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Discussion Starter #1
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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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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Discussion Starter #4
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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Discussion Starter #6
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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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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Discussion Starter #8
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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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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Actually synching the carbs is about the most important part of the entire process. ft it's not done, the job isn't finished.
 

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Discussion Starter #12
I did bench sync them after I installed the new jets, but I haven't synced them with a manometer. I talked to my local bike shop and they said if I have a nice smooth idle and lower RPM then the carbs are real close to synced and wouldn't cause the problem I've been having. That being said, I'm going to build a manometer and dial em in.
 

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Discussion Starter #13
Ok well messing with the PMS has done nothing for me. This weekend I will be pulling the carbs and installing bigger main jets as Nick57 has suggested. Also I will be syncing the carbs better on this go around. I'll let you know how it turns out. Thanks
 

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Discussion Starter #15
Alright...... after pulling the carbs and changing jets about 3 times I have finally landed on a combo I like. I ended up with FTC 125 in the front cylinder and FTC 122.5 in the rear. Basically the same jets you get with a Hypercharger. I have a Hypercharger and the Cobra drag pipes so I also made some needle adjustments. Bike is running great. I will be checking the plugs for the next few rides and making small adjustments as needed. Thanks to everyone for all your input!
 
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