another taotao50 no start

[scottcsu]

hey folks.

apprecaite you taking the time to read;

a colleauge dropped off his son's TaoTao 50cc scooter because they have not been able to ride it all winter and now it won't start. it has ~2K miles and has probably never been serviced until now.

at first I figured it was a gummed up carb or bad gas. However now, I'm a bit stuck.

I've been referencing your forums for a month or so now and they've been quite helpful. thank you.

here's what we/I have done thus far.

replaced the spark plug.
confirmed the plug gap matched the gy6 manual (generic_owners_manual_JL50QT_18.pdf)
checked the valve gaps
adjusted the valve gaps to match the forum instruction specs.
changed out the gas with fresh gas
confirmed spark to chassis
confirm proper grounds are connected
measured the primary coil impedance to be 0.3 Ohms
measured plug cap to coil leads at 8kohm
measured the Pickup Coil at 145 Ohms
measured charge coil at 506 Ohms
pulled the carb and cleaned the carb out after having to machine slots in the float bowl screws.
tested the auto-enricher and it seems to test fine.
tested the fuel petcok which seems to be OK.
checked the fuel filter too - no issues.

I had it running awhile ago after cleaning the idle jet, but then it stalled after I ran it up and down the street a few times.

If I run the starter and give it just a hair of throttle, it'll sound like it's really really close to kicking over and running...but it rarely ever takes off on its own.

I'm trying to acquire a timing light from someone at work to verify the CDI. Is there another method to check this?

can someone point me in a new direction? I'm running out of ideas and feel like I'm missing something obvious...

one odd thing I found was that the Idle Mix screw was originally set to ~2-2.5 turns, maybe 3. Now I've got it completely closed and if I open it up the engine stalls.


thanks for your help.
-Scott

[skuldur]

have you tried kicking it over manually, ive had the same problem, everything you listed checked out fine, but i would always kick over instead of using the push button to start it.
check your air filter? i had a problem with an older ped a couple years ago strangely, was getting to much airflow(i know weird right) make sure your filter is dry, and all the screws are tight on your airbox, what about your transmission, have you checked in there? make sure nothings broken, and also check all your lines to make sure nothing is cracked or split, even the smallest split in a hose can cause problems...
these damn taotaos drive me crazy lol, its like a neverending story just tryin to get the damn thing running smooth, best of luck to you

[90GTVert]

:welcome2:

The fact that you have the mixture screw completely closed makes me wonder if you've got all of the passages inside the carb completely clean (carb cleaner and compressed air should be sprayed through all openings). All the way in should be the leanest setting if I'm not mistaken, been a bit since I played with a GY6. Check the float height to be sure it isn't too high, which can make it run rich. Is the air filter clean?

[felliott]

All the way in on a/f mixture screw is rich.

[scottcsu]

Thanks for the replies.

I'm running with the airbox off right now becuase I was concerned it isn't getting any air. The filter is a bit soggy at the bottom, I'm suspecting from the valve cover breather line.

I did try kicking it over manually becuase I've killed the battery twice during multiple attempts to start the darn thing. The kick has a pretty small swing I've noticed, but doesn't seem to be able to start it either.

I read in the GY6 manual that you should be able to measure the output coil voltage to be near 120V is that correct? Would I be able to measure that with my DVM or do you need a HV probe? I kinda figured it'd be closed to kV to arc across the plug, but I don't know.

I got the timing light today and I'm going to work on it this afternoon. I figure the CT for the timing light should give me a good gauge if there's enough juice to fire the plug or not and the measured advancement angle may give me an idea if the CDI is working properly. I'll keep you posted.

pulling off the carb again is a good idea. I sprayed carb cleaner into all the orfices and watched for fluid to come out of an exit, but didn't do compressed air. thanks!

I'll give the 90* bend from the carb output to the intake a good look over again too for cracking.

thanks guys.
-scott

I forgot to mention in my OP that compression is at 150psi.

[scottcsu]

Hey guys,

so I finally got around to working on the scoot this morning and was quite suprised.

I killed the battery last week and my neighbor took back his charging setup. So I ran the scooter off my Jeep this morning and it started up quite fast but would not maintain idle.

so I hooked up the timing light and watched while turning over and it was positioned on the "F" line. once I gave it gas to keep it going, it was nearing the advanced mark in front of the F.

interestingly, the light flickered...and I don't mean that it flickerd like it's supposed to, but rather the idle was dithering forward and back between the "F" and the advanced line and occationally the light would skip and blackout...so I'm assuming that means the plug is occationally missing.

after turning the throttle setscrew clockwise till it was buried and then slightly tinkering with the mix screw it was holding an idle with a minimal ammount of tire roatation...it'd occationally kick an inch or 3, but otherwise was stationary.

I ran it up and down my road briefly and then brought it back onto my drive pad, and it died again. This time I tried starting it off the taotao battery and it would do the little bit where it sounds like it wants to kick over and run, but cant...

Any thoughtS?

I'm starting to think I may have a weak spark on this guy. Perhaps the battery doesn't have enough CCA left to push the spark? I Ohm'd the plug wire and it seemed to be in spec and the plug is new...but maybe i need to just go get new plug and wires?

next step would be to pull the carb again and clean it a 2nd time.


thanks.
-scott

[dirtymoosetaint]

try looking (if you havent already) at the intake manifold, were the carb goes into it. On mine the brass ring thing that tightens the hose to the carb was not tight enough and it was causing my ride to die when not giving it gas. I had to cut the end of it off cuz it was not allowing me to tighten it any further than it was...hope that might help..lol

[Deleted]

tight valves.
i would do a compression test too.

[usmcdoc]

maybe the main jet is plugged,...or petcock is bad..pull carb fuel line off.....then vac line from the intake.....suck on intake line.....gas should shoot out the carb intake line....

[larry001964]

Hi scottcsu,
I have a suggestion, have you checked the enrichner ?

[scottcsu]

hey Guys,

really appreciate the feedback.

like I said earlier, the fuel petcock is working; I did as USMC suggested a few weeks back. I also cleaned the snot out of the carb at that time, but could do it again.

I'll check the compression again, but it was 150psi a month ago.

Larry, when you say enricher do you mean the idle fuel/air mix or the auto enricher? If you meant the latter, I took it into my lab too and connected it to a 12V source and measured the needle displacement. seemed to be working properly.

so, looks like my list is:
1.) Battery Test
2.) Compression Test
3.) Intake manifold check
4.) Check the carb again

oh, one oddity I noticed yesterday which may provide someone with insight; I can't run it without the airbox installed and the feedback from the valve cover in place...which is providing some really smokey air. I've really tried to run the bike without this and the airbox so I could try shooting starter fluid in and for some reason it'll quickly die or not even start - even with starter fluid - without this feedback coming into the carb. However with this feedback line, the bike may run or just sit there and struggle to turn over.
Thoughts?

thanks a bunch folks;
-scott

[larry001964]

Hi scottcsu,
My thought on the airbox is your main jet is to small to run without it, your getting too much air and not enough fuel,, Same with your valve cover tube. It's possible that with it's removal your sucking too much air, normally they plug into the back of the carb ( either the tube leading from the airbox to the back of the carb. or the norkel tube on front of the airbox it self ).. and use the small amount of vacuum created by the air passing to the carb to pull out crank case gasses, if it's open on the tube from the airbox to the carb or on the snorkel it will draw air throwing your A/F mixture off.. Think of it as the old PCV systems they used to use on older cars before fuel injection there's no PCV valve but it's pretty much the same principal...

These little things come pretty lean from the factory anyway.. so without up jetting a little there's very little room for any changes to the airbox setup...

I was thinking the auto enrichner as I hadn't seen it mentioned..

[scottcsu]

I'll have to pull the carb back out and check the jets. Will it matter if I'm in Boulder, CO? my motorcycle was jetted for high altitude before I bought it, but don't know if it really makes a difference.

Friday I worked on the TaoTao, starting it off my car battery.

Compressiong was around 130psi.
I also removed/reinstalled the intake manifold and it seems fine. I was able to get it to kinda turn over by spraying starting fluid straight into the intake valve which was nice.

So I was able to get it running after awhile of coaxing. Once I had it running, I had to continue to give it throttle, but I was able to take a handful of voltage measurements...wanted to post these in hopes they'd tell someone something.

wires at the connector for the pickup return:
White = 15.34acV/-0.62dcV
Green = 0.026acV/0.031dcV
Yellow = 12.48acV/-0.480dcV
Blk/Red = 81.0acV/49.5dcV
Blu/Yel = 0.810acV/0dcV

at the CDI:
Blu/Yel = 0.780acV/0.00dcV
Red/Blk = 80.4acV/49.4dcV
Blk/Yel = 0.088acV/0.027dcV
GRn = 0.029acV/0.010dcV
Blk/Wht = 77.1acV/52.0dcV

Battery = 12.59/12.59


I'm guessing these voltages are expected values, which points me back to a gas/carb issue again.

after reading that newest post about the sealed carb issue on these scooters, I'm pondering if I should get a new carb? might that fix all the problems?
( I machined slots to pull the bowl and adjust the air/fuel mix into this stock carb so that it'd be adjustable.)

thanks for the continued support.
-scott

[Deleted]

Apr 22, 2012 23:03:47 GMT -5 scottcsu said:

Compressiong was around 130psi.
I was able to get it running after awhile of coaxing. Once I had it running, I had to continue to give it throttle

a new carb is not going to fix a low compression problem...and 130psi is not near enough. to crank easy and run good it needs at least 175psi
take a length of vacuum hose and stick it down the spark plug hole and then put some oil down the hose..a generous amount..but it doesnt have to be overflowing either.
do the compression test again and if its higher its rings. if it doesnt go higher its valve seats or a head gasket but thats rare...9 times out of 10 on these little motors its rings...and on a taotao 99 times out of 100 its rings

after the oil test is confiremd...a ring/piston job would probably fix it. next step is to take it apart and measure the bore to know what piston and ring set to get but if its a 'sunny' style taotao its 44mm 63cc they all are

however...now is the time to do a 50mm 83cc big bore

[scottcsu]

Thanks for the input...rings sounds a little more discouraging for my skills.

Maybe this is a stupid question, but I guessI don't know the answer.

The owner of the scooter took it to the actual motorcycle shop here in town. they measured compression at 140psi and said it was good.

if 130 is bad compression and 140 is good compression, where's the limit? I'll check it again this week when I get a chance.

thanks.
-scott