jetting recommendation please

[super jim]

I am purchasing a new to me CBX. 1980 with 14,900 mile in excellent condition. Stock except a kerker 6-1 header, K&N air filter and dyno jet kit. It has been sitting for a while and the carbs need to be rebuilt. A local guy is about to do the work. He is former Honda dealer mechanic and has done CBX carbs in the past and is supposed to be very good on carbs period. My question is: Should we stay with the Dyno jet kit or go with factory jets and needles? Then what sizes and needle settings? I am at 500 ft elevation in SC.

Thanks, in advance for your help.

Jim

[daves79x]

Jim:

The Kerker has almost no effect on your jetting. The K&N has more, even though it's in the stock airbox (I'm assuming). If the jet kit in the carbs is a stage 1, it might be close, but a stage 3 kit will have them way too rich. And further, I can't tell you how to tell the difference. Personally, I'd go with stock needles and the 110 mains the '80s came with. Plenty rich enough on top. You can shim the needles .020 with small 3mm washers to richen up the low end a bit. You have to pocket the aluminum hold-down screws with a 1/4 inch drill to give the shimmed needles their 'float' back - that is very important. Otherwise, stock stuff works the best with your set-up. Oh - make sure the carbs are VB62. Other models had different size mains stock.

Dave

[Jeff Bennetts]

I am purchasing a new to me CBX. 1980 with 14,900 mile in excellent condition. Stock except a kerker 6-1 header.

Jim

I'm not sure who started the whole Kerker dealio but Kerker hasn't made a CBX exhaust systems in many years, what you most likely have is A D&G 6 into 1 with a Kerker canister on it.

As usual, Dave has given you good advice on the carbs but I don't find it necessary to pocket the aluminum hold down fasteners, just wrap the threads 2 or 3 times with Teflon tape, tighten it down until the needle just stops moving freely then back it off until it does move freely.

[rider3]

Ok I gota ask why is very important that the needles remain loose after shimming. I just got done doing this to my 79 to get rid of a rough spot right at 3000 rpm. worked great, very smooth now but the needles were tight when I reinstalled the slides. Did not notice any difference at idle or any where else, so I assume the slides are closing fully.

[daves79x]

The needles can bind in the needle jet if they aren't allowed to float - most of the time they don't, but Honda designed them that way for a reason.

Dave

[Larry Zimmer]

Essentially, reason being that all the tolerances can't be held that would be required to have the needles move freely in the jets if they are set tight in the slides. As Dave said, if they happen to get positioned OK, no harm. But, if they are off a bit, they will rub to some degree in the jets. You might not notice it; but, they will rub; and, eventually, wear either the jet, the needle or both.