2005 Minarelli Aprilia 2 Stroke 50cc Issue [Pls Help]

ty2212 · 04-05-2024, 09:51 AM

was out for a couple hours riding, parked and then went to leave 20 mins later;

Didnt want to start, WOT it starts and instantly started sputtering wanting to die so gave it 1/3 throttle to keep it from dying for a few seconds then let go and it died. Fuel was spilling out the bottom of the airbox. Has not started since. Left it for days still no start.

Put new spark plug in and held against frame turning over has spark and plugs wet gets fuel but no go

Have had the PHBN12 carb off apart everythings clean looks good, blew it out and float works is also non adjustable

Have swapped a new PHBN17.5 carb on no start it previously ran good with it

I am unsure where to go from here any ideas? It is a simple 2 stroke, very familiar with them. it has fuel and spark but wont start. Only thought is maybe reeds (7000km on scoot) Thanks in advance

sc00ter · 04-06-2024, 11:22 AM

If the air filter is wet it won't start. I recently dropped a string trimmer air filter in a jar of gasoline and shook of the excess fuel and re-installed it. Would not start. I had to blow the filter out with compressed air. So your air filter might be wet with fuel and oil.

I've had reeds split before. Mostly the metal ones. Carbon fiber reeds are cheap insurance that if they fail they drop a piece of carbon in the motor and not metal. Always replace stock metal reeds with carbon fiber on 2-strokes.

Is the spark plug throwing a strong spark at the electrode? Alternators will usually suddenly fail without warning. On most 2-strokes an alternator failure is rare but it still happens. Also a faulty voltage regulator or even a failing coil can cause weak spark.

Last thing I can think of is a bad petcock valve. They are vacuum actuated and sometimes get stuck open, flooding the carb Again, rare but it can happen. You'll have to do a quick test to see if its closing in a timely manner and not getting stuck.

Let us know what you find. Knowledge is power and it needs to be shared.

ty2212 · 04-22-2024, 12:04 AM

Took the reeds out they look mint no sunlight coming thru. Kind of at a loss. Will have to learn to test wiring with multimeter.

I took air filter out its brand new and oiled

Theres what looks to me like a good spark when grounded against frame and turned over. Just doesnt want to start

Petcocks working its getting fuel to the spark plug when taken out its wet

sc00ter · 04-23-2024, 10:51 AM

I hate doing blind diagnostics, as in, your'e there and I'm here. So anyways:
You have spark.
Air (is the air filter supposed to be oiled or is it a dry filter?).

I've had a Zuma flood like what you described. It turned out to be a bad float. It got warped a bit and was hanging up. Just thought it was dumb because it didn't really give me any warning.

I've also had a bad spring in the spark plug boot cap. It would randomly loose contact. Zuma's when modded love to beat the boot cap up. Cracked boot, contact inside cap breaking free from wire as well. We learned how to bullet proof them.

The way you described the sudden no start is hard to guess on. So, I'll go farther.

Is the scooter stock?
Modded? What was done if modded?
Is it beat-up or well kept?
How many miles?
Is it the air cooled or liquid cooled version?

Only other thing that pops in my head, and I highly doubt this, is a compression issue. Like it somehow got a soft seize. Again, highly doubt it. Those Aprillia scooters run a version of a Minarelli motor, and they are very reliable motors. I'll ask a friend his opinion if I see him. He was my riding buddy until we both kinda walked away from 2-strokes. I might be stupid though and pick up either a moped or a new Genuine RH50 though.

04-06-2024, 11:22 AM	#2
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 609	If the air filter is wet it won't start. I recently dropped a string trimmer air filter in a jar of gasoline and shook of the excess fuel and re-installed it. Would not start. I had to blow the filter out with compressed air. So your air filter might be wet with fuel and oil. I've had reeds split before. Mostly the metal ones. Carbon fiber reeds are cheap insurance that if they fail they drop a piece of carbon in the motor and not metal. Always replace stock metal reeds with carbon fiber on 2-strokes. Is the spark plug throwing a strong spark at the electrode? Alternators will usually suddenly fail without warning. On most 2-strokes an alternator failure is rare but it still happens. Also a faulty voltage regulator or even a failing coil can cause weak spark. Last thing I can think of is a bad petcock valve. They are vacuum actuated and sometimes get stuck open, flooding the carb Again, rare but it can happen. You'll have to do a quick test to see if its closing in a timely manner and not getting stuck. Let us know what you find. Knowledge is power and it needs to be shared.
	1

04-23-2024, 10:51 AM	#4
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 609	I hate doing blind diagnostics, as in, your'e there and I'm here. So anyways: You have spark. Air (is the air filter supposed to be oiled or is it a dry filter?). I've had a Zuma flood like what you described. It turned out to be a bad float. It got warped a bit and was hanging up. Just thought it was dumb because it didn't really give me any warning. I've also had a bad spring in the spark plug boot cap. It would randomly loose contact. Zuma's when modded love to beat the boot cap up. Cracked boot, contact inside cap breaking free from wire as well. We learned how to bullet proof them. The way you described the sudden no start is hard to guess on. So, I'll go farther. Is the scooter stock? Modded? What was done if modded? Is it beat-up or well kept? How many miles? Is it the air cooled or liquid cooled version? Only other thing that pops in my head, and I highly doubt this, is a compression issue. Like it somehow got a soft seize. Again, highly doubt it. Those Aprillia scooters run a version of a Minarelli motor, and they are very reliable motors. I'll ask a friend his opinion if I see him. He was my riding buddy until we both kinda walked away from 2-strokes. I might be stupid though and pick up either a moped or a new Genuine RH50 though.
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