Topic: CB350F Not running right.

[AddLightness]

So recently I completely cleaned my carbs on my 72 CB350F (newly acquired) and I can get the bike to idle well. It revs just fine in neutral when it is warm to up and over 5K RPM. Problem is, when I am in gear the bike moves fine under easy and low acceleration but once I start to get on it, the bike just sputters and has no power.
The bike may very well have done that when I bought it, and unfortunately I wouldn't know if it did as I bought it as is with no road test. The price was right, but obviously I should have done more to test and haggle in retrospect.
So now I am wondering if it is due to the bike's carbs or worse yet, no proper compression. Any pointers before I start to tear the bike apart?

Thanks,

Martin

[hoodellyhoo]

First of all, how deep/thurough did you go when cleaning your carbs?

Second, are you running with an oem airbox and filer? pod filters? nothing?

Also, have you done a full tuneup? (points, timing, valves, etc)

[MoMo]

+1 to last post, what you described sounds like the midrange needle jets are blocked-if the bike was sitting for any period of time they are.

[fmctm1sw]

A compression test is one easy thing you could do.  Also, make sure your air intake path isn't obstructed. 

[camelman]

I've been where you are before, as I'm sure plenty of others on this forum have.  I have a feeling that you need to pull your carbs apart again and clean out your emulsifier tubes.  Then, check you ignition points setting and replace the spark plugs.  I HIGHLY recommend a new air filter too.  I have a feeling that your bike will run like a champ if you do all of that.  Make sure that you have the entire intake system in place too.  If you are missing pieces/covers, then you will have some bad operational issues crop up.

Camelman

[AddLightness]

I would say I cleaned them very thoroughly as I took apart practically every single piece and if it wasn't rubber, it sat in carb cleaner for a day. I used a brass brush too. (Broke a slow jet, but that was another post)

Air box is OEM.

I did the points and timing yesterday which did seem to help. I am going to buy new plugs and wires soon as I am now more aware as to how lousy they are. Valves I have not done and I will leave them for the last as I have no clue what I am doing there. I will let ya'll know how it goes once I get new wires and plugs put in.

Oh, and I did the redneck compression test of sticking a finger in the spark plug hole. At least I have decent compression on all of them, but there could certainly be some low compression as I wouldn't be able to feel the difference.

[flybox1]

I've been where you are before, as I'm sure plenty of others on this forum have.  I have a feeling that you need to pull your carbs apart again and clean out your emulsifier tubes.  Then, check you ignition points setting and replace the spark plugs.  I HIGHLY recommend a new air filter too.  I have a feeling that your bike will run like a champ if you do all of that.  Make sure that you have the entire intake system in place too.  If you are missing pieces/covers, then you will have some bad operational issues crop up.

Camelman

+1 on carbs, clean air filter,timing.
probably not compression.

carb therapy is needed 
pull out your press-in main jets, and underneath, are brass tubes(emulsifiers), get all 4 of them out and clean them well.  they have tiny holes along the sides make sure they are all perfectly clean.
do a bench sync of your carb slides.  this will get you close (but not perfect) to the proper vacuum.
Set your floats to 24mm.

[fletcha221]

Sounds like she is starving for fuel. Make sure you can see through the slow and main lets. Simply putting them in cleaner is not enough. Use a piece of wire to clean the jets. You should be able to see light through all of them. The emulsifier tubes are crutual, they have to be spotless or the 350 will not run correctly. What color are your plugs? This should paint a pretty good picture for you. Did you clean the petcock?

+1 on everything Flybox said......These things will run on 3 of 4 cylenders, but won't run for crap if the carbs aren't perfect.

-Christian form Cendse

www.cendse.com

[AddLightness]

I did actually run a piece from a wire brush through all of the main jets. I really don't think they will get any cleaner as all holes are free of debris.
I put in new spark plugs this evening which helped a lot. It runs much better up throught the RPM's but I have to leave just a hair of the choke on. The second I am entirely without choke it dies. So I agree that she must be starving for fuel.

I think that syncing my carbs could be helpful. Yes, no? I have a vacuum pressure tester, but it is only one (not 4 as recommended) and I am missing a brass fitting to insert into the hole for the tester. It may be tedious, but could I test each one separately, and is there any suggestions on how to use one without the proper brass fitting?

[fletcha221]

Hey! If it's notting running with the choke off, I believe a sync is the least of your problems. I would make sure the fuel lines and petcock are completely clean. Also, I'm assuming this bike has a stock exhaust? Also, I'm not being condescending, but you cleaned the pilot jets as well? (the ones that screw in?), because they work together with the mains to supply the total fuel the bike needs. My experience with these bikes is, the most simple and obvious cause IS the problem. I'm guessing your petcock is completely gunked up. Let me know! I'm curious!

[AddLightness]

Yes the bike has a rather stock exhaust. Two into one on both sides - cylinder 1 and 3 go into one exhaust and then 2 and 4.
Regarding the petcock...is that something I can clean or does it have to be replaced?
Certainly not condescending at all with your questions, and yes I did clean all the pilot jets. Thanks so much for the help everyone.

[fletcha221]

my 350f was my first SOHC, and I ran into just about every pitfall you can imagine with the bike....just trying to lay out on the table the dumb crap I did!

In regards to the Petcock, it is something you can clean. You will need to disconnect the fuel line, remove the tank, and drain any fuel into a bucket. This is a good time to leave a little gas in there, then shake the bejesus out of it to loosen any debris or sediment in the tank. After you drain it, I would put in some more gas and repeat for good measure. Afterwards, completely remove the petcock from the tank. After that, remove the bowl from the bottom of the petcock and you will find  ind a screen and an o-ring. I'm guessing this bowl and screen will be pretty gunked up. Clean the screen and bowl, use forced air to clean the petcock body if you have it.

The short cut to all of this would be to simply turn the petcock to off, and remove the bowl. Your choice!

You can check the 350 I built here www.cendse.com

[flybox1]

I did actually run a piece from a wire brush through all of the main jets. I really don't think they will get any cleaner as all holes are free of debris.
I put in new spark plugs this evening which helped a lot. It runs much better up throught the RPM's but I have to leave just a hair of the choke on. The second I am entirely without choke it dies. So I agree that she must be starving for fuel.

I think that syncing my carbs could be helpful. Yes, no? I have a vacuum pressure tester, but it is only one (not 4 as recommended) and I am missing a brass fitting to insert into the hole for the tester. It may be tedious, but could I test each one separately, and is there any suggestions on how to use one without the proper brass fitting?

...but did you pull out the emulsion tubes and clean them? ( you didn't say   )
you also didnt say if you did a bench sync either, whether you cleaned your slides (if you did, did you reinstall them incorrectly?), or set your float heights, or verify your float valves did their job.
did you have sediment in your bowls, tank, fuel lines.  running an inline filter?  Does gas flow freely from your PC?
i really suggest getting in there again.  i know pulling carbs is a PITA, but you're good at it now

once warmed up, your choke lever should be pressed all the way down.  
use your idle adj screw to bring idle down to 1200-1300rpms.
is your battery new/fully charged?  what is its voltage reading?

1 gauge will take forever, you should have at least 2, and 4 is infinitely easier than just 1 or 2.  
a set of 4 of those little brass carb tuning fittings can be found online for about $20. they come with caps so you can leave them in.

Hey Fletcha!

[fletcha221]

WHATS UP FLYBOX!!

If the PC clean doesn't work, Flybox knows what he's talking about! You will need to pull them again. Do you have any pictures of what they looked like when you pulled them last? They need to clean.

Like Flybox said, if you don't want 4 Cylinders fighting eachother, you will need to bench Sync them. (I used a 1/8 inch drill bit).

Just a thought......but was your spark advancer in good working order? The springs do break or become stuck.

Let me know!

[AddLightness]

Ok, excellent info and I will start looking into all of these suggestions. I will say that I felt the pipe coming out of the second cylinder yesterday as it had was starting up and it was not hot (while the others were), so my next step is to get pug wires as I know that wire running to the second cylinder is extremely ratty.
A member of the forum suggested that I go to http://www.z1enterprises.com
I think I will go with the Dyna Ignition Wires - 7mm copper core , unless there is some other suggestion.

[flybox1]

You might be able to just cut that plug wire back and reinstall the cap.
you'll only know when you start cutting the wire back far enough to get to clean wire.
if its too short to reach your plugs, then search out new wires.
check for a good blue spark from your plug against the head.

[camelman]

There's a thread in the FAQ section about rebuilding your coils by replacing the wires.  It isn't just a simple swap process if you want new wires.  It isn't hard though, just a bit more entailed than the usual.

Regarding your carbs... PULL THE EMULSIFIER TUBES!!  I went through three carb cleanings before I knew what emulsifier tubes were on my 350F, and it made a HUGE difference getting them cleaned up.  They are totally hidden away, and if they didn't fall out when you were cleaning your carbs, then I can assure you that they are gummed up.

The carb sync will help your idle, but what you are describing doesn't have much to do with carb sync issues.

Camelman

[AddLightness]

A little update, although this will soon get derailed with impending work needing to be done on the wife's car.

The 2nd cylinder fires very weakly. I gather that because the exhaust pipe stays cool to the touch long after the others are hot. After running it down the road today it did get hot, but only then. I did a spark test by testing arc to the head, and it was fine. Although it could be weak which makes me wonder about the coils.
Emulsifier tubes: now I'm second guessing myself. Are they not the tall (inch or so) tubes with very tiny holes on the sides? I think it is something like 4, 3, 4, 3 in hole pattern. I'll see if I can get some pics posted.

Also regarding the choke, the bike starts really well off of choke, and then I have to move it to some choke to keep it running. Time frame is within 20 seconds.
Back to the coils, I have to be honest, it looks like a level of work that is beyond my ability. I have to cut the coils open?

[flybox1]

Emulsifier tubes: now I'm second guessing myself. Are they not the tall (inch or so) tubes with very tiny holes on the sides? I think it is something like 4, 3, 4, 3 in hole pattern. I'll see if I can get some pics posted.

yes, those are them...

[Duanob]

How about the valves? I would do that before the carbs. Takes about an hour and that's to double check them. Well worth it. Also check for vacuum leaks at the intakes. Not familiar with 350F but I assume there are intake gaskets that can get dry and brittle and crack. You can redo your carbs until the cows come home but if there are other issues it doesn't help. Also you can check for spark without replacing the coils and wires. Still lots to do before dumping a bunch of money into it.

[AddLightness]

That is comforting that I can check so many things without having to throw money at it but a little overwhelming too. I was hoping to enjoy the good fall weather but I think I may have more lasting memories by knowing how to fully tune my engine. I will keep you all posted. I'll try not to "waste" too much time on my wife's car in getting it back on the road.

[AddLightness]

So I have a little time and I want to discuss cylinder #2 not firing properly.
On start up, the cylinder apparently doesn't fire (or fires very little) and the pipe only gets hot to the touch one I have ridden the bike up and down the street.
I know I have spark, as I have tested it off of the head, but I wonder if perhaps it is low spark as the wires are not all that good. I am going to take off the carbs again and thoroughly inspect that particular carb tonight so I hope to eliminate it entirely from the equation. If I replace the spark plug wires, do I have to cut into the coils?

Feel free to ask any question as I don't get offended easily and I really am a novice to all of this.

[flybox1]

FIRST...try cutting back the #2 wire ( back far enough to get rid of any corroded wire if there is any) and reinstalling the cap.

you're sure your timing is right?
cleaned/gently filed/gapped the point recently? might want to recheck.
set your valve lash yet?

[AddLightness]

Over a year since I have got back to this.....shameful 
Well at least I am back at it now, sort of, since I had to take the 350F to a friend who knows what he is doing.
So now he tells me I need the intake manifolds or perhaps they are more commonly known as the carburetor holders? Does anyone have some that they are selling?
Also, the float bowl gaskets that I installed originally just aren't holding up unfortunately. I went with some off brand gaskets which are not molded to that  pentagonal shape so I had to use a tiny bit of superglue. does anyone know if the OEM float bowl gaskets can be found?
I really hope to get this bike going soon so I can enjoy it in late fall and early winter of Georgia.....cause soon I will have a little girl due in February and I see my bike riding going down to a minimum .

[flybox1]

What is wrong with the carb "boots" that would make your friend think they are unusable?  are they too cracked to repair?  take pictures of the issue.
(dont throw them away yet - search wintergreen oil on the forum )

nothing wrong with non OEM gaskets, as long as they are(the correct size) for a 350F. 
why arent they holding up? did they expand/swell when they can into contact with gas? have trouble keeping them in the grooves?
i used superglue on mine (round ones from a 350F carb kit) and had no issues for 2+ years.