150cc runs for a few miles then dies

[codeyell0]

Let me say the exhaust is not connected and I was told the engine heats up and dies from that.

I have not had this happen to me yet as i just got the scooter from a friend who told me it did this but he knows very little about mechanics.

would this be the reason the engine dies after say 10 miles?

[techie610]

To get straight:
You can start her up, run for "say 10mi" and it shuts down.
How long before she can start again?
Is it during hard running?

You should have an Ex. pipe on it, even if it is just 10".
Have you checked your valves?

[Lefty]

Yes, not good running without an exhaust, your lucky so far that you have not burned the exhaust valve as well as not completely seized the motor.
Lefty

[qwertydude]

Without the exhaust there's no backpressure and without retuning the carb you'll run lean. Could be you're overheating.

Does it slowly lose power and erratically idle then die? Or does it just dies all of a sudden?

Since the scooter is new to you it's possible it's not exactly in the best of condition and on top of needing an exhaust it could need a tuneup or might need repairs from running a long time with no exhaust.

[skuttadawg]

Without the exhaust and not upjettint to compensate the additional airflow it will be too lean , run hot and will damage your engine in a short time . A buddy who drinks too much wrecked his scoot and the pipe broke off . He rode it for almost a month and the exhaust valve head came off and ate up the piston , head and cylinder . Running like that can also cause it to seize up and have the piston crack too . The pipe carries away heat from the engine as well as having some restriction to build up backpressure . I removed my muffler on my Echarm with EFI that adjusts itself and boy it was so loud it reminded me of riding a Honda XR 250 . It did have just a hair more on the takeoff but it lost top end speed .

Running it like you have you may get the valves out of adjustment too . All 4T engines will need to have them adjusted at least once with some requiting this right out of the crate . Here is a shop manual http://www.chinesescooterreference.com/pdf/50_150cc_gy6_shop_manual.pdf You may need to get Adobe Acrobat Reader ( it is free ) www.adobe.com look on bottom right corner

[codeyell0]

Thank you

I'm rebuilding the engine since both exhaust studs broke off in the head or at least replacing the head.

[techie610]

Thank you

I'm rebuilding the engine since both exhaust studs broke off in the head or at least replacing the head.

Hows the build going? :)