Vintage and Classic Hondas

bench sync carbs. locking nut issues

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kid A

bench sync carbs. locking nut issues

So I'm having a problem with my lock nut when I'm bench syncing my carbs on my 76 cb750f. I've adjusted the big adjuster nut to where I get a enough clearance snug a 1/16th wire between the carb and the slide. But when it comes to lock it down with the lock nut, I barely have enough thread to screw on to. After that, when I test the throttle out it opens up to my clearance on my slide. Spring issue? I'm not sure what is going on. This is my first time messing around with carbs too.

TOOLS1

Re: bench sync carbs. locking nut issues

Administrator

What is happening is, you are setting them too low to start with. Try just setting them all to have one thread above the locking nut, this is how the Factory Service Manual says to set them. Then sync them with a set of gauges after they are back on the bike.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
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kid A

Re: bench sync carbs. locking nut issues

Ahhh, I see now, I tried that and it worked just fine! Better never skip a step next time! Thanks.

realjakebaker

Re: bench sync carbs. locking nut issues

In reply to this post by TOOLS1

I have stripped out the threads in my lock nut and need to see about getting a replacement. I have a 1980 cb750c. Do you have any idea what the pitch or thread of the screw is so I can try to find a replacement nut? nothing I have on hand seems to be working. The OEM Honda part has been discontinued, but I did see one on eBay for around $40. I thought that was a little pricey for a screw, a washer, a spring, and a nut.

1980 Honda CB750C

shinyribs

Re: bench sync carbs. locking nut issues

Administrator

Your best bet is to carry it in to a hardware store and match it up.

Home Depot sells a hardware gauge for a few bucks. Some more industrial places may carry a better version. The one i saw at Home Depot was pretty flimsy. I bought mine for a local place (Automotive Fasteners) and it's real sturdy. Oh so handy to have around.