Issue between 2500 to 3000 rpm

[AshishNJ]

Hello.

Bike idles starts and runs great except for between 2500 to 3000 rpm. It seems to bog/hesitate in that range .

Any clues what to look at ?

[daves79x]

Refresh my memory - do you now have the stock exhaust and intake, with a STOCK air filter?

Dave

[AshishNJ]

all stock so far

[tevan]

It doesn’t have a k&n filter does it?

[AshishNJ]

No . Stock airbox, filter mo carb kits or aftermarket pipes

[daves79x]

That’s pretty low rpm for a pipe or K&N filter-induced flat spot anyway. Even one slow-speed circuit being plugged or partially plugged can do this.

Dave

[AshishNJ]

Dave.
Any recommendations where should I start ? All newly build carbs and no other issues other than this weird range of rpm.

[daves79x]

Hate to ask, but who exactly rebuilt the carbs, and when? Sitting over a few months time with ethanol gas will do it.

Dave

[AshishNJ]

Rebuild by person a few months ago when entire bike was restored. It may have sat for a month or two. Are there any additives I could try that would help ? Or could I try some carb cleaners ?

[daves79x]

Run some Seafoam through with a couple of tanks of gas. Best you can do without removing the carbs. WHO actually rebuilt the carbs is the key. Lots of guys think they know how, but few really do. My guess is something was missed. With correct carburation, a CBX should pull smoothly away in 5th gear from about 2000 rpm. No stumbles, no flat spots. Lots of guys have never ridden a CBX that was perfectly carburated.

Dave

[AshishNJ]

I will try sea foam. I bought bike from Mike209 . He did an awesome job restoring it. I am assuming he knew what he was doing

[itsacbx]

Im in Canada, eh and I have an identical problem on my 79......sorta......
My bike has a K & N and Kerkers and I had the carbs off 4X, yes you read that right....FOUR freaking times.
There was an upside - I can now do a carb removal in 20 minutes tops!!!!!
My initial problem was created by giving the carbs to my local Vintage Club guy who had just acquired a soda blaster - well f#@* me it took me a week to get what I thought was all the soda residue out of the carbs, add my Randakks bits and pieces and shove her all back together.
Bike started perfectly but then ran on 1 or 4 or 2 or 6 cylinders .
Long story short it now idels perfectly and runs unbelievably well except for the burble/miss/stutter at a point where I believe the pilot jet doesnt function anymore as it transitions to the main jet.
Im also starting to think it may have some megaphonitis from the Kerkers.
I also see there is some issues about the K & N.
Lucky me I have a set of stock pipes and a stock filter, so once the damn rain stops Ill try those before I take the carbs off again.
Al

[itsacbx]

Whats seafoam???

[tevan]

Sea foam is a brand of carb. cleaner you can get at the auto parts stores. It is available about everywhere in the states but I don’t know about other countries.

[itsacbx]

we have lots of carb cleaners here, just wasnt sure if it had special properties such as the ability to make bikes run perfectly without any effort......