TOPIC:

Sorry. Hot start.

Playing around and put the OEM carbs on with the air box. Runs good, but on a hot re-start it will barely idle. Starts at like 200 rpm, sometimes have to crack the throttle to get it going. Then after running for several seconds it climbs up to normal idle speed and everything is fine. Screws are at 2 1/4 turns out, and air/fuel meter is showing 13:1 when idling normal. During the hot start problem it's showing lean.

Have you checked the fuel level in each carb?

TexasKZ wrote: Have you checked the fuel level in each carb?

Yes, confirmed with ruler and fuel hose.

Jets are clean. Wondering if I have a pilot passage plugged up?

The cold start enrichment helps hot start?

Could be a clogged pilot circuit, though it seems like it would stay clogged hot or cold.

TexasKZ wrote: Could be a clogged pilot circuit, though it seems like it would stay clogged hot or cold.

Maybe it's just having a bigger effect hot. I'll tear them down and check them all. Originally carb #2 overflowed when I opened the gas valve. Cleaned the float needle and seat it it's seems ok now.

How has your engine top end been upgraded?
What carbs were you running before switching to the BS34's?

daveo wrote: How has your engine top end been upgraded?
What carbs were you running before switching to the BS34's?

10.5:1, APE street porting and 410 cams. Also have FCR35s, and this problem doesn't happen with them.

Almost seems like a hot soak condition. Shut down hot engine, gets hotter from stopping air and fuel flow, fuel boils in the carbs. Never heard of that on a bike though.

What pilot and main jets?

I'm no expert, but my guess is the BS carbs are jetted way too lean for the engine setup, and the air box is significantly restricting air flow.
Kinda like wearing a stupid Covid mask while working your a$$ off.

I think I got it. The choke levers are all bent keeping the plungers in the wrong positions.

And the #2 carb is wrong. Doesn't have the ball and spring for the choke rod detent.

Fixing the choke took care of half the problem. I think the other half is fuel boil. Going super rich on idle mixture seems to fix that. Read in another topic like high 11s afr at idle works best.

I'm thinking about putting the idle mixture back where it should be, and run it on non-ethanol gas from Home Depot. This would prove the issue is with the lower boiling point of the the gas with ethanol.

I'm also gonna check temperatures after a hot shutdown to see which is hotter, the carb bowls, lines, or fuel valve? I have a chrome Pingle valve which is close to the head.

Has anyone else been having heat soak issues? I know it's been an issue for awhile. Especially when they're still pumping winter blend fuel in the hotter months.