50cc idles but won't Rev By hitshane (Read 18,022 times)

[hitshane]

Hi,

    So I have a 2013 50cc TaoTao ATM50-A1. I have put 1200 miles on it since I bought it new. I use premium fuel and have followed the maintenance schedule. I have a new carb installed, vacuum lines, fuel lines, fuel petcock, fuel filter, and sparkplug. It has ran great since I got the new carb a few months ago.

While I was driving home last week it felt like it was losing power and slowed to about 20MPH, but made it home. I thought it was the rear tire as it has a leak and I have been looking up replacements for it.

I started my scooter yesterday to go to the store and it started just fine. I let it warm up till the RPM's dropped into a nice idle and went to give it gas. No power at all and it bogs down like its choking. If I let off the throttle quick enough it catches back into idle otherwise it dies. After doing this a few times it started not staying at idle and was bogging out no matter what. 

I pulled the carb and took it apart. Every part inside of it looks brand new and shiny. I used compressed air and blew through every orifice and the jets. I can feel air coming through the other side of every thing I blew it through. The diaphragm looks nice and new and I can't see any holes in it. The needle was not stuck or the floats.

I reinstalled the carb today and while starting it I saw fuel come through the lines and into the carb. After a few tries it started right up, but idled bad. I opened up the gas cap thinking maybe it was vapor locked and it starts but still wont rev without choking out. I opened the air box and still the same thing. I blocked the air intake with a T shirt and it didn't get better. I felt the exhaust and the pressure feels nice and strong coming out at idle so it must not be blocked. I normally have the fuel mix screw between 2 and 2 1/2 turns out. I had to turn out the screw about 6 turns to get it to idle correctly. Still bogs out the same. I swapped out my expensive spark plug for a basic NGK it came with just for the hell of it and it didn't change anything.

Just touching the throttle bogs it instantly. Turning the fuel screw out makes the idle higher and turning it in kills it. It is not where I normally keep it though and it is turned out about 3 times more than normal operation to keep it idling nice and strong. If I turn it out anymore the screw is going to come out.

Can someone tell me where to diagnose next please. I don't see where it could be losing vacuum and it is getting fuel. The intake and exhaust aren't blocked. The carb isn't clogged. The enricher is still functioning. The engine sounds fine now at idle with the current carb screw position. The plug I pulled looked fine. It has proper oil and there are no fluid leaks or buildup anywhere. Could the PAIR system be clogged up? Could it be exhaust valve? Could it be the CDI? My next step is draining the fuel and replacing the CDI and coil. Should I buy a compression tester? Replace the carb first? 

Can someone jump in and share some knowledge please

-Shane 

[Alleyoop]

Adjust your valves both to .003 inchs
Alleyoop

[hitshane]

Do I need a torque wrench to reinstall the valve cover bolts? Should I buy a new gasket first?

[Bashan]

No and no. The gasket is embedded in the valve cover, just leave it be. The aluminum in these engines is soft so just snug the bolts down firmly, don't wank them down, it is a non pressurized environment, it doesn't need mega torque. Use a 1/4" drive for the socket, you'll stand a lot less chance of turning a bolt out. It would be better to err to the side of not tightened enough than stripping threads. You can always go back and tighten a little more if it's dripping a little oil. Once you strip the bolt you'll be transferred to another forum....and you don't want that.

[Alleyoop]

TRANSFERRED TO ANOTHER FORUM GOOD ONE RICH, that is funny.

Yea just snug up the bolts no need to tighten them up like a HE MAN, it has a rubber o-ring gasket all around the cover to seal so oil does not drip out.
Alleyoop

[hitshane]

OK,
so I had a window today of no rain and went to work. I aligned the timing mark and double checked the cams placement. The engine rolled into the sweet spot to work on the valves.

I checked them before I loosened up the nut and both in and out were .005". The shop I got it from said they adjusted the valves to get the best performance out of it when I bought it, so I'm guessing that's where they put it at. The ripped rubber gasket reinforced this conclusion.

I set both valves at .003" and tightened them up carefully. I rotated the engine a few times from the air fan and rechecked them. Perfect! I reinstalled the valve cover, being careful not to strip the bolts! So far so good...

I put the carb fuel mix screw where it should be and it wouldn't start. I turned out the screw until it was about to fall out and was able to get it to slow idle. Turning the throttle even a hair, causes it to bog out. It actually was idling better before I made the valves tighter. I might go out to .004" after I get it running, but I still have to do that first.

What is the next thing I should do? Should I order a carb? Can someone send me a link to a carb that is good and not Expensive as hell! I have the one with the black plastic diaphragm cover on it now.

-Shane

[Alleyoop]

BUMMER, leave the valves alone, the problem is NO FUEL. IT should actually start pretty good just with the ENRICHER. So maybe the ENRICHER is not working and is stuck in the EXTENDED position.

Do this take the ENRICHER OFF and look at it and SEE the plunger is retracted or extended SEE THE PICS BELOW, Pic #1 is RETRACTED and Pic #2 is EXTENDED. Then COVER THE HOLE WITH YOUR THUMB and hold it there and see it it starts better and idles better. KEEP YOU THUMB OVER THE HOLE for at least 3-4 minutes IF the motor stays idling.

What you have is a FUEL DELIVERY problem.
TAKE A PIC OF THE CARB AND THE HOSES AROUND IT you may have a really bad leak that we can spot.

Alleyoop

PIC #1: RETRACTED


PIC #2: EXTENDED

[hitshane]

OK, when it stops raining I'll do that and edit it into here. It would always idle and even rev while the enricher was engaged though, before it warmed up... It also would run and idle from the warmed up position. Being Florida hot here I don't think it even needs the enricher, but in any case warm or cold it would start or rev. I don't see why it would stop idling from a cold start with the carb mix screw in the proper position. I do think it is a air/fuel issue though. The only hoses I have not replaced are the PAIR system...
-Shane

[Alleyoop]

Your right Shane, you really do not need the ENRICHER in Florida only when it gets down to below 60 degrees then it helps the motors start right away rather than cranking them a few times to get enough fuel in there.

But it is definitly a fuel issue so take some pictures of the carb area and hoses and LOOK FOR ANY CRACKS in the INTAKE MANIFOLD,AIR TUBING , AIR BOX, VACUUM HOSES WITH SPLITS Etc..
Alleyoop

[hitshane]

I stripped the screws on the enricher and ill have to go get a dremel I don't own. Will have to get replacement hex screws too at Ace. I will try to get them today, the wife should be home soon with the car. Here are some pics of the carb and bike. The hoses are all new except the PAIR hoses. I cant see a crack on them or the intake manifold. I also blasted the entire area with starter fluid and the RPM's didn't raise a bit...

[Alleyoop]

That Spark plug boot looks like it is not straight on the plug to me. Also the fuel line to the carb is that going to a PETCOCK or a fuel filter AND DOES IT GO DOWN HILL to the CARB? It is a Gravity feed system on yours and no loops or up and downs should be on the hoses going to the carb.

I also see a PAIR SYSTEM on your motor and a hose from there should be going to a canister with vacuum as well.

Fuel hose from where ever should be as short and straight as possible to the carb when you have a Gravity Fed system.

Take a picture to the RIGHT a little more so I can see the hoses and petcock and connections there.

[Alleyoop]

That Spark plug boot looks like it is not straight on the plug to me. Also the fuel line to the carb is that going to a PETCOCK or a fuel filter AND DOES IT GO DOWN HILL to the CARB? It is a Gravity feed system on yours and no loops or up and downs should be on the hoses going to the carb.

I also see a PAIR SYSTEM on your motor and a hose from there should be going to a canister with vacuum as well. Take a picture to the RIGHT a little more so I can see the hoses and petcock and connections there.

Fuel hose from where ever should be as short and straight as possible to the carb when you have a Gravity Fed system.
All looks good just two questions: read what I texted in the pictures below.

[hitshane]

Yes the spark plug boot is NOT how I normally keep it, I had swapped to the old plug throughout this ordeal. I ran the fuel lines downhill from the gas tank, to an oversized high flow fuel filter, to a fuel petcock, to the carb. The lines are as short as possible. I did the suction test with a flavor injector on the vacuum line and fuel flows out very fast. It has been setup this way for 600 miles and worked great. I drained the tank completely when I got home and will refill with fresh gas tomorrow.

I was able to cut flat head slits into the stripped screws and get the enricher out. I bought replacement hex screws for it. I have now replaced every screw on the carb lol. I will check the enricher tomorrow for proper function and plug the hole with my finger while the engine is running and see what happens for a bit. I pulled off the intake manifold and it looks brand new. There is still one vacuum line coming from the intake manifold that goes to the PAIR system, that I have not replaced yet. I will do that tomorrow. Is the canister it connects to serviceable?

Tomorrow I will replace everything and make it tidy. I'll take some more pics also. Thank you for all the help so far

-Shane



 

[Alleyoop]

How does the ENRICHER LOOK RETRACTED OR EXTENDED since you took it out?

[hitshane]

It is not extended out...