78' cb400 no power at low end

gsf1200R said:

if not

ur best friends in Carb Country are

Compressed air.

Guitar string G or B.

Carb cleaner. a carb solution vat if possible but pinsol should work.

grease for the boots.

carb part names: Jet, Pilot Jet, Jet Needle, Float , Float valve. diaphragm, Float bowl, Float Bowl Drain Screw. as well there are o-rings and and gaskets (which are all RUBBER) and springs. im sure im missing things
take note of how the parts come out where they came out from. hoses included.
when u pull the pilot screws take note of how many turns they turn in and then go all the way out with them.

take the mother fuckers apart down to the bones, remove all rubber i repeat all rubber.
do not separate the carb banks EVER.
theyre a bitch to take apart and put back together right.
soak all needles jets jet needles, floats carb bank in cleaner for 1 hour to 24 hours depending on how bad they are.
( this chemical will Fuck up the rubber so be sure its all removed.)
then pull all the parts out.
spray dry them with compressed air, then take all the jets and run the guitar string thru them even the holes in the emulsion tubes.
then spray all parts with Spray Carb cleaner and let it set in.
then air dry yet again.

now reassemble the badboys taking note along the way of how they came out where they came out. TAKE PICTURES IF YOU HAVE TO not everyone has Photographic memory. set your pilots to where they were

most carbs have 2-4 brass screws called jets in the carbs that atomize the fuel liquid into tiny tiny particles these more than likely are the Culprits to your problem that and passages in the carb body.

then reverse the order of operation. go back together with the som bitches. also clean or replace the air filtration device. the carbs to the manifold good n tite. then bolt the Air box to the carbs good n tite. get fuel flow to the carb bowls via tank or fuel bottle. use the drain screws to see if ur getting flow.

then turn bike on, pull choke and letter rip. (in neutral of course) (dont ask me how i know)

now a sure fire way to see if you got a air leak of some sort spray the rubber intake boots and around the air box with brake clean or spray carb clean and if the RPMs change ur a leakin and the ship wont sail properly. if the rpms stay the same your winning the game

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kawibobber said:

hey, why don't you try reading and you'll see the first sentence of this post says "AFTER cleaning the carbs on my 1978 Honda cb400 the bike is still having problems from beginning to half throttle." applying some simple comprehension skills would tell you it sounds as though he took gsf1200r's helpful info to heart and cleaned his carbs.

here's a little bit of info dan didn't mention that i thought may help determine the problem...i helped dan pull the carbs and he then took them apart, soaked everything in cleaner that wasn't rubber, ran guitar string through it all, and took careful notice where everything went and how many turns it should sit at. we then got the carbs back in and dan took it for a spin and it ran like a top, save for wanting to bog down at idle. no throttle hesitation whatsoever. however, when he pulled it back in the garage, we noticed gas dumping out the right carb, and we determined the hinge on the float was stuck which was flooding it, hence the bogging. dan has since pulled the carbs again to fix the hinge, and now that it's fixed he is having problems with hesitation again.

now, my thought is (though i'd need some more knowledgeable input) since there was not throttle hesitation when the carb was getting too much gas, but is hesitating again now that the float hinge has been fixed, shouldn't it just be a matter of tuning it so that it gets more gas in the mix? jumping up a jet size or something as dirty_f2 suggested?

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thaOrleanyte said:

Why dont you try reading........


after cleaning my carbs could mean he sprayed the outside with windex

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dwallz006 said:

after cleaning the carbs on my 1978 Honda cb400 the bike is still having problems from beginning to half throttle. Past half throttle the bike runs and responds like a champ. Petcock was cleared of gunk, no leaks as far as I can tell anywhere... added sea foam to gas today hoping that might help over time. what should I try now? the carbs are over 30 yrs old - should I just buy new replacements? or try to rebuild them? HELP!

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marty.zellerbach said:

Have you found a solution? I have the same problem...

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