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Discussion Starter · #1 ·
I have redone my 1981 CM400C. I removed the air box and went with pods but retained the stock rubber runners. I also went with reverse cone megaphone mufflers.

I totally cleaned and redid the carbs. I used a jet kit from 6Sigma. They provided an 80/127.5 kits.

I can get the bike started but it stalls if I put the choke in. My air/fuel adjustment screws are about 3 turns out.

I have no intake of exhaust leaks that I can see. Gas has a bit of oil in it. The bike has sat since 1987 and I totally cleaned the tank, and washed with Marvel Mystery oil to prevent rust. I also put 1oz in each cylinder and rotated the wheel while in gear to crank the motor. The plugs get a little oily but I have new ones to install once I get it Tuned.

Any thoughts? I was thinking going up from the 80 but I wanted to ask the forum 1st. I have called and emailed 6sigma multiple times but customer service seems to be non-existent
 

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Proper jets for your bike are 72/118. If all was stock going to 75/118 would be suggested. Going to pods pretty much throws all that out the window but 80/127 should still make it run.

Whatever main jets you have has no effect on idle unless they are totally plugged. IIRC the correct initial setting for your mixture screws is 1.5 turns out but 3 turns out would make it rich and your symptoms sound like lean. If I understand you correctly the bike will start with the choke applied (knob pulled out) but dies as soon as you push it in. Some bikes will only start cold with the choke fully pulled out and require the choke be slowly pushed in over a minute or so as they warm up. Float levels will mess with this but yours are non-adjustable so shouldn't be an issue.

Best wild guess is that you have a plugged slow jet or one of the passages in the primary main/slow/idle jet circuit is plugged.

When you did the carbs did you use this?

https://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html
 

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I always spray carb cleaner through the low speed passages and verify They are open all.the way

Sent from my SM-J320V using Tapatalk
 

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Discussion Starter · #4 ·
Thanks for reply. When I cleaned I did not totally disassemble. I replaced all jets, needle, float, springs etc. I sprayed GUNK through out the carb. I spoke to a mechanic and he suggested the same thing you did...that I have a clog someplace. He recommended taking out the jets and running something thru the channel....like a guitar string (sorry), to clean it out. Followed by more GUNK.

I will give it shot!
 

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Thanks for reply. When I cleaned I did not totally disassemble. I replaced all jets, needle, float, springs etc. I sprayed GUNK through out the carb. I spoke to a mechanic and he suggested the same thing you did...that I have a clog someplace. He recommended taking out the jets and running something thru the channel....like a guitar string (sorry), to clean it out. Followed by more GUNK.

I will give it shot!
Your carbs are not clean! This is most likely your problem.
 
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