The International CBX Owners Association

Can you change the accelerator pump without ....removing carbs?

No

confound it!

There is much more to getting the accelerator pump circuit working than changing the diaphragm. If the carbs are working fine otherwise, I'd never remove the carbs just to work on the accelerator pump. Most pumps stop working effectively within a few thousand miles anyway. There is just too much fiddly linkage associated with the system. Oil and road grit accumulate around the center of the carb bank and gum up all the moving parts of the system, plus the pump diaphragm gets stiffer and stiffer as it ages. Very few carb sets I see still have a working accelerator pump.

Dave

CBXTed wrote: ↑

Wed Mar 27, 2024 1:34 pm

Can you change the accelerator pump without ....removing carbs?

In lieu of what Dave mentioned what symptoms are occurring that you think the accelerator pump isn't working properly?

Indeed - I should have started out by saying that if you are having running problems, it likely is not due to the accelerator pump. When were the carbs last completely rebuilt?

Dave

From My own experience from a few years back is when there is a good flat spot and stumble as you accelerate moderately toward 3-4000 RPMs almost always
Bought kit to rebuild and problem solved starving for fuel under load and demand
Credit Daves79x with the diagnosis

Just FYI: My 82 has always had a 'flat' spot between 3k and 3.4k. Not a stumble -- just a flat spot. Could be wrong (not the first or second time!) but it doesn't really seem to me to be carb related. My thought is that it's an exhaust thing. (Mine is stock) If I'm accelerating through that it is hardly or not noticeable. At least, to me. Acc pump doesn't affect this for me. Mine pumps like a fire hose. Just serves to waste gas. But, it does prevent stumble!

Thanks all, the bike is a school bike I acquired with 2 miles on it and as best I can tell, never had gasoline in it. After repairing petcock and brake job, it started right up but stumbles off the line unless I really bring the revs up and slip the clutch. But, after 15 minutes or so, that stumble disappears, and it runs normal. It seems flat when accelerating from say 3000 thru 6000 but better up top. I am running sea foam thru it and I have about 60 miles on it...hope to avoid a carb rebuild but whatever it takes.

Viton will be your friend, sooner or later.

Did you check the ignition advancer? Sounds like it may be frozen. But you are not going to avoid the inevitable - a full carb rebuild.

Dave

School bikes can't be trusted. I've had 4.
EVERYTHING needs to be inspected and verified, especially the carbs which had fuel in them at some point and not properly prepped for long term storage.

You'll have to bite the bullet sooner than later.

i hear what you are saying. I was a mechanic at the "House of Honda" in Mamaroneck NY when the CBX came out. Uncrated the first one for our Snap-On tool man who pre-tipped me a ratchet set to be careful with his bike. I put it together, did all the checks, fueled it and rode it. I don't think that happened with my school bike. I don't understand the whole process because the JH2 preamble is missing from VIN stamp which means they were destined to be school bikes from the get-go...so why would a dealer do a prep and test ride? I don't know but as best I could tell from looking at the petcock and inside the fuel tank as well as the float bowl drains, there was never gas in my bike and the spark plugs looked out of the box new. The bike runs really well in most ranges after a good warmup. I like the idea of checking out the ignition advancer...maybe it frees up after full warmup? Very strange that a bike would take 15 minutes to warm up.

No '81 had JH2 stamped - just on the VIN tag. No '81 was destined at the factory to be a school bike. As far as whether they were ever actually serviced as new bikes - who knows? I've rebuilt several sets of school bike carbs that 'never had gas in them'. There is usually no free lunch with CBX carbs. Just bite the bullet and go through them.

And as JR correctly points out, check everything else too.

Dave

Thank you for clarifying my misunderstanding of the JH2. Bike is running beautifully and the "stumble" disappears even sooner in the warming weather here in Philly (55f vs 75f). Also leaving a touch of choke for the initial part of the warmup eliminates stumble. It feels like "normal" cold engine performance except it takes too long to "warm up"....like 5 to 7 minutes. Ignition advance mechanism moves freely. Ive got 100 miles on on the clock!