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Discussion Starter · #1 · (Edited)
Greetings from North California. this looks like a great group!

we have another Honda two wheeler. my first motorbike ever was an sl100 turned into a dirt bike. it was almost indestructible and was what i learned respect for life, limb, speed and aerial trajectory on. it never died- -c'est la vie!

we just picked up a 1980 cm400t. they said it was crashed up scrap but it actually isn't bad. the shifter rubber has a slight rash and the speedo took a hit but low miles and very clean internally. the main problem is that it's been subject to some sloppy tooling of some would be hooligans.

cylinders cleaned and oiled, carbs cleaned up/jets and circuits cleared and blown out, turns over fine and has spark (kinda weak looking) filled up float bowls with gas, pulled choke (choke cable not yet attached properly but can pull it closed for test purpose) does not start yet. had a few good pops then nada.

It seems the choke is essential to startup with these carbs and the accelerator pump type thing on one side looks involved BUT.. upon pulling the choke closed and/or opening the throttle, the pump shaft does not move. I think something is missing in the choke assembly that activates the accelerator pump shaft??

that last part was a question for the pros out there. i'm finding these carbs had varying choke setups when exploring diagrams online.. should i skip this part and get some 34mm mikunis?:)
 

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The accelerator pump is activated by the throttle, it's not affected by the choke.

If you got these carbs right on the first try without a guide you are truly an anomaly. Here's a tutorial that could help you out on that count.

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

Even so, notwithstanding some major plugging, it should start and at least idle even in it's current configuration. While you're cranking it give it a shot of starting fluid. If that makes it catch you've still got fuel problems.

Your pod filters and the modified exhaust will precipitate the need for some jetting changes. This might give you an idea of where to start (your stock jetting is 72/118).

https://www.hondatwins.net/forums/6...4-cb400-cv-carbs-pods-how-make-them-work.html

From the looks of that right side spark plug wire there has been some other tinkering done. Hard telling what all you're going to find, but here's a guide that will suggest a few places to look:

https://www.hondatwins.net/forums/6...n/16105-basic-checklist-new-you-old-bike.html


Did you get a title?

Oh yeah, welcome to the group.
 

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Discussion Starter · #5 ·
thanks JT!

there must be some accelerator pump actuating pieces missing unless its vacuum actuated.. going to get the spark stronger before i fiddle with carbs any more. yes, it came with a title.
 

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The accelerator pump diaphragm has a rod which extends upward. The rod is actuated by a lever connected to the throttle shaft. Sorry I can't seem to find a good picture.
 

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Actually, if adjusted properly, the accelerator pump squirts a shot of fuel into the throat just as the throttle is opening from idle to assist in the fuel supply transition from the idle jet to the slow/main jets.
 
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