Originally Posted by sucker
I bought a 2001 bonneville a few months ago and it's never run quite right. I've done some research and am trying to rule out one thing at a time. I replaced the pickup coil and it helped a little but still not right. So I bought it with a keihin cr35 in it and I'm not sure if it was ever jetted right since its always been in Denver at 5280 feet. It appears to be running pretty rich, the plugs are really dark. The main jet is a 110 and the pilot is a 55 but it came with spares of 115 and 58. I assume the previous owner tried to rejet it. My question is how can a find decent starting point of what sizes these jets should be. It would be great if I know how they would set it up for this altitude if I bought it new. I also moved the needle from the notch second from the top to the top notch and it still seems rich.
Any help would be appreciated. I've already found a lot of good info on this site. This is my first bike so I'm learning a lot.
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A couple of things to consider here..
CR 35's are fine carbs but have pretty much been supplanted by the FCR line... So finding a lot of knowledge on their jetting and the effects of elevation, may be limited..
Your best bet would probably be to contact either Carlos @ TPUSA or Mike @ BellaCorse for recommendations and a good starting point for your situation/elevation... Either one should be able to get you in the ball park... Mike has a good bit of experience with the CR's... I'm sure Carlos does too... I know he's got the FCR's down pat...
If I remember correctly, the CR's were typically set up with 55 pilots... at 5500 ft. they're probably on the large side.
I would also pull one of the needles and get the alphabetic marking/code off of it as knowing what needles you have will affect jetting choices or tell you if you if you need a different needle profile.
Be sure to let them know what you intake configuration is (pod filters?), the exhaust system on the bike and the typical/average elevation range you'll be riding in.. You should be able to cover the pilot jet selection range with two sizes (ie" 55 & 58's ) and it would be a good idea to get main jets one size larger and smaller than the recommended size... This should give you what you need to cover pretty much everything you might need. Also, having a couple of needle shims wouldn't be a bad idea as they can be handy to fine tune needle height settings between clip slot adjustments... a shim will give a half step movement between slots...
Also, google "tuning Keihin CR carbs" and there is a lot of information on what affects each adjustment makes and the ranges of tuning overlap (how jets size/screw settings/needle profile-height/clip setting-shimming interact) are... After you get things set up, and you feel it's running pretty well, you should consider finding a good shop that does dyno tuning. Armed with your extra jets and shims, I'd then go get things dialed in on the dyno...