Scooterotica

Hi guys, wonder if anyone can shed some light on what is causing a starting problem on a mates scooter. It is Li 150 fitted with an alloy 185 kit 22mm Dellorto PHBL and a ScootRS exhaust BGM stator @19 degrees, the problem is it is a bitch to start. When you kick it over for the first time if it starts you have to keep it running (Fuel on or off, Choke on), if it fires but doesn't start it then takes ages and plenty of kicks to get it running. Once running you have to hold it on the throttle as it won't tick over regardless of idle screw / mixture screw adjustments. Once running if it dies then it won't start for ages, however if you swtich it off with the key it will start straight away no problem!

I have tried all sorts of ways to start it and fuel off choke on, fuel on choke on no throttle, no fuel no choke - I give up!!!!

Any ideas most welcome

Sounds likes it's flooding, maybe the pilot or choke jet is a bit on the big side.....

that last line makes me wonder if its electrical fault, you turn it off with key then back on and it starts, surely that has to point to a dodgy ignition item somewhere

blocked pilot jet?...

Well, so far we have completed a leak down test and had to replace the mag flange gasket so thats now eliminated. changed to another BGM stator off a known runner, changed carbs to another 22 PHBL, 22 JETEX x2 and now a 26 PHBH. Each time a leak test completed to make sure the manifold was sealed properly. Tried with the green wire for the ignition removed and in place.
With the 26mm fitted it has even been set up on the dyno so that the fueling is right.

Still the same, if it starts and you keep it running it is ok, switch it off and it will start again. If it dies then is a bitch to start. Confused you bet I am.

Going round tonight to check the ring wear and see what that is like, other than that it's a gallon of petrol and a match!!!

Any ideas greatly received.

Clutching at straws but some engines like to have the throttle fully closed during starting, in fact that was the recommended starting procedure quoted in the owners manuals. Most of my setups have liked the throttle shut but not all.

Other than that, have you tried fresh petrol on the off chance that there's water in the fuel? Changed plug/lead/HT Cap?

Piston round the wrong way? You don't state whether it is open mouth or filter. Could it be spit back collecting in bellows giving over rich re-starting causing the prob as that can be a common problem?

Well I think we have found the problem, stripped the top end to find there is 0.25mm clearance between the piston and bore and i can fit a whole set of feeler gauges between the ring gap! so to confirm this we are fitting a standard cast 150 kit.
Obviously a soft steel liner in the alloy barrel as it has done less than 2000 miles in 3 years.

All being well it should be up and running again tonight and problem solved!!! I bloody hope so.