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Raptor 660 Information => 660 General Discussion => Topic started by: Duner on November 12, 2008, 07:49:40 PM

Title: backfiring going down hills?
Post by: Duner on November 12, 2008, 07:49:40 PM
What do I need to do with my carbs? Going down the dunes in 2nd, 3rd, or 4th doesn't matter it just pops like crazy. Other than that runs great. Got a little rainy and it seemed to just bogg down after like half to full throttle, just on flat ground. Its an 02 660 with K&N, full exhaust,  and jet kit from ct racing.
Title: Re: backfiring going down hills?
Post by: Smiley on November 12, 2008, 09:14:14 PM
Have you checked/adjusted your float levels?
Title: Re: backfiring going down hills?
Post by: Duner on November 14, 2008, 08:05:43 AM
yes I have. and replaced all seals. I'm wondering if changing needle position would help?
Title: Re: backfiring going down hills?
Post by: Flynbyu on November 14, 2008, 08:31:08 AM
If it's popping on deceleration, you're running rich.

The backfire is unburned fuel reigniting at the end of the tail pipe when it meets oxegen.

What are your jet settings now? What size mains are you running?

~Brian
Title: Re: backfiring going down hills?
Post by: Peelz on November 14, 2008, 08:53:42 AM
Quote from: Flynbyu on November 14, 2008, 08:31:08 AM
If it's popping on deceleration, you're running rich.

The backfire is unburned fuel reigniting at the end of the tail pipe when it meets oxegen.

What are your jet settings now? What size mains are you running?

~Brian

+1 to that and check your A/F screw position for idle. Sounds like you are rich at zero throttle. May need to turn them in (lean) a bit.

Ahhhh I feel better now, a carb question, not one of those new fangled jobbies! :lol:
Title: Re: backfiring going down hills?
Post by: Smiley on November 15, 2008, 10:06:46 AM
Flynbyu and Peels speak good advice :). Check those settings.

Since you mentioned "only down hill", I was thinking the "Rich mixture" is due to "float bowl spill over".  You can get it from a loose needle seat, needle not seating correctly or the float level is set too high.

What method did you use to set the float?  Just the measurement method or the tube method?
Title: Re: backfiring going down hills?
Post by: Duner on November 15, 2008, 12:14:58 PM
I have had the carbs out like 6 times the past 2 months, but haven't noted the jet sizes. just eye balled the float level measurement. Isn't it supposed to  be level with the carb while holding upside down
Title: Re: backfiring going down hills?
Post by: Flynbyu on November 15, 2008, 12:17:05 PM
I've not noticed myself if it is level, but I would assume it should be level.

~Brian
Title: Re: backfiring going down hills?
Post by: Peelz on November 15, 2008, 02:10:49 PM
I am still betting air fuel screw, or pilot size wrong.
Title: Re: backfiring going down hills?
Post by: Duner on November 15, 2008, 10:48:23 PM
hoping for some free time tomorrow to check it out I'll re post with what i find
Title: Re: backfiring going down hills?
Post by: Smiley on November 16, 2008, 08:13:47 AM
Quote from: Duner on November 15, 2008, 12:14:58 PM
I have had the carbs out like 6 times the past 2 months, but haven't noted the jet sizes. just eye balled the float level measurement. Isn't it supposed to  be level with the carb while holding upside down

Sorry about the cross-forum link - Maddog helped me out with this a long time ago:

http://www.raptorforum.com/forums/showthread.php?t=538