Upjetting a moped.

[Pompey_Jake]

Hi,

I need to upjet my moped and I was just wondering if you could help me out..

I have a Speefight 2 with a stock carb, I have a sports covered air filter, a leo vince tt exhaust & a 70cc kit, what jets should I be looking at?

thank you.
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Jtill.

[spannermonkey...]

Not that easy every machine is different. Not a simple bolt on task. you have to feel, listen, look and learn.

You have to set the idle circuit, then the slide/cutaway then look at the main jet.

How does it run will all those bolts on's?

Can you buy different jets and carb parts?

What is happening from idle to 1/4 turn throttle? 1/4 to 1/2 and 1/2 to 3/4 and 3/4 to flat out.

From that you can start to address the carb issues. If you struggle to get the carb to work it may need a bigger one. Have you played with port timing and shape?

If the engine run in first before you open it flat out and wreck the rings?
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Current machines - Aprilia RS250. Kawasaki H1A 500. Past machines - Kawasaki ZX7r P6, Yamaha RD250E (the one that got away), BSA Racing bantam (revs over 10'000 sweet as), Yamaha RXS100, Suzuki GP100, Suzuki GS500K2 - best all year machine ever - come rain, sleet and snow just epic.

[andys675]

did the standard exhaust have a catalyst?

as they had an even smaller jet as standard, best to go much bigger as running rich only foul's the plug, running weak holes the piston
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Some people feel the rain, others just get wet.

[Pol Anorl]

Hardly worth it... itll open up a world of pain.
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[stevo as b4]

Pay for a set up on a dyno with proper gear.
Or if you know someone with a similar bike, and similar mods/same parts fitted etc, then use their set up and see how it works.

You can't successfully home tune and set up the fuelling etc on a bike with messing about with plug chops etc. I've been there myself many times.

Also people think auto tuning is easy, but there's lots to consider.

You need the jetting to be close to be able to spec the roller weight and clutch engagement speed etc, but then you need the transmission set up so that you can ride at the load/speeds where you need to optimise the jetting.