Topic: cb350f running issues + pics (new video on page 5)

[davis96]

Hi everyone,

   I am not one to post without researching first, and I have been doing that for a while now, finding no for-sure answer to my specific situation. The bike is a '74 CB350F i bought on craigslist for 500 big ones. The price I think reflected the fact that she was ugly as all get out, but ran good. And it did run well for the first few weeks (though I didnt ride it much because I was waiting to figure out some wiring problems etc.) Here's where I'm at now, I'll try to give you all the pertanent information I can:
 
   When I bought it, the guy said (and I really do believe him) that he took the bike to a mechanic and it has pretty remarkable compression for its age. He replaced the battery, plugs (D8EA), changed the oil etc.

I should mention that a week after buying the bike, it ran well, but the 4th cylinder took longer to heat up than the others.

   Its been running a little sluggish lately, and about a week ago, the revs would drop and the bike would die when I came to a stop (I chaulked this up to a charging issue, since my battery voltage read low--like 11.4 or something volts-- after such an annoying stop-and-go ride. Now it seems that there could be another culprit).
   It now starts just fine and idles well (a little low, but I figure I'll adjust that later with the tune up). However when I put it in gear and attempt to ride, it will die when I give it any throttle (I couldnt even rev up and ride the clutch for very far before it died). Upon researching I again thought this could be attributed to an electrical issue (regulator or rectifier) which was causing the coils not to get sufficient spark under load...when I pulled the plugs today to check the gap, they appear to be oil fouled. I'm no expert but I feel I know carbon buildup when I see it and carbon fouled plugs are typically black and dry, right? The plugs do look black at the electrode, but they also appear wet for lack of a better word, even on the threads; and it seems to smell of oil (though it could be a gas smell, and I just cant tell the difference).

   So does these symptoms look familiar to anyone? I'm hoping against hope it actually is an electrical issue and had planned to test the electrical systems and diagnose such a problem today, but was stopped in my tracks when I found the plugs. Somebody give me some good news, I am currently in college (read: broke with little free time), borrowing a friend's garage to work on this thing, with a semi-limited selection of tools i brought from home, and rreeaallyy dont want to pull apart the motor for something like valve guides (not to mention I cant even ride it to a shop to have them take a look. They would probably mis-diagnose and overcharge anyways.).

Thanks alot guys, I am new to motorcycles and being able to ask people like you all who know these bikes inside and out can be a real a life-saver.

Oh and Roll Tide!

Davis

[flybox1]

Davis96, nice purchase!
do you have....
Stock airbox with a clean/new filter?
inline fuel filter?
Clean tank?
clogged fuel lines?

sound more like an air-fuel mixture issue.
for little to no cash money out of pocket and a few hrs, you'll need to do a full tune-up.
valves, points gap and timing...
..and definitely a good cleaning of your carbs.
clean all jets, fuel valves, emulsifier tubes, set float levels to 24mm, air screws to .75 turns out.
bench sync slides.  clean up those plugs if they can be.
vac sync your carbs last, and keep us posted!

[camelman]

Hmmm, keep it out of the Tide.  "Tides" usually have corrosive properties on metal.

It sounds to me like your carbs need to be cleaned.  Don't go taking the whole bike apart yet.  I recommend searching for how to clean and bench sync 350F carbs on this forum (quite a few recent posts on it).  The wetness is probably just unburned fuel, and the rough running conditions sound like typical dirty carb issues... especially with the cold #4 header.

All you need to clean your carbs is a can of carb cleaner.  It will take about two hours start to finish (if you haven't done it before).  You might want to buy a tube of gasket sealer too, just in case the carb bowl gaskets don't go back together well.  Clean the spark plugs too.  I use SeaFoam to do it if I'm too lazy to buy new plugs.  Then, put some SeaFoam in the fuel to help clean out the intake, valves, and cylinders.

Ah, what the hell, here's a copy of one of my carb cleaning responses:
--------------------------------------------------------------------------------------------------------
Sounds like you might have missed some passages in your carb.  There is more to clean out than just the stuff inside the bowl.  I should have listed this out for you before, so here goes:

1) remove bowl and jets
2) spray carb cleaner through each hole in bowl area
3) spray carb cleaner into each opening in the front of the carb (there are holes in the venturi - where the air flows)
4) spray carb cleaner into the fuel line until you see some flow into the bowl location
5) repeat for each carb body individually
6) WEAR GLASSES/GOGGLES when you do this
7) Bench sync the slides, or it will run like poop

The choke really isn't needed much on these bikes.  They are pretty warm blooded in the stock configuration.  You will need a little choke, but probably not full choke.  When the carbs are clean and adjusted correctly, it will need a bit more choke.

Fuel ran out of the overflow tubes because the float valves don't seal well on these bikes if they get dry.  When you put the carbs on (or if you ever run out of gas) you need to tap lightly on the side of the carbs once fuel starts to flow into them.  This unsticks the floats and lets them seal.  My bike does the same thing with freshly rebuilt carbs.

I highly recommend pulling the petcock apart for a good cleaning.  A lot of junk collects in there.  You don't want that crap getting into your carbs.

Good luck.  I imagine it will run well after this final cleaning.

Camelman

[fletcha221]

I have a cb350f and mine did the same thing.........really simple answer....the float is stuck. Its getting some fuel, but not enough to fire. Hit the bowl with a rubber hammer and see if it works. If not, I have to say what everyone else is, you need to rebuild the carbs.

[fletcha221]

On a further note, you will find that a hammer is the solution to most of your problems with the 350. Here is my nightmare:)


http://cb350fcafe.blogspot.com/

[camelman]

I forgot to mention in my last post.  Make sure to remove and clean the tubes underneath the main jets.  They might be a bit tough to remove, but they MUST be clean.

I second the comment about loosening up the stuck float.

Camelman

[davis96]

Thanks for the quick responses guys! I was wary of thinking it was some sort of oil leak, as I don't see oil on any part of the exterior of the block or head... I'm really hoping you're all right, the last thing I need is to try top-end work or anything of that nature.

Flybox1:
   -The airbox is stock (I'd do pods, but I'm afraid of having to rejet) and it looks quite clean to me.
   -I do have a fuel filter, its a cone-type filter with what appears to be a copper screen in it (the housing is clear, so i can see the filter element, and it looks clean)
   -The tank is not rusted, its got the basic clean-ish bare metal look on the inside, def. no obvious rust.
   -As far as the fuel lines go, I'm not sure how I would go about determining if theyre clogged...

Camelman:
   -As far as the Tide is concerned, it seems to me that its just going to keep on rolling regardless haha
   -I'd been wanting to avoid having to do a carb cleaning, but I dont mind it if that will help my issues... might be a fun little project
   -So you're saying that with cleaned carbs, it might want to run a little lean and the choke would be necessary? that seems wierd.. As of now, i'd have to open the choke a bit to stabilize the low idle anyways, but i think if i cleaned the carbs and set the idle mixture, this would solve alot of my problems
   -I happen to have a can of seafoam taking up space in my room, do you think if I get the (possibly) stuck float dislodged, that the seafoam might help to cure some of my woes, or at least clean up the fuel system some, which is always good... also, how much seafoam did you add to, say, a full tank of gas? I dont have a full tank, but just for comparison sake..

Fletcha221:
   -Now this is the sort of post which oft put a smile on my face; simple, cheap, possibly a solution to the whole problem
       I realize this may not work, but the hope that it will keeps my spirits high
   -So just tap each of the float bowls a little to hopefully unstick the stuck float? Did you notice an immediate improvement afterward?
   -I have actually followed your blog for a few weeks now, its always good to see what someone else with my same bike is doing to cope with the joys of trying to build an antique which will be ridden at highway speeds hah... on a side note, when i first saw you get those coker wwII-looking tires, I was hooked. Could you pass on some info about the sizes youre running etc? (I'm assuming we run the same size rims, yours is a '74 as well right?)

So since I just got to my buddy's garage, I'm going deliver a little tappy tap to the float bowls and cross my fingers, if not I'll begin consulting the manual and sohc4 about pulling the carbs and giving them a good cleaning. If all goes according to plan I can start my tune up tonight after sorting this problem, I'll keep you all posted!

Cheers,
Davis

[davis96]

In addition to the above questions^... Is there a way for me to drain the float bowl and remove it while the carb is in place, just so I can see whats going on? I know I know I should remove the whole assembly and clean, but I havent ridden the damned thing in weeks, and I reaaalllyyy just want it to run reliably ASAP so i can ride. I did indeed give each of the bowls a little love tap, but it didnt run any better, the idle is still at a dismal 800-900 rpms. As far as I've tried it will not even rev past 5k in nuetral :/

Oh and I looked and discivered I've been running sans-overflow tubes.

[fmctm1sw]

Is there a way for me to drain the float bowl and remove it while the carb is in place, just so I can see whats going on?

I think this can be accomplished with a very small screwdriver.  I'm not sure what kind of cleaning you can expect from that technique though...

[davis96]

Is there a way for me to drain the float bowl and remove it while the carb is in place, just so I can see whats going on?

I think this can be accomplished with a very small screwdriver.  I'm not sure what kind of cleaning you can expect from that technique though...

I was just thinking in terms of if there is a float stuck, i'd be more acurately able to diagnose which one and dislodge it, maybe take a peek at the bowls and see how rough they are, just trying to get my best result while avoiding pulling the whole carbs assembly for now.

[fmctm1sw]

Is there a way for me to drain the float bowl and remove it while the carb is in place, just so I can see whats going on?

I think this can be accomplished with a very small screwdriver.  I'm not sure what kind of cleaning you can expect from that technique though...

I was just thinking in terms of if there is a float stuck, i'd be more acurately able to diagnose which one and dislodge it, maybe take a peek at the bowls and see how rough they are, just trying to get my best result while avoiding pulling the whole carbs assembly for now.

One problem I ran into with that is that I couldn't get the main jets to stay in when I was trying to put it back together.  Decent, non crushed o rings would probably make them stay put tough....

[davis96]

Is there a way for me to drain the float bowl and remove it while the carb is in place, just so I can see whats going on?

I think this can be accomplished with a very small screwdriver.  I'm not sure what kind of cleaning you can expect from that technique though...

I was just thinking in terms of if there is a float stuck, i'd be more acurately able to diagnose which one and dislodge it, maybe take a peek at the bowls and see how rough they are, just trying to get my best result while avoiding pulling the whole carbs assembly for now.

One problem I ran into with that is that I couldn't get the main jets to stay in when I was trying to put it back together.  Decent, non crushed o rings would probably make them stay put tough....

Forgive my ignorance, but are you saying that if i do remove the float bowls that a bunch of parts will fall out?

[fmctm1sw]

Forgive my ignorance, but are you saying that if i do remove the float bowls that a bunch of parts will fall out?

The main jet is held in by a leaf spring of sort that rests on the bottom of the float bowl.  The force of gravity was enough to make my jet fall out.  I couldn't hold the leaf spring while putting the bowl on it.  Eventually you have to let go of it to get the bowl back on.  A new jet (from a rebuild kit maybe) would probably have an o ring tight enough to make the jet stay in by itself. 

[davis96]

Forgive my ignorance, but are you saying that if i do remove the float bowls that a bunch of parts will fall out?

The main jet is held in by a leaf spring of sort that rests on the bottom of the float bowl.  The force of gravity was enough to make my jet fall out.  I couldn't hold the leaf spring while putting the bowl on it.  Eventually you have to let go of it to get the bowl back on.  A new jet (from a rebuild kit maybe) would probably have an o ring tight enough to make the jet stay in by itself. 

Oh ok, I think I can handle it... I  cleaned up the plugs (they are literally brand new, so i have no qualms about reusing them), I think from here my plan is to first run some seafoam through it, in hopes that the carbs are not rediculously crapped up since the guy said he "had the carbs done" whatever that means. If that doesnt improve the way it runs and unstick the problematic float, I'll drain and pull the bowls, clean everything up down there and put em back together. Then a tune up and hope for the best.

[fletcha221]

Davis,

My bike (actually a 1973) looks a little different right now, the front forks are lowered 1 1/2 inches and I built custom exhaust that really looks great......and it might even be legal! I need to rejet it.................Again, went from the 75, to the 80, built a full exhaust, and it STILL needs 90+ Jets. I did the pod filters, and built the battery relocation bracket. For what it's worth, keep the airbox as is and use the correct battery. I have a smalled battery now, and with the new Dyna-S Ignition (HIGHLY HIGHLY RECOMMENDED), the bike runs off a deficit voltage wise.....so basically it drains you battery at idle. So, i need to ride around like a lunitic to keep the sucker charged.

I have some advice for you.....that I learned the hard way.

1. Carbs: pull them off, keep the airscrews at the stock setting, rebuild them correctly replace the main and slow jets. Use an air compressor to clean out all the passages. CLEAN THE BOWLS TO A MIRROR FINISH, MAKE SURE THE FLOATS ARE FREE and they are contacting the pins correctly. These steps will save you HOURS down the line. Ive pulled my carbs off 7 times....post "halfass rebuild". Do it right, once.

2. Your carbs will keep sticking (either not enough fuel, or too much....you will find your bike peeing quite often), see advice #1.

3. Become really good friends with www.bikebandit.com

[davis96]

Yes I definately plan on doing a thorough cleaning on the carbs a little bit down the road, but right now i just want to ride it, but it is unrideable.. Every day that its nice outside I get so mad that I cant enjoy the bike ive put so much time into.

btw, the bike looks great, I'm not super surprised you'd have to use such big jets, i mean that exhaust is minimalist to say the least ha, I wanted to do the same thing (straight dump) with my MAC 4-into-1, but I don't want to have to deal with rejetting. Hell im even scared to take the silencer/baffle out for the same reason...
So could you let me in on what size tires you went with? I'll assume we have the same 18inch wheels..

[bender01]

You need a strong battery also!! A new one if yours is in doubt! I really think that will help! Alot.

[fletcha221]

Hey, sorry I forgot to mention the tires. yes, the rims are stock powdercoated cb350f 18 inch rims. I need to find the exact specs for the tires, but they are firestone replicas from coker.....and they are a tight fit:) Dont plan of keeping your fenders if you want that look. I just wanted to give the little bike some "bulk", so I went with a bigger seat and the nobby tires.

Jetting the carbs is cake, all you do is replace the main jet (the one that the butterfly clip holds), go with the MAC exhaust, with the baffle in, the bike wont run right without a baffeled exhaust. I made my custom exhust with some exhaust adapters from pep boys (used as crude torque cones) and pips and baffles from a 1979 harley sportster.

As far as the urge to ride, I hear ya man! But.....I dont like being a nay-sayer, but the bike isnt going to run until you do it. Seriously, pulling the carbs, cleaning them, and putting them back together might take a few hours tops. Spend the next rainy day with a case of beer, a can of carb cleaner and a dremel....go nuts. Bench sync the sucker and put in back on......she will run like a bat out of hell. Also, take some fine grit sandpaper and clean your points.

[flybox1]

Yes I definately plan on doing a thorough cleaning on the carbs a little bit down the road, but right now i just want to ride it, but it is unrideable.. Every day that its nice outside I get so mad that I cant enjoy the bike ive put so much time into.

(insert yoda voice)
the urge to ride is strong with this one! 
Do not give in to the dark side Davis96.


most of us suggest pulling your carbs and giving them a good cleaning as well as all of the tuneup steps.
...but what do we know! 
there are WAAAY too many parts in there that, if left dirty, stuck, incorrectly measured/set, etc., will have a big effect on air-fuel mixture.  your bike will never run as it should until you get in there.
You say you want to ride, awesome!
....but do you want to walk/push home?!
fouled plugs w no spark, not running on all cylinders, overflowd bowls leading to fires...dude, take the time and do it right!.
get good at pulling your carbs.  especially if you plan on rejetting to a different exhaust.
the first time i pulled my carbs to refresh them took 2.5 hrs.  i had to do it several times after to get the floats set right, again for another bench sync, and then again to for jetting.
now, 30 min flat to completely take them off, adjust, and reinstall.

you must un-learn what you have learned! 

[fletcha221]

I second Flybox! The hardest part of the carb on/off is putting the throttle cables back on.....which is an art in its own right. Spend the time and do it right, you will be proud of yourself....and you will also not be on fire....which is nice as well.

[davis96]

Ok i spent sometime with the bike today and my schedule freedup some today so you guys convinced me to pull and clean em up... A few of these screws are giving me hell and im wondering how you guys handle these little buggers? Im hesitant to take an impact driver to such ostensibly fragile parts...

[fletcha221]

Do you mean the little screws that hold the bowls on? They suck, Liquid wrench, let them sit for a few. Bad news oem replacement ones are hard to come by...good news, you can get similar fine thread ones at home depot, etc. I flip the carbs upside down, and rest them against a 2x4 block, then you can use your body weight to press down on the screwdriver and get them off.

I would suggest lots of profanity.

Keep telling yourself "this would cost me a fortune having a "real" mechanic do this.....this would cost me a fourtune having a "real" mechanic do this....."

[HondanutRider]

I wonder if those float bowl screws get stuck on because of sealant someone may have used on the gaskets for the bowl bottom?  I've never had that problem, but I can relate.  One suggestion might be to try heating them with a heat gun or even a hair dryer.  I wouldn't try any flame as a heat source and I'd still advise to make sure all the gas is drained before any heat is applied.  I would expect the heat might soften anything that is "gluing" those screws.

BTW this technique of heating also works great to free stuck slides which have become frozen from old gas evaporating and gumming-up the insides - that I do have experience with.

[flybox1]

yeah, someone might have sealed them up good years ago.
liquid wrench, pb blaster...either of those would be good to soak and release those screws.
be careful as the threads on the carb body can be stripped when you are reinstalling the bowls.  hand tight is all you need.  the heads were all effed up on mine from the PO, so i went for new zinc plated screws from a local specialty screw shop.  $.15 ea.

[dave500]

spark plug caps,make sure they are good first,do the points and condensors but check the caps,5kohms.if they are as old as the bike they could well be your demon.a lot easier than pulling carbs over and over.get that ignition tip top first!