Buddy 125 dies at full throttle

[jimusik]

I've been having some odd problems lately with losing power at higher speeds. There is a bit of drama going into this but I'll keep it short.

What Happens: Scooter starts just fine, idles just fine and even rides at lower speeds without any issues. Get on the road and full throttle it for about a quarter mile and she starts to sputter and die (or just loose power till I lay off and let her idle. Seems starved for fuel.

Fuel Filter is good. Mechanic put an aftermarket filter that is see through, no visible grime and if it's sputtering I can visibly see that the filter is not getting enough fuel.

I pulled the Auto Cock Comp off the bottom of the tank but there is no way to visibly see if there is anything wrong with it. Looked inside the tank and the screen feeding the Auto Cock looks pretty clean. Tested the vacuum hose and I'm getting good suction.

I put pump gas in for the first 2k. The last 2k I've used an additive (Lucas Safeguard Ethanol Fuel Conditioner). Scooter never sits. The issue seems intermittent tell yesterday.

1) Anyone know how to get that filter out of the inside of the tank? Tried to push down through the threads from the inside of the tank but it won't move and I'm scared I might damage it.

2) Can't find any loose electrical issues, spark plug is brand new, carb was just cleaned out, battery has full power. Any ideas of other issues to pursue?

3) Auto Cock Comp seems to run about $11-15 but would that really fix my problem?

Any suggestions greatly appreciated before I take it in to my mechanic.

[Throwback7R]

could be too much fuel " flooding" what else have you done to the scooter? I would check the intake see if that has no leaks in it.

Also I would fully check the carb.

[jimusik]

could be too much fuel " flooding" what else have you done to the scooter? I would check the intake see if that has no leaks in it.

Also I would fully check the carb.

Thanks Throwback7R. I believe if it was flooding I'd be getting some backfiring. Part of the drama is this issue happened at my mechanics and it was flooding and dying. He claimed it was electrical (crummy deadhead wiring on my part) and it's been running just fine for about a month now (I redid everything with good wire straight to the battery and added a switch). All of a sudden it died yesterday. Disconnected all my mods right away to make sure that wasn't still the issue. It really does feel starved verses flooded.

Could it be that the aftermarket fuel filter is allow too much fuel through? I'll check the intake and start contemplating pulling the carb apart. I guess I should double check all the points he claimed to have replaced a month ago.

[Tocsik]

I know you say it seems like fuel starvation as the filter does not look to be filled but sputtering at high revs sure sounds like a stator going bad.

[jimusik]

I know you say it seems like fuel starvation as the filter does not look to be filled but sputtering at high revs sure sounds like a stator going bad.

Any suggestions on how to test the stator?

[ed85379]

I had this problem after I got a bad tank of gas. When it was full, it would be fine, but once the tank got to about half empty, it would lose power or stall when at high throttle.

So I brought it to the shop and they emptied out the fuel and cleaned the carbs. This, however, did not fix the problem. I had to bring it back. The second time, they simply replaced the spark plug, and that solved it.

So I guess it doesn't matter how "new" the spark plug is. If something gunks it up, it is gunked up and needs to be replaced.

[Stinkdyr]

How many miles on this puppy? If in excess of 7000 and it has been ridden a lot in winter/rain etc, then you should suspect your stator. It is located low on the bike and susceptible to corrosion. (ask me how I know this!)

My 2009 RH50 with 9700 miles on her was gradually losing power under load during the last 6 months. I tested/swapped out every part up the food chain....spark plug, ignition wire & coil, cdi, and then...............the stator. Stator was the fix. BE ABSOLUTELY SURE YOU GET THE CORRECT REPLACEMENT STATOR, not just one that kinda looks like it might work in there. Make sure the wire connectors match up.

[tortoise]

Fuel tank venting issue.

[Dooglas]

Fuel tank venting issue.

Remember - the test for this problem is simply partially open the gas cap and see if the problem goes away.

In the OP's post, I see a mention of the carb being "cleaned out" but no indication of what was done. I always suspect a clogged jet or leaking diagram in a case like this and try to eliminate that possible cause first.

[BuddyBliss]

Had the same problem and it was the venting issue, happened on a group ride where some experienced with this problem removed the gasket on the cap, allowing for the venting until a hole could be drilled in the cap

Scary when it happens!

[jamey9160]

Scooter starts just fine, idles just fine and even rides at lower speeds without any issues. Get on the road and full throttle it for about a quarter mile and she starts to sputter and die (or just loose power till I lay off and let her idle. Seems starved for fuel.

I used a tiny bit of fuel conditioners/carb cleaner in mine once, and my bike rn crappy for weeks until I finally took it to the shop & had them clean out my carb & jets. Then everything ran fine again. I never added anything after thaat & it's always run perfectly since the carb was cleaned.

[ericalm]

Some of the issues described above would only happen occasionally or under certain circumstances.

I do think stator is most likely issue from what information is here, but more would help.

Does this happen every time you open up to full throttle?

And does it start easily after it dies?

Any other trouble starting or idling?

[kmrcstintn]

this is gonna sound weird, but have your shop check the spark plug boot...I was having similar performance issues above 3/4 open throttle; on a recent trip to the shop they found a loose/broken connection between the resistor & clamp (the part that attaches to the spark plug) when I asked them to replace the spark plug...new replacement boot = better connection and I have restored performance

[jimusik]

Thanks everyone for the suggestions.

So far:

• I've pulled the petcock off, emptied the fuel, put new gas in and checked and rechecked the fuel filter.
  I've blown out the jets and checked the carb (everything looks like new in there).
  Pulled and checked the spark plug. Gap is perfect, coloring is just right for the 200 miles I've put on it.
  I have a second 125 so I've swapped the ignition coil to eliminate boot issues or coil cable problems.
  Battery is brand new and I keep throwing it back on the conditioner to make sure it's fully charged.
  Checked the Stator both visually and with a voltage meter. I'm getting solid 14+ volts when at 1700 rpm.
  Just swapped the CDI with the other scooter and will test in the morning.

I am running out of options. This is what I've figured now in riding it hard for a week.

1. It only happens at temperature.
2. When it starts to misfire it happens mid-range and above. It's at full throttle that it will literally die.
3. When it dies, it completely dies. If I wait a few seconds I can start it again. Sometimes I can get it running again but mostly it will just idle and sputter dying every time I try to give it more than 1200ish rpms.
4. When it cools off it will start and ride like normal. Since I've been tearing it apart I've managed to get it to fail for me almost every time I take it out. It's always about a mile into the ride and at full throttle when it will die.

Posting in the hopes to help someone else out with similar issues, will keep you updated with the fix...if I ever find it.

Any other suggestions are greatly appreciated.

[RoadRambler]

So is there any chance it's just the vacuum/vapor fuel venting issue several others already suggested? Since you said it only happens at temperature.

Did you test that possibility out already (pulling off the gas cap and letting it sit a couple of minutes to see if it restarts)?

Anyway, I had the issue with both my 125 and my Psycho until I got the vented cap, and the symptom was losing power and then out-and-out dying at speed when the engine was hot. The fix is super easy, getting a vented gas cap or drilling a vent hole in your current cap.

Sorry if you already investigated this, but it seemed worth mentioning again.

[jimusik]

So is there any chance it's just the vacuum/vapor fuel venting issue several others already suggested? Since you said it only happens at temperature.

Did you test that possibility out already (pulling off the gas cap and letting it sit a couple of minutes to see if it restarts)?

Anyway, I had the issue with both my 125 and my Psycho until I got the vented cap, and the symptom was losing power and then out-and-out dying at speed when the engine was hot. The fix is super easy, getting a vented gas cap or drilling a vent hole in your current cap.

Sorry if you already investigated this, but it seemed worth mentioning again.

RoadRambler - It's a great suggestion! I have pulled the cap and also investigated the whole vacuum system on the tank. Buddy's have a whole venting system with ECC if I understand it correctly. I also have a clear aftermarket fuel filter that I can watch which shows that gas is flowing properly into the carb even when it's mis-firing.

Tested the CDI this morning and she didn't even make it to the end of the block. Threw the other back on and I'm getting misfires just a little above idle. I'm stumped.

[tortoise]

Checked the Stator both visually and with a voltage meter. I'm getting solid 14+ volts when at 1700 rpm.

Test the stator wrapped ignition winding and trigger coil . . as compared to the battery charging output . . guidelines.

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[jimusik]

Checked the Stator both visually and with a voltage meter. I'm getting solid 14+ volts when at 1700 rpm.

Test the stator wrapped ignition winding and trigger coil . . as compared to the battery charging output . . guidelines.

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tortoise - I've tested the suggested ohms and voltage and everything looks good accept I think I must be doing something wrong. The Ignition Trigger Pickup doesn't give me the 140-180 ohms that all the videos and documentation suggests. Instead I get very low readings. I checked the other bike, and it's the same situation. Am I doing something wrong? I set the meter to 200 ohms and connect to the Ignition trigger Input at the CDI and ground to the bike. I get between .8 and 1.2. I even went directly to the wire coming off the ignition trigger and tested on three different ground points and still get between .8-1.2.

The stator is giving me upwards of 80 volts when cranking and the ignition trigger gives me about .6 volts when running (I think I'm reading that correctly). All in all, since the scooter is running and the electrical is checking out I'm again back to ground zero on this with no explanation.

It did however run worse this morning in the cold weather. I'm going to put the whole thing back together and see if I can get it to die again and maybe test some of the voltages at temp to see if they change.

[jimusik]

For anyone curious the issue turned out to be a loose negative plug on the Ignition Coil. Somehow it had gotten just a little loose, enough that the right g-force would let it slide a bit. Once it was not fully connected the vibrations (typically full throttle) created the perfect oscillation that I could actually watch the boot slide backwards. Reduction in voltage to the coil created the misfires, flood the engine and put me on the side of the road. Enough time and vibration put it back in full contact and I could ride again.

Completely intermittent and had nothing to do with the carb, stator, plug or evap system. Nightmare to diagnose. Pair of pliers tighten the prongs and no more problem.

Thanks for all the suggestions.

[jrsjr]

For anyone curious the issue turned out to be a loose negative plug on the Ignition Coil. Somehow it had gotten just a little loose, enough that the right g-force would let it slide a bit. Once it was not fully connected the vibrations (typically full throttle) created the perfect oscillation that I could actually watch the boot slide backwards. Reduction in voltage to the coil created the misfires, flood the engine and put me on the side of the road. Enough time and vibration put it back in full contact and I could ride again.

Completely intermittent and had nothing to do with the carb, stator, plug or evap system. Nightmare to diagnose. Pair of pliers tighten the prongs and no more problem.

Thanks for the follow-up! I'm an electrical kinda guy so everything sounds like an electrical problem to me. However, in this case, it sounded like a classic case of spark suppression due to some kind of problem. My money was on the plug wire either being bad or not making good contact at the plug end, so at least I was somewhere in the right neighborhood for once.

Again, thanks for the follow-up. Wish everybody would do that.

[Syd]

^^And I don't know an ampere from an ampule, so I was guessing it was fuel starvation caused by a crimped fuel line. Glad you got it figured out, jimusik.