What causes that dying when you open the throttle?

[Perkin]

You know, like when the engine is cold and the mixture is condensing on the cylinder wall. You pull the choke to throw a bit more fuel in and it's OK after a couple of minutes.

Mine is doing it when warm so possibly I have a blockage. It's a fairly standard LML 150 reed engine with SI20 carb. Is it likely to be the pilot or main jet? It will rev OK with a few twists of the throttle to build up the gas velocity through the carb, but from tickover it's initially just buuuuuur.

Is it possible to get these symptoms just from being too lean on the mixture screw? 

Thanks, Andy

[mijapxman]

Perkin, was it running fine on these jets before?

If yes, clean the pilot and idle jet, while your in the carb you may as well clean the main jet stack too. I would also clean the small gauze petrol filter in the carb too.

If not ,try richening the mixture an see if that cures it.


Mij☺

[3narf]

Thanks! (this is he, not sure why my username changes according to which device I use)

It was running OK, although it had an air leak meaning I had to replace the flywheel side seal. I set up the mixture before then so I need to do it again, but I was wondering if the symptoms I have were consistent with the idle mixture being out... Anyway, I have cleaned the jets but I haven't had chance to run it yet. Tbh I should probably drain the tank and chuck the fuel away as I've no idea how old it is.

[mijapxman]

Andy, was forgetting you have an LML engine, not sure how hard it will be to set without the 10mm carb spacer, if you don't have one fitted? You could try asking mista freak moped for more information, again? 👇. If you read his comments at the bottom of this video, he mentions a spacer,( You may need to look at the video on YouTube to get the comments.) He says the si carb is unsetable without the spacer!. 

Let us know how you get on, as they seem hard to set up.Feel free to ask for more help if you're still stuck, though 😉.

Jim/Mij☺

[3narf]

Thanks, I'll take a look! It was running OKish so there's definitely a fault (besides any design fault), but interesting if it can't be set accurately.

[mijapxman]

3narf, I don't have any experience with LML motors, but I believe a few of the guys on this site do.They seem a good bunch.

modernvespa.com/forum/forum19

Plz let us know how you get on or if we can further help in anyway 😉.


Good luck.


Mij☺

[3narf]

I'll take a look. I know it's not far off running properly. All the jets are definitely clean now but I may have to get some air through the carb body.

Thanks again

[3narf]

Ok, well it seems to be running well enough now that I could just about ride it. There's a bit of a missfire but I think a new plug and new fuel (tank was full in February when I bought it and it's still almost full now) will sort it.

Not entirely sure if I have the right idle jet; the engine does cut out if I screw the mixture screw fully in, but once it's out half a turn or so it doesn't seem to make a lot of difference.