Topic: cb350 running rich and all over the place

[wingman]

Hey everyone

I have just finished rebuilding the carbs on my 350f - the PO said he did and they have probably never been rebuilt, but that is another story.  The kit I used was a K and L kit.  I am running the stock air box (Just can't bring myself to do pods, although I do have them for this bike) and OEM airfilter (new).  I installed new plugs (gapped to factory spec).  The bike will start and running, but twisting the throttle does very little - usually rev to 3 or 4k sputter and die.  The mixture screws are at 2 turns.  The bike is a bear to start and when it does, it hunts for idle.  I pulled the plugs after trying to figure it out and #1 looked ok, the rest looked like they had been dunked in used oil.  I check to make sure that all cylinders have spark - they do - and cleaned and regapped the plugs.  Cylinders 2 and 3 get hot and I mean really hot - fast. Within a minute you can boil spit on the exhaust - I touched one on accident yesterday and invented some new words to describe that pain.  I see smoke out of 2 and 3 and the exhaust coming out of there is much more forceful than out of 1 and 4.  My bike has drag pipes - 4 into 4 - I have new exhaust on the way because I am tired of the neighbors making fun of my "lawnmower motorcycle".  Would trying the pods be a bad idea with the stock jetting - I have not changed that.  I know these bikes run rich, but with the pods would that lean it out?

I adjusted the valves (intake and exhaust) and checked the timing on the bike (when it isn't "hunting" for idle).  Needless to say I can adjust the sync of the carbs because well - it doesn't seem to idle right.

What am I missing?  I have tried everything I could find in the clymers manual.

Thanks in advance for any help.

[mlinder]

sounds like 1 and 4 arent firing.

Verify, and work from there.

[wingman]

what is the best way to verify that they are firing. 

Sorry, I don't mean to be stupid.  I know that they are getting spark.  There is some backpressure coming out of the cylinders, just not as much or as smokey as 2 & 3

[mlinder]

when you start the bike, and let it run for a bit, when you can get spit to sizzle on 2 and 3, how hot are 1 and 4? Can you touch them?

[wingman]

After it gets warmed up, the exhaust on 1 and 4 gets hot, but not as hot as 2 and 3 (which are untouchable after 30-45 seconds of running).  I also think that one and 1 and 4 are firing due to the fact that plug 1 looked the best after I pulled all four plugs (the least amount of build up) 2, 3 and 4 were bad.  

How to proceed from here?

[bistromath]

if a plug isn't firing at all, it's not going to get much build up =)

if you can touch 1&4 AT ALL without flash burns when the bike is warmed up, or if spit on the headers doesn't sizzle immediately, they're not firing. since it's 1&4, it's almost definitely an ignition problem. the usual culprits: coils and points.

[flybox1]

Does your stock airbox have holes in it?
did you do a bench sync while your carbs were off? adjust the slides?
Did you adjust/check/verify your float levels are at 22mm?
do the float needles operate as they should?
after all the above was done, did you do a carb sync?

2turns out on your A/F screws sound way rich.  
stock is in the area of 7/8 to 1.5 turns

more details please!
post pics of your plugs and indicate the # cyl they came out of...

I would suggest pulling your carbs again and doing a bench sync.  while they are off, verify the internals are clean, clear, and that the floats are at 22mm.  
check your filter.  clean it or get a new one. perform a carb sync with AF screws out 1 turn.

if you are still running rich, you may need to go up one needle clip setting to lean them all out.

[wingman]

I will pull the carbs tonight and check float level.  Not to be dumb, but I can't find instructions on how to bench sync the carbs for the 350.  Any instructions somewhere I have missed?

[flybox1]

check the FAQ's, tons of info, but here it is in a nutshell.
while the bank of carbs is off, set the idle screw so it just touches the tab which controls all the slides(its on the right side of #4)
remove the throttle return spring from its top clip(between 2 & 3)
remove all the teardrop shaped covers on the top of the carbs. (4) look inside, there is a nut on top of each of the slides.
bend down the tang which locks the nut on top of each of the carb slides. (one in each carb) and loosen the nut.
do the following for each carb separately..
insert a 1/8" drill bit into the airbox side of the carb intake, and gently press the slide down on top of the drill bit. 
Tighten the nut to seat the slide in position and bend the tang back up to secure the nut. replace the carb top gaskets/covers.
once all 4 are done, and you peer into the airbox side of the bank of carbs, they all should be seated at the same height, with a small opening, and open at the same rate when the idle screw is adjusted.

[wingman]

Thanks for everyones advice so far.  I pulled the carbs last night.  When I went to drain the bowls, there was no gas in 1 and 4.  None.  Totally dry.  2 and 3 had gas in them.  Guess that explains why I had great spark to 1 and 4 but they still weren't firing.  I each carb out of the carb mount plate and cannot figure out for the life of me why 1 and 4 don't have gas.  All lines are clear.  Last week I took each carb apart, cleaned in simple green, blew out all the passages with compressed air and carb cleaner and carefully reassembled them.  

What are the small black hoses (maybe 1/4 inch long) that connect 1 and 2 and 3 and 4?  I thought they were vent lines.  2 and 3 have attachment for hoses (which I installed).  There are the thicker connectors (hard plastic) that have 4 O rings that should carry the fuel from the connection at 2 and 3, correct?

Thanks to everyone so far.  I am going to figure out this gas issue, bench sync the carbs and get this thing running!

[Lars]

The CB350F has only one fuel line coming in between carb 2 and 3. Check the distribution channel for carb 1 and 4.

The 2 small brass pipes dressed with small rubber hose between carb 1 and 2, 3 and 4, are vent channels which start at carb 2 and 3. They align the asmopheric pressure inside the floatbowl, thus pressing the fuel from the carb bowls into the venturies.

To bench synch the carbs, first give the idle adjustment screw a couple of turns - to be able to adjust back later if necessary. Loosen the four locknuts between the carbs 1 and 2, 3 and 4. Find a suitable long and hard unit like a tiny drill and put it into the venturi under the slide and asjust the slide down - exact similar on all 4 carbs. I use this method only as a presynch, always synch the carbs with an instrument - Morgan Carbtune -when carbs are back on bike.

Air screw is to be set at 0.75 to 1.00 turn out.

Lars

[flybox1]

The CB350F has only one fuel line coming in between carb 2 and 3. Check the distribution channel for carb 1 and 4.

Lars

+1
blow air or carb cleaner into the holes of #2 and 3 where the float needle sits to clear the fuel channels.
wear eye protection 
or check to see that the float needles you used arent stuck somehow.  with carbs installed, and the bowls empty or low on fuel, the floats fall and release pressure off the float needles.  if this needle doesnt release fuel wont flow.
Keep at it.

[wingman]

The floats were way way way out of measurement - I made a float level gauge out of a floppy disk and got them all set at 21mm.  If the floats are way out of adjustment on 2 and 3 would that prevent fuel from getting to 1 and 4?

I didn't wear eye protection last night and got an eyeful of carb cleaner.  Fortunately I flushed my eyes fast and pulled out my contacts.  No damage but man did it burn.  The passages all appear clear but I will give it a go again tonight.

[flybox1]

no, the floats will only control the levels for that bowl.
if 1 and 4 are still not getting fuel,  you might want to boil or soak the bank of carbs in simple green or lemon juice to free up the passages. 
worst case, you'll have to separate them.

[wingman]

I have already separated them - for like the 5th time, I am getting good at it.  When I spray carb cleaner through 2 and 3 towards the inlets for 1 and 4 it goes through fine.  I will recheck 1 and 4 tonight to make sure there is flow going through them.

Is it possible I damaged my engine running it with only 2 and 3 firing?  I would say it ran for a total of about 1 hour with a fan cooling it while I tried to figure out what was going on.

[flybox1]

ok. Do your bench sync if you havent already.
then...here's how to check that fuel gets to each bowl, and that your floats are doing their job.
Get a 2' section of 1/4" hard clear tube from your hardware store.  not the surgical tubing.
cut it in to (2) 1' sections.  mark the middle of each and slowly heat it with a heat gun or over an open flame.  heat it slowly and stretch it.  this will create a taper in the middle.  cut it at the smallest area.  do this for the other section of tubing as well.  take all of your bowl drain screws out, and screw in this section of tubing..  loop the tubing up next to each bowl and tape or secure it in place. like a snorkel for each bowl.
set your gas tank in front of you on a cinder block or a few phone books.
hook up your fuel line to your carbs. support them and see they are level, as if they are installed.  turn on your petcock.  the fuel will pass to each bowl and fill it.  it should fill to 4mm below the bowl gasket seam.  you can verify this by looking at the tubing next to the carb body.  if some are too high, or overflow, you can make adjustments to your floats, or check the fuel float valves again.

[wingman]

I reinstalled the carbs yesterday.  I did what flybox suggested and made sure that carbs 1 and 4 were getting gas - why they weren't before I don't know, but they are now.  Did a bench sync while I was at it.  Fought with the stock airbox for a while and finally got it on.  Bike fired up right away and after a little tuning, runs good. 

The only problem now is that I have to leave the choke 1/2 to 1/3 open to get it to run smooth.  My idle screws are out 7/8 of a turn.  With the choke half open, it idles perfect and pulls to 10k like the little monster it is.  I guess I need to back out the idle screws a little bike to make it idle without the choke open?  I don't have any more visible smoke coming out of the bike so I got that going for me. 

I didn't have time last night to pull the plugs or mess with it too much.  I also have a new airfilter on order - should get it saturday.  The one that is in there now appears to be the original and is a pretty shade of grey from all the crap it has accumulated.  I am gonna guess that this is part of the problem. 

[flybox1]

nice one.
once your bike gets hot, you should be able to push your choke all the way open, and fiddle with your idle set screw to get it to idle down near 1000.
another thing you might want to take a look at is the seals around the airbox boots.  (sorry its after the fact, and yes, i know getting that bugger in and out is a *itch) most boot seals will delam over time.  check yours. i picked up some liquid black electrical tape and gave them 2 good coats. it stays pliable but will seal the airbox from leaks so all the air is passing thru your filter. 
i new clean air filter does wonders. 
Only when you are sure the air into the carbs is coming thru the filter, and you verify your plug readings should you adjust your a/f screws to improve perf.
if it still doesnt get better, a carb sync then a series of plug chop tests will be of great help.

check this if you get to that point.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html