People S250 loses power with throttle wide open

[carrielsal]

I posted this in the Kymco S250 forum. I thought I would post it here also, since this seems to be more of a technical/repair section of the forums.

I was looking at scooters for my daughter in college and test drove a 2009 Kymco People 250S at our local dealer. It only had 3000 miles on it.  I've always ridden motorcycles and fell in love with the People, so much that I brought it home for myself! The first month I was mainly riding it on county highways with a top speed of 60-70 mph on the speedo and had no problems.

I finally took the scoot on a 600 mile round trip when I first experienced the issue. I'm hoping someone here may have some ideas.

I had been on an interstate for about 60 miles when I first experienced the problem. I had been riding about 80-85 MPH on the speedo and found myself between 2 semi's. I opened the throttle all the way and lost power (wouldn't you know it would occur between 2 semi's!) All the electricals were on, but it felt like the gas had been cut off. I let off the throttle and power came back at around 60 MPH. Since then I have found this is an intermittant issue.  With the throttle wide open or close to wide open (80-90 mph on the speedo), the scooter will lose power. All the electricals are still on, but it feels like the fuel has been cut off.   It I let off the throttle and drop the speed down to around 60 mph, power returns. If I pull off the interstate and completely shut the scooter off for a few minutes, the issue may not return at all; or the scooter will fine for a few miles with the throttle wide open then the problem start back up again. I can never tell for sure when it will happen. I have driven 100 miles and not experienced the problem, or had this problem within the first 5 miles of a trip. There is nothing I have found that will make the scooter do this. It can occur with the gas tank full, half full, or close to empty. I talked to the mechanic at our local Kymco dealer, and he has never seen this problem. I am concerned that if I take my scooter to the dealership, the issue may not occur when they test ride it.

Has anyone else experienced this problem?

Thanks,
Carrie

[tortoise]

Fuel tank parts diagram indicates a vacuum-operated pulse-pump.  Minimum intake vacuum at wide-open-throttle may be resulting in fewer pulses to pump . . reducing outlet fuel flow and not maintaining an adequate carb fuel bowl level (temporary lean).

[carrielsal]

Fuel tank parts diagram indicates a vacuum-operated pulse-pump.  Minimum intake vacuum at wide-open-throttle may be resulting in fewer pulses to pump . . reducing outlet fuel flow and not maintaining an adequate carb fuel bowl level (temporary lean).

Thank you for responding. I don't have a login to the link you referenced, but I can see the pump on this page, http://bit.ly/2dtAXVg. If there is a minimum intake vacuum with the throttle wide open, then wouldn't every People S250 have this problem?
Every article I find discusses issues with scooters running or not starting like this one, http://bit.ly/2cXkvy5. I cannot find a single post where anyone discusses issues with running any scooter at top speeds, much less a Kymco People.

Carrie

[Redk]

Carrie, I would give a plus 1 to what tortoise has said...

You did ask why everyone/others did not describe the same problem?
I would suggest the speeds you mentioned are probably not typical for scooter riders, even maxis.

You are pretty much at the racer's edge of your machine where it will no longer perform at it's best.
FI might be an improvement???

If you require extended 80-85mph speed runs and optimal performance, I'd suggest a superbike would fit your needs well.
redk

[CROSSBOLT]

May be your vacuum valve is stuck blocking the gas tank vent.

Karl

[MJR]

I would suggest the speeds you mentioned are probably not typical for scooter riders, even maxis.

True most don't typically ever ride above that though I do frequently take my maxi scoots over 100 mph.

[Redk]

True most don't typically ever ride above that though I do frequently take my maxi scoots over 100 mph.

Of course ! 
And it's fun, too !  :-)

I would probably guess typical cruising speed to be in the neighborhood of 70% max speed, or top end.
Carrie mentioned running, and experiencing that problem, at near full throttle.

I suppose it could be re-tuned for optimal running at WOT, yet that might cause similar problems in the normal operating range where most of us spend our time

Then think about those 4 cylinder quart sized bikes just coming into the cam's torque band at that speed !  Wahoo !!

Gosh MC's are fun !
redk