PWK 28 Carbs running trouble on Hybrid

headcoats · Post by **headcoats** » Sun Jun 14, 2009 10:03 am

Now run the Hybrid (LC) in and altough it runs like a good'n in the powerband,part throttle is a different story

Biggest problem is if you roll the throttle off as in approaching a corner etc
the engine feels like it wants to tie itself in knots,it's baulking and lurching and just won't have it until you power into the band again.

It's part throttle i think so is this a needle problem or airscrew problem
or something else ?
YPVS engine with allspeeds,PWK 28's,V force 3 reeds,Ramair filters,premix

Carb settings are

Pilot jet #40
Airscrew 1 1/4 out
JJH needles from Allens
# 150 main jet (big jet but seems to need it,rev's right out with this)
Needle in MIDDLE position

One other thing is i seem to have 2 different lots of needle jets
The one set sits in the carb mouth 1mm higher than the other set
Would this affect anything ?

Any advice would be great as i'm pretty stumped

the-elf · Post by **the-elf** » Sun Jun 14, 2009 11:46 am

The airscrew affects the very low revs. Your best bet is to het it on a dyno so you can replicate the problem but then ur'll be able to know where in the rev range its running rich and/or lean and you'll know in which direction to go.

headcoats · Post by **headcoats** » Sun Jun 14, 2009 5:15 pm

Had a fiddle today

and much better now

I put the airscrew to 1 turn out and it has improved that.

I also put the needle to leaner as in dropped the needle to 2nd from top
Rolling off it still stutters and baulks a bit but is much,much better and i feel i can live with this for now.
I had forgot how much fun these 2 strokes are