Carb Questions

[Buffalo Breath]

colortune

I got mine off of ebay its an ok tool for ball park, but plug readings are the right way to go, and more accurate

[chef1366]

New issue, the decel popping stopped but sometimes reappears when letting off the throttle when going 80 or faster for a couple of miles. It starts to bog and can't get the throttle to "grab" I then can stop with a normal idle and take off like nothing happened. I am going to try a throttle check tomorrow and see where I'm at. I understand that low rpm depends on the primary air jet and the pilot screw setting, the mid is a combo of the pilot jet and main and the high is the main jet. If I am to lower the pilot jet size would it directly effect my high rpm performance (do they work together or only the main and jet needle) Also I'm stil not happy with my high rpm accel, seems a bit garbled. Could be rich or lean, I'll find out tomorrow. By the way my petcock is good.

[chef1366]

Would riding in thirty-five to forty degrees F make any difference with rich and lean. Should I block off my oil cooler during the cooler riding season?

[KEITH KRAUSE]

I am going to try a throttle check tomorrow and see where I'm at. I understand that low rpm depends on the primary air jet and the pilot screw setting, the mid is a combo of the pilot jet and main and the high is the main jet. If I am to lower the pilot jet size would it directly effect my high rpm performance (do they work together or only the main and jet needle) Also I'm stil not happy with my high rpm accel, seems a bit garbled. Could be rich or lean, I'll find out tomorrow. By the way my petcock is good.

Be more concerned with throttle position than rpm's.
Info varies some, but closed throttle is the pilot air jet and pilot jet and the mixture screw. Just off idle the jet needle and primary air jet kicks in and gradually takes over. About 1/5 to 1/4 throttle, the pilot circuit has minimal overlap effect and the jet needle takes over. At about 3/4 throttle the main jet will completely regulate the flow.
Yes, colder weather with "normal" humidity will mean a leaner mixture. With a correctly jetted bike, cold weather won't be a problem. With a bike that's lean to begin with, it will be a problem.

[gwhunran]

Colortune?

Chef,

I have been having some carb troubles too, although everything is running pretty good now. I am interested in info about the colortune too.
I have one, but have not used it yet. I purchased it along with a morgan carbtuneII to help syncing the carbs. I got a local bikeshop mechanic to come by the house and give me some training on working on the carbs, installing a jet kit, and other assorted things. When it came to the colortune, he had never used one and wasn't too interested in using it, so I still haven't tried it yet. It seems like it would be pretty useful in adjusting idle and low/middle rpm settings.

Richard

[chef1366]

Did a throttle test today and come up with lean conditions across the board. Did a high speed chop test on the road and came up lean. When I decel a little after going 3/4 throttle or about 80 mph for awhile the bikes wants to die. During this I hit the kill switch and checked my plugs on the side of the highway and they were lean. Could'nt get it to start unless I gave it full choke and then it took off like nothing happened. This sounds like fuel starvation to me but how come at mid throttle and not at full throttle? This could be a float or needle jet adjustment? The lean conditions is probably why my bike likes the 100 degree F + summers.

[KEITH KRAUSE]

If you're lean at 1/3... 1/2 throttle position, this is a lean jet needle. As I said earlier, the pipe and the filter, even with the air box lid on, will make the needle circuit run lean. If your jet needle isn't adjustable, you need a stage 1 jet kit or shim up the needles.
I also asked how you set your float levels and what part of the float did you measure at? Float levels must be set within the factory range before re-jetting.

[chef1366]

The floats are set at 22 mm. The Clymers manual states 21.4 mm to 23.4 mm. The used carbs I bought have a dynojet jetting kit in it. The needle jets have 6 notches and currently they are set at 4 notches down from top. The Dynojet websight stated to start at 3 down for stage 1. If I were to put these needle jets in can I still go with the jet sizes I have now. Also, the Dynojet instructions stated to drill the slide lift holes and if this was done to the diaphragms I am using currently would this cause a leaner condition? I also noticed the diaphragm springs were much shorter then stock springs. Is this why you drill the lift holes? Should I get 120 main jets or do you think this will cure my high end woes.

[KEITH KRAUSE]

The floats are set at 22 mm. The Clymers manual states 21.4 mm to 23.4 mm. The used carbs I bought have a dynojet jetting kit in it. The needle jets have 6 notches and currently they are set at 4 notches down from top. The Dynojet websight stated to start at 3 down for stage 1. If I were to put these needle jets in can I still go with the jet sizes I have now. Also, the Dynojet instructions stated to drill the slide lift holes and if this was done to the diaphragms I am using currently would this cause a leaner condition? I also noticed the diaphragm springs were much shorter then stock springs. Is this why you drill the lift holes? Should I get 120 main jets or do you think this will cure my high end woes.

For the floats, be sure you set the level by measuring from the bowl surface (no gasket) to the top of the rounded float body...not the arm that supports the float (common mistake) or where the float "steps up".
I would use the DJ needles because you should be lean at the needle circuit. I can't say where to put the needle e-clip. If DJ suggests position 3 from the top, try it (?) and test. I find most of their "base setting" recommendations are on the lean side. I would probably try position 4 from the top, but I'm simply going by gut feelings. A 1/3 throttle test will tell you what to do. Mark the throttle housing and grip to be sure. Don't guess. Because you have 3 separate jetting circuits that regulate mixture at different throttle positions, you can stay with the current pilot and main jets but as always you have to test for each circuit. I like to get the needle perfect, then I simply install the largest main jet I can that will not create any bogging during a roll-on at 60 mph in top gear. Generally, you install the main that provides the best top end, but in some cases, this will create a bog during the roll-on. To me, the needle circuit is the most important and I won't compromise passing power/roll-on quality for a few more mph. You should not have to keep this kind of bike revving high to get good burn/acceleration. You shouldn't have to tap down a gear or two to avoid bogging. It should pull like a train from 3,500/4,000 rpm in top gear up to its top end.
When you say you tested at "3/4 throttle or 80", I'm not exactly sure what you mean. 80 mph in top gear on your bike is maybe 1/4 throttle. When testing for the main, go full throttle. Then there's no possible overlap with the jet needle. I realize these are high speeds but it's the only way I can suggest to test without a Dyno. I can't say if the 117.5 or 120, etc, is the correct main. You have to test and find out.
The purpose of drilling out the vacuum ports to the diaphragm/piston assembly is to improve throttle response. It's generally necessary when you run pods or modify the airbox. Your airbox is stock. The K&N filter doesn't change anything here. I wouldn't touch the ports or change springs.
By the way, are your two floatbowl lines clear, not kinked and run under the seat?? Some people connect them together and other stuff that will cause major fuel starvation.

[chef1366]

I measured the floats on the body, the flat area, without a gasket. I tried these needles once when I first tried these diaphragms. Even though at that time I tried the 45 pilot and 112.5 mains I had a terrible flat spot at 1/4 to 1/3 throttle. I don't know if this was the jetting or the needle position. Trial and error on jets, shoot I should just pod the carbs for easier tear down.

[chef1366]

Looking back It looks like I have to reset my floats. I only checked the floats but did not adjust because they appeared to be in line. Would this cause it to run lean? If the hole was already drilled in the slide pickup could this pose a problem? Man, my whole jetting plan could go in the sh***** if something as basic as my float adjustment is off.

[RacingJake]

If you got free flowing filter's and exhaust then 120 mains ain't going to cut it. If you using DJ mains then take off 8 points cause in Mikuni land that's like a 112 jet size.

Don't know how you guys get away with running those small jets. Must be the Texas air cause my bike will fall flat on it's face with anything smaller than a 140 and that's when it was a 1075 street motor and 34cv's :? must be those resticted exhaust systems you guys are running

[KEITH KRAUSE]

RacingJake, he's got a stock airbox. Pipe is the only mod'.

[KEITH KRAUSE]

Looking back It looks like I have to reset my floats. I only checked the floats but did not adjust because they appeared to be in line. Would this cause it to run lean? If the hole was already drilled in the slide pickup could this pose a problem? Man, my whole jetting plan could go in the sh***** if something as basic as my float adjustment is off.

Float adjustment is a basic. It must be correct before re-jetting. I've mentioned this several times in my replies.
The purpose of drilling the slide vacuum ports is to increase/improve throttle response. This is necessary when modifying the air box or running pods. If the slides are drilled with a stock intake, I would have to think the slides are too sensitive to throttle openings. But I have no experience with this combo.

[RacingJake]

I see.............

Thanks
Jake