Scooters - 125 to 300 > Movie 150

2013 Intermittent Stumble and No Start

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kkraft:
Hello, I can use a little help here with making a proper diagnosis on a 2013 Movie 150 with 1400 miles. I acquired this scooter back in May and I have yet to get it running properly. This has been a little tricky for me because the problem does not typically happen long enough for me to make a diagnosis. What it does is when it gets hot, after 20+ minutes of running, it will intermittently stumble and die on me at an idle, usually it will start back up but idles rough. If I throttle it too quickly it dies or sometimes it just dies with no throttle. Other times it starts back up with no symptoms and runs fine. But most often it has issues after it is hot and sits for a few minutes.

The previous owner replaced the fuel filter, spark plug and had the carburetor cleaned. When I got it I adjusted the valves, one valve had 0.00 clearance and the other 3 had 0.003. Supposedly the shop adjusted them before I got it. I tested the compression and it was 170 psi, 180 with oil and the manual says 213 at 570rpms. So I am not sure if that is causing problems. Coil tested bad so I replaced it, then the new one tested bad, then I chucked my multimeter, now they are both fine, oops. Crank sensor ohms was well within range. Auto bystarter was out of range so I replaced it. Which brought me to the CDI with no good way of testing it I replaced it. The new one brought the idle up 700 rpms but the problem persists. I did have one time when it would not start and I checked spark which was still good, sprayed some starting fluid in the plug hole and got nothing. Timing is good when it is running well but I haven't had a chance to check it when it is acting up. Spark plug is really clean, not sure if this thing burns super clean or what. Any ideas are much appreciated, I am not sure what to check next or if maybe it is a compression issue. Thanks!

And on a side note, I double checked the manual and is does say compression pressure 213.3 psi which sounds absurdly high.

CROSSBOLT:
That one valve with 0.0 clearance may be burned....

kkraft:
I was kind of thinking that but it appears to have plenty of power no matter the temperature. Do you think a burnt valve could intermittently cause a no start issue? Maybe a hot check on compression is in order.

CROSSBOLT:
No, it would not. Neither would slightly degraded ring sealing indicated by the 10 psi increase with oil. The fact that it seems to have good power belies the "book" compression value. Many of these service manuals have horrible mistakes in them so several of us treat the specifics with a grain of salt! So, to your symptoms. Something loose, bad contact, loose part, intermittent air leak. Key word "intermittent." Very tough to find. Requires huge commitment and lots of time to find. Don't give up!

Just re-read your intro and all the posts. Try this next time it pukes: quickly open the gas cap and see if there is a difference. This is carb, right? Check if you haven't, the vacuum operated fuel valve.

kkraft:
Just went back through the book again, I could have sworn the compression was close when I first checked it. The engine section says compression pressure 213 psi, the cylinder head section says 12.8 kg/cm2, which is 182 psi. So that is pretty close. I was going to say that I was annoyed there is no wiring diagram in a 700 page manual but I just found it on a unnumbered page stuck in the back of the book. Wish I found that a few months ago.

It is carbed with a TPS sensor and a vacuum operated fuel pump. I can't find a valve but I am guessing this model maybe different than most and has the tank under the floor rather than up high. Tried popping the cap but never got a suction noise and I tried running it with the cap open with no change. I suppose the next time it dies I can try draining the float bowl and see if there is any fuel present.

Thank you for the suggestions I will try focusing more on looking for loose parts, wires and the vacuum system and see if there is something simple I overlooked. Thanks again!

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