their bike would notice. My bike was very lean and it was driving me crazy riding around town. Either way it's worth changing the needle position to find out. I raised my needles and it went away, although I had to chase down a few other issues. Right now is running just fine, not perfect but I'd rather fish than work on my carbs! Your bike should run well so it's not part of the character. If it's new to you but not new, and you don't know where the jetting is, it may be worth either figuring it out or starting clean with a jet kit. I may jet mine again if I run out of time to ride it or if I break my leg and can't ski. Good luck.
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