Topic: I am just too rich... needle clip position help needed

[TwoTired]

Something you my wish to try.
Buy some brand new plugs and take them with you on the ride, along with a spark plug wrench.
With the engine all warmed up  Find the area of road where you believe the engine is weak.
Put in the clean plugs and operate the engine in "weak mode" for as long a duration in time as you can.
Hit the kill switch, pull in the clutch, and coast to a stop.  Put the old plugs back in and then take some pictures of the spark plug white insulators so we can see the strap, the as much of the porcelain as possible.  (will tell us if the mixture is correct)

Also, find and measure off 1/4 mile.  From standing start, time how fast you can reach the 1/4 mile mark and what speed you have on the clock when crossing the line.  (Will tell us if the bike is performing correctly)

If you want to pass a vehicle at 60MPH and really want to scoot, expect to downshift at least 2 gears (or even three) and that should get you around whatever is blocking your path pretty quickly.  If you have plenty of space and patience, it should pick up speed even in top gear.

With the smaller displacements, the transmission is half as important as the twist grip and work together as needed.  The rider is more responsible for anticipating what gear is needed before the acceleration is actually needed.

I didn't have my 400 very long, as I didn't like how "skittish" it felt overall (compared to my Cb550s).  But, I don't recall any issues on the freeways or long hills.  Obviously grade matters.  But, then I'm used to just having the trans is whatever gear is necessary to get the job done or keep the engine in the power band.

If all you've ever used for acceleration is the twist grip, I can't imagine you ever being happy with using your left foot as much as your right hand.

Cheers,

[Doctorlumen]

I agree with Two Tired. The plug chop and 1/4 mile run are pretty telling. Unless you have access to a Dyno.

Ya know, my bike is way more impressive feeling in the lower gears as well, so you may be on to something with the "ride it like you stole it" mentality. Rev that f***er and shift, at minimum, 7k. Honestly, I shift my 400f at 8k in town regularly, if not always. On the freeway, I feel like she runs out of room quick, but not at 60. And it takes at least 1/4 mile in top gear to see all she has to offer.

Some of your up-hill woes may be due to your gearing. I'm not sure what the stockers run, but you should take a look and report back. Along with the plug chop and report on your "squid" ride. It may very well be a sweet little bike, and you are just used to something a tad bigger or more modern.

[kpier883]

The main jet should be a #75 in the 400's.

When you pulled the carbs to clean out the emulsion tubes, did you check the jet sizes?  The main jet will usually have a number on it that indicates the size. 

Someone might have put larger or smaller jets in this bike which could lead to running rich or lean at higher RPM and throttle openings.  The main jet is the primary fuel metering device at higher RPM and throttle openings.  The size that is stamped on the jet indicates the size of the orifice in the middle of the jet.  This is where the gas is drawn up from the bowl and into the carburetor to mix with the incoming airstream.

Below is a picture of a Keihin jet like my CB750 or CBX use.  I assume, but don't know, that the 400 uses similar jets.  The plug chop and analysis will indicate whether you need to use a smaller or larger size jet. 

Keep after it and you will get it dialed in! 

[DarcyCB400F]

Thanks for the pointers guys!
I synched the carbs today... I couldn't believe how much they were off by adjusting the floats and cleaning the emulsion tubes! Number three was the only cylinder that was drawing any vacuum at all!

After synching the carbs, I rode it like I stole it! Very nice ride indeed! I gained more rpm easliy with my intention to get them up to 10,000 before shifting... keeping the revs up kept the power up and was due to both the recent tuning AND my more agressive throttle!

7000/65mph/5th gear was great... I could gain speed and rpm without shifting and if I dropped a gear, speed and rpm responded nicely!

6000/65mph/6th gear remains unresponsive for the most part.

Tomorrow, the gas analyzer gets hooked up to see if I am still running rich... TT's plug pull procedure is appreciated but wouldn't the exhaust gas analyzer give me a reliable diagnosis also?

At is stands now, I think I am close to the "Holy Grail" on fine tuning... (I hope ) what say you??

[DarcyCB400F]

The main jet should be a #75 in the 400's.

When you pulled the carbs to clean out the emulsion tubes, did you check the jet sizes?  The main jet will usually have a number on it that indicates the size. 

Someone might have put larger or smaller jets in this bike which could lead to running rich or lean at higher RPM and throttle openings.  The main jet is the primary fuel metering device at higher RPM and throttle openings.  The size that is stamped on the jet indicates the size of the orifice in the middle of the jet.  This is where the gas is drawn up from the bowl and into the carburetor to mix with the incoming airstream.

Below is a picture of a Keihin jet like my CB750 or CBX use.  I assume, but don't know, that the 400 uses similar jets.  The plug chop and analysis will indicate whether you need to use a smaller or larger size jet. 

Keep after it and you will get it dialed in!

I noted the jet size was 75... I believe this is the stock jet...?

[seanbarney41]

Tomorrow, the gas analyzer gets hooked up to see if I am still running rich... TT's plug pull procedure is appreciated but wouldn't the exhaust gas analyzer give me a reliable diagnosis also?

At is stands now, I think I am close to the "Holy Grail" on fine tuning... (I hope )

...not unless your on a dyno!...or that exhaust gas analyzer is somehow portable...main circuit fuel mixture can only be acurrately checked with the engine under a load!

[kpier883]

The main jet should be a #75 in the 400's.

I don't know the main jet size for the 400.  CB Jamie said 75 earlier, but I can't confirm.  If you need to try a different jet, z1 enterprises seems to have very good prices - $1.57 each, but I don't know if they have the size you need:

http://www.z1enterprises.com/SearchResult.aspx?All=True&KeyWords=keihin%20jets

These guys show all the sizes, but are more expensive.  Might be worth a call to Jeff at Z1 if you do need some.

http://www.motorcyclecarbs.com/Keihin_Main_Jet_99101-393_C78.cfm

[TwoTired]

Tomorrow, the gas analyzer gets hooked up to see if I am still running rich... TT's plug pull procedure is appreciated but wouldn't the exhaust gas analyzer give me a reliable diagnosis also?

Fuel requirements change with engine loading at every throttle position.  You set mixtures for max power, rather than just overcoming internal friction.

Cheers,

[david 750f]

DarcyCB400F,
I spent a summer in Calgary (3500 ft elevation) many years ago. I shipped my bike out by train from Toronto (250 ft elevation).

I had very similar symptoms on my bike till I re-jetted. The bike would happily red-line the lower gears but not in top gear. I can't remember exactly (over 30 years ago) but I know that I dropped the main jet size and I may have moved the needle clip as well.

Perhaps someone from a similar altitude (3500 ft) as you could chime in with their jetting changes.

Good luck,
David

[-CB-Jamie-]

The main jet should be a #75 in the 400's.

When you pulled the carbs to clean out the emulsion tubes, did you check the jet sizes?  The main jet will usually have a number on it that indicates the size. 

Someone might have put larger or smaller jets in this bike which could lead to running rich or lean at higher RPM and throttle openings.  The main jet is the primary fuel metering device at higher RPM and throttle openings.  The size that is stamped on the jet indicates the size of the orifice in the middle of the jet.  This is where the gas is drawn up from the bowl and into the carburetor to mix with the incoming airstream.

Below is a picture of a Keihin jet like my CB750 or CBX use.  I assume, but don't know, that the 400 uses similar jets.  The plug chop and analysis will indicate whether you need to use a smaller or larger size jet. 

Keep after it and you will get it dialed in!

I noted the jet size was 75... I believe this is the stock jet...?

It's definitely a #75 stock, I have the workshop manual too and it's in this.
Jamie

[DarcyCB400F]

DarcyCB400F,
I spent a summer in Calgary (3500 ft elevation) many years ago. I shipped my bike out by train from Toronto (250 ft elevation).

I had very similar symptoms on my bike till I re-jetted. The bike would happily red-line the lower gears but not in top gear. I can't remember exactly (over 30 years ago) but I know that I dropped the main jet size and I may have moved the needle clip as well.

Perhaps someone from a similar altitude (3500 ft) as you could chime in with their jetting changes.

Good luck,
David

Thanks David for the insight regarding altitude! I would love to hear more about how jetting can help me here...

TT's suggestion about pulling the plug after a shutdown (abreviated instructions for sure ) is something I plan on doing regardless... let's see what the results of that are.

[Doctorlumen]

It isn't uncommon for 400 drivers to pop an #80 main in while running stock airbox and muffler. I run #95 mains, needle one notch richer than stock (center notch is stock) and a #38 pilot (1 point leaner than stock.) But I run pods, so my bike sucks a bunch more air. Your ride is stock, right Darcy?

I eagerly await your plug chop info. Its going to tell us a lot.

[TwoTired]

But I run pods, so my bike sucks a bunch more air.

No, it doesn't.  Pods just reduce the carb throat vacuum.  The throat vacuum is what sucks the fuel up from the bowls, less vacuum= less fuel.  To compensate you MUST use a larger jet orifice size so it will flow the same amount of fuel as before the induction change, in order to correct the air fuel mixture.

If your bike really did suck more are, the venturi pressure drop increase would draw more fuel from the stock jets, making it too rich, and you'd be forced to reduce the jet size.

That's basic fluid dynamics for ya!

Cheers,

[DarcyCB400F]

Just a question to better my understanding of jetting...
If the stock jet is a 75, and IF I am too rich, and IF jetting is the corrective measure, what Jet size should I look for?

Also, IF I am too rich, am I better off to start with needle clip position or jet size or both??

FWIW...I took the needle out of #4 tonight to see where it is set... middle position...

[DarcyCB400F]

Is Camelman's experience relevant???

http://forums.sohc4.net/index.php?topic=88097.0

[camelman]

Wow, lot's of good advice here. 

Darcy, I think you should take another look at your emulsion tubes.  If 1 and 2 were really dirty, then the holes they slip into are undoubtedly dirty too.  If you didn't clean those holes out, then your emulsion tubes will start to fill up immediately with whatever is left in the holes.  I suggest checking all four holes for dirt, and getting a good look in there with a flashlight.  get something firm but soft in there to pick away with too.  I went through this exercise three times with my 350f before I realized that I needed to clean the holes the emulsion tubes fit into, and I had very similar symptoms to yours.  Also, if you haven't already done so, then stick the tube from a can of brakleen into the orifices to blast them through.  Do it outside though, that stuff makes you really stupid really quickly.

Your 400f should pull pretty well in 6th on the highway, even if you are only going 60.  It won't pull like a freight train, but it should accelerate you.  Heck, my 350f accelerates well from slower speeds in top gear with a passenger on the back.  If the emulsifier cleaning doesn't show anything, then try using tape on your throttle and throttle housing with 1/8 increments marked so you can see at exactly what point in the throttle twist you are getting your burbling.  That will help to figure out which area of the carb to adjust.

Camelman

[TwoTired]

Just a question to better my understanding of jetting...
If the stock jet is a 75, and IF I am too rich, and IF jetting is the corrective measure, what Jet size should I look for?

Also, IF I am too rich, am I better off to start with needle clip position or jet size or both??

FWIW...I took the needle out of #4 tonight to see where it is set... middle position...

It depends on what throttle position you are too rich and if you are dead certain the carbs are squeaky clean. 
If all throttle positions are affected, then lowering the carb bowl fuel height is the proper correction.
If only too rich in the midrange throttle position, then lowering the throttle valve needle is the proper correction.
If only too rich in 3/4 to WOT then a smaller main is the proper correction.

[Doctorlumen]

Two Tired is absolutely right....my bike dosen't "suck more air". Brotha knows his chit. Sorry about the poor wording.

But, my bike does suck a crapload of fuel...my mechanic buddies are baffled every time we throw her up on the Dyno. So I guess my point was more that Darcy's bike may in fact be running too low a main jet and need a tad more in the top end.

[DarcyCB400F]

Well guys I messed up today! I didn't follow TTs advice. My bad!
Let me explain... I read the Clymer manual and it said float height should be set to 21mm so I raised them to this from 23mm. If I had stopped long enough to consider TTs advice about lowering the float height, I would have gone to 25mm!
Now the bike won't idle below 3000rpm and not run very smooth either! I have next to no vacuum on the balancer either. Now I really am too rich by a LOT! It runs like a piece of #$%*!!!

All is not lost... I did follow Camelmans advice and super cleaned the emulsion tube tubes. They were a little gritty but a q tip and parts cleaner made them sparkle.

Now I have to pull those damn carbs again which is such a pain in the ass with the air box always in my way.

TT, your advice is spot on and I wish I paid more attention to it when I read the manual!! Now I pay the price of doing it all over again. 

[TwoTired]

Bowl fuel height is in inverse relationship to the carb float measurements.  The higher the measurement number, the lower the fuel level and the carbs will make leaner mixtures over the entire operating range.

If you get the actual fuel level too low in the carb bowl, it's starves the pilot jet (it's inlet is higher than the main jet entrance).
But, a lower fuel level does lean the entire operating range of the carb.  I don't know if that is appropriate for your bike as I haven't seen a Dyno fuel map, or any spark plug deposits at any operating range.

At the moment, I'm surprised that the standard float setting has been diagnosed as a problem for your carbs. (Unless you aren't measuring correctly)    Anyway, I question why the stock settings would not be appropriate for you bike.  What mods would make your bike have different requirements?

Do the 400 carbs have brass floats that can get holes and sink?  (Thought I recalled they were molded plastic.)

Cheers,

[DarcyCB400F]

Just a question to better my understanding of jetting...
If the stock jet is a 75, and IF I am too rich, and IF jetting is the corrective measure, what Jet size should I look for?

Also, IF I am too rich, am I better off to start with needle clip position or jet size or both??

FWIW...I took the needle out of #4 tonight to see where it is set... middle position...

It depends on what throttle position you are too rich and if you are dead certain the carbs are squeaky clean. 
If all throttle positions are affected, then lowering the carb bowl fuel height is the proper correction.If only too rich in the midrange throttle position, then lowering the throttle valve needle is the proper correction.If only too rich in 3/4 to WOT then a smaller main is the proper correction.

This is the advice I didn't follow that applies I believe ...  aside from idle, it's my belief that all throttle positions are affected so I dropped the needles and adjusted the float to spec (whcih in fact raised the fuel level inside the bowl - exact opposite from what I should have done to reduce the amount of fuel inside the bowl. 

The floats are in fact not brass but a molded plastic.

I have absolutely no mods... it's a complete st ocker. Perhaps altitude is in play here?... 3500 - 3800 feet above sea level.

I cut a piece of cardboard in a U shape to measure the float. It bridged the main jet so I measured middle of the float... not the hinge end or the toe...right in the middle.

Thanks for your help on this TT! I appreciate your input and embarrassed I didn't follow your suggestion!

I will get some plug shots for you when I get it running good enough to ride it... as it sits now, not a chance!

[TwoTired]

Don't know if this helps.  But, I'll just throw it out there.
With carbs on their sides, the float is positioned so the float valve is seated and the spring pin fully extended but in contact with the float tang.  Then, the bottom of the float is measured to the bowl base gasket interface.  The tang is then bent until the specified measurement is achieved.

FWIW

Cheers,

[DarcyCB400F]

Don't know if this helps.  But, I'll just throw it out there.
With carbs on their sides, the float is positioned so the float valve is seated and the spring pin fully extended but in contact with the float tang.  Then, the bottom of the float is measured to the bowl base gasket interface.  The tang is then bent until the specified measurement is achieved.

FWIW

Cheers,

Thanks TT!
That's zackly how I did it... had the carbs resting so that the float would just barely rest on the needle. If I tipped them over much more, the floats would fall away from the needle... Then I measured from carb bottom to bottom of float. Never thought of taking a picture... silly me!

[DarcyCB400F]

I am not rich anymore...

Thanks for all the pointers team! Especially TT for keeping me on track!

The end result I have delayed posting till I was sure I had my "richness" resolved... 250 miles now and she's a screamer! I cleaned and recleaned the carbs, set the floats at 23mm ( I know 21 is spec) raised the needle clip position for more lean ( as per local Honda carb guy who said no issue at all!! ) and now she pulls nice and hard all the way to 60 mph in 3rd and beyond... 4th pulls real hard, 5th is good and 6th will pull too (but not at all like 3rd lol).

I did a plug chop today, took pics which didn't focus (oops  ) and they were nice indeed! They were a nice light grey, no soot and very clean... muffler tip is turning a nice grey too from a gross black oily sooty mess...

In the end, I had a plugged main jet even though I had cleaned it before, two plugged idle circuits which contributed too I am sure!

Thanks guys for all your help! I couldn't have figured it out without your input and attention to details!!