28ml PHBH four stroking

[steve_lawrence]

I recently had an RT195 kit fitted to my Li Special. It has a brand new Dell’Orto PHBH 28ml carb which is proving virtually impossible to set up for a non-spluttery ride. My friend, a motorcyclist and scooter rider for many years has tried many jetting set ups but it has got him beat. The scooter goes well, but once you ease back on the throttle the 4 stroking kicks in. Under load it’s fine, but ease off to steady the speed and that’s when the issue starts. Would a dyno session possibly cure it?
The current set up is 50 pilot, 126 main, X13 needle second clip from the top, 264 atomiser. I’m not using the air box but there’s a foam air filter fitted directly on the carb.
Any advice would be gratefully appreciated.

[hullygully]

Ive used a 55/57 pilot in 2 x mates 28mm dellies on rt195's but with open carb
what's your air screw & slide bud, plus exhaust?
have you tried without filter?

[steve_lawrence]

It’s a 40 slide. I’m not near the scooter at the moment so I can’t check the air screw.

[Adam_Winstone]

Leaking float with fuel in it?

[Warkton Tornado No.1]

The slide is too rich. Dell’Orto carburettors - perhaps unsurprisingly - tend to need the same slides across the range & 45 is the normal choice.

If possible, borrow a 45 slide to try.

The good news - apart from it having a round slide - is that the 40 slide is easily convertible to a 45 via material removal from the edge…..

[Rich Oswald]

A 45 or even a 50 slide would probably help your issue.

[hullygully]

there is also another range of atomisers, the AS range as opposed to the AV's, which have the same no. range but are slightly weaker