Carb Machine Gun Stutter

headcoats · Post by **headcoats** » Mon May 06, 2013 8:48 am

This is driving me up the wall

The left carb at small throttle openings sounds like a machine gun then clears and runs fine

It didn't do this before and now had carb apart several times,changed pilot jet,checked float height etc to no avail
Changed plugs and swapped HT leads over too
It is a part throttle problem so I guess the slow running circuit is the culprit ?
Don't know what else to try

fred · Post by **fred** » Mon May 06, 2013 11:41 am

does this happen coasting or on load ? what did you change pilots from to ?

headcoats · Post by **headcoats** » Mon May 06, 2013 12:47 pm

These are in my YPVS 350 engine with ramairs so I guess it won't be perfect but it was running great a short while a go

It runs nice under load,it's just as you apply the throttle from almost closed and seems to happen about 3-4 K

I run big pilots as in #45 as when on a closed throttle it would hunt and jerk about and bigger pilots cured it

Post by **500bernie** » Mon May 06, 2013 1:02 pm

Hi Martin,
Swap the carbs just to check, it is the left carb.
If it moves to the right, swap over the tops/slides, if it still stays on the right, the carb needs really good clean.

headcoats · Post by **headcoats** » Mon May 06, 2013 1:23 pm

I will try that Bernie

I do keep the carbs spotless and can do them blindfolded now

I take the security screws out to get them completely apart and I use fishing line to get in the tiny drillings then spray WD40 through using the red straw to see how it flows out

Post by **500bernie** » Mon May 06, 2013 3:07 pm

Do you have inline fuel filters going to each carb?

headcoats · Post by **headcoats** » Mon May 06, 2013 4:39 pm

dave32 · Post by **dave32** » Tue May 07, 2013 1:30 pm

How can you tell its the left carb while riding with filters over the carb mouth,or does it do it in neutral aswell?
Backfiring/banging out of the carb is usually caused by an over rich fuel mix,are you positive the slides are opening at exactly the same time/amount?
are you still running the reed block balance pipe?
Dave

headcoats · Post by **headcoats** » Wed May 22, 2013 11:03 pm

Sorted

Even though it was only the left doing it I lowered the needles I clip to middle and cured it

Maybe I should have tried this first before I took the left carb apart for the umpteenth time

dave32 · Post by **dave32** » Wed May 22, 2013 11:35 pm

So it was running too rich,glad its sorted now,amazing how quick you can do stuff when you do it so many times (taking carbs off and changing settings).

headcoats · Post by **headcoats** » Wed May 22, 2013 11:45 pm

I can do these carbs blindfolded now