Author Topic: cb400 poor acceleration (Read 13849 times)

txterror · « **on:** January 26, 2013, 12:07:55 PM »

Just finished getting bikes intake system back to stock. Went for a ride and it had poor acceleration. Removed air box lid and it ran good. Bike is stock. Filter is new. My question is, what would cause this and what should i do to solve the problem. Carbs hav been cleaned as well as gas tank. 75' cb400

dave500 · « **Reply #1 on:** January 26, 2013, 12:14:04 PM »

is it a genuine filter?some aftermarket ones may be more restrictive?go over your ignition.

txterror · « **Reply #2 on:** January 26, 2013, 12:34:44 PM »

It is after market. Its ok to run bike without lid?

hoodellyhoo · « **Reply #3 on:** January 26, 2013, 12:40:56 PM »

In a nutshell, you should be okay without the airbox lid. You'l just get a little more intake noise

I wonder, though, if the problem is more related to your seat. Sometimes they sag a bit and end up chocking the intake snorkel at the back. If this is the case, removing the airbox lid would certainly allow the engine to breath again.

txterror · « **Reply #4 on:** January 27, 2013, 08:09:19 AM »

I think hood was right seems like seat is choking snorkel

txterror · « **Reply #5 on:** January 30, 2013, 06:27:15 AM »

Seat isnt the problem, what might be my culprit? Bike starts and idles fine but stumbles when accelerating.

hoodellyhoo · « **Reply #6 on:** January 30, 2013, 09:25:28 AM »

What condition is your igntion system in? Is the timing set?

txterror · « **Reply #7 on:** January 30, 2013, 11:07:51 AM »

Ignition looks good to me, but i could be wrong. Ill try to adjust timing, again. Ill also try to reset points. I will update tonight. Thanks Hood

dave500 · « **Reply #8 on:** January 30, 2013, 11:23:50 AM »

try it with the actual filter removed?

txterror · « **Reply #9 on:** January 30, 2013, 11:45:34 AM »

Hi dave, If it does run better with filter removed. What should i do about filtration. Filter i have in there now is new, I forget brand.

flybox1 · « **Reply #10 on:** January 30, 2013, 11:51:43 AM »

Quote from: txterror on January 30, 2013, 11:45:34 AM

...If it does run better with filter removed. What should i do about filtration. Filter i have in there now is new, I forget brand.

an option is to leave the filter in there, and go with smaller main/pilot jets...
what sizes do you have in there now?

dave500 · « **Reply #11 on:** January 30, 2013, 11:55:06 AM »

its an aftermarket filter and its new so if it runs better removed its a piece of crap,dont swap the factory jetting to compensate for a crap filter thats just dumb,use a genuine one maybe,but go over your ignition fully before you tamper with any carb settings,read and understand reply #1 !

flybox1 · « **Reply #12 on:** January 30, 2013, 12:13:49 PM »

Quote from: dave500 on January 30, 2013, 11:55:06 AM

its an aftermarket filter and its new so if it runs better removed its a piece of crap,dont swap the factory jetting to compensate for a crap filter thats just dumb

absolutely agree dave, crap filters are crap filters, but seeing that he just switched back to an airbox, he may have oversized jets in there that could be too rich for a OEM honda or oiled K&N....hence the question...what sized jets do you have in there?

dave500 · « **Reply #13 on:** January 30, 2013, 12:20:26 PM »

ok,in the first post he states bike is stock,after going over the ignition you might drop one bowl and check the numbers on the main and slow jet if its still has poor power,is it blowing black smoke with black sooty plugs?

txterror · « **Reply #14 on:** January 30, 2013, 12:22:20 PM »

Jets are stock. no black smoke, but blk plugs

flybox1 · « **Reply #15 on:** January 30, 2013, 12:32:26 PM »

if youve got 75s/40s in there, and black plugs, yes, dave is correct. filter is too restrictive.

txterror · « **Reply #16 on:** January 30, 2013, 12:33:11 PM »

Filter is EMGO brand, thanks for the tips guys

txterror · « **Reply #17 on:** January 30, 2013, 08:02:24 PM »

Crap filter is the culprit, ordered oem filter. Thanks again guys

iron_worker · « **Reply #18 on:** January 31, 2013, 06:37:26 AM »

Let us know how it turns out.

IW

txterror · « **Reply #19 on:** January 31, 2013, 07:24:26 AM »

It ran pretty strong with the filter out so im assuming it will run pretty good with stock filter. If it wasnt for this wonderful forum i would have never guessed that the crap aftermarket filter was causing the problem. Thanks again dudes. I dont know if these filters only effect CB400's, but dont buy EMGo filters cb400 owners.

txterror · « **Reply #20 on:** February 04, 2013, 09:46:07 AM »

Update, well guys i got the new (oem) air filter in and the bike still runs poor. Its better than it was with after market filter. But still runs better without filter. What gives, any taughts. I can hear it running real boggy, not as much as it was but still a little

hondamatteo · « **Reply #21 on:** February 04, 2013, 11:00:33 AM »

Float height? What's it set at?

dave500 · « **Reply #22 on:** February 04, 2013, 11:26:40 AM »

you say the carbs were cleaned,did you remove the emulsion tubes aswell to clean them?

txterror · « **Reply #23 on:** February 04, 2013, 11:44:20 AM »

float height 21, and Emulsion tubes were removed and cleaned. Also do you guys know what NGK caps i can use. I found VB05f and SB05f on ebay but not sure if they will work on my bike.

dave500 · « **Reply #24 on:** February 04, 2013, 11:53:09 AM »

you need XDO5F for 2/3 and VDO5F for 1/4,click here,scoll down.
http://www.davidsilverspares.co.uk/CB400F-SUPER-SPORT-1976-USA/

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Author Topic: cb400 poor acceleration (Read 13849 times)