vespa malossi 43mm 64cc cylinder kit

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vespa malossi 43mm 64cc cylinder kit

Postby karl » Tue Oct 22, 2013 9:49 pm

what jetting do I use with this, I have a tfr with I put the 13mm carb on the stock set up with a proma ciruit exhaust
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re: vespa malossi 43mm 64cc cylinder kit

Postby karl » Wed Oct 23, 2013 7:49 am

that's with the new kit, vespa malossi 43mm 64cc cylinder kit, Do I need to up jet to the 80s range or is there something else wrong. Anyone got any ideas.
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re: vespa malossi 43mm 64cc cylinder kit

Postby RebelRider.Mike » Fri Oct 25, 2013 2:06 am

I'm not familiar with that setup, but in general, the spark plug will indicate if a need for re-jetting is needed. A jet that lets through a proper amount of fuel will leave the plug with a brown coloration like this:
Image
Any lighter, and you need a larger jet, as the mixture is too lean.
If the plug gets wet or oily, there is too much fuel getting through, and you need a smaller jet.

When in doubt, use a bigger jet. Running engines too lean can cause damage.
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re: vespa malossi 43mm 64cc cylinder kit

Postby karl » Fri Oct 25, 2013 7:52 am

Thanks, I tried 72,74,76,79 and drilled one to 105 LOL. No go. Someone said from moped army go down to the fifties. Seems counterintuitive since I went from a 49.9cc to a 64cc. But I will go down and see what happens. He said the larger carb was dumping in to much gas, but it was fine with the 49cc, good cooler with the plug. But now the plug is wet like you said. Any comments on this would be appreciated..
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re: vespa malossi 43mm 64cc cylinder kit

Postby RebelRider.Mike » Fri Oct 25, 2013 8:45 pm

It's counter-intuitive, but I've heard of people having to make the jet smaller after adding performance parts. I think it happens a lot when folks get more free-flowing exhausts. But there are so many different factors that can affect how much fuel the engine needs, that it's usually a trial and error thing.
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re: vespa malossi 43mm 64cc cylinder kit

Postby JD » Sat Oct 26, 2013 10:37 am

Bear in mind that the jet doesn't control the amount of fuel going into the cylinder. It controls the MIX of fuel and air going into the cylinder. When you start changing components that affect the demand for, or supply of, gas or air, you're going to knock the mix out of whack. That's why choosing the right jet is often more art than science.

Keep testing and doing proper "plug chops," as described in Fred's guide in the Moped Repair section. Your spark plug will tell you when the jet is right.

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re: vespa malossi 43mm 64cc cylinder kit

Postby karl » Sat Oct 26, 2013 5:14 pm

Yep, I just saw a post on the other forum where a guy has the same set up as me and has the same exact problem. But they gave him a hard time and he disappeared. He tried jets from 54 through 80 range even numbers.
He never resolved the issue or at least posted again. I put a new plug in today and put the 66 jet in. It wont idle unless I give it half throttle. If I let off it dies.

My elevation is almost 4000 feet.

I sprayed carb cleaner all over and nothing happen... But I sprayed it on the carb where it slides attaches and it kills it. But I wonder if it is just being sucked in and around through the airbox.

Should I go into the 80s, 66 through 79 not much different. Will check compression to night.
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