Finally cleaned out my carbs, idle running too high now. - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 2 (permalink) Old 11-26-2012, 03:11 AM Thread Starter
striderx240's Avatar
Join Date: Oct 2011
Location: Fresno, CA
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Finally cleaned out my carbs, idle running too high now.

Monster m750 2001.
So yeah, finally got bike motor running after cleaning my carbs, idling at 3k now, I've set the idle screw all the way down, but idle is still at 3k. Also when I rev up to around 5k, my engine backfires. I've read that it has something to do with the mixture running to lean. Any ideas?

Also, cold starts are such a pain, any remedy for this?
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post #2 of 2 (permalink) Old 11-26-2012, 07:06 AM
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Well you don't say if you use the choke for cold starts, that's the easiest way.

You need to get your carbs professionally synched as it sounds like you are unfamiliar with doing that yourself. You probably don't have utubes or gauges for testing with. You could use the dead cylinder method on that particular bike, but if you are unfamiliar with the method I'm not going to explain it out, feel free to google and good luck. I just don't want to tell you the method and then you end up over your head and way out of spec.

Another very good reason you are having troubles getting it dialed in, and probably the main reason for the high idle, would be a bad cable routing after hooking them back up. How did you remove the cables from the carb, it's a real pain in the ass. There are 2 jam nuts, did you back them off, or did you leave the set that faces the handlebars exactly where they were before removal? I ask because those jam nuts will affect the pull on the cable, thus the butterfly plate within the carb may not be able to set down, regardless of how much you fiddle with the idle screw. Same can be said at some throttle tubes as they have an adjuster there. How much free play do you have in your cables? You don't mention this.

Another high idle, and lean condition, is a poorly seated or torn intake boot. Also check that you did not knock off any of the vacuum lines from the intake system, nor any blanking test caps for synching carburetors. Any openings will allow air past the carburetor and void all settings. A quick test is to get a can of carb cleaner and using the little straw, lightly spray around all mechanical joints of the intake system behind the carburetor. If the idle begins to climb, you have a leak.

CV carbs are difficult to synch compared to solid slide carbs, be it round, D, or flat. If you have a local shop with a competent tech, they should be able to get you running correctly within an hour if your rebuild went well, and there is no other damage. You'll get a bike back that has been properly synched and should have been ran on an EGT type machine to get the fuel/air mixture correct. Basically I'm saying you'll get a much better tune letting someone with those tools do it versus doing it at home. I've tuned hundreds of carburetors at home by feel, however the bikes that my friend came by and tuned with the correct tools always were just that much smoother running than I did by ear.

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