Author Topic: I am just too rich... needle clip position help needed (Read 14731 times)

DarcyCB400F · « **on:** April 20, 2011, 09:10:29 PM »

My stock CB400F is far too rich (off the dial) at mid to high RPM. 4000 +. Exhaust gas analyzer confirms this result in the shop tonight. Idle mix is perfect. Idle is very smooth. We took out the stock air filter and retested with no effect on results.

The stock muffler tip has a black sooting finish rather than a nice clean grey one.

On the road I get very slight burbbling at 6000 if my gear selection is too high. 60mph/6th gear/full thottle = slight burbble and no acceleration to speak of.

Do I need to change my needle clip position and if so, how do I change the needle clip position setting on my 400F and to what setting should they be. Does it matter that I live at 3500 feet above sea level??

I have searched the carb FAQ and the rest of the site and found info needle clip position regarding lean issues but came up empty handed on my issue. Forgive me if I have overlooked a thread that addresses my concerns... please point it out to me.

dave500 · « **Reply #1 on:** April 20, 2011, 09:21:46 PM »

has the bike got the standard main jets?if you dont know id have a look.

TwoTired · « **Reply #2 on:** April 20, 2011, 09:29:55 PM »

Do you know if the emulsion tubes are clean/clear?

DarcyCB400F · « **Reply #3 on:** April 20, 2011, 09:41:26 PM »

Dave.. I don;t know if has standard jets or not. I purchased the bike last fall after it sat for 10 years. It's stock so far as I know.

TT, not sure what an emulsion tube is... sorry...we pulled the carbs this winter, dropped the bowls, did a good cleaning, and reassembled. We pulled the needles (on the float), used a micro wire to probe the (jet?) orrifices and found some plugged.

I am embarrased that I don;t know the names of the parts n pieces inside the carb... please forgive

The bike runs 100% at idle, balancing the carbs was pretty easy.

TwoTired · « **Reply #4 on:** April 20, 2011, 10:22:26 PM »

Ok,
Remember the main jet? It reaches deepest into the bottom of the bowl. I don't know the size of the orifice. Maybe #80 ish.
Anyway behind that jet is the emulsion tube and extends all the way to the carb throat, where the needle jet orifice is. It pushes out the bottom of the carb.
This tube takes air from the air jet at the mouth of the carb and mixes air into the fuel, making an air/fuel emulsion which then travels to carb throat. The tube has small holes in the side of it for air to get in. If the holes are plugged, the mid to high range will be rich.

I think I'd make sure the emulsion tube was clean and clear before changing any other settings.

Cheers,

dave500 · « **Reply #5 on:** April 21, 2011, 12:02:31 AM »

if you didnt have commpressed air to blow it through it may not be truely clean,even if you used a pressure can of cleaner,,these have some very small easily blocked jets and other small holes.

-CB-Jamie- · « **Reply #6 on:** April 21, 2011, 12:21:39 AM »

The main jet should be a #75 in the 400's. Have a look here, the emulsion tube is no. 86 in the pic and it's about 2" long maybe.

Maybe you already cleaned it and just don't know the name of it. They just slide out after you pull out the main jet but if it's a bit clogged from sitting for years it might not have come out and you didn't know it was there, if this is the case then it sounds like this is your problem.

To get it out now you will have to take off the float bowl and take out the main jet. You will then have to take off the carb top and remove the slide, it's held by two bolts with locking tabs after you take off the top and it just slides out after you remove the bolts and you just have to pull it off a ball joint type thing that works it. You can then tap out the emulsion from the top using something softer than the tube itself like a wooden dowel.

I actually have a set of 400f carbs completely stripped at the moment so I can take pics of any part so if this would help let me know

Jamie

faux fiddy · « **Reply #7 on:** April 21, 2011, 03:26:41 AM »

Needles are one of the projects I watched my friend work through on a rz-500.

He wanted things perfect, had his first project on a machine shop grinder with ones he had bought in kits.

It appears that the needles in kits are often made to work with many configurations and applications. His rz project involved many carb removals and adjustments in the machining of what he had for needles. Lots of test rides evaluating hesitation from first crack of the throttle up to WOT and everywhere in between. A little bit of whittling in the grinder of a few tens of thousandths here and there, matching all four.

It can become as complicated as you need it to be in search of perfect, but as above, start with perfectly clean emulsion tubes.

Some threads here on adding holes to the emulsion tubes, a couple extra holes in the emulsion tubes are even being blamed for better gas milage in one thread.

MoMo · « **Reply #8 on:** April 21, 2011, 04:54:50 AM »

Darcy, I've rebirthed at least 7 CB400fs in the past 4 years, all had been sitting long periods of time and those that did not have the gas drained required total carb disassembly. The emulsion tubes were blocked or partially blocked in every bike that had gas. They are somewhat of a pain to get to but as stated you will want to check before changing needle position(that is another painful project)...Larry

DarcyCB400F · « **Reply #9 on:** April 21, 2011, 06:09:03 AM »

Look at you guys come to the aid with such advice that I don't even have any questions as your suggestions and direction are incredible!

Thanks for very much!

Now I just need to find those tubes. I took them out and threw them away cause I didn't know what they were there for...

DarcyCB400F · « **Reply #10 on:** April 24, 2011, 06:20:12 PM »

Well guys, I took the carbs out and apart and found the emulsion tubes

!
Number 2 was completely plugged on all holes and number 1 was partially plugged.
A nice fine strand of wire cleaned them up real nice.
I put everything back together, and took it for a 30 mile run. It seems to have a bit more power (60mph/ 6000 rpm/ 5th gear is good ... 6th gear can barely hold 6000 rpm) but still has a burbble when on the kick stand and reving 5500rpm...
The floats were off too... one high, two low and one about right... I was thinking another carb synch is in order...?

What say you?

MoMo · « **Reply #11 on:** April 24, 2011, 06:32:53 PM »

Darcy, glad you found the tubes

On the bikes I have done it was usually 1 and 2 that were clogged as the bike on the side stand has a tendency to fill for want of a better word those carbs. After all that you should definitely synchronize the carbs again...Larry

Doctorlumen · « **Reply #12 on:** April 24, 2011, 06:37:56 PM »

I've spent quite a lot of time futsing with the carbs on my 400f....If you have pulled them, cleaned them and there is still some wonk to the ride, then you may need to start over with new brass. Those emulsion tubes are notorious for being out of round, and it causes all kinds of headaches.

A couple of questions: Does the "burbling" change when the bike is warm or cold? Does the throttle "hang up" anywhere in the rev range? What do the spark pugs look like?

DarcyCB400F · « **Reply #13 on:** April 24, 2011, 07:05:16 PM »

Quote from: photolar on April 24, 2011, 06:32:53 PM

Darcy, glad you found the tubes On the bikes I have done it was usually 1 and 2 that were clogged as the bike on the side stand has a tendency to fill for want of a better word those carbs. After all that you should definitely synchronize the carbs again...Larry

Thanks Photolar!
A carb synch is worthwhile then.. thanks! I wasn't sure if if this point it would have changed anything... there is still hope!

DarcyCB400F · « **Reply #14 on:** April 24, 2011, 07:21:30 PM »

Quote from: Doctorlumen on April 24, 2011, 06:37:56 PM

I've spent quite a lot of time futsing with the carbs on my 400f....If you have pulled them, cleaned them and there is still some wonk to the ride, then you may need to start over with new brass. Those emulsion tubes are notorious for being out of round, and it causes all kinds of headaches.

A couple of questions: Does the "burbling" change when the bike is warm or cold? Does the throttle "hang up" anywhere in the rev range? What do the spark pugs look like?

Thanks for the insight/suggestions Doc,
Burbling was just warm enough off the choke to idle without it... so then we reved her up to 5500+/- which I am sure she got pretty hot in quick order... so I would say the answer is warm/hot.

The throttle doesn't hang up anywhere at all...

I didn't check the plugs after my ride tonight but did earlier before the emulsion tube fix, they were slightly sooty around the threaded part but the electrode/center was greyish white.

Is the loss of power at 60mph typical of this bike? I would love to see it gain speed at 60mph enough to make a decent pass or climb a nice long hill while accelerating (which it can't right now) ... Am I asking too much from 400cc's perhaps?? Maybe I have tapped all the HP/torque this little monster can muster..

?

FWIW...One thing worth mentioning (perhaps?) is that today after the emulsion tube fix, it seemed to climb to rpm and speed much nicer/quicker than before! I thrill to ride to say the least! 1st, 2nd, 3rd full thottle 9000rpm shift was exilerating!! 4th seems to do nicely but not nearly the punch of the first three then 5th holds 6000 and can build to 7000 to 8000 with some effort... grab 6th, and all it can do is hold 6000 rpm on the flat.... any hill and I lose rpm/speed. the ride today was mostly in 5th and 6000 rpm to hold highway speed.

Spanner 1 · « **Reply #15 on:** April 24, 2011, 08:00:16 PM »

Yeah, almost fixed

.... hey Darcy how is your fuel delivery to your carbs ? Even tho' your float levels may be correct if fuel flow is slow to the carbs ( due to gummed-up petcock/ filter ) at higher speeds and more throttle opening a fuel supply to the carbs that is slow would not 'keep up' with the demand of the main jet and result in a low fuel level in the carbs and a ' lean' condition, seewhatimsaying ?
This may be more common than folks think, I think

Whoops, should have added; open the 4 drain screws on the carbs with the drain tubes directed over a clean can ( return the gas to the tank ), turn the gas on and let the fuel flow for about 1 to 2 mins. Each tube must give a good steady flow... should be worth trying at least, good luck.

DarcyCB400F · « **Reply #16 on:** April 24, 2011, 08:04:27 PM »

Quote from: Spanner 1 on April 24, 2011, 08:00:16 PM

Yeah, almost fixed .... hey Darcy how is your fuel delivery to your carbs ? Even tho' your float levels may be correct if fuel flow is slow to the carbs ( due to gummed-up petcock/ filter ) at higher speeds and more throttle opening a fuel supply to the carbs that is slow would not 'keep up' with the demand of the main jet and result in a low fuel level in the carbs and a ' lean' condition, seewhatimsaying ?
This may be more common than folks think, I think

Thanks Spanner for a great idea/suggestion! Makes sense to me that this could affect what I am experienceing but I had to replace the fuel cock three weeks ago due to old one leaking so I doubt this is the issue this time.

seanbarney41 · « **Reply #17 on:** April 24, 2011, 09:19:44 PM »

Darcy, have you ever tested the ignition advancer? I'm not sure on the 400, but if it's similar to the 750 you just have to remove the points cover and then the points plate. The advancer uses centrifugal force from the end of the crankshaft to overcome some springs, so that the ignition advances for better power at high rpm. The advancer often gets gummed up or stuck and won't allow the ignition to advance properly...the result is a bike that runs fine at idle and low rpm but kinda poops out sooner than it should. If you have a timing light, it's easy to hook it up with the engine running, rev it up, and watch for the timing to advance...or you could just take it apart and make sure that it is moving freely.

MoMo · « **Reply #18 on:** April 25, 2011, 01:32:59 PM »

Darcy,, is the air filter new?...Larry

DarcyCB400F · « **Reply #19 on:** April 25, 2011, 04:10:34 PM »

Quote from: seanbarney41 on April 24, 2011, 09:19:44 PM

Darcy, have you ever tested the ignition advancer? I'm not sure on the 400, but if it's similar to the 750 you just have to remove the points cover and then the points plate. The advancer uses centrifugal force from the end of the crankshaft to overcome some springs, so that the ignition advances for better power at high rpm. The advancer often gets gummed up or stuck and won't allow the ignition to advance properly...the result is a bike that runs fine at idle and low rpm but kinda poops out sooner than it should. If you have a timing light, it's easy to hook it up with the engine running, rev it up, and watch for the timing to advance...or you could just take it apart and make sure that it is moving freely.

Thanks Sean, I have terrific acceleration in the first three gears... 9000 rpm is real easy to get (higher if I want to I am sure... no issues with a tach climb in those gears... wooo hooo

) so I would like to assume the timing advance is working... am I right to assume that?

DarcyCB400F · « **Reply #20 on:** April 25, 2011, 04:13:20 PM »

Quote from: photolar on April 25, 2011, 01:32:59 PM

Darcy,, is the air filter new?...Larry

Hi Larry, the filter is not new but extra clean... not a spec... we also removed the filter while the exhaust gas analyzer was hooked up and the removal made no difference to the result. I thought perhaps it was plugged and was throwing the bike into a rich burn... nope... no change at all.

DarcyCB400F · « **Reply #21 on:** April 25, 2011, 04:19:58 PM »

Guys? Am I chasing my tail here? I am starting to wonder if perhaps I am just not aggressive enough with the rpm in higher gears? 6000 at 60mph is just starting into the torque curve isn't it? Perhaps I need to wring out 10,000 rpm before grabbing the 4th gear or higher?

I will for sure rebalance the carbs in the next day or two and then ride it like I stole it... is this perhaps the answer?

I am used to the torque the Harley gives me while at the same time am learning how to ride a rev monster like the 400F.

I am totally OK with 400cc when running as they should.... that is what I am after here... is my 400F running as it should? Once I figure out it is, I will gleefully go revving around town on my 400F with a big #$%* eating grin on my face!

Thanks for all your help!

seanbarney41 · « **Reply #22 on:** April 25, 2011, 04:26:15 PM »

Quote from: DarcyCB400F on April 25, 2011, 04:10:34 PM

Quote from: seanbarney41 on April 24, 2011, 09:19:44 PM
Darcy, have you ever tested the ignition advancer? I'm not sure on the 400, but if it's similar to the 750 you just have to remove the points cover and then the points plate. The advancer uses centrifugal force from the end of the crankshaft to overcome some springs, so that the ignition advances for better power at high rpm. The advancer often gets gummed up or stuck and won't allow the ignition to advance properly...the result is a bike that runs fine at idle and low rpm but kinda poops out sooner than it should. If you have a timing light, it's easy to hook it up with the engine running, rev it up, and watch for the timing to advance...or you could just take it apart and make sure that it is moving freely.

Thanks Sean, I have terrific acceleration in the first three gears... 9000 rpm is real easy to get (higher if I want to I am sure... no issues with a tach climb in those gears... wooo hooo ) so I would like to assume the timing advance is working... am I right to assume that?

yeah, that sounds right to me...maybe not the most likely cause of your problems

dave500 · « **Reply #23 on:** April 26, 2011, 04:24:39 AM »

if your ignition is spot on and carbs well clean???,have you got acess to a compression guage?check the compression,double check the ignition with a dwell meter and timing light ,if you havent done this your in the dark,your ignition cant be just ok it must be perfect,especially on the smaller engines.,if you havent synced them yet,take of the tops and check the needle clip position,,you wont know for sure otherwise,if the bike sat for ten years the valve seats aint going to be perfect,sure bikes run ok after a ten year sleep like that but if your chasing horses,your throwing away a few here and there with not quite right adjustments,the 400 compared to your harley is like a 125 two stroke compared to a late model 500cc thumper.

DarcyCB400F · « **Reply #24 on:** April 26, 2011, 08:14:42 AM »

Thanks Dave!
Timing and dwell spot on- "check"
clean carbs - "check"
synched carbs - check - uncheck - will synch again since cleaning emulsion tubes (oops missed them the first time around

)
new fuel cock - check
CB400F compared to Harley - no contest on torque - check
'99 XR400R in the stable too... real nice torque

- check

needle clip position - haven't checked... what should I be checking for?

News:

Author Topic: I am just too rich... needle clip position help needed (Read 14731 times)