CB350F plugs

[Gnievomil]

Hey everyone, i have a CB350 motor that is giving me fits, the carbs have been completely gone over this past fall so lets talk about that later, I have white smoke and the brand new plugs in the 1st and fouth are black fluffy and white smoke out of the stock exhaust. 10k miles and pampered bike. New coils so thats not it. i tried the compression test last night but it didn't give me anything to stand on as all levels are within normal range. the thing runs smooth but wants to choke out everyonce in awhile.

Any suggestions and if you suggest a leak down test then i would like to know how to do it

anything is appreciated.

 

[crazypj]

Sounds like rings fitted upside down
White/blue smoke is oil burning
What numbers did you get for compression?
Throttle wide open?
Leak down test is easy, you can use compression test adapter, just remove Schrader valve so air can get into cylinder.
Set 100psi at compressor gauge, put cylinder your testing on TDCC, connect compressor to adapter and see how much air leaks past rings/valves. 10psi drop is fine, more than that indicates a problem
Remove dipstick and listen for air in crankcase, listen at carbs, listen at exhaust, you can get a pretty good idea what's going on

 

[teazer]

I don't think it's a leak down issue. Black plugs implies rich mixture, so it's back to the carbs and air filter(s). 1 and 4 are on one coil and 2/3 are the other and that makes one think points/condensor or some related issue on that side. You could try swapping the coils and see if it's a weak coil on one side. If that makes no difference, check the poinst for that side.

I'd also check the carbs for leakage past the float valves, oversized jets (may have been drilled out or damaged or replaced by a PO) or other anomalies.

 

[crazypj]

White smoke implies oil burning rather than rich mixture.
Was motor 'stuck' at any time?
Could be rust in bore or broken oil rings? (or rust in bore caused broken ring?)

 

[Gnievomil]

Thank you all for your insight. A few things, the engine was never struck and the bike never laid down. the coilds were replaced this pas week(maybe i need to redo the timing?) compression was running in the 140's with standard airbox filter no pods. Im unsure about the rings since i haven't gotten that far i was looking toward your input before heading down that road. Ill go over the carbs again this weekend. They were rebuilt by a pro....shade tree carb guy who had some of the parts upside down and caused it to dump gas into the carbs i had a shop look it over and correct that. any ideas on where to start ?

 

[crazypj]

Thanks for the extra info, makes trouble shooting slightly easier ;D
What's the temperature and humidity like where you are?
It could possibly be water vapor or just damp in something?
There is a possibility it's previous flooding and faulty coils?
Re check points gap and timing, 1 & 4 fire at same time so it does seem more ignition related (should have read a bit slower earlier )

 

[Gnievomil]

THe humidity and temp is pretty high here in Knoxville. today i got it out and revved it just to see what happens if i run it longer and i was going to swap the coils but family showed up for the day and had to stop playing. but then i noticed a gas and oil leak from the number 2 exhaust pipe connection. Sigh im about to just part it out. i already found 2 750's for 500 each that run i might as well just start with that. instead. CrazyPj it's not water vapor or a build up of oil as far as i can tell. the previous coils before i just put on these were original and toast. Ill check points again and get a timing gun this week to test that. I have the feeling that ill end up completlely rebuilding this engine before i can enjoy this bike.

 

[Gnievomil]

Well i tried adjusting the airscrews and it pretty much solved the problem for my #4 but #1 didn't change. I really don't want to have to take the carb apart or take it to another shop that will tell me they know what it is and charge me 300 just to be wrong again after i ride it home. Did i mention that fuel is leaking out of the exhaust mounts as well and smoking.

next week ill look at it again but i'm to the point of just driving it into a lake and smiling.

Any suggestions?

 

[crazypj]

It's carbs, float level or dirt in shut off valve, or both
It's a PITA to get carbs on and off with stock airbox but you may as well do it yourself

 

[Gnievomil]

Alright, Tonight i finally got around to yanking my carbs off. Yes it is a PITA to do witht he stock airbox. I ened up destroying one of the ring clamps pulling it out. I eventually won the fight though and pulled the whole assembly out getting it all back in looks to be a nightmare.

Anyways the carbs. the other day i adjusted the airscrew to #4 and that pretty much solved the issue there. But #1 had zero change so i pulled the carb tonight and looked at the jets and cleaned it really well, and inspected the floats. Now upon inspection just by looking at them #1's floats seem to be lower than the others. Would that cause my flooding issues? and if not then i don't know what else it could be since everythine was clean and looked fine. ill submit a picture next post in a minute.

 

[Gnievomil]

pictures.