Author Topic: jetting questions on a cb400/4 (Read 5461 times)

stay youth · « **on:** February 27, 2007, 04:36:49 PM »

hi, im having some jetting issues with my cb400f, im running pod filters and a mc-again 4 into 1 exhaust. I have #92 mains and #40 slow jets in there I also dropped the needle one notch. the jets were put in by the previous owner, do these sound like the right jets. I have been running rich on #1, #2 and #3 are running a little lean and #4 has not always been firing. I put new plugs in and rode the biek then when i pulled the plugs #4 was just wet with gas. Just curious what other people htought about this jetting set up? thanks

number13 · « **Reply #1 on:** February 27, 2007, 04:47:39 PM »

If you are using pod filters that usually creates
a lean condition, if you lowered your needles, then you have
leaned it out even more!!
I just did my 400 carbs this weekend and I recall the slow
jets are #40 and the mains are #74(I think!) so your mains
may sound too rich at 92.
Try retrurning everything as close to stock as possible and just make one
modification at a a time.

stay youth · « **Reply #2 on:** February 27, 2007, 04:53:13 PM »

ok thanks thats what i was looking for, so your mains are #74, then mine must be letting in way too much fuel. i'll reset the needle position and try to get some mains closer to #74. Are you running stock? thanks for the reply

heffay · « **Reply #3 on:** February 27, 2007, 04:55:36 PM »

you can't just assume that #74s are what you need... what altitude are you guys at.
are you both running pods, etc?
carb clean?
carb synch?
checked for spark on #4?

stay youth · « **Reply #4 on:** February 27, 2007, 05:02:21 PM »

hey thanks for the reply im riding at sea level. im brinign the biek to the shop to have the carbs synched, compression test, timing, valve adjustemts etc. i was just trying to get an idea as to where i should begin my process of dialing in my bike. i have not checked for the spark that will alos be checked. my carbs are very clean and seem to be in good shape.

heffay · « **Reply #5 on:** February 27, 2007, 05:22:21 PM »

good... unless you have some sort of part failure the bike should run a lot better once those repairs/adjustments happen.
if you're at sea level stock jetting should run better than what you're running now. you might need to richen it up due to the pods but, not a whole lot.

stay youth · « **Reply #6 on:** February 27, 2007, 05:26:06 PM »

awesome thank im still new to bikes but ihave figured out enough that my adjustmentts arent right. When im WOT the bike seems to bog down a bit. so you think i should try to get closer back to the stock settings? maybe try like an #80 for a main? ok thanks again

heffay · « **Reply #7 on:** February 27, 2007, 05:31:15 PM »

i'd say jetting could be stock to start and make adjustments to the needles.
that's a lot easier and makes smaller increment adjustments than jets (cheaper too).
but, you could look at it the other way and get 80 mains and adjust the needle leaner.

your first step though is figuring out #4

stay youth · « **Reply #8 on:** February 27, 2007, 05:54:57 PM »

is it possible that #4 might not fire because of too much fule gettting in there? or would that problem happen to all of them. ok thanks again

heffay · « **Reply #9 on:** February 27, 2007, 06:39:17 PM »

Quote from: stay youth on February 27, 2007, 05:54:57 PM

is it possible that #4 might not fire because of too much fule gettting in there?

yes... most definitely

wardmoto · « **Reply #10 on:** February 27, 2007, 07:57:29 PM »

I have a 350F with open velocity stacks and open 4 into 4 meggas and I drilled my mains to #84's, up one notch on the needles and still playing with the air screws, but they are not that far from stock. Get everything correct as Honda would like it and then address the carb changes to work with your mods. The 350/400's seem to be picky when you start to mess with them, so you compound the problems if you change too many things (read: more than one) at any one time. If other things are not right, you are increasing the likleyhood that you will dowse the whole lot in gasoline and light it off, retiring to the study for a pint and a phone call to the insurance company. Being employed in law enforcement and having a wife who is an insurance adjuster...the aforementioned option is not one for me...(except for the pint(s!)). I venture to guess you will run pretty good with everything to stock (carb jets,float height, bench sync at least, lash, and timing). This should allow you to address the problems you may, or may have not (?) created by your pipe and pods. You might be surprised how close the stock set up might get you after everything else is done! Get it on the road and give it hell. If you have obvious problems, do some plug chops at that rpm range...there is some good stuff on the carb FAQ. Get it right and let us know.....

bshadbolt · « **Reply #11 on:** February 27, 2007, 08:36:07 PM »

I thought the stock jets on a 400 were #80. My 350 has #75 as stock and I was planning on going to #80 as a starting point when I get the 4-1 and pod filters on.

Also, as previously stated, lowering the needle will make it leaner and you should be a bit richer than stock with pods/4-1.

It sounds like your carbs may not be jetted correctly nor tuned (synced) since you are getting different readings on each cylinder.

I'd go back to stock jetting, sync and tune the bike and go from there.

Cheers,

Brett

stay youth · « **Reply #12 on:** February 27, 2007, 10:08:08 PM »

awesome thank you all so much for the tips. like i said before im still learning all this and it can be so goddamn confusing. i guess after rebuilding my carbs a bunch and i will start to figure this #$%* out. so im gonna bring the bike back to stock then begin testing from there.

wardmoto · « **Reply #13 on:** February 28, 2007, 03:32:58 PM »

Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

bshadbolt · « **Reply #14 on:** March 02, 2007, 05:33:35 AM »

Quote from: wardmoto on February 28, 2007, 03:32:58 PM

Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

I just bought a set off ebay for about US$30, with various sizes, I think they had others for sale.

Cheers,

Brett

heffay · « **Reply #15 on:** March 02, 2007, 09:59:22 AM »

Quote from: bshadbolt on March 02, 2007, 05:33:35 AM

Quote from: wardmoto on February 28, 2007, 03:32:58 PM
Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

I just bought a set off ebay for about US$30, with various sizes, I think they had others for sale.

Cheers,

Brett

how many did your set include for that price?

tmht · « **Reply #16 on:** March 02, 2007, 10:53:30 AM »

Quote from: wardmoto on February 28, 2007, 03:32:58 PM

Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

Try http://www.sudco.com/keityppre.html for the jets.

350F stock mains are 80, 400 are 75 I've swapped jets between them a few times now.

Also, I second the opinion that you should put it back to stock and make one small change at a time. The 400 is a picky bastard when it comes to fuel air mixture. (Mine runs like ass if I forget to put the airbox lid back on, I'm talking barely ridable.)

stay youth · « **Reply #17 on:** March 02, 2007, 12:31:30 PM »

ok thanks for the tip about the jets. i got an extra set of carsb that got #75 so im gonna drop those into my set thanks a bunch to all who replied

tmht · « **Reply #18 on:** March 02, 2007, 01:05:02 PM »

Quote from: stay youth on March 02, 2007, 12:31:30 PM

ok thanks for the tip about the jets. i got an extra set of carsb that got #75 so im gonna drop those into my set thanks a bunch to all who replied

Make sure that the o-rings are still good. If you are leaking fuel past the outside of the jet, it is going to cause some problems.

bshadbolt · « **Reply #19 on:** March 02, 2007, 07:22:48 PM »

Quote from: tmht on March 02, 2007, 10:53:30 AM

Quote from: wardmoto on February 28, 2007, 03:32:58 PM
Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

Try http://www.sudco.com/keityppre.html for the jets.

350F stock mains are 80, 400 are 75 I've swapped jets between them a few times now.

Also, I second the opinion that you should put it back to stock and make one small change at a time. The 400 is a picky bastard when it comes to fuel air mixture. (Mine runs like ass if I forget to put the airbox lid back on, I'm talking barely ridable.)

I thought it was the other way round - 350F has #75 stock, while 400 has #80 stock? But having said that, I haven't checked mine yet since the whole bike is being rebuilt and I haven't got to the cards yet (just bought card kits and jet kits).

Cheers,

Brett

bshadbolt · « **Reply #20 on:** March 02, 2007, 07:25:34 PM »

Quote from: heffay on March 02, 2007, 09:59:22 AM

Quote from: bshadbolt on March 02, 2007, 05:33:35 AM
Quote from: wardmoto on February 28, 2007, 03:32:58 PM
Finding jets other than the stock sizes for the 350 and 400 (regardless what they are) will be an exercise in futility. I drilled mine with no problems...if you search this topic you will get many mixed reviews!

I just bought a set off ebay for about US$30, with various sizes, I think they had others for sale.

Cheers,

Brett

how many did your set include for that price?

4 x #75
4 x #85
4 x #90
4 x #95

should be enough to play with and the sow jets shouldn't need changing hopefully.

Cheers,

Brett

Uncle Ernie · « **Reply #21 on:** March 02, 2007, 07:53:33 PM »

After a year of this and that and wanting to grab a hammer and hit everything that moves, I found that STOCK WORKS BEST even thugh I have Uni-pods on.
AND use Honda parts only. They are the only parts that fit well. Aftermaeket stuff saved me some money until I finally figured out I needed stock Honda parts. Stock stock stock
stock sizes, too.

Bodi · « **Reply #22 on:** March 05, 2007, 12:25:28 PM »

I needed smaller pilot jets to get it right with overbore, cam, pods, and header. 88 or 90 mains (my tuning notes are elsewhere right now), and some work on the needles to get more gas in the midrange.

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Author Topic: jetting questions on a cb400/4 (Read 5461 times)

bshadbolt

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tmht

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