50cc Hard to "Cold" Start

[rlshepard]

Hi Dawgs,

I'm hitting a wall so I thought I'd ask ya'll for help. Got a TaoTao ATM-50 that is really really hard to 'cold' start. I put cold in quotes cause its 70-75 outside these days. it's nearly new, bought it brand new in April. Not my first rodeo, we have 4 scooters total in the family and I've worked on all of them. but this one is giving me fits... so here is what I know.

Scooters at about 1100km
After first start I installed the blue 'racing' CDI and the fancy orange coil.
Oil change at PDI, 500km and just recently at 1000km
I adjusted the valve clearance (.003in .005ex per the manual) at about 600km and installed a new NGK Spark plug
checked and readjusted valve clearance when this issue popped up. I plan to quadruple check that again but pretty sure we are good there
Got Spark
Got Fuel
Airfilter is clean
All indications were that it was the auto enricher/choke don't know alot about that part but I ordered a new one since they are cheap and replaced it... no change. I don't really know how to test it but, but I can say when I have it out and I turn the key on, nothing happens... isn't supposed to retract or something?

For grins I have reinstalled the factory CDI and Factory coil no change.
I've checked for vacuum leaks and found none.

It cranks over well and if you give it just a little throttle is try to start but doesn't quite catch. If I connect a car battery and crank and crank and crank while giving it a little gas it will eventually start. once it starts and runs for a bit I can start it right up IF I give it a little throttle - only a little while cranking.

Once started it seems to run "okay" not great, the boy has been complaining about a lack of power recently leading up this current development.

This is my younger boys scooter, he's 'crashed' a couple of times but no major damage. they were fairly low speed crashes so just some scratching to the plastic. so I don't think he damaged anything.

I don't have a compression gauge but I may invest in one... but given age and low mileage that doesn't seem a likely issue.

My next thing I guess I'm gonna do is tear apart the carb and see if somehow something has gotten in there?

Are there any other thoughts? I'm kinda grasping at straws here I mean these things just aren't that complex, at least I didn't think they were....

TIA for any help

[Shadowfire]

It does seem like the enricher circuit isn't working.

After the enricher replacement didn't fix anything, I'd say your next step is complete carburetor disassembly and cleaning. It sounds like the supply line to the enricher valve (or the jet itself) may be plugged. Drain the fuel tank too, while you're at it, there may have been junk inside it when you bought it.
An ultrasonic cleaning bath will work wonders for this, but you should be able to quickly check the passage by spraying one end with carb & choke cleaner (through a straw) and seeing if you get a small stream out the other side of the passage. The passage is usually in the lower part of the float bowl, and connects the area with the main jet, to the area with the autoenricher jet.

Then check the enricher jet itself, the same way.


With the complaints about performance, it is distinctly possible that the carb has somehow been gummed up, although to be honest I would never expect it to happen that quickly.

[skyrider]

Is a vacuum or other hose loose? I had a similar problem and maybe its just a loose hose or poor hose connection somewhere.

[blueboy5000]

re-check your valves. If they are on point (.004" exhaust, .003" intake) the next step is to verify you have correct compression.

Sounds to me like you either have a "hanging" valve or low compression.

[rlshepard]

Checked the valve clearance several times today, it's right at .003in and .005ex. Valves are moving freely when I rotate the engine.

Effing screws on the carb bowel don't have heads! what is that about?

Guess I'll order a carb and compression gauge...

but seriously why lock me outta the carb

I really suspect its the carb, I just feel in my gut that she is starving for fuel...

[bull]

fwiw.. my thinking is fuel is draining from the float bowl when parked. Check the fuel drain system on the float bowl for leaks.

As to a sealed carb, that is an EPA mandated thing to keep you from changing jets, etc. Those screws can be drilled out very carefully by simply removing the head initially, testing / cleaning / repairing then replace the screws with new ones with Phillips heads.

[Firehawk989]

Also check the electrical for the enrichener to make sure it's getting voltage. I believe they are retracted at start-up to enable the enrichener circuit and then extend once warm to block it off for normal running. If it doesn't extend and cut off the circuit then the scoot won't run well because it will be getting too much fuel.

[dwint51]

I had the same problem and bought a manual one from scooter tuner for twelve bucks.never had a problem since

[rlshepard]

So I pulled the fuel system apart. replaced the fuel filter, drained the the tank and replaced the carb with a brand new one from Scrappy Dog Scooters, plopped in and now she starts pretty consistently but somethings still not right. I still have to give her a bit of throttle to get her to start, not much at all but just a little. The worst part is that she has no power now. Sitting on the center stand she fire up and I can hit the throttle and all seems good. put her down and go to take off it's like one of those "power wheels" cars... won't hardly pull at all. It's like it's stuck in high gear...

Maybe it's something to do with the variator? Perhaps I'll look in to that...

I'm so confused, I feel like I'm over looking something simple... Thinking about pulling the head off to see if something is stuck in a valve or something. But then I think... nah that's aint it....

[rlshepard]

Pulled the variator cover all and all looked good the variator was fully and retracted and in low gear that doesn't seem to be the problem. checked the electrical for the enrichener voltage it looked good... at least it was getting voltage while the scoot was running.

Plugged exhaust maybe? Maybe when he wrecked he knocked something loose in the pipe? I'll try to check that...

[rlshepard]

So did a compression test 30 PSI with the throttle closed, 34 at WOT... guessing I have a stuck valve or some thing... Guess I should listen to my instinct...

[blueboy5000]

Called it!

Buy an assembled head on Amazon, they sell for about $30. I would not chance repairing a head as the aluminum is very cheap and ductile. A valve issue 99% of the time will distort the valve guides beyond repair.

[rlshepard]

Originally Posted by blueboy5000

Called it!

Buy an assembled head on Amazon, they sell for about $30. I would not chance repairing a head as the aluminum is very cheap and ductile. A valve issue 99% of the time will distort the valve guides beyond repair.

So, I'm having this mental argument with my self... I could:

1. Pull the head apart clean it up and lap the valves.
2. Buy a complete replacement head w/vavles installed
3. buy a BBK kit with a complete head.

Sounds like Option 1 may not be a good idea.... I suspect that option 3 would require me to re-jet the carb get new rollers and lead me down the path of spending a bunch more money to get it to run right?

I mean it's not all about the $$ but I don't want to spend the money for a BBK and then have to spend a bunch more time and money to get it and keep it running right.... Kinda wanna bring this to a close and go back to tinkering on my scoot

Option 2 sounds like the best option? I mean I need the kid to have a fairly reliable scooter, daily driver and all that... of course he is interested in more speed but I don't want to spend every weekend tinkering on his scooter either.

I'm a little shocked... the other ATM50 in the family has been a tank! My oldest son has it at school, rode it all winter, has put it through 3000 miles (not KM) of the hell of college life and it still runs awesome. guess you never know?

Anywho dawgs before I order parts I ask your opinion? lap the valves? stock new head? BBK? if you have experience with a BBK as a daily driver I'd be interested in hearing it.

[rlshepard]

I'm really leaning towards this kit:
http://www.amazon.com/Cylinder-Upgra...m+cylinder+kit

It seems like I should just do it while I've got torn apart... Doing some reading it seems like the 47mm kits give a decent performance boost without having a huge impact on reliability on only minor additional adjustment potentially jetting the carb.

Does anyone wanna talk me out of it?

[bull]

Not going to try & change your mind.

It is a decision that you must make. I have enough experience with the different engines and can tell you from experience that your thoughts in #13 are somewhat on target.

When you increase the engine from 39mm, to 44mm or 47mm, there is very little that needs to be done to MOST carbs, IF you are using a stock 39mm head.

You gain a lot from cvt tuning them though.

Currently trying lots of different setups on a 50mm to get it to start & run just right. Even using a 5 gas to tune in the jets, which I am custom drilling. After the break-in I'm sure the jets will need some more fine tuning.

Then I'll start tuning the cvt.

As to which kit you buy, just make sure that it has the stock, thin metal head gasket. Bought 1 from John Dikov (valley scooter parts) that had a composite head gasket that created cam journal and chain stresses. btw- he does have the right gasket, but it must be purchased separately. and he has inventory and ships quickly.