Topic: CB350F hesitates when warm

[deanoevans]

Hi guys,

I have a '73 cb350f.
I rebuilt the carbs put them back on and synced them. It starts ok, idles great, runs great when it's cold, but after it warms up it hesitates on the throttle. And I feel like it's a little louder.

Any ideas?

Additional info that might be helpful:
I previously had a problem of a vacuum in the gas tank after I replaced the gas tank and put my old key latch on the new tank. The latch was pulling the new gas cap too tight and blocking the air flow. So I put the old latch back on and rebuilt the petcock just to be sure. Gas flows nicely from the petcock now.

[1timduke]

Does the hesitation happen throughout all throttle positions?   Check the condition of the plugs after it warms up.   If they're fouled, you might have a faulty choke.

-Tim

[schwebel]

I have had the same problem. Freshly sync'd and rebuilt carbs, tming set, new plugs ...etc. It would run great, until about 10 minutes later. Then it felt like it was studdering on acceleration from a stop. Mine ended up being that is was running too rich. It has been much warmer around here, and as the bike was warming up the air going into it became hot and less dense. I turned out my air screws about 1/2 of a turn and problem solved. Do you get any backfiring? Has it been hotter outside where you are?

[deanoevans]

It only hesitates when accelerating from idle. Other than that it seems to run great.

I checked the plugs and they look black. I thought it might be rich. I adjusted the air screws but it didn't do the trick. It just seemed as if it was running slightly lean.
I adjusted them back and synced the carbs. I also set the timing. It does run a little smoother now. But it still hesitates from idle and will occasionally stall, but only after the engine warms up.

In what way could the choke be faulty?
I haven't fiddled with the choke as of yet.


Thanks for the help guys. This website is great!

[fmctm1sw]

Has it been hotter outside where you are?

I saw this talked about in some other posts.  My '73 ran very well until a month or so ago.  It bogs a little at full throttle now.  Replacing my air filter (which I now know is one thing that the dealer can't beat eBay in) went a long way in helping but it still will do it.  Now that I think about it, it was right about the time it got real hot here.  It is miserable here.  Temperatures in the mid to upper 90's week in and week out.  I didn't think it was possible for it to be rich at full throttle, considering the exhaust is wide open.  Guess I'll ride my '72 when it's hot and my '73 when it cools off...