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Discussion Starter #1
Ive always had a thing for old Hondas, Ive had a couple cb 550s and 750s all from the late 70s. I recently got my hands on a mint 78 Gl 1000 with 58K. Biker runs and cruses great but has a couple gremlins in it Im trying to chase down. after i got the bike i noticed its idle was a little rough and high and the bike had a shake to it and I could hear the primary chain making noise, I got a sync kit and synced the carbs and all that went away, although now it appears i made another problem, now when returning to idle the RPMs will dip below idle speed and kick back up, also if i rev the bike slowly it will stutter for a split second around 3K and kick back up. adjusting the idle mix screws had no effect and i double checked the carbs and they are staying in sync, the bike is riding fine and a mix of city and highway driving I get around 38 mpg ( would be better but im not that easy on the throttle) any help or advice would be most welcome!
 

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Suspect carb issue,if the carbs aren’t clean then the sync will be off,put some injector cleaner,Seafoam,RXP from auto zone and run it kinda hard for a tank and see if it runs different.
 

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A sync is not a cure or fix for an improperly running engine, it is the icing on the cake and is done lastly when all else is in proper operation and tune. Start with the basics, a compression test is always advisable along with plug wire and spark quality available to the plugs, ignition timing and valve lash check/adjustment.

Then it is on to carbureation checking which cylinders are running rich, lean or correctly.
 

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Discussion Starter #4
Valve clearance and timing is all good, compression is 152 to 155 cold on all cylinders, I was told it could be running rich or it has a vacuum leak, adjusting the idle mixture pilots rich or lean makes no real difference, only it runs worse when I turn them in, right now they are all set 2 1/2 turns out per the book
 

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I think you have an air jet plugged causing the stumble at 3K and possibly the air cut off valve has been blocked off causing the drop below idle. And fuel treatments won't cure either.
 

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Discussion Starter #6
Thanks I'll check that out. If it looks like the carbs could need a rebuild, I might just wait until it's starts getting cold out and have a pro do it, it runs well enough so I just want to ride while I can
 

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carb

put a tooth pick in the idle jet. i have a 93 gl1500 64k. bike had sat alot and stumbled the rpm at idle would go from 550-1500. local shop put in a carb kit and synced them but still wouldn't idle right. a shop somewhere posted this fix.i tried it and it worked. hope this helps.lb in this pic i used a black boot but it has a tendensy to pop off, so use a tooth pick, leave it long enough so you can pull it out
 

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put a tooth pick in the idle jet. i have a 93 gl1500 64k. bike had sat alot and stumbled the rpm at idle would go from 550-1500. local shop put in a carb kit and synced them but still wouldn't idle right. a shop somewhere posted this fix.i tried it and it worked. hope this helps.lb in this pic i used a black boot but it has a tendensy to pop off, so use a tooth pick, leave it long enough so you can pull it out
Now that's a real redneck fix.:ROFL:
 

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put a tooth pick in the idle jet. i have a 93 gl1500 64k. bike had sat alot and stumbled the rpm at idle would go from 550-1500. local shop put in a carb kit and synced them but still wouldn't idle right. a shop somewhere posted this fix.i tried it and it worked. hope this helps.lb in this pic i used a black boot but it has a tendensy to pop off, so use a tooth pick, leave it long enough so you can pull it out

Sometimes it is hard to beat "Hilly Billy" or "Redneck" engineering. It really does work in some cases.

I'll give you an example: Once we lost the "pin" in the reverse lever system. No fear, we made one from a "nail" that was the exact diameter. Oh yeah, we flattened the end, drilled the appropriate hole and cut to proper length.

Sometimes it is important to think just a little "outside the box"...!:grin3:
 

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I think he means you should use a toothpick to clear out the jet like a pipe cleaner.
No, I have seen this before, it is to plug the air jets so it compensates for a vacuum leak or whatever else is actually wrong.
 

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Discussion Starter #17
I think he means you should use a toothpick to clear out the jet like a pipe cleaner.
No, I have seen this before, it is to plug the air jets so it compensates for a vacuum leak or whatever else is actually wrong.
Where would the air jets be on these carbs? My understanding is that you can only get to the idle pilots from the outside
 

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Where would the air jets be on these carbs? My understanding is that you can only get to the idle pilots from the outside

brownfoxx1 brought GL1500 carbs into the thread, whole different creature. Wouldn't fix your problem if they were the same.
 

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Discussion Starter #19
Where would the air jets be on these carbs? My understanding is that you can only get to the idle pilots from the outside

brownfoxx1 brought GL1500 carbs into the thread, whole different creature. Wouldn't fix your problem if they were the same.
Ah yes, that makes sense, thanks! I'll just keep on chasing it down. I'm not too concerned as of now, went for a 60 mile cruise last night and bike did great, issues aside, it's more annoying than anything
 

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There are few good carb rebuilders left. Most have or are retiring. A Randakk kit is a start. Float valves 9 out of 10 times can just be reused if they are original Honda. Cleaning properly requires an ultrasonic cleaner, but they aren't so expensive. Still, just riding with good alcohol-free regular gas and Seafoam or Techron added TO LABEL INSTRUCTIONS!! can often recover from mild issues. Don't over-dose with the additives, though - you can make things worse.
 
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