Author Topic: cb400 poor acceleration (Read 14427 times)

jneuf · « **Reply #25 on:** February 04, 2013, 01:17:48 PM »

I seem to remember from a past thread you had the big OEM battery placed under your seat. Thinking back, where it was might have been covering the intake tube.

I haven't been on the forum for awhile, and since you say the bike is stock, I'm thinking you relocated the battery back to the stock location..?

RickB · « **Reply #26 on:** February 04, 2013, 11:13:00 PM »

I know you looked at the seat, but the condition you are describing sounds a lot like when I have ridden my bike without the seat on and have accidentally sat over the intake snorkel.

I wouldn't go pulling your carbs apart if you know the jets are all stock sizes. It sounds to me that you have an air problem, not fuel or spark.

Especially since you took pods off of it. If you can take some photos of your air system, post them here so we can all double check everything is installed as it should be.

Rick.

dave500 · « **Reply #27 on:** February 04, 2013, 11:14:29 PM »

make sure the advancer mechanism is working.

jneuf · « **Reply #28 on:** February 05, 2013, 06:36:41 AM »

I went back and found the thread where you posted about the placement of your battery: http://forums.sohc4.net/index.php?topic=116023.msg1308305#msg1308305

If you left the battery where it is, it looks like it would be sitting right on top of the intake.

txterror · « **Reply #29 on:** February 05, 2013, 07:03:08 AM »

Pods are gone, ordered oem intake parts and got her back to normal, besides clubmans. Ill take pics tonight of intake.

jneuf · « **Reply #30 on:** February 05, 2013, 07:10:12 AM »

Is the battery in the stock location? or still on its side under the seat?

txterror · « **Reply #31 on:** February 05, 2013, 07:13:50 AM »

stock

flybox1 · « **Reply #32 on:** February 05, 2013, 07:47:39 AM »

move your float height to 22mm and make sure your needle clip is in the middle position.

jneuf · « **Reply #33 on:** February 05, 2013, 08:43:34 AM »

How many turns out are your air screws?

txterror · « **Reply #34 on:** February 05, 2013, 08:47:33 AM »

Ive had them at stock specs but bike seems to like it at 1 1/2 - 2 turns out. Bike runs rich at stock position

iron_worker · « **Reply #35 on:** February 05, 2013, 11:59:17 AM »

Are you positive the jets are stock size?

IW

txterror · « **Reply #36 on:** February 05, 2013, 12:04:39 PM »

scunny · « **Reply #37 on:** February 05, 2013, 02:31:24 PM »

Quote from: dave500 on February 04, 2013, 11:14:29 PM

make sure the advancer mechanism is working.

easily overlooked, good call Dave

dave500 · « **Reply #38 on:** February 05, 2013, 03:46:15 PM »

see reply #1

txterror · « **Reply #39 on:** February 05, 2013, 08:32:22 PM »

stevenclemmons · « **Reply #40 on:** February 06, 2013, 05:04:02 AM »

I've been struggling with a very similar issue on my '77 400f for awhile now too, after a minute of riding, the bike hesitates heavily (almost stalls when in 1st) at 1/4 throttle position until I roll further on the throttle. Thing's I've tried: new rings, valves lapped, set valve clearances, adjusted timing, vacuum synced carbs, reinstalled factory airbox and a more restrictive muffler. My air screws are fully out, i haven't checked them at Idle since i put the airbox and exhaust back on so I'll report back to let you know if I'm still idling rich

http://forums.sohc4.net/index.php?topic=116296.0

txterror · « **Reply #41 on:** February 06, 2013, 08:24:16 AM »

Cool let me know how it turns out steven

dave500 · « **Reply #42 on:** February 06, 2013, 11:26:50 AM »

have you used a keyster jet kit?

flybox1 · « **Reply #43 on:** February 06, 2013, 02:04:09 PM »

no way would I trust that hose.
it looks to be 2-3" too short, AND the banjo fitting should be angled at roughly 45deg(hard to tell w your pic#1 ) to match the route of the SS brake line.

RickB · « **Reply #44 on:** February 06, 2013, 06:45:26 PM »

Is it me or does something look off about the way the airbox connects to that throat that goes into the filter? You look very close to the end of the metal air duct.

If that's leaking you'll have boggy performance. I know because my seal there was split.

http://forums.sohc4.net/index.php?topic=51957.msg964402#msg964402

Rick.

txterror · « **Reply #45 on:** February 06, 2013, 08:23:50 PM »

Im not sure how its supposed to look rick, but i didnt notice any tears in the rubber when i removed them to clean/paint airbox. By the way rick, very nice bike sir, inpressive build. Learning as i go over here.

RickB · « **Reply #46 on:** February 07, 2013, 05:08:20 AM »

Just double check that you have that metal duct far enough in to the back of the airbox and the metal band/clamp is sealing everything. The screw for this should be at the top of the airbox (at the 12 o'clock) so you can that it's sealing (presently, you have it upside down).

Take the air filter out and use your fingers to verify it's in far enough. You could even use a small flashlight and shine it in through the air-filter side to make sure everything is sealed.

I knew nothing about motorcycles when I started my CB400F, so we're all learning mate!

Ridgerunner · « **Reply #47 on:** February 07, 2013, 05:38:18 AM »

There is also another potential problem. In your earlier post you said "Bike starts and idles fine but stumbles when accelerating." I had the same problem on my 750 four. The pilot jets were plugged. The bike would start and idle fine after it warmed up. It would accelerate OK as long as I did not give it too much throttle. Once it got the RPM's up it would take full throttle.

Just a thought from a guy that doesn't know anything about a CB400.

txterror · « **Reply #48 on:** February 07, 2013, 06:53:42 AM »

Alrighty thanks Rick, ill check it out. I put some new NGK caps on last night, and from what i can tell it ran better. Wasnt able to push it because i hav no front brakes at the moment. Waiting for brake pipe to come in. I will update as soon as i get her out. This learning process can be quit frustrating but is very rewarding once you get it right. Also, i tried rotating the left hand controls but noticed they are fixed by a stub that goes into the bars. My question is, Am i stuck with the left controls at this position?

iron_worker · « **Reply #49 on:** February 07, 2013, 07:01:37 AM »

I believe the reason for the alignment dowel is so that the controls do not rotate and start to chafe the wiring that runs into the handle bars. If you ran the wires outside the bars or move the hole you could run them in any position you want, really.

IW

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Author Topic: cb400 poor acceleration (Read 14427 times)