Stalling, Dying, Chugging, Bogging, Sputtering 4t

[pesce]

Hello Everyone!

Today I took a wonderful 75 mile ride on my 2010 4t (w/ 1200 miles). Before I started I filled the tank all the way to the rim, checked the tire pressure, oil and for loose parts.

The scoot performed beautifully for the first half of the ride, best it ever performed actually! The ride was primarily up hill (maybe 1%-2% grade)

When I got to the "top" of the ride (Auburn CA) I stopped and manually checked the fuel level with my eye (maybe 2/3 left). I let it idle for about 5 min and let it sit off for about 10min. The scoot didn't immediately start up and took a good 3-4 kicks to get going, I ignored it and set upon my journey home.

The path back had one hell of a ~mile long drop into a gorge, and a hell of a climb back out. Immediately following the climb was a few mile straight light-grade downhill ride. The scoots performance was stellar so far!

Next came a steeper downgrade and I was flying! Woo Hoo! I glanced down and the speedometer read 65 baby! I was full open throttle, downhill, wind at my back, and felt like the speed racer!

Then it happened! Odd engine sound kind of over-muffled, low tone and deep coupled with immediate loss of power... then almost immediately back to normal. It stuttered back and forth between these two states about 5 times before I figured I should let off the throttle. I pulled over, the bike immediately died and figured I was out of gas (as that is exactly what the symptoms were)

I manually eyed the fuel level and noticed it was a little less than half full. I remembered everyone here having issues with the EVAP system, vacuum in the tank, non vented cap as well as my personal experience of only being able to use about 0.8 gallons of fuel in my scoot before I switch to reserve (I've never run on reserve for that long). I thought now would be as good a time as any to test if the reserve actually drains the tank. I threw the lever to reserve, started her up and away I went, bat out of hell style!

I got about 1/2 a mile further down this grade before it happened again. This time I gave it less gas (half throttle) and the engine responded but full throttle would cause the symptoms. Keep in mind I'm flying downhill, and the scoot is rapidly loosing power and gaining power and loosing power and gaining power in a violent jerking fashion. During this craziness, I missed my turn.

I pull over and wondered what was happening. I opened up the fuel tank... yes still had seemingly lots of fuel. I tried to restart it with the electric start... and the starter struggled to turn the motor over. I thought uh oh, and checked the oil... nadda...

I thought hopefully it was just overheating, so I let sit for about 10 minutes while I wondered how the hell I was going to get home.

Well it started up nicely and immediately with the starter. Since I missed my turn I headed back up hill, full open throttle, expecting the whole time to experience the problem again. The problem didn't return until I made my turn and started going back downhill. I thought well, perhaps going down hill is causing the fuel to roll forward and miss the drain.

But then I noticed the problem was intermittent. It happened on slight downgrades but not on steep ones. Then it would happen on steep downgrades and not on slight one. (never up hill) Practically the whole ride back was a rolling downgrade with periodic upgrades.

The problem would happen at both extreme ends of the throttle. I wouldn't get a response from the engine until about 1/3 throttle and then at the last 1/3 the scoot would cut in and out of power as I described above.

Finally made it back to civilization and it died on a flat straight away. I pulled over and figured I was finally out of fuel.

I had about 2-3" of fuel left in the tank and filled it with less than a gallon.

Either way, with a freshly full tank the problem didn't happen again. I tried to replicate it by going up and down every big hill I could find. Eventually I grew tired and just gave up.

Has anyone experienced this? Does anyone have any suggestions?

I am going to take the same 75mi route again, this time in the cool early morning and see if I can replicate the problem. This time I will also immediately fill the tank after it starts to happen.

The only modifications I have done to the stock engine is replacing the sparkplug with one step cooler one. And properly adjusted the points. Which was done because it seems I always have a very, very hot right foot wile riding, and it's always been that way. The right floor board near the cowell is VERY hot!

I'll keep everyone posted. Thank you!

For reference:
topic23073.html
topic23202.html
topic19584.html
topic19445.html
topic17930.html
topic19337.html

[rondothemidget]

I have this problem as well. With a full tank, my Stella 4T runs perfectly at 60 mph for 25 miles or so. Not even at WOT. Then when it gets down to 2/3 or 1/2 a tank, it starts acting like it's out of gas and has the same symptoms as you described. It only does it with less than a full tank and trying to maintain a speed around 60. It will run perfectly again if I top it off. I can run the tank down to fumes with no problems as long as I vary speeds and go less than 50 or 55.

It doesn't matter if the choke is on or off. And I believe I've eliminated the evap system as a possible cause. It will do it with the gas cap loosely sitting in the hole, not twisted at all. But it will run fine with the evap system connected and the gas cap twisted tight at speeds less than 60. It also doesn't make a difference if it's regular or premium gas. I haven't been able to find the right size fuel line as I'd like to try cutting it down to the shortest possible length. It does seem to take a long path to get to the carburetor. My uneducated hunch is that the gravity-fed carburetor just can't get enough fuel with less-than a full tank at a high speed. However it could be something about the jets or some other mechanical engineering thing I don't understand.

Please keep us posted if you find a solution.

[psssniper]

A Stella 4T has points? Do you mean valves?

Just wondering out loud, right foot area really hot=some type of exhaust leak at the head?

[Robbie]

Check for a fuel line that was cut too long.

My dealer mentioned that many of the 4ts have been coming in with the fuelline so long a slight kink develops, restricting fuel flow as the tank level (weight) drops.

They cut and route the line so no kink can develop and the problem disappears.

Good luck,
Rob

PS....There is a catalyst in the exaust pipe under the right side floorboard....this is likely the heat producer....not really a problem, more of an annoyance.

[pesce]

@Psssniper sorry. Yes valves.

Thanks for the tips everyone. I will give it a look and report back

[jimmbomb]

I've wondered in another thread Like this on.. that an exhaust leak of some kind was heating the carb,bowl,fuel line, somewhere and causing vapor lock by boiling the gas. only at extreme rpm/wot ... just wondering..

[pesce]

Any quick suggestions on how to test for an exhaust leak?

Soapy water? Lol

[pesce]

Took the same ride today. It was about 10-20 degrees cooler. I didn't change anything. The problem didn't occur.

[pesce]

Note the street name "Stella Blue Lane" No... I didn't photoshop it

[jimmbomb]

Note the street name "Stella Blue Lane" No... I didn't photoshop it

very nice!

[pesce]

Took the same ride today with my lady on the back, no problems. I wonder what it was.. It was about 10-20 degrees cooler than the time the problem occurred.

[Tipper]

It could be your coil. The coil on the 2T LML's is prone to breaking down and producing a weak spark.

The problem often comes and goes,sometimes only happening once the engine has reached a certain temperature.

The symptoms are very similar to fuel starvation/overheating.

Luckily its a fairly cheap part,

http://www.scootermercato.com/Scooter-P ... ls/132299C

Although I would take it back to your dealer and get them to replace it under warranty.

[pesce]

I think back on it, and I Remeber looking at the fuel line and seeing it was attached above the carb, causing the line to dip about 1" around where the fuel filter is. I remember removing the hose from this attachment therefore almost eliminating the dip in the line. Perhaps this dip was causing the issue? because now i have access to more of the fuel in my tank than ever before. About 1.2 gallons instead of 0.8

[ericalm]

I think back on it, and I Remeber looking at the fuel line and seeing it was attached above the carb, causing the line to dip about 1" around where the fuel filter is. I remember removing the hose from this attachment therefore almost eliminating the dip in the line. Perhaps this dip was causing the issue? because now i have access to more of the fuel in my tank than ever before. About 1.2 gallons instead of 0.8

I tried this and it's made no difference for me.

[Nettar]

Topic sounds like the third verse of We Three Kings.