tuning question? what jet to change?

[crf50 2008]

mates got a honda 88 with a 20mm carby has a flat spot if you throttle up quick it dies.
when you put the choke on half way it runs sweet.
obviously its to lean yes he gets that.

what jet should he change is the question the pilot or the main?
which one is more likely to fix the problem the best?

.

 

[sean01]

what reaction does the mixture screw have when screwing it in and out.. does it still run with fully it screwed in?
also have you checked for air leaks and adjusted the valve clearance?

can ya tell us what jets are installed in it and where the needle is positioned?

 

[crf50 2008]

when you screw mixture screw in it dies.
idles fine from about 1/2 out to 2 turns sitting on 1 1/2 at the moment.
checked for air leaks havent done valves though.
jets are stock sheng wey ones 35/89 clip is one richer from middle.
ran good before with stock pipe just put a new exhaust on with 1" diameter header. thats whats caused the issue.
should he go up in the main or get a bigger pilot?

 

[sean01]

nah the mixture setting you said sounds spot on.

whats it ride like when only going to 3/4 throttle?

it works like this..
0-1/4 throttle is pilot/mixture circuit
1/4-3/4 is slide needle
3/4 to full is main jet

 

[crf50 2008]

will give it a try on sunday and will see what it runs like
ive got a bunch of different jets to throw at it too
fingers crossed we sort it

 

[westy465]

hey man you remember what jet you had in the stock carb when you had your pro circuit T4 and uni air filter? its been running ok with the stock filter, but have uni filter coming now, and am anticipating a lean machine.

 

[crf50 2008]

yep honda jet #62 can get from any honda dealer
the order/catalogue number is 99101-1870620 for a genuine honda one

 

[westy465]

dardy. thanks man.