The International CBX Owners Association

Well, I've gone where no man has gone before: I am the first person to ever remove the stock air box from a Honda GB500 and replace it with a K&N filter mounted directly on the CV carb (well, at least the first to publicly announce it). I have also fitted a custom exhaust and a Factory Pro carb kit. The exhaust and carb settings were worked out by a fine fellow down in California and I've copied his settings for my baseline. The bike runs great, except when you barely open the throttle. She surges, pops, stutters and generally runs lousy until you crank on the throttle. Fortunately, I only run like this when puttering through traffic and stoplights, otherwise the performance is exceptional. Here's my question for you CBX carb gurus: when you switch from the airbox style filter to individual pod filters, what is typically required to retune the carb? I'm a novice with CV carbs and the combination of mixture screw, pilot jet, needle, and main jet is a bit daunting.

My initial carb settings with only a Supertrapp muffler/header was: Pilot 48, stock needle with one shim, 148 main jet. Performance was decent but there was relatively poor roll-on throttle response until you really opened it up some.

The recommended settings from the fellow who designed/manufactured/tested the custom exhaust is a 52 pilot, Factory Pro needle on the 3rd of 5 clip positions,a 155 main and the mixture screw at 2.5 turns out. He lives at 1800 feet of altitude. That's what I'm running now and everywhere through the rev range is great, except that just-off-throttle position. I don't know if I should increase the pilot jet size or go down, or what. The only difference in my bike and the exhaust guy's is I am running a single K&N filter on the carb with no airbox restriction.

Sure will appreciate any help or advice you can provide.

Eric

I may or may not be able to help.

What sort of choke does it have? Actual choke plates or an enriching circuit?

When the choke is slightly closed, how does it react?

I have had bikes, where I ran without any air filter and they would stumble of idle. If a little choke cured it, it meant it was helped by a richer mixture and larger idle jets were needed. You may find that or that something is a little clogged, but didn't become a problem until more air was added to the mixture.

ericfreeman wrote:Well, I've gone where no man has gone before: I am the first person to ever remove the stock air box from a Honda GB500 and replace it with a K&N filter mounted directly on the CV carb (well, at least the first to publicly announce it). I have also fitted a custom exhaust and a Factory Pro carb kit. The exhaust and carb settings were worked out by a fine fellow down in California and I've copied his settings for my baseline. The bike runs great, except when you barely open the throttle. She surges, pops, stutters and generally runs lousy until you crank on the throttle. Fortunately, I only run like this when puttering through traffic and stoplights, otherwise the performance is exceptional. Here's my question for you CBX carb gurus: when you switch from the airbox style filter to individual pod filters, what is typically required to retune the carb? I'm a novice with CV carbs and the combination of mixture screw, pilot jet, needle, and main jet is a bit daunting.

My initial carb settings with only a Supertrapp muffler/header was: Pilot 48, stock needle with one shim, 148 main jet. Performance was decent but there was relatively poor roll-on throttle response until you really opened it up some.

The recommended settings from the fellow who designed/manufactured/tested the custom exhaust is a 52 pilot, Factory Pro needle on the 3rd of 5 clip positions,a 155 main and the mixture screw at 2.5 turns out. He lives at 1800 feet of altitude. That's what I'm running now and everywhere through the rev range is great, except that just-off-throttle position. I don't know if I should increase the pilot jet size or go down, or what. The only difference in my bike and the exhaust guy's is I am running a single K&N filter on the carb with no airbox restriction.

Sure will appreciate any help or advice you can provide.

Eric

Will, thanks for the reply. The carb uses an enrichener circuit that has had no effect on the off-idle roughness until it's engaged enough to cause further stumbling. The carb is completely clean. I'll be starting with the mixture adjustment first, since it's external and easy to get to.

Eric