Topic: 1982 CB900f - Reving, Redline Problem

[eofa]

Here's some background:

1982 Honda CB900F

Stock carbs have been rebuilt. Sonic cleaned, lubed and new seals springs, even friggin' stainless allen screws through (cosmetic of course.) The only thing I haven't bought new is the float needles, float valves and plastic float bowls. The floats are not adjustable in my stock keihin carbs. Nor are the float/slider needles adjustable. As much as I hate the huge plastic annoying airbox, I put that back on since I was trying to use pods.

I have a 68 in the primary and a 105 in the secondary. Pilot screws are turned out to 2 1/2. Hook it all up, idles great, but give it a rev and it will stick and 2 rpm and then continually increase to redline. Will not come down unless I quickly turn out the fast idle adjustment then quickly screw it in for when it falls and I can keep it at a 1rpm idle.

It's not the cables, it's not the manifolds, I can't figure it out. Trust me it's not the cables. There plenty of slack in them. Choke is closed properly. I know my bike is running really rich because my plugs have becoming black carbon fouled. Sprayed plenty of carb cleaner around the manifolds to see if there's any air leaks. No change in idle sound.

I can't figure out what the hell is the issue.

The correct push/pull is set up correctly. I'm thinking it's more of a fuel flow issue now.

Here's a video of what's going on:
IjcIjnET0VY[/youtube]

[cb650]

Is that stock jetting on the 900?  Dont sound right.  Did you clean the carbs while they was off?  Tank clean?

[eofa]

Rebuilt, sonic cleaned. Everything has been taken apart and new everything from springs to diaphrams. The 68, 105 are the stock jets for this bike.

[cb650]

Are the idle jets removable?        the mains are 118 on the 650 in  82 so thats why I was wondering.   Did you ask on the DOHC site?

[somesuch]

not that it would cause the rich running that makes the plugs black, but the air cut-off valves on the side of the carbs have thin rubber diaphragms that at times get holes in them....also what about needles, are they shimmed/worn/etc. are the black plastic covers over the air corrector jets under the top round cap in place? rubber plugs covering idle jet installed?

[somesuch]

BTW, do not be afraid of the pods on those bikes. I have had many CB900F bikes, and many had individual K+N filters on them and ran great with K+N jet kits (from long ago though) K+N changed their kits over the years, older ones had the glue-in air jet restrictors, the newer ones do not. Those bikes become much more fun to ride with the pipe/jet kit/K+N filters. ..... lighter, rev quicker, and a lot more power up top.

the kits had slide springs, drills to drill out the slide lift holes, main and slow jets, and air corrector jet restrictors.

[eofa]

I've had so many issues at this point, I just want to cancel out any problems with the stock setup. Even though I know the engine has a big bore kit on it and a Supertrapp exhaust. The jets are still the stock ones. I just need it to get me through this season because over the winter I'm getting a set of CR33's.

[somesuch]

I do not remember the jetting I ran with a pipe and the airbox, but I think it was something like 72 112-115

[Iron Spade Cycles]

Funny I have this same bike and I'm about to add the K&N pods as well but what you have going on doesn't at all sound like an air leak, although it should be. If your getting black plugs your running rich, and an air leak you'd be running lean, IE white pugs. The slow jet adjustments are really just to fine tune the idle jets and be a tell tale if you need to go larger or smaller in size (idle jet). Are you certain when you rebuilt the carbs that you got the butterfly valve plates back on correctly? Were there seals on the shaft that might have been omitted? Somewhere your getting extra vacuum causing the CV slides to open and draw more fuel in, stock jets with pods and a pipe should be getting a really lean plug reading (white). Too many factors are not adding up.

Any suggestions on who sells the K&N jetting kit for these bikes? I'm thinking I might need one.

Good luck. Later Travis

[eofa]

I pulled the carbs all apart again on monday and tues. There were some issues. 2 pilot jet setups were installed wrong.... tiny o-ring/washer were reversed. I also cleaned them out again. There was a little left over gunk in the slow jets. I also did the bench sync high E-String method to get them all matched up as close as eye-ball possible.

Waiting on new float needles, airbox cleaner and I'm going to do a compression check on the engine.

For the jets, you might try this place. I bought my insulator/manifold booties there. http://www.dynoman.net/carb/dynojet.html

Also: this carb rebuild manual is awesome and detailed:
https://docs.google.com/gview?url=http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revD.pdf&pli=1&chrome=true