[fergi]

hi guys new to site hello to all
recently bought a t140v the amals where a bit tired so have just fitted a new pair of mikuni's
are supposed to be jetted for bike but its chucking more fuel back out than is going in

can anyone advise on the correct jets carbs are 30mm vm range

 

[Sunshine Jim]

real problem is?

"it's chucking more fuel back out than is going in"

wonder what's causing that? wheres it coming out?

is it air coming back out the intake passage? that would indicate a valve leak or a real timing prob.

we probably need a more specific problem description.

may not be a jet problem as much as a setting problem.

heres a good piece on Triumphs and Mikuni set up

http://www.jba.bc.ca/Bushmans Carb Tuning.html

look down the page a bit for the "MIKUNI CARBS FOR BRITISH MOTORCYCLES" header.

 

[pookybear]

but its chucking more fuel back out than is going in:

Fergi,

Welcome to the group. I think the word you are looking for is
reversion. This is when the air has already atomized the fuel
into vapor, than for some reason the newly mixed charge is
forced back out of the carburator. Now this will happen a little
bit with these bikes. This is because of the short intake track
and the return wave of air/fuel backing up in the intake track when
the intake valve goes back onto its seat. However, in a normal
engine this is very little amount and is sucked right back in during the
next intake event.

As Jim stated, if you have a lot of this going on something is
a miss with the sequence of the events for the intake charge.


Pookybear

 

[fergi]

thanks guys for input
the reversion is happening at 1/4 throttle and above, and stalling engine if the throttle is opened normally can coax through it if throttle is feathered
will try playing around with needle settings in the morning
will keep you posted.

 

[fergi]

ok have got it sorted it was running very weak have lifted needle right up and also found a link pipe joining the inlet manifolds and have plugged them of ( wow what a difference from them old amals )

just need to fine tune jetting thanks for the link to the bushmans site a great help