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750F Slow Return To Idle


CBVFRbikeboy

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At the point you're eliminating the unknowns... if the condition of the O rings are unknown then you might entertain replacing all 4 to eliminate the possibility of bleeding... I've had great success getting the little buggers out by shaping a hook out of .032 safely wire or a robust strand of copper wire...

sure thing. I have had them out when I put the carbs through the ultrasonic bath, and did exactly as you suggest with the wire hook. They looked OK, so I put them back in. Just awkward to get them out on the bike :wacko:

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  • 4 weeks later...
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Still searching frog. I did check the valves and most were pretty good.  #4 intake were both a little loose, which gave me cause to thank that that could well be the problem. I buttoned it all up and fired her up, but the problem persists. I'm about to pull the carbs off again and adjust the float levels down a bit. As far as I can tell, they're at 7mm, but in case I'm measuring wrong I'll set them all to 8mm and see what happens. Nothing to loose. :-(

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  • 2 months later...
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My problem with the pilot screws is that 2 of them, (carb #1 and carb #2) seem to be stripped: they don't come out and they don't move in to seat.  The other two are fine. I can't understand how the bike even ran at all, but it was strong up to about 8000 rpm. I'm cleaning and rebuilding the carbs because the P.O. left gas in the tank for years.  Any tips on removing these would be a big help. I want to get this right the first time because of the "fun" of getting at the carbs.  Thanks in advance.

 

Stan

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That's gonna be tricky :-( I haven't had to do that, but perhaps a left-hand drill, or easy-out might be your only options?

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If you do find the solution I would be glad to hear it. When I watched your youtube vid, I didn't think it was too bad. It does return to idle and I don't think it's that slow.

My VF500F would be similar. However if I screw in the pilot circuit adjusters, my bike will stop, unlike yours. I expect this is what you need to determine, how the bike will run with the adjusters screwed home.

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  • 1 month later...
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Well, it seems I've cracked it. Turns out #3 was cutting in and out, and I could remove the plug lead without having any effect on the idle. Good, I thought, electrical. I replaced my coils, I replaced the spark units, replaced the leads, swapped the (new) plugs around, checked voltages and resistance everywhere. Even managed to squeeze my compression tester down that tunnel. 150PSI on both rear cylinders. Nothing. Spark was good at the plug through all this, so I returned to fuel. Put another set of carbs on, but before I did, I swapped #1 and #3 boots around, and reversed them.

 

Bingo! #3 is firing fine, and will cut the revs if I remove the lead. Idle is nice and smooth, and it now behaves properly. Too wet to test ride, but I'm confident I've nailed it :wink:

 

Thanks for all the suggestions gang.

 

cheers

idle.mov

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