Scooterotica

What would be the symptoms, if I were running a too large main jet in my 24mm PWK?

Cheers
Dave

djh66 wrote:What would be the symptoms, if I were running a too large main jet in my 24mm PWK?

Not a lot below 3/4 throttle but above that it would tend to not want to rev out fully and may even 4 stroke a bit. The plug would be dark brown to black and oily depending on how much it was too big. SWhat symtoms do you have?

coaster wrote:

djh66 wrote:What would be the symptoms, if I were running a too large main jet in my 24mm PWK?

Not a lot below 3/4 throttle but above that it would tend to not want to rev out fully and may even 4 stroke a bit. The plug would be dark brown to black and oily depending on how much it was too big. SWhat symtoms do you have?

Whilst going up hill it died on me, got it started, and carried on. Seemed to want to die if I was cruising about 50mph, with throttle half - 3/4 open, I had to keep it revving with the clutch in. I upped the main jet at the weekend, do you think I should go back down a size?

A few moe details about your set up would be useful but when you say 'it died' do you mean it cut out completely or was it sputtering and did changing down to 3rd help? It might be a fuel starvation problem, have you checked the fuel flow with the pipe disconnected from the carb? I tink t should be about 1/2 litre per minute.

coaster wrote:A few moe details about your set up would be useful but when you say 'it died' do you mean it cut out completely or was it sputtering and did changing down to 3rd help? It might be a fuel starvation problem, have you checked the fuel flow with the pipe disconnected from the carb? I tink t should be about 1/2 litre per minute.

I'm pretty sure it's not starvation, It's a CamLam fast flow tap, feeding a PWK 24mm carb, Li 150 Special, with ali 185 kit, 42mm big bore.

QUOTE: Whilst going up hill it died on me, got it started, and carried on. Seemed to want to die if I was cruising about 50mph, with throttle half - 3/4 open, I had to keep it revving with the clutch in. I upped the main jet at the weekend, do you think I should go back down a size?

with the above info its not your main jet at fault. check the needle clip hasnt come off causing the needle to drop down.

fairspares wrote:QUOTE: Whilst going up hill it died on me, got it started, and carried on. Seemed to want to die if I was cruising about 50mph, with throttle half - 3/4 open, I had to keep it revving with the clutch in. I upped the main jet at the weekend, do you think I should go back down a size?

with the above info its not your main jet at fault. check the needle clip hasnt come off causing the needle to drop down.

OK, cheers, I'll check tomorrow and report back.
What effect will that have? I know the higher the clip (the lower the needle) the leaner it runs, but I thought that affected 1/4 to half throttle, my problem seems to be 1/2 to 3/4 throttle.

After numerous carb alteratioins and test runs today, I seem to be going round in circles

I'm now running a 40 pilot, jjh needle clip in middle position and 118 main jet. Seems to tick over well, having set the airscrew, accelerates ok, but when I shut down throttle the open quickly again, it burbbles and tries to die, sometimes if I get the clutch in a rev, I'll manage to keep it going, if not, it will start ok.
I keep reading the PWK set up instructions on scootrs, but I'm now getting myself confused!

djh66 wrote:After numerous carb alteratioins and test runs today, I seem to be going round in circles

I'm now running a 40 pilot, jjh needle clip in middle position and 118 main jet. Seems to tick over well, having set the airscrew, accelerates ok, but when I shut down throttle the open quickly again, it burbbles and tries to die, sometimes if I get the clutch in a rev, I'll manage to keep it going, if not, it will start ok.
I keep reading the PWK set up instructions on scootrs, but I'm now getting myself confused!

40 pilot seems WAY too big, I would hgave thought 32-34 would be nearer the mark JJH is known to be too rich for most lambretta setups, GJH is leaner at half throttle.

coaster wrote:

djh66 wrote:After numerous carb alteratioins and test runs today, I seem to be going round in circles

I'm now running a 40 pilot, jjh needle clip in middle position and 118 main jet. Seems to tick over well, having set the airscrew, accelerates ok, but when I shut down throttle the open quickly again, it burbbles and tries to die, sometimes if I get the clutch in a rev, I'll manage to keep it going, if not, it will start ok.
I keep reading the PWK set up instructions on scootrs, but I'm now getting myself confused!

40 pilot seems WAY too big, I would hgave thought 32-34 would be nearer the mark JJH is known to be too rich for most lambretta setups, GJH is leaner at half throttle.

I was on a 34 pilot, but changed it today to 40, just to see hown it runs. I will change it back. I also ordered a GJH last week,and I'm waiting for it to be delivered. So I'll report back. I'm getting a bit panicky, as I'm due to go to Skeggy in a couple of weeks!