cb 400 engine backfiring

this is a bad video because the backfiring is usually a lot worse than this. im posting this and one other in the hope of a diagnosis of the problem(s)

Category:

Autos & Vehicles

Tags:

• cb400t
• cb
• 400
• cb400n
• honda
• problem
• mechanic
• repair
• help

[alanshark]

which carbs did you end up buying? my 400t is doing the exact same thing and it won't even start unless I give it full throttle and choke. shuts off as soon as i let off the throttle.

[007wolfen007]

sounds like an air leak - check the inlet rubbers for leaks. also have you changed or checked the idle screw?

im not entirely sure the tyype of carbs i bought i just went to kelso and bought carbs that looked like they might have done the job and they did. the outlets of the carbs were a different size but all the rest was the same and they worked perfectly, all i had to do was overtighten the carb rubbers to make a good seal.

[nedopisa]

Hi, where have you found the spare parts for the carb? I also have a problem with the ignition, and i think the problem is in a fuel regulation valve, with a spring and a membrane which is now broken. Can I find this part somewhere?

[007wolfen007]

hi, i actually bought a couple of carbs from ebay (not perfect matches but they did the job). as for getting the spring and diaphragm i think your best bet is those carb repair kits you see on ebay - they usually contain the diaphragm and the spring as well as the seals and float needle. it cant hurt to replace em if there broke. i would just buy 1 or 2 of the kits, depending on whats broke. if you still have problems post on here and ill try and help.

[007wolfen007]

well this is the final post on this video.

thanks to all that have helped - the problem is now aced. a replacement set of correct carbs and a bit of tuning and balancing has killed the backfiring bug. she has another bug but i know whats causing it. once again thanks to all those who helped.

[bobctx]

i think valve ratting?

[InstantChicken]

But be careful. The engine is more powerfull with more air, but is more voulnerable to critical brakedowns such as a burned hole in the piston.

Its better with a fatter mixture then.

[InstantChicken]

Im not the most experienced, but i know that air explodes in in high temp.

I think your mixture is too thin which make the engine very hot caused by the lack of cooling from gasoline, and make the air explode.

Turn the pilot adjuster screws all the way in on both carbs (when the engine is turned off of course), then turn them out 1½ turns Excactly. This is the factorystandard.

Soot=too much gas=Turn pilot 1/4 out=more air

Adjust both of them while the engine is hot after some rides.

[bricktop11]

ITs either timing or valves simple as that

[mauromoita]

da hora esse barulhão que ela faz mano!

Great this sound!  brother!

[splatmaster]

hey man i just bought a cb400t not too long ago and had the same prob. well this might sound stupid (especially comin from a 15 yr old) i just ran it every say and it seems like it blew all that junk outa the carbs and now they work great.. ?

[turtlemann14]

check your valves and air mixture