Engine goes lean while accelerating under half throttle

[Rubarotary]

Hi everyone,

Last week i went For a Drive For the First Time in a couple of years And everthing was ok accept that the engine goes lean ( 15,6 ) while accelerating under half throttle.

It's a freshly rebuild engine everthing original except Air pump removed .
Afr on idle is 12,6 And full throttle it's 12,2

Any Help would be appreciated.

Ruben

[TOOL]

Idle is controlled via idle circuit.
Half throttle is primaries.
Full throttle is primaries and secondaries.

I suggest you check the primary jets aren't blocked.
There's access screws at the bottom of the bowls. No need to disassemble but probably a bugger in situ.

[Rubarotary]

Ok thanks For the explenation i'm gonna try it tommorow .
I don't know much about carbs only basics so many thanks

[Rubarotary]

So i checked the primary Jets And they were ok there was a little dirt in the bowls though, but i dissasembled the carb to see if the next Jets in line weren't blocked but these were Fine as well.
Since i had the carb open i cleaned up everthing And there was one Jet blocked it's the one on the left side at the bottom of the Picture it's a size 150




But since i did this the front rotor almost gets No Gasoline And the rear one gets Plenty.
In the weekend i'm gonna try to measure Flow on each Port but in the meanwhile if somebody has any ideas there very welcome

Thanks ruben

[TOOL]

It almost soundsike you've dislodged a blockage and shifted it somewhere else.

Check the needles and seats.

[Rubarotary]

I'm guessing you Mean the needles And seats in the float Chambers ? Is it helpfull to lap the needles Back in to place ?

[TOOL]

Yes, that's the ones.

The washers underneath the seats set the height so keep them together.

Also check the coarse filter at the inlet to the carb.

[Rubarotary]

Ok Will try this All this Evening, thanks a lot For the support

[Rubarotary]

Coarse filter is Clean, needles And seats are ok as well i'm gonna try to measure Flow in each barrel but i measure the clearance between the primary throttles And this was the Same so i don't think this is gonna be a problem .

Just one question at idle the primary Jets shouldn't give any fuel Right ? Because fuel should be coming from the idle jet

[TOOL]

Correct.

Activate the throttle and the accelerator pump will squirt a jet of fuel into each primary to help the transition from idle to primary circuit.

Check for air leaks too.