Scooterotica

had just run my 225 rapido in prior to going to Weston at the weekend,so hadn't really given it any abuse prior to that.I'm a A road user more than motorway (by choice anyway unless I have to) so most of the time at 50-55 mph,scoot goes fine.When I was on a few stretches of dual carriageway opened it up to about 65 and when I closed the throttle it surges.The set up is:
static electronic ignition 16 degrees strobed
48 mm clubman
delly 30 open mouth -tea strainer filter -hole in panel with mesh
main jet 122
idle 55
X7 second clip
300 float jet
AV266
mixture 3 turns out
Did have a 125 main jet in whilst running in,but bogged a bit when the throttle went onto the main so dropped to a 122 and its a lot crisper.The barrel has had 1.5mm taken off the bottom of the base gasket face and the inlet/outlet ports matched.plug is colour OK if not a little on the rich side.I'm wondering is it too lean as the revs drop,definitely don't get the pop pop pop from the exhaust.Tried it with a AV264 and X13 in various positions,didn't run very well.Its a very torquey motor so changing it to a 16X46 over the weekend.Any info much appreciated ,there is a thread on the LCGB forum but to no significant outcome..the only info I can find is this off the old MB site "Main jet Adjustment Whilst Running In
.http://www.mbdevelopments.co.uk/archive/mag42.html
A classic example of a weak main jet is when you are flat out and you shut off to slow down, or change gear, if your motor actually speeds up (not to be confused with clutch slip!) then increase the main jet.

If your slide is a 40 with that pilot and airscrew adjustment its probably weak where you are shutting down from.
For example if you were cruising at 65 between 1/4 and 1/2 or just over 1/2 and then shut down and it surges it's likely to be your needle. If it is at full throttle or 3/4 it's likely to be your main.
To get a true plug reading of this you would have to run it at the same speed/revs where the problem is at the same throttle position for a couple of miles which i wouldn't advise if its running that lean!
Iron out the problem first then check plug colour at those speeds.
A larger main may cure it as a simple cure but on the other hand if you have dropped your main recently to cure richness at full throttle it could well have made your needle lean so try going up a position on that or try an x13 on top clip or 1 and a half setting.
If the needle is the problem and going richer ,either with your x7 or x13 cures it but it runs a bit spluttery at low revs you may then have to lower your pilot to clean it up a bit.
Only do that if its definitely the needle though!

flick the choke on at full throttle see if it splutters(too rich) if main is about right it wont splutter on choke ,then roll off and see if its better or worse with choke on or off but mark off your throttle 1/4 1/2 3/4 to see at what position the problem is at then you can relate it to main jet , needle, pilot etc and apply the change

Thank you chaps for some good advice,I'll have a go at it this weekend and hopefully come back with a good result,got to get right as I'm going to the Glevum Stax do the weekend after.

Not fuel starvation is it? Float bowl running dry at high speeds and then suddenly filling as you slow down causing the scoot to rev. Check breather hole in petrol cap is clear and there is nothing blocking fuel flow anywhere.

Just a quick update,sorted it.When changing to 16X46 on Friday I had ordered all new bits for the front sprocket-sliding dog,sprocket top washer and spring.Checking the original Innocenti spring against the one from camlam,the original one was quiet a bit shorter and the original sliding dog had seen better days compared to the new one .Put all the new stuff in and also put washer on the needle to give a half position (so now X7 2 and half notches,thank you nelson pk and eibar http://scooterotica.org/forum/viewtopic.php?f=7&t=22706) no more surging took it out yesterday and today ,no more surging forward when slowing down.Next one is how much fuel its drinking which is pants but I'll save that for another thread