A solution at last for my Series 3

[EddieStone]

I've struggled getting my Li150 Series 3 running well for quite a few years. I would be seized with enthusiasm, try some stuff, fail, and then retire it to a corner again.
The problem was getting it jetted. It just wouldn't run right - being rich in the midrange and it would splutter and machine gun at about 30mph. It was loud, annoying and frustrating.

Yesterday I sorted it, and it runs so nicely I can't wait for summer.

I've had this scoot for years, decades in fact. As a standard 150 it ran well, on points no less, covering all four corners of the country. Then I decided to increase it to 175cc and it ran...ok. Then I got hold of a 20mm carb, it ran sort of OK.
I tried to dial in the 20mm carb but it just wouldn't. I bought electronic ignition. No difference. Next plan was a more a dial-in-able carb - a 26mm PWK. Needles and jets galore. It was sort of better but the 30mph splutter was still there. It was timed to 19 degrees. The carb ran through the air filter and airbox. I tried drilling holes in a spare airbox. I tried just mounting the air filter without the box. It was still spluttery and too rich. Then it seized.

So next step was to send the 175 kit off to AF Rayspeed to have them look at it. They tidied up the ports, rebored it and found a 40 year old piston for it.

And still it would splutter and machine gun. Into the naughty corner. I can still find all my posts on here trying to solve it.

Recently, I took the plunge and decided to buy a Scootopia 185 kit. Two reasons - people rated it, and the suggested jetting was pretty consistent. I'd fit the kit, set the carb, and ride off into the sunset.

Or not. After all that it was still spluttering. I tried a few leaner jets but I didn't want to go leaner than suggested with a nicasil bore. The drilled airbox was fitted - no difference. Stumped now. Is the airbox neck too narrow? I decided to remove the air filter but still connect up the airbox and scoop to see if that was the restriction. It fired up, and it flew - a bit lean, admittedly but absolutely rideable. So the air filter is the problem? I ordered a new one, fitted it and it was the same as no air filter. A quick re-jet and how sweet it runs - I've been bimbling round this evening in the cold just enjoying how nice it rides.

So the problem was the bluddy air filter. Comparing it to the new one, it's a terrible version - good enough for a standard 150 but not for anything bigger. So there's my lesson. Never assume anything! I just assumed the air filter worked, but it was causing my massive problems for the past 5 years.

Hope this helps someone!