Imola set up

[Chris Brad]

Hi guys. I’m sure this has been covered hundreds of time but I’m running round in circles. I’ve got an early version 1 imola kit on my LI 125 special. Dellorto PHBH 28mm. It’s a flyer but runs 4 stroking at about 1/4 to 1/3 throttle in any gear then goes like stink right to the red line. Current jetting is main 132. Idle jet 50, needle x7 on top clip. AV 266 atomiser and 55 slide. I originally had 45 slide but was that rich it was unrideable. Had it on dyno in Kirby where we tried 50 slide. The 4 stroking was still there but not as bad. Tried 55 slide when I could get my hands on 1 and it’s much better but still stutters and 4 strokes about 1/4 to 1/3 throttle. Trouble is no one I’ve talked too has ever used a 55 slide !! Was gonna try av264 atomiser to try and cure it. Any thoughts / help appreciated. Thanks


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[Chris Brad]

Forgot to add it’s running a JL3 pipe too


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[Padge]

Hi Chris, I have a couple of Imola’s
My wife’s set up is
30 phbh
40 slide
AS 266 Atomiser
X2 needle second clip
135 main
55 pilot
Mix screw 1 ¾ turns out
Franspeed supertourer
Augusto 600 retard unit
It four strokes a little off idle but pulls fine
Personally I would think anything over a 50 slide is too weak and an av 264/x7 would be far too weak as well
Unfortunately you will always struggle at part throttle with a round slide carb because of the way they work, my other imola is exactly the same set up as above but I run a TMX30 on that an it’s a bit quicker, but far smoother

Here is a quick video of my wife riding hers "gently" as the engine had about 30 miles on it at the time and I had only just built it !!
https://www.youtube.com/watch?v=nnhqCOpYPzg&t=213s

[Chris Brad]

Hi Chris, I have a couple of Imola’s
My wife’s set up is
30 phbh
40 slide
AS 266 Atomiser
X2 needle second clip
135 main
55 pilot
Mix screw 1 ¾ turns out
Franspeed supertourer
Augusto 600 retard unit
It four strokes a little off idle but pulls fine
Personally I would think anything over a 50 slide is too weak and an av 264/x7 would be far too weak as well
Unfortunately you will always struggle at part throttle with a round slide carb because of the way they work, my other imola is exactly the same set up as above but I run a TMX30 on that an it’s a bit quicker, but far smoother

Here is a quick video of my wife riding hers "gently" as the engine had about 30 miles on it at the time and I had only just built it !!
https://www.youtube.com/watch?v=nnhqCOpYPzg&t=213s

Hi Padge. Thanks for the advice. If I run a 40 slide it will not pick up at all until I run fully wide open. A 45 slide is more or less the same running as a 40. A 50 slide is better but still very very rich part throttle. Just out of interest I’ve seen advertised pre jetted 28mm dellies from a well respected tuner with av264 atomisers fitted suitable for reed valve engines. Hence the reason I’m going round in circles. Bloody scooters starting to wear me down


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[Chris Brad]

Quick update to this. Turns out that my carb is a phbh powerjet but power jet pipes been taken off and new bowl fitted. but left the jet in place and left the stubs on the body that the pipes originally fitted on but not been blanked off. Fitted 2 small pipes onto stubs on body, plugged with bolts and taken powerjet out and plugged hole with M5 bolt. It flies now !! Will teach me not to totally trust someone when they tell me it’s just been purposely jetted rich !! Hey you live and learn.


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[Padge]

Happy days !! Just out of interest, what jetting did you eventually end up with ?

[Chris Brad]

Happy days !! Just out of interest, what jetting did you eventually end up with ?

AV 266. 135 mains. X7 needle 2nd clip. 55 pilot 45 slide. Mixture screw 2 1/2 turns out. Still feels a slight bit weak on midrange before it comes on pipe so gonna experiment tomorrow with needle height and maybe try X13 or X2 Runs pretty smooth though as it is. Thanks for you help


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