Help ... troubleshooting issue By beau87 (Read 4,266 times)

[beau87]

I am relatively new member to this forum and would appreciate some help troubleshooting scooter issue I have. Let me give some background, last fall I was given a used 2008 Tomos Nitro 50 with roughly 4400 miles. The scooter ran pretty good and the family used it sporadically before putting it away for the winter.

When I attempted to start the Tomos a few weeks ago, the scooter would turn over, but wouldn’t actually start. I figured that the carburetor would need to be freshened up and proceeded to disassemble and clean the whole carburetor. While reassembling the carburetor I broke the electronic choke. So I ordered a generic choke that looked to be very similar to the original and reinstalled in the Tomos original carburetor. The scooter started, displayed swings in the idle speed, would bog down if I opened the throttle and wouldn’t stay running if I quickly let off throttle.

Well I used all the adjustment advice I could find on this board and others, but could never get the engine to idle or accelerate smoothly. So I decided to track down an electronic choke from a Tomos parts bike off eBay, which I did. I reinstalled the choke from eBay and got the same idle result. So I ordered a new carburetor and cleaned the original carburetor again and put it to the side.

With the new carburetor adjusted and installed on the Tomos, I could never get the Tomos to actually run; it would turn over, but never ran. In desperation, I reinstalled the original carburetor and the bike started and ran fairly well. Well enough in fact for me to take a couple mile test drive around the neighborhood.

So yesterday, a day after taking the scooter for a test drive, the scooter would start and idle, but completely bog down if I opened the throttle and wouldn’t stay running if I quickly let off throttle. I don’t understand where I am going wrong with this scooter. I feel like I chased down every possible cause for this possible behavior and still come to the same conclusion … something is not correct on the carburetor.

[Alleyoop]

Does your carb look like this:
Alleyoop


Also make sure you do not have any Air Leaks around the carb where it connects to the INTAKE as well as by the Air FIlter. Did you Clean out your Air FIlter it may be clogged with dirt and gas.
Turn the Air/Fuel Mixture Clockwise in until it stops and Count the Number of turns it takes to stop. Do NOT FORCE IT just until it stops, Then turn it out 2 turns and start it. NOW LET IT Warm up about 5 minutes.
When you first start it the IDLE SHOULD BE high around 2000 rpms Because of the ENRICHER(CHOKE) allowing more fuel to come in. In about 3 minutes or so the Idle SHOULD start to come down to around 1500-1800 RPMS, that means the ENRICHER CLOSED off the Extra Fuel. Now you can Adjust the Air/Fuel mixture.

IF THE IDLE DOES NOT COME DOWN then I suspect the ENRICHER IS NOT SHUTING OFF the EXTRA FUEL. IF that appears to be what is happening then take the enricher OFF after the engine has warmed up and IF YOU DO NOT SEE A SPRING BETWEEN the Plunger and the Rubber Holder it is NOT EXTENDING to shut off the extra Feel. The Enricher Should Be Warm when you take it OFF if its NOT check the wires and connections where you plugged it into they may not be making contact.
When you take it off after the engine has run for about 5 minutes and you take the ENRICHER out it should look like this EXTENDED:
If it is RETRACTED after 5 minutes then it is not working.



You want to get the Highes RPMS as you adjust your Air/Fuel Mixture.

1.So first try 1/4 turn Counter Clock wise and wait 10-15 seconds and IF the IDLE GOES up.
REPEAT 1 Until on the Last 1/4 Turn the RPMS either Go Down or DO NOTHING then Turn it Clockwise 1/8 turn.

2. If on the First 1/4 Turn ON one the IDLE GOES Down or NOthing then Turn it CLOCKWISE 1/4 wait 10-15 seconds, If the IDLE GOES up REPEAT 2 Until on the Last 1/4 Turn the RPMS either GO down or DO NOTHING Then Turn it Counter CLockwise 1/8 turn.

After 1 or 2, set your IDLE using the IDLE SPEED SCREW to 1500-1800 wherever it Idles the smoothest and the REAR WHEEL JUST BARELY wants to turn.

Then Give the Throttle a quick twist and see if it Bogs or Hesistate If all is correct it should rev up and come down to where you set your Idle at.
Alleyoop

[skooter]

Almost excellent advice Yoop!

I too am going to adjust my idle just a bit. I finally got my scooter running! Now I'm addicted and can't wait to buy/build another scooter.

[beau87]

Tried the idle adjustment again, just like I did two times before and detect no change in idle speed. I didn't check the electric choke. I did check choke before I installed originally, I will double check choke over the next couple of days. On another note, how is it that a brand new carburetor doesn't even run at all. Thanks for all the help. I am determined to get this machine running again.

[beau87]

I might add that I bought the 18MM CV CARBURETOR from scrappy dog scooters and it was suppose to be a direct replacement for a 50cc gy6. Is it it not jetted properly for my application? Is there any jetting chart?

[sprocket]

Buy a set of jets... it is mostly trial and error. Just do the main jet. Leave the idle jet alone...

[tvnacman]

valves , plug connections on coil coil boot , fuel filter , plug , pull and read plug .

[beau87]

k, thanks for all the feedback so far....

Here is the latest update. removed old carb because I believe electric choke is messing up air / fuel screw adjustment. Before I put new carb on scooter, checked idle jet and mains against old carb and noticed that old carb jets looked bigger. Installed bigger pilot jet on new carb and adjusted to 2 full turns. No start, except if I "pumped" throttle repeatedly. Adjusted air / fuel screw to 5 1/2 full turns and scooter idles, but hesitates when turning throttle. So my question is what are the standard size jets that I would need to buy? are they universal fit on all scooters?

Modified terms

[Alleyoop]

Beau87,
Are you turning the Air/Fuel Mixture screw or the IDLE SPEED SCREW? The Idle Speed Screw is the one with the SPRING on it right by the Throttle Cable.

Which Screw did you TURN 5 1/2 FULL TURNS that the scooter THEN Idles?
Alleyoop

[sprocket]

Put the new carb back to the way it was. Why did you change the idle jet anyways?

[beau87]

In your picture above it would be the air / fuel adjustment. Sorry for any confusion. I got to 5 1/2 by using the adjustment procedure in the other section of the forum. It wouldn't even sputter without being a minimum of 4 1/2 turns out.

Sprocket - because as stated above the new carb would never start at all.

[Alleyoop]

WOW!! I re-read the start again because lost how it ran originally. And from reading that the Original Carb was fine the way it was setup. The only difference is that it sat for a long time and then it started to act up.

So back to basics, I think the orginal carb is Fine and it has CLOGGED PILOT JET PASSAGES or you have an AIR LEAK, because you said the idle would swing up and down which means it is running LEAN.

Take the old carb, take the Bowl off and Use Carb Cleaner it comes with a Small Thin Straw and SPRAY INTO THE PILOT jet. With your hand Turn the Throttle Valve and when Spraying into the Pilot Jet you should see the SPRAY coming out of the Following Holes:



THEN, unscrew the AIR/FUEL mixture screw out, You should have a Spring, Small Washer and a Small O-Ring. If they don't come out fish them out from inside the hole. Then Spray the hole and again you should see spray by the throttle butterfly. Then put the Spring on the Screw, Washer and then the O-Ring in that order and screw it back in all the way and turn it out 2 1/2 turns an give that a shot.
Alleyoop

[beau87]

Alleyoop thanks for the patience and advice. I have cleaned the original carb twice, maybe three times. That includes disassembly, soaking in carb cleaner, rinsing and blowing out all openings with compressed air at 90 psi. That is why I have concluded there is some malfunction with electric choke. Also sprayed all hoses and connections to diagnose if there was any vacuum or air leak and found none. I have been reading and working on this problem for a month before posting.

Again thank you everyone for your feedback.

[Alleyoop]

Beau87,
Not a problem man, but from re-reading the Carb was fine.

When you say you sprayed and and blew into it DID SPRAY COME OUT OF THE PILOT JET Passages by the Butterfly? IF SO then its somthing else.


So there are only a few things (1) your Valves are not Adjusted correctly and or You have lost Compression.
Now if the Valves are Tight you will Loose Compression and it will be hard to start and have enough suction to work the Petcock or Fuel Pump whichever you have.

You can see how the suction is working by takeing the Fuel line off the Carb and putting into a container and CRANK it, Fuel SHOULD STREAM OUT.
Alleyoop

[sprocket]

There is a right way to clean these jets.

You need to run a fine metal wire, like from a guitar high E string or twist tie or welder's tip cleaner through the jets scraping the sides... This removes built up varnish.

They may appear clear when you blow through them and as soon as the gas softens the varnish on the inside walls of the jets, the jets plug-up....again.

And no, carb cleaner will NOT clean them well enough...