CB650SC will one lose main jet cause it to not run? - Great Lakes 4x4. The largest offroad forum in the Midwest

booblinker · July 31st, 2012, 10:53 PM

Rebuilt the carbs, ran before they got dirty. Didn't do any adjustments, just cleaned and new I rings. Ran great, revved great etc, got a half mile revved it and stopped running. Pushed it home. Will only run at 1k with .75-full throttle. I'm assuming it was the main jet that was loose when I pulled it apart. But to me it just seems like 1 loose jet wouldn't make it not run, since 3 cylinder still run.

Large_Time · July 31st, 2012, 10:58 PM

I doubt it seriously that 1 jet would cause all of that trouble. I would check for a bad leak by where the carbs push into the rubber manifolds.

Or check the coil wires, I had a KZ once that would act wild and it was a coil pack connection that went bad.

It could also be a choke setting....

Give it a good look over, a visual inspection will most likely show you the out of place item.

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bdd1469 · August 1st, 2012, 07:47 AM

The only way one main jet would stop it from running is if that cyl is seizing up. I would pull the petcock out of the gas tank,clean the tank and replace the petcock first.
I cant remember if you have one coil,or several,but it sounds like a coil breaking down also.
Check the intake boots for leaks

Large_Time · August 9th, 2012, 09:33 PM

Did you get it running better?

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booblinker · August 11th, 2012, 02:28 PM

Put them back on and noticed the plug for the wires going to the coil was half connected. Just enough to let it run, but not rev. Still isnt running great, but revs fine. I just have to take it to someone to have the carbs synced.

Large_Time · August 12th, 2012, 10:30 AM

Thats cool. A visual inspection usually finds the goods!

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July 31st, 2012, 10:53 PM	#1
booblinker Trailer Trash Join Date: 10-29-06 Location: Leonard, mi Posts: 8,240 iTrader: (5)	CB650SC will one lose main jet cause it to not run? Rebuilt the carbs, ran before they got dirty. Didn't do any adjustments, just cleaned and new I rings. Ran great, revved great etc, got a half mile revved it and stopped running. Pushed it home. Will only run at 1k with .75-full throttle. I'm assuming it was the main jet that was loose when I pulled it apart. But to me it just seems like 1 loose jet wouldn't make it not run, since 3 cylinder still run. __________________ -1993 Ranger 3.0 4X4 5 Speed STX -A Metric Butt ton of three wheelers -1985 V65 Magna -1983 Nighthawk 650 -1969 F250 Highboy built 360

August 11th, 2012, 02:28 PM	#5
booblinker Trailer Trash Join Date: 10-29-06 Location: Leonard, mi Posts: 8,240 iTrader: (5)	Put them back on and noticed the plug for the wires going to the coil was half connected. Just enough to let it run, but not rev. Still isnt running great, but revs fine. I just have to take it to someone to have the carbs synced. __________________ -1993 Ranger 3.0 4X4 5 Speed STX -A Metric Butt ton of three wheelers -1985 V65 Magna -1983 Nighthawk 650 -1969 F250 Highboy built 360

July 31st, 2012, 10:58 PM	#2
Large_Time Newbie Join Date: 07-11-12 Location: The Thumb Posts: 24 iTrader: (0)	I doubt it seriously that 1 jet would cause all of that trouble. I would check for a bad leak by where the carbs push into the rubber manifolds. Or check the coil wires, I had a KZ once that would act wild and it was a coil pack connection that went bad. It could also be a choke setting.... Give it a good look over, a visual inspection will most likely show you the out of place item. Sent from my DROID X2 using Xparent Green Tapatalk 2

August 1st, 2012, 07:47 AM	#3
bdd1469 bdd Join Date: 04-12-10 Location: alto mi Posts: 1,948 iTrader: (1)	The only way one main jet would stop it from running is if that cyl is seizing up. I would pull the petcock out of the gas tank,clean the tank and replace the petcock first. I cant remember if you have one coil,or several,but it sounds like a coil breaking down also. Check the intake boots for leaks

August 9th, 2012, 09:33 PM	#4
Large_Time Newbie Join Date: 07-11-12 Location: The Thumb Posts: 24 iTrader: (0)	Did you get it running better? Sent from my DROID X2 using Xparent Green Tapatalk 2

August 12th, 2012, 10:30 AM	#6
Large_Time Newbie Join Date: 07-11-12 Location: The Thumb Posts: 24 iTrader: (0)	Thats cool. A visual inspection usually finds the goods! Sent from my DROID X2 using Xparent Green Tapatalk 2