NEED HELP! Stumped on 50cc Scooter! WONT RUN

[atv1234]

I am trying to get a 50cc scooter running after it sat for roughly 8 months. I drained the fuel, replaced the fuel filter, cleaned the carb, and replaced the spark plug. I also did a compression test which came out to 150 psi. I have a spark when I test the plug against the valve cover also, yet still can't get it to fire up, it sounds so close. I sprayed some brake cleaner into the carb to see if it would run for a second or so, but nothing. The timing seems right too (T mark and 2 holes on timing chain sprocket line up).

Any ideas on what else I may be missing? I am not sure what else it could be. 

Also, I noticed the brake light is always on when the key is on, and both wires (yellow and black) going to the brake switch have power. I am not sure if this relates to the starting issue. 

Thanks!

[Rebel]

Sounds like it should run, is the spark blue or yellow? If it is yellow try a new coil.

I am not sure brake cleaner works well for a starting fluid, it may eat up some plastic or rubber parts, I have heard of people using carb cleaner, I still use old fashioned starting fluid.

Did you adjust the valves?

is gas getting into the carb? If the vacuum valve is not working that could be stopping the fuel from getting there.

[Deleted]

Apr 9, 2013 1:09:20 GMT -5 Rebel said:

Sounds like it should run, is the spark blue or yellow? If it is yellow try a new coil.

I am not sure brake cleaner works well for a starting fluid, it may eat up some plastic or rubber parts, I have heard of people using carb cleaner, I still use old fashioned starting fluid.

Did you adjust the valves?

is gas getting into the carb? If the vacuum valve is not working that could be stopping the fuel from getting there.

many 50 cc bikes have reed valves that do not adjust but sometimes must be replaced, don't sweat that now.

BET YOUR CARB IS DRY, NEED TO FILL FLOAT BOWL WITH GAS

brake cleaner will smother your oxygen out and choke bike from starting.

is the plug wet with gas, i bet not.

get a eye dropped and fill it with low test gas, by pulling vac line off carb and put gas right down the tube into gas / air intake and replace tube to intake throat , use about 6 drops

make sure kill switch is set right, side kick stand is up, use center stand only.

pray for help from the bike god "GWONDO KNOCK-A-LOCKUS" AND HIT START BUTTON.

never run start motor longer then you can count to 10, you'll fry start motor brushes..

if it starts and then dies, pull plug, if it is not wet, your pet cock may be froze shut.

pull pet cock valve air suction hose, put in mouth, and blow and suck till you here it move.

you should see gas bubbles come up in filter.

also try moving gas drain hose up till it faces sky, pull shut off..OUT ..off , with eye dropper keep putting gas down it till it will take no more.

try starting again.

another trick to fill carb bowl with gas is plug up air intake a second and turn motor over a few times,

this will pull gas up into the throat intake big time.

may be wrong but sounds like brake switch is broke in the on position, replace it

if this does not work, come back and tell us, and we will help,

just teasing about kwondo the bike god.

[jmkjr72]

Try starting fluid modern carb and brake cleaners dont burn the same way older ones starting
did for starting

Check all your intake hoses to make sure they are hooked up
Did you pull the jets and look in them to make sure they are clear
Also makd sure the exhaust isnt plugged up

Try to figure out which brake switch is stuck and unplug it for now as long as you hold the brake that works when you try to start it should be fine

[Deleted]

Apr 9, 2013 8:38:41 GMT -5 jmkjr72 said:

Try starting fluid modern carb and brake cleaners dont burn the same way older ones starting
did for starting

Check all your intake hoses to make sure they are hooked up
Did you pull the jets and look in them to make sure they are clear
Also makd sure the exhaust isnt plugged up

Try to figure out which brake switch is stuck and unplug it for now as long as you hold the brake that works when you try to start it should be fine[/quote]


ALSO some bikes only one of the brakes handles supplying current to the starter solenoid,

make sure both supply juice to starter.

[Rebel]

reed valves are only in 2 stroke motors, Since you have a valve cover I didn't think it was a 2 stroke.

[atv1234]

I appreciate all the responses! I am still trying to figure it out. I took your guys advise and went and got starter fluid, but it yielded the same result. I thought before it was a fuel issue, and the plug appeared dry the other day so I had cleaned the carb out again, taking the jets out and clearing them out as well. But if it was a fuel issue I would think the starter fluid would make it run? I could be wrong.

When I put my hand over the intake side of the carb, it seems to draw up fuel because my hand gets wet with gas. Also, the vacuum line to the fuel petcock seems to work. It had bubbles in the filter when I would blow into it, and it flowed freely when you suck on it. I checked the drain on the bottom of the bowl and it seems to have fuel.

I'm not sure how to tell the color of the spark. It seems ok to me, with what looks to me to be a bluish white constant spark. But it seems like it would make sense that it may be something with the plug simply because the engine has compression and fuel, even if it was just for a second with the starter fluid.

I sprayed fluid onto the plug when I was testing it against the valve cover,and it caught fire, which is what I was going for, but maybe its not enough under the compression of the engine?

TERRA NUVO, you had mentioned the reed valves as a possibility? How would I check that?

I've been praying to the scooter gods for about a week now, maybe I should step it up with some candles and a tranquil atmosphere lol.

[atv1234]

Oh ok, yea its a four stroke, so no reeds then?

[Rebel]

yeah reed valves are in a 2 stroke. Check your valve adjustment, set them at 0.004 or 0,005 of an inch.

Valve adjustment is a big issue with these motors. If the spark looked whitish/blue it is probably hot enough.

It seems to me that you have done most everything you need to rule out a fuel, compression, spark problem. So check that gap on the valves.

You were right about the starter fluid, that in there would make it fire up if it were fuel,

[atv1234]

Oh ok, thanks! Well I will check the valve clearance and post back on the results.

I forgot to mention too about the brake switch again. I guess though if that was an issue, it would keep a spark from happening at all, I'm guessing. But I know it was suggested that the brake switch was bad, which I first thought. But when I disconnect the wires from the switch, the wires are both still hot. I have only found one switch, on the rear brake lever, unless there is another that is giving this one power. I figured the black wire was the hot wire and once the brake was depressed, the switch would power up the yellow wire as well, sending the power to the brake light. I was wondering if maybe since both wires are powered that it could be causing some sort of short.

Plus, I was expecting the rear brake light wires (brown, green, yellow) would be a hot a ground, but it seems the brown and green are the ground, and the yellow is hot from the switch. Does that sound right? I thought the green would be ground and the brown would be hot, since it branches off to the license plate light.

I am just thinking out loud basically but am throwing that out there because it seems somewhat questionable, and I know these things have switches so you have to hold the brake and many times have the kick stands up for it to start.

Once again though, it may have nothing to do with it not starting since I am after all getting a spark.

[Rebel]

As long as you are holding down the hood brake switch the bad one won't keep it from starting. At least that is my opinion.

[jmkjr72]

The switch will either stop it from cranking with the starter or stop spark
Being you have spark we can rule out the kill or brake switch i say to disconect the bad one so you dont drain the battery the stop light draws enough to draw some scoots down if stuck on

So now it is narrowed down to a massive vacuum leak timing/valve train or pluged exhaust

Check your valves then make sure the keyway on the flywheel didnt break

[atv1234]

I checked the valves, the exhaust valve seemed a little tight so I adjusted it. Still won't start. I will check the key in the flywheel tomorrow. However, when I turn the flywheel I can see the timing chain and valves move, would this suggest that the key isn't sheered? Or would I still need to check it?

Also, are there any typical areas where there could be a vacuum leak? The only vacuum I can find is from the petcock to the intake.

[Rebel]

The manifold the carb is on is normally a rubberized plastic that frequently will crack, if it is not bolted down firmly to the head you can have a leak there. Look for a nipple that is open to air. All these would be on the carb or downstream from it.

[jmkjr72]

I have seen the key shear and spin 180 deg and stop on itself again