Performance Issues after Jet kit install - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 15 (permalink) Old 04-01-2015, 11:07 AM Thread Starter
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Performance Issues after Jet kit install

I have a 2004 Vstar 1100. I have Cobra drag pipes without baffles. I was originally experiencing back fire on decal like many others probably have. I eliminated the AIS and installed a Cobra stage 1 jet kit. I followed Cobra's instruction on what main jets to use in each cylinder and placement of the needles with my current exhaust configuration. Since rejetting my bike has had a loss of performance on the lower end. At idle, and up to half throttle, it is fine. But as soon as I get above half throttle I get spitting, sputtering, and backfire out of the bike. Any ideas???
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post #2 of 15 (permalink) Old 04-01-2015, 07:05 PM
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Griff, tell us more about your setup. What jets did you install? How many turns on the PMS screw? Did you sync the carbs?

More info will help us help you.

2009 Stratoliner S

A few things added and more stuff to follow


https://sites.google.com/site/vstar1100kb/
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post #3 of 15 (permalink) Old 04-01-2015, 08:03 PM
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loss of back pressure would cause poor low end performance,torque cones ebay $20.00.
The only modification being exhaust,all you would have had to change is to up the mains one size, and turn the pms screws out a quarter turn.i think with these kits they raise the needle to get a rich middle and lower the mains so they don't flood out.click on the link below corsairs signature to the wiki web site it has all the info about 1100s
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post #4 of 15 (permalink) Old 04-01-2015, 08:31 PM Thread Starter
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I used the CJ110 In the front cylinder and CJ108 in the rear cylinder. I turned the pms out 3 turns on each carb as instructed by Cobra. No I did not sync the carbs because I've read that alot of guys have rejetted and the bike ran great without syncing. Could that simply be the problem? And I thought I was taking care of the lower back pressure problem by installing this jet kit?
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post #5 of 15 (permalink) Old 04-01-2015, 09:03 PM
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dont know about cj jets,but when you compare a mikuni,dyna and keihan jets by same number mikuni is the largest. so maybe your mains are two small.your pms is about a half turn rich.
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post #6 of 15 (permalink) Old 04-01-2015, 09:11 PM Thread Starter
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I'll try adjusting the pms on each carb. Should both carbs be set the same or does one cylinder run differently than the other due to temperature?
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post #7 of 15 (permalink) Old 04-01-2015, 09:53 PM
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set them both the same,check your plugs after 200 miles you can adjust the pms according to color.these plugs run pretty light almost white.
i think your mains are small.if you have the stock needles put them in, then set the pms to 2.5 as a starting point.pilot jet 17.5. Mains mikuni 115 in both cylinders you can get these at a harley dealership.using the parts you have i think your mains are to small what do your plugs look like?
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post #8 of 15 (permalink) Old 04-02-2015, 01:51 PM Thread Starter
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My plugs actually look like I'm running a little lean. I wondering if I'm starving for fuel when I get into the second half of the throttle??
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post #9 of 15 (permalink) Old 04-02-2015, 03:41 PM
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when i did pods and rejetted my plugs looked almost white,so i backed the pms screws out an eighth turn at a time until i started to show a bit of color.i guess its the ethinol that whitens the plugs.when you open the throttle and begin to sputter try pushing the choke on to see if it makes it better or worse.
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post #10 of 15 (permalink) Old 04-02-2015, 03:53 PM Thread Starter
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That's a good idea. That should help me determine if I'm running lean or rich. I'll let you know. Thanks
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