Troubleshooting Stumbles From Idle

Hey all,

I am just getting my project bike on the road a bit. I've been fixing problems as they crop up but I'm looking for some feedback on on issue I'm seeing.

When I start the bike, it idles fine after firing off a single kick. Every time.

Then when I pull the throttle up to take off the first time or two, it jumps right to it without a problem. No hesitation whatsoever.

However, after riding a few miles, as I come up to some stops she idles down just fine. As I go to throttle up to take off from those subsequent stops she stumbles and *almost* chokes out / dies. The RPMs drop dangerously close to a stall and I have to very very carefully feather the throttle in to get her to pick up RPM enough to let the clutch out.

My suspicion is a pilot jet setting? Seems odd to me that it would only occur after the bike has warmed up though.

What model and year of bike? What carbs are we talking about? etc. etc. etc.

sounds like fuel delivery maybe. is your tank clean? do you have an inline filter on the bike?

We are talking about a '75 CB 360, inline fuel filters brand new and clean. Stock carbs. Non-stock jetting though I don't remember each jet size off hand, I do know that the main jet is the only one non stock.

Carbs have been very thoroughly cleaned and rebuilt with all new jets (excepting the main jet). Bike has less than 40 miles on a newly rebuilt engine (and the newly rebuilt carbs).

bikes run richer as they warm up.
i would turn out your carbs air/fuel screws maybe half a turn (lean it up just a bit) for the off idle stumble. re-adjust your idle accordingly
(when bike is fully warm)

PJ recommends float levels to be around 20mm instead of the stock 17-18mm as well, this could lean it up, but that would effect the full range of fuel delivery, not just off idle.

i have a cb360 as well, and love it, although its been finnicky with recent temperature fluctuations.

i traded my keihins for some mikunis, and i have to say i do miss the vacuum slide operation as it automatically corrects for changes in air density, but those keihins were a PITA to change the main jets on.

let us know if this helps.

Turning out the screws makes it richer. Gotta find out the size of those mains

Check out that petcock and see if it still does it with a full tank of gas.