Elite with UBF 24 BS carburettor problems

[George]

Dellorto UBF 24 BS carburettor settings as on bike.
Needle E10D on middle notch of three notches
Needle jet 260B
Slide 70
Main jet 98
Pilot jet 38 1 1/2 turns out
Float 6.5 gr

Spares catalog Specs.
Needle E11D on middle notch
Needle jet 260B
Slide 70
Main jet 98
Pilot jet 35 to 40 start point 1 1/2 turns out.
Float 6.5 gr

When bike is warmed up and idling if I lean bike to nearside engine speed decreases and if I lean bike to offside engine speed increases. Is this normal on remote float carbs?
I can find no reference to correct float height and wonder if anyone would have some idea of how much below top of needle jet petrol should be and if necessary how to alter float height, lighter float? extra fibre washer on float bowel banjo top? I have moved bowl forward as far as possible.

The other fault is that exhaust is popping when closing throttle indicating rich mixture and could be related to carb settings.
All comments are welcome

[veloduke]

Hi George

When bike is warmed up and idling if I lean bike to nearside engine speed decreases and if I lean bike to offside engine speed increases. Is this normal on remote float carbs?

In my experience (limited) yes. The Amal Monobloc experiences the same symptoms, as did the Amal TT15 on my cammy Velo.
Tilting the bike over effectively raises or lowers the fuel level at the jets, being offset to one side.

Overcome by having a concentric design carb (later Amal, Mikuni, ...).

I must admit that I thought a popping exhaust was a weak mixture, or possibly a leaking exhuast.

[Bevel bob]

On the SSI carb , the float has to be up against the frame tube to get the fuel high enough. Even then you can still get the leaning effect. I would raise the fuel level till the carb floods then lower enough to stop . Even far better fit a remote float on a sliding mount ,I did and most of my issues dissapeared

[Duccout]

Hi George,

Popping in the exhaust can be due to a rich mixture allowing unburnt fuel to fire in the hot exhaust, or a leak in the exhaust system.

As to the float level, I wonder if Eurocarb may have some information on that? They are very helpful people and may be worth a try.

Colin

[George]

Thanks for replies.
Borrowed friends carb from SS (same engine different name) all jets etc same. Fuel level in needle jet little higher.
When stripping carb I found two fibre washers at top joint of float banjo lowering float level by 1mm. On removing one washer banjo leaked so I am guessing washer added to stop leak. Put the extra washer on bottom banjo joint. result is float level increased by 1mm.
Replaced and started bike much improvement with just an occasional pop screwed idle in 1/4 turn no popping. Conclusion weak mixture good call Max.
If I try to have a slow tickover there is a slight hesitation when opening slowly increasing tickover cures hesitation I can live with that.
These carbs seem very sensitive.
Again thanks for advice

[Duccout]

George, that slight hesitation when just opening the throttle slightly is almost certain to be a pilot jet slightly weak or rich. It may be worth trying a couple of sizes up or down to see if it cures it.

Cheers,

Colin

[George]

80 miles ride last night with no problems. First good ride since a loose bolt jammed between rear chain and wheel sprocket at 60MPH. Broken chain and ruined sprocket. Chain damaged crankcase, now repaired. Fortunately no damage to me managed to stay upright this time. Bit of a shock to transmission though. After reading of Bill's misfortune I might check out clutch.