Scooterotica

Just to recap rebuilt GP with Imola with 30mm carb Franspeed exahaust you may remember I had it on the Dyno which improved the running but the spark plug is really black and oily and it runs really lumpy when cold with the choke to the point I can turn the choke off after a couple of minutes. Also when ideling it smokes a bit. I have checked the gear box oil just to make sure it's not the drive side seal and the gearbox was still full so I don't think its that.

When it was on the Dyno the main jet was changed down to a 128 and but the needle moved to top clip. I also run it on 3% mixture and I have done about 300 miles since the re-build.

Would changing the pilot which is currently a 65 help.

Tried to put as much info as i can any ideas ?

Have you spoken the the dyno guy? What does he say? If he hasn't set it up correctly then he needs to re-check it. Running the choke for a couple of minutes is fine.

Jeff T wrote:... the pilot which is currently a 65...

on the larger side then, where's the mixture screw at ? [is this on a PHBH ?]

Yeah it's a PHBH, mixture screw was set at 1.5, although not checked it recently

65, you need a 55 or a 50 this will sort your cold/ choke starting

I rang the guy who dynoed it and went through the results seems it's set ok through the rev range apart from it runs rich at about 3000 revs, with the set up I've got so Franspeed race pipe, gearing etc and not being used to an Imola may need to ride it differently. But now I have thought about it still no wiser.

Did he explain why it's rich @ 3k?

Jeff T wrote:I rang the guy who dynoed it and went through the results seems it's set ok through the rev range apart from it runs rich at about 3000 revs,

3000 revs would be the area covered by the overlap of the pilot jet and the needle (I think). The needle you say is in the top clip position and if its still rich then it needs a change to the needle length or profile and or a smaller pilot. My money is on a smaller (55) pilot but be prepared to lower the needle clip a notch or 2.

What's the rest of the set up for the carb/engine?

Set up I'm running is a Franspeed stainless JL pipe PHBH 30mm carb, I've just been for a smaller pilot jet and showed him the carb set up which is now a main jet 128, slide 40, 266 atomiser and a needle of X2 on top clip, the bloke tells me an X2 is used in a Vespa set up and not Lammy and should be an X7 and go back to where I bought it frrom. Both are reputable dealers but I have changed jobs so don't use the bloke I bought it from.

So as I have had it set up on a Dyno and I know the issue is running rich around 3000 revs should I just change the pilot to 55 and see how it goes or is my set up completely wong and start again.

An AV266 atomiser is I think usually used with an X7 needle, the X13 has the same profile as the X7 but is a little longer so would probably make it weaker lower down but should be used with the AV 264 atomiser. I don't know about the X2 being only used in Veps although the 28 PHBH in my old T5 Classic had one fitted.

I'd be inclined to try the 55 pilot first then play with the needle position if necessary.