CB350F poor starter runs irratically

[Budgie955]

Hi
I picked up a 350 four cheap but I'm struggling to get it to run right. It fires up eventually without choke won't rev cleanly ,just runs generally rubbish . Pots 1 and 2 down pipes are hot , 3 and 4 Luke warm.
It's running on electronic ignition, timing is spot on , valve clearances are spot on . I've had the carbs off cleaned the jets out  cleaned the bodies out with carb cleaner . Blown through with compressed air, I put the bodies in ultrasonic cleaner at 80 degrees for an hour .Float height checked ,  I put it all together, no different. Still struggles to start . Runs terrible
I've not checked compression yet as I'm waiting for the correct adapter to come . As this is my 1st four cylinder (I'm used to honda twins) just wondering if there's something I have missed ? I was convinced it was carburetion because putting the choke on killed the engine even from cold . It's also had new plugs new battery. The spark is good on all pots ,
Any advice welcomed
Thanks
Dave Sheffield UK

[K2-K6]

What's the air filter element like ? Old, new, suspect origin  ?

They are very sensitive to flow of anything to do with intake volume/ vacuum etc.

From your description,  it sounds rich, too rich.

Try without filter in place to see what you get.

[Mikep328]

Some thoughts...

 Of course if the compression check reveals a problem, that has to be sorted first.  ASSUMING there is no issue there...

Are the ignition advance weights free and moving properly/weight springs present and in good condition?

I know you said you are getting a good spark but it's still worth checking...are the ignition coil spark plug wires connected to the correct cylinders - left coil (as you sit on the bike) goes to 1 and 4, right coil goes to 2 and 3).  IOW, if correctly connected, your cool cylinders are each fired by a different coil which would tend to eliminate a coil as a problem.  I know you said there was good spark but coils can do strange things...

It sound like it's running rich.  Are you SURE the idle/slow speed passages/emulsion tubes are clear AND undamaged?  I pulled the carbs on my poor running 400F twice before discovering two distorted emulsion tubes (damaged by some previous owner's disassembly/reassembly) and one clogged idle air passage that I was sure I had cleaned thoroughly.  The bike went from being somewhat recalcitrant to totally smooth acceleration - no hesitation/flat spots.  As others more knowledgeable than I have pointed out, the idle/low speed system on these bikes has greater effect on higher RPM ranges than is usually considered "normal."  The bad emulsion tubes had holes that were compressed and egg-shaped.  As others have noted - aftermarket carb "brass" (jets emulsion tubes/float valves needle/seat) seem to be randomly unreliable compared to the OEM Honda parts.

E-ignitions can cause problems in odd ways - components/connections become intermittent/fail.   One of my old bikes with an aftermarket E-ignition ran horribly when I bought it. I removed the E-ignition and installed the OEM points system and the bike ran perfectly...  

GOOD LUCK!!!! 

[Budgie955]

Thanks for the pointers , the air filter is good . I'm trying to get it sorted without it in place , just easier to get carbs off. Advance weights are fine too. Pots 1 and 4 run off the same coil, pot 1 is hot 2 is luke  warm. So it's not the coil . I have the carbs off again . I'm going to clean again just in case .
I'll keep you all posted
Cheers

[K2-K6]

Also have a read of this thread https://www.sohc.co.uk/index.php/topic,32423.60.html should be page 5 as it details recently made inspection of needle and jet interface for wear etc.

If there's substantial wear in the main jet/emulsion tube/needle etc, then uncontrolled fuel from that source will overwhelm the concise metering needing and delivery via the idle circuit at this lower rpm operating range.

[Otis]

When I first got mine it ran but didn't feel right. Re did the tappets and carbs to no avail. Checked the electronic ignition and it was spot on.

By chance, a neighbour who knows a helluva lot more than me was assisting and felt something wasn't quite right with the ignition. We advanced the ignition a tad and the bike suddenly came alive.

Might be worth playing a bit?