cb450/500t Keihin 751A carb rebuild

So lets start off with why i am deciding to rebuild the carbs. When i first initially took the carb apart to clean it out everything looked pretty good. I soaked all the jets and went through with a couple threads of electrical wire. Then on the carb body it self i sprayed carb cleaner through all the wholes to make sure that it not clogged. After cleaning it all up I put it all back together. Benched Synced it, then put it back onto the bike. i attached the vacuum port stem on the carb to attach my manometer to fine adjust the sync.

I got the idle to sync at 1000-1100 rpms. But as i was doing so i noticed white smoke coming out of the left exhaust, I figured it might be because i haven't set the A/F mixture screw. So i did that. then I also synced the carbs at 3000 rpms following:

http://www.hondatwins.net/forums/56-fuel-supply-carburation/10404-1976-cb500t-idle-2.html

Got it all synced at 3000k. But still have White smoke.

After talking with 66Sprint thinking it might have low compression issues. I did a compression test. I let the bike warm up, I connected the the compression gauge, open the throttle and started the bike, both sides read roughly about 188psi. Which I believe is still in spec.

I also did a a vacuum leak test. and everything seem to be ok

i Also did a float adjustment using

http://www.hondatwins.net/forums/56-fuel-supply-carburation/750-float-level-adjustment.html

i also noticed that the header to exhaust connection has smoke coming out of there as well. i took it apart and noticed that as much as i tighten coupling i could still pull the header from the exhaust. so i don't know if that could be an issue.

so now i'm back to the carbs. I think i'm just gonna replace all the jets in the carb.

Unless anyone else has any suggestions on what else i can check.

1) where can i get a carb kit?
2) what carb rebuild kit to get?
3) if i just wanted to upgrade the whole carb unit period, what are my options.

i would post a picture of the 2 plugs and some more history how long have you owned the bike miles on it ect

when did the smoking start

you said that smoke was coming out the exhaust joint did the smoke start suddenly or has it always been there?

where are you located

I've had the bike since march this year. it has 7300 miles on it. I just replace the ignition could with dynas, it has brand new points on it. the valve have been adjusted. timing has been set, it has a sparckmoto R/R, new spark plugs,and the inside of the gas tank has been stripped and recoated.

The smoke came recently, right after i took apart the carb and cleaned it up and cleaned the jets.

this is where the smoke is is leaking from

did you measure/set the floats on the carbs

are you sure the chokes are connected properly and working can you check ?

does it smoke with the air filter box off?

I did the float adjustment according to this:

http://www.hondatwins.net/forums/56-fuel-supply-carburation/4612-carb-syncing-help.html

there is now smoke coming from the air filter box.

I'm almost 99.8% sure the choke is installed correctly but i can check again and give an update.

are you driving the bike like this?

so you set the float at 20mm?

No i am not driving the bike but i do turn let it run every other day.

yes i set the float to 20mm

Hmm this sounds really strangely familiar to me... I had the exact same issue with my 450, spent 3 months trying to diagnose it. Final outcome? Microfracture in the main jet holder. Try this, run the bike, let it warm up until it starts to smoke and stumble (dont rev it), shut it down, then stick your finger into the carb and feel around where the needle comes down into the main jet. Are you feeling a lot of fuel pooling around the needle? Now check the side thats running properly, I bet you wont find any fuel there. If you check the plug and its really black even though youre suuurreee that both sides are synced, I would bet this is your problem.

Also a word of warning, if this is your problem, and you end up buying a new (used) set of carbs, MAKE SURE THE CHOKE PLATE SCREWS ARE TIGHT, preferably replace them and locktite them in place. My 450 got exactly 5 miles of road time after a full rebuild and finally fixing this issue. Ill give you one guess as to why

However, you might as well try the rebuild kit first because it might just be a worn needle something. Any rebuild kit for a 450T or 500T will work, the only difference will be the jet sizes if the kit comes with jets, and the 500T kit might have more gaskets for the extra air flow control valve on the side (I forget the exact name of it, but it regulates the vacuum under idle to help smooth it out). This one will work for you:

http://www.oldbikebarn.com/Honda-CL-CB450-68-71-Carb-Repair-Kit

or you can find one on ebay or other old bike part sites.

If you want to upgrade the carbs, the ones that come on the 500T are a good choice, they provide a bit smoother idle but are otherwise identical and bolt right up. You can also look at the Mikuni VM carbs, which are slide carbs rather than CV carbs, but I wouldnt recommend going that route as it will be expensive and the benefit you see out of it will not be that much.