Another Amateur Carb Jetting.

[GreenoBeano]

I'm having a hell of a time trying to get my carbs right on this bike.
I am a complete noob when it comes to this stuff, but theres no other way to learn other than doing it!

It has a K & N lunch box, shorty exhaust 150 main, 40 pilot & 2 washers on the needle.
Recently went through and cleaned/replaced all the gaskets.
 

I can get the bike to idle with the choke on at about 3-3500RPMS, when i let the choke off it drops to under 1000RPMS and dies out unless i blip the throttle. It also has back fired through the carb.
I did drive it around the block with the choke on, and while on decel it backfires through the exhaust pretty badly.

I've sprayed WD40, all over to check for vacuum leaks, new plugs, fresh gas.
I didn't think this combo was uncommon, looks like the K & N filter was a pretty popular upgrade.
I don't have the stock box to try that, nor the O/E Can. I got the bike this way as a non runner.

I'd appreciate any help, i looked on the wiki to try and follow what has worked for others.
Am i missing something? are my adjustments way off?
Bike is more of a cafe racer, so i'd really like to try and get the K&N working for aesthetic reasons.

Again any thoughts or a step by step to help eliminate some possible problems, mucho appreciated.       

[Iolo]

Idle speed, with the choke on, at 3-3.5k is too low. Ideally, on a cold start with full choke, the bike should be idling at 5-6k.

Otherwise I'd double check that you replaced all the o-rings / seals. Ones that are missed regularly are the ones included under the carb slide caps, idle mixture screw assemblies, and carb boots.

Did you set the idle mixture screw settings correctly? - I just finished rebuilding the carbs on my 1989 Gs500e. 3 turns out for each one worked fine on my bike with 40 pilots, an aftermarket exhaust, and pod filters.

[GreenoBeano]

Thanks Lo, I didn't realize there was o-rings under the mixture screws. I was wondering why there were some extra orings in the kit  . Just to clarify, should go > oring > spring > Mixture screw?


I'll replace those, and report back!
thank you for the help! 

[Iolo]

Just to clarify, should go > oring > spring > Mixture screw?

Almost correct. It should be:
O-ring > washer > spring > idle mixture screw.

Without the O-rings on the mixture screws, the carb will leak extra fuel into the cylinders and make the bike run very rich. This may be the cause of the backfiring you experienced (i.e excess unburnt fuel being dumped into the hot exhaust headers).

Take care to remove the old O-rings and washers after taking out the idle mixture screws. The old O-rings and washers tend to get stuck in the carb body. After removing an idle mixture screw and spring, you can dig out the corresponding old O-ring and washer with a bobby pin or piece of stiff wire.