Hitchcocks Forum

I recently acquired a 2009 Electra X in rather good shape but needing some tuneup which I have been working on bit by bit. I am noticing something odd with the carb tuning (Mikuni/UCAL BS29 ).

Going by the manual this is what I did -
-I set the pilot screw to 3 whole turns out(ant-clockwise) from fully closed.
-Started the bike(choke closed) and set idle to 1000 RPM.
-When I turn the pilot screw in (clockwise) the RPM goes up and at fully closed the RPM is about 2400+.
I would have expected the RPM to go down and the engine shutdown completely with the pilot closed all the way in. Any idea what is causing this? Is it an air leak issue?

Note that I can set the pilot to 3 turns out and idle to around 900 RPM and it starts up on first kick without choke and runs fine.

Thanks
-uv

You probably need to turn the idle down as the revs increase. It's a CV carb so more revs = higher venturi velocity = more throttle opening.

At 2400rpm you probably won't be running entirely on the idle jet, the throttle will have opened and you'll be metering on the throttle valve cutaway.

So tweak pilot screw for higher revs, turn down idle, tweak, adjust, tweak, adjust until you find the sweet spot where turning it either way will drop the revs.

Interestingly, the BS29 has more recently been fitted to 350 UCE bikes by the factory, carb-fitted 500s have been getting a BS33. Possible upgrade for an Electra-X?

A.

Thanks. I tried this, but I may have done it wrong.

This is what I did -
I turned pilot screw in a turn at a time and adjusted the idle screw to lower the revs at each step to keep it ~900 RPM.
At fully closed position I lowered the idle screw down to the point the engine was in sort of a long loping mode barely staying on. Then I turned the pilot screw out half a turn at a time. But the revs went down instead of up. I had to adjust the idle screw up to keep it from shutting off.
So net result - I never found a point where turning the pilot screw in(clockwise) made the revs went down.

Did I do this wrong or could it be some other issue here?

Thanks for your help.

-uv

One method of setting the idle – but there are others – with most carburettors (I think the same will apply to the CV carb on leanburn engines) is with the engine at normal running temperature and the twist grip fully closed

i. screw out the throttle stop screw until the engine beings to falter

ii. screw air adjusting screw in or out until engine runs faster and more smoothly

iii. carefully screw out the throttle stop screw until the engine runs more slowly just begins to falter

iv. adjust the air screw to achieve the best slow running setting.

If the engine still runs too fast repeat these steps to achieve best idle setting.
The sequence is pilot air screw – fast; throttle stop screw – slow.

The final position of the air screw isn’t critical – it doesn’t have to be ‘1 ½ turns out’. Not critical that is unless it’s either fully in or fully out – in which case the pilot jet may need to be changed for weaker or richer.