Riddle me this????

axeugene27

New Member
Been working on the bike all day and am perplexed. I was kicking at this thing all day wondering what was the deal. No go... I gapped the points set the timing, synced the carbs. adjusted air screw to 1.25 turns out. Could not get it to start. The spark does not look great kind of weak but it is there and it is blue. stopped for half hr and ate dinner came back and kicked it over started up. I quickly adjusted the air screw and set the idle. Had it running real nice for about 2 minutes. Then it sputtered and died. Would not kick over again..... I have had this thing do this a few times. I don't understand if the carbs are to a point the bike can idle well one day or even one minute and not start the next. This leads me to believe that 1. I am somehow flooding the engine. 2. the spark condenser is going bad and the spark is only good sometimes. Any thoughts?
 

axeugene27

New Member
n0 it's a 350 no the bowls were plenty full of gas all day. Took the carbs off like 3 times. Playing with idle stuff.n It doesn't appear to be a flooding issue either as the plugs are pretty dry. I don't know maybe my battery is dying? You don't think a condenser would cause that issue?
 

Swapmeet Louie

Put some metal in yer eye....
condensors dont prevent anything but voltage spikes. You can run without them for a bit before you fry your points.
 

MotorbikeBruno

Active Member
Swapmeet Louie said:
condensors dont prevent anything but voltage spikes. You can run without them for a bit before you fry your points.
Didn't know that...not that I want to try, but good info to know.

If your plugs were dry...you aren't getting fuel. If you kicked it over several times, and they aren't wet.....look into bowl heights? Verify that pilot passages are clear? Will it fire up with a little ether? If so. Its fuel related.
 

Swapmeet Louie

Put some metal in yer eye....
Dude, I'm not trying to make you feel like any less of an enthusiast. But honestly, I've bought so many bikes where the p.o was selling it because they were un sure on how to use a pet cock with a prime setting. And if the bowls are dry it takes several minutes to work. If not given enough time, one would kill there battery try to start it. I know a cb 350 doesnt have a prime. But, when the bowls are dry, it will take a few minutes to fill. Especially if your petcock is not flowing at maximum potential. It really is the only reason for it not to fire if everything is dialed and your battery had a good charge.
 

MotorbikeBruno

Active Member
Swapmeet Louie said:
Dude, I'm not trying to make you feel like any less of an enthusiast. But honestly, I've bought so many bikes where the p.o was selling it because they were un sure on how to use a pet cock with a prime setting. And if the bowls are dry it takes several minutes to work. If not given enough time, one would kill there battery try to start it. I know a cb 350 doesnt have a prime. But, when the bowls are dry, it will take a few minutes to fill. Especially if your petcock is not flowing at maximum potential. It really is the only reason for it not to fire if everything is dialed and your battery had a good charge.
I agree. I was giving one more option...as I was hoping the original poster had already figured the petcock into play. If he has not, the easiest thing I do is run the bike without the tank to verify this. I do this on all the bikes that come into the shop, so that I know MY carb cleaning was done correctly, if there's a problem it's usually the owner's gas tank that is the problem. Get a small funnel, hook it up to the gas line and watch the gas go down until it stops. If it never stops...and you are pissing fuel everywhere, you know that's an issue, if it stops, then the floats/needle are stopping said fuel. At which point if the plugs are still dry, you have a float setting/ jet setting/ or just plain dirty carbs. I have to use the prime feature on my KZ550 every time I start it if it's been sitting for more than a day. I installed clear fuel filter and can verify fuel is going in that way.
 

axeugene27

New Member
No offense taken louie I have done dumber shit than that before. Just to clear things up I have clear line/ with inline filters and brand new mikuni carbs The petcock has been cleaned and fuel flows freely though both lines.I can see the inline filters are full of gas Also every time i take the bowls off the carbs they are full of gas so idk seems like that is not the issue. It acts like it's flooding but the plugs are not wet I don't get it. Those carbs are new so they can't be dirty Unless some gunk escaped the filters and clogged a line somewhere. I don't think so though I ordered some variable jets so when i put those in I will try spaying out all the passages with carb cleaner. I don't know man I had it running today and even rode it for like 10 min acts like it's rich I say that because when i loose power at around 3k rpm it doesn't improve with choke. Pulled plugs when i got home and they were black with soot. Let it sit another couple minutes wouldn't start. WTF. IDK maybe it's the gas tank vent or something. Even if it's running rich it shouldn't flood out and if it was flooding the plugs should be wet right? I kind of think it's a fuel starvation thing at start up I will check the float height but in a brand new carb i don't see how that can be off unless the spec height isn't right for this machine????
 

Big R

Heaven is so far away.
Mikuni carbs have their own float height - regardless of what they are mounted to. And the height can be set at Mikuni, but due to handling in shipping it can be off when they arrive at your door.

If you think it's running dry, pull the inline filters off, check you gas tank vent, petcock filter (if installed), and the carb vent tubes. All of these can restrict flow to the carbs. Sooty plugs are caused by the air/fuel mix being off - which isn't always jetting. Dirty air filters, timing, weak spark, etc can all throw you a loop.
 

axeugene27

New Member
I know it isn't running dry I pulled the carbs so many times and always have to drain the bowls. I also have ensured fuel flow to the carbs umpteen times. That is not the problem. I do however wonder if float height would cause this> I also find it awfully strange that i cannot get it to start with choke on. it seems that the choke circuit does nothing when i choke it during idle (when i can get it to) it nearly kills the engine. BOy oh berto
 

joeybaggadonuts

comin in hot, hit em wit it
could it be a restriction from the air filter? too crudded up or something? When I had this problem on my bike I took out the fuel filter and reset the float height. but my bike also would spew gas randomly like an a-hole so i knew it was a float height problem. took the filter off because it would occasionally not get enough gas.. so i'd say definitely check float height and air filter. and while your at it, might want to check for vacuum leaks on the boots? That'll mess you up. Just my amateur two cents...
 

MotorbikeBruno

Active Member
Yup. What are your air/mixture screws set to? And does this have needles with clips on them? Could it be pulling gas from main jet if the needle isn't low enough? If anyone knows if that's even possible, I'd like to know the answer to that... ???
 

Sonreir

Oregon
DTT SUPPORTER
MotorbikeBruno said:
Yup. What are your air/mixture screws set to? And does this have needles with clips on them? Could it be pulling gas from main jet if the needle isn't low enough? If anyone knows if that's even possible, I'd like to know the answer to that... ???
Anything is possible, but this is pretty darn low on the list of probabilities.

If the problem is truly intermittent, my vote is going to be an air leak of some sort. Any clogging would be repetitive in nature and should be reproducible.
 

axeugene27

New Member
thanks for the input guys. The needle clip is set at the center position I wasn't gonna start messing with the needle jet until i could get it to start/idle well as i am under the impression that is a mid range issue.
Tomorrow my plan is to
1. tear carbs down completely check float level which doesnt apear to really be changable or needing to be changed.Question on that though -->what should the float level be set at for vm30's on a cb350?? is it the same height as spec for the keihin carbs? the standard float height for the VM30 is 22-24 mm should i go with that ?
2. Blow through all carb passages with some spray carb cleaner.
3. reset points gap- although i am sure it is perfect.
4. Recheck ignition timing- although i've done it 3x
5. check valve clearances again.
6. recheck compression- last check was 170 on left 175 on right.
6. I don't know how to check a gas cap vent for functionality but i will attempt to clean the vent. (though i think this is a non issue as it doesn't matter if the vent tank cap is open or closed.
7. I will check petcock again for gunky crudiness but i think this ship has sailed.

I ordered some new jets from dcc. But i think my set up right now should at least provide idle I will tweak the jets once i get this figured out. Here is my set up right now.

Main:190 ( i know it's prob too big i ordered 140-150 to work with later)
Pilot: 30 ( i don't know where to go with this one but i figured it should at least start with this and then i can plug chop to figure it out) I have 20,25, and30s only jet i have i can get it to run with is the 30s I ordered 40,45,50 because i saw dcc was selling their carbs with 50s installed so we will see.
Needle: 6f4 clip is in center currently.
Needle Jet: 159 p5
Slide: 2.5 cutaway

ANY HELP OR THOUGHTS ON CARB SETUP OR ANYTHING ELSE I SHOULD CHECK REDO WOULD BE WELCOME. THANKS AGAIN DTT

I bought these as they stated they were "set up" for a cb350 I'd like to punch that guy in the nose.
 

Swapmeet Louie

Put some metal in yer eye....
some carbs have no mixture screw. A close pilot and needle adjustment is the only way to get it to idle... your float level i have no idea... I'd have to look it up.
 
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