over heated

[dwint51]

I was riding for a few miles 40 -45 mph and it shut down.i let it cool and started back up but lost power on the hills.this has happened a few times in the past but I thought it was reving high and running out of gas.antway it doesn't start any more and when I put my finger over spark plug it has no compression.so my guess is it got hot and cracked my rings.it is a 72cc with only 1500 miles and I fried it already.found a 2002 zuma for sale and bought it so maybe my ill have better luck.i wont push this one as hard.i was running 8-9000 rpms for miles and the little engine couldn't take it

[blueboy5000]

Sorry to hear.

I'm actually surprised, I run my Mirranelli at 10k all the time, and it never overheats.

Perhaps yours was lean.

[rks]

What a sad story. Very well could have been running lean that caused an over heated condition, but I have to ask....how many times had you checked/adjusted the valves in those 1500 miles?

[blueboy5000]

Mirranelli engines are 2-stroke. They do not have valves.

[rks]

Whoops.....you are correct blueboy. My bad for not realizing what brand and model scoot was being discussed.

Still a sad story....and hpoefully something was learned, so a repeat performance, isn't in his future.

[dwint51]

ive been checking my plug all the time and it was very dark.in fact it was so rich I had to wait a long time for it to warm up aqnd lean out.i also put a cap of oil in the tank

[blueboy5000]

You probably didn't need the extra oil in the tank.

Extremely rich can cause overheat, but that takes a long time, and a lot of carbon residue in the cylinder.

I'd guess improperly set rings, or really screwed up carb.

My two Mirranelli bikes max at 12k, and have handle d 10k+ rpms for thousands of miles. I am surprised yours died without being pushed to the upper RPMs

[cheapeto]

[Mirranelli engines are 2-stroke. They do not have valves.]
I did not know that either.
That is why I read here, to spruce up my old brain.

[dwint51]

kinda glad it happened now I have a zuma that should be more dependable

[Firehawk989]

Putting extra oil in the tank actually leans out the mixture as the oil displaces some of the fuel. Therefore less fuel gets mixed with more air, which = leaner.

Also for a proper plug read you should run at full throttle for a while and kill the engine while still holding full throttle. When it stops, swap in another plug and take the other one home to inspect.

You could've been very rich at idle and lean at full throttle. The lean at full throttle is what kills an engine.

[dwint51]

that makes sense.i put a 17.5 polini carb on it a little while ago and open air filter.probably didn't have it dialed in good.once it was warm it wasn't smoking even at idle.

[skyrider]

Very sorry to hear dwint51. I often worry when running full throttle that the engine could seize and I would have a horrible accident. So I can see where getting a 150 and license would put my mind at rest and the only thing putting me from getting one is fear of failing the motorcyle test!!LOL!!!

[Firehawk989]

Originally Posted by dwint51

that makes sense.i put a 17.5 polini carb on it a little while ago and open air filter.probably didn't have it dialed in good.once it was warm it wasn't smoking even at idle.

The good news is that a lot of those parts will work on your Zuma, including the Polini carb once you get yourself a 70 kit for the Zuma. Just make sure you stick with the stock airbox and get yourself a main jet set for that carb. Probably want to start with an 85 or 88 to be safe.

If you want more zuma-specific help, zumaforums.net is a good place to go. I jump back and forth between here and there.

[dwint51]

the shop I just bought it from just put a 72cc kit on it so im already ahead of the game.i just put a crank on the china scoot so maybe I could use that too.so you think I should stick with the stock airbox?

[Firehawk989]

Originally Posted by dwint51

the shop I just bought it from just put a 72cc kit on it so im already ahead of the game.i just put a crank on the china scoot so maybe I could use that too.so you think I should stick with the stock airbox?

Yep, stick with the stock airbox but remove the little rubber snorkel from it to get some extra airflow. The 100cc Zuma uses the exact same airbox, so you don't have to worry about flow issues. If you try using an aftermarket filter they just become a PITA to tune.

If the crank you bought is a good one like Stage6 or Malossi or something then steal it from the China scoot and put it in the Zuma. It will be more reliable in the long run and you won't have to worry about over-revving it. Make sure you replace the crank bearings and seals if you do that. New wrist pin bearing as well.