jetting
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Novice
Joined: Mar 2014
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From: Colorado Springs
jetting
So I pulled my keihin butterfly and replaced all the gaskets and what not, but I was wondering about jetting. This old girl was last run in upstate NY. It has a 170 main jet and a 75 pilot. I'm in Colorado springs now with an riding range of elevation that will probably be between 5000 and 7000 ft, but may occasionally rise to 11000 or 12000 ft. Anyone have any experience jetting for the high country?
thanks for the help
thanks for the help
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Novice
Joined: Mar 2014
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From: Colorado Springs
It seems to run alright at WOT, and it will idle ok without the choke, but if you try to blip the throttle it wants to die. I took the low speed mixture screw out one full turn and it seemed to improve, but if I come out much further with it I am afraid that it is so loose it will vibrate out of the hole. The thing is I'm not sure what that means as far as jetting. Tweaking a carb is where I am weakest mechanically. It's all magic.
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Joined: Oct 2011
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From: Costa Rica
Not sure what type of carb you have,but you will have to go to smaller jets with high elevation.I would think buy 4 sizes of each jet and start experimenting. I went from 600 ft to 5000 ft and i have a mikuni carb and when from a 320 jet to 220 main,and a big defference so i would think 100 120 for your main and 50 for the other one,you will have to try these jets and see how it runs etc. Also check the plugs you want them a tan colour,not white then you are to lean.
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Joined: Nov 2006
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From: la la land jerzey
It seems to run alright at WOT, and it will idle ok without the choke, but if you try to blip the throttle it wants to die. I took the low speed mixture screw out one full turn and it seemed to improve, but if I come out much further with it I am afraid that it is so loose it will vibrate out of the hole. The thing is I'm not sure what that means as far as jetting. Tweaking a carb is where I am weakest mechanically. It's all magic.
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Novice
Joined: Mar 2014
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From: Colorado Springs
Thanks Guys
My carb is a Keihin Butterfly. The issue with the off idle stumble was that the accel. pump was not working. I pulled it apart again and managed to squirt my self in the eye, not once but twice! I'm painfully sure the accelerator pump is not plugged up now. Now it runs a lot better, but you can tell it isn't quite right. I'm debating whether to tackle this myself. I've always wanted to figure carbs out, but I'm afraid of screwing around with it all summer too. I just thought maybe someone might know of a chart that would give you a starting point. I can't seem to find one. I'm not sure how much it will run me to take it to a shop. Anyway once I figure it out I'll post the jet sizes I end up with so that down the road if anyone finds this thread they will have the benefit of the info.
Thanks again
My carb is a Keihin Butterfly. The issue with the off idle stumble was that the accel. pump was not working. I pulled it apart again and managed to squirt my self in the eye, not once but twice! I'm painfully sure the accelerator pump is not plugged up now. Now it runs a lot better, but you can tell it isn't quite right. I'm debating whether to tackle this myself. I've always wanted to figure carbs out, but I'm afraid of screwing around with it all summer too. I just thought maybe someone might know of a chart that would give you a starting point. I can't seem to find one. I'm not sure how much it will run me to take it to a shop. Anyway once I figure it out I'll post the jet sizes I end up with so that down the road if anyone finds this thread they will have the benefit of the info.
Thanks again
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Joined: Nov 2006
Posts: 12,878
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From: la la land jerzey
only 2 different jets are in that type of carb
low speed === high speed -- and an idle adjust screw < count the turns out and make a list of what is in the carb so you can re start at the spot you are at now
low speed === high speed -- and an idle adjust screw < count the turns out and make a list of what is in the carb so you can re start at the spot you are at now
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