Buddy 50, Stumbles under load

lake effect · Post by **lake effect** » Wed Nov 27, 2013 12:39 pm

Obviously, first post on the forum... I've been searching, but probably searching the wrong terms... If you know the answer, you don't have to type it all out, some really good hints on the search terms will be fine, assuming that my problem is a common one...

Daughters Buddy 50, 3500 miles since May, ridden almost every single day, rain or shine, hot or cold. It's her independance, and has become part of her identity... In other words, she loves it, takes care of it, runs Motul 800T or the Spectra synth oil... The variator was modified (properly) to allow the higher (45mph) speeds.

Starts fine, idles fine, accelerates from a stop fine. Cruises at low speed/low load fine.

At higher speeds/load (about 25 to 30 mph on flat ground) it stumbles/stops developing power, it feels to me like a fueling or carb issue.

She took it in to have it looked at, no problem found in the transmission, clutch was cleaned, sparkplug was changed. No change in the problem. The plug did look like it was running very rich.

Compression checked out good, air and fuel filter checked out good. I believe they checked the exhaust, but don't know for sure.

Tech is currently looking at the carb and reed block.

Any thoughts on what it might be?

I'm pretty good when it comes to cleaning carbs, my son races 125cc 2 stroke karts, and I race a carbed motorcycle, so it seems there is a disassembled carb in the ultrasonic almost every night of the week.

However, I'm used to seeing dirty carbs causing low speed issues...

Any help, thoughts, guidance, is truely appreciated.

BuddyRaton · Post by **BuddyRaton** » Wed Nov 27, 2013 1:30 pm

When in doubt rebuild the carb!

lake effect · Post by **lake effect** » Wed Nov 27, 2013 2:10 pm

Thanks, if they don't have it figured out today, I'll bring it home and do that. I just want to make sure there's no secret scooter technology that would look like a dirty carb that I don't know about yet...

gitsum79 · Post by **gitsum79** » Wed Nov 27, 2013 7:20 pm

Vacuum leak or air leak? Main jet dirty? Check the slide and needle jet? Float bowl level?
Fuel pump or fuel filter? CDI or ignition coil? Oil pump working correctly?

agrogod · Post by **agrogod** » Thu Nov 28, 2013 9:45 am

Sounds like the problem I was having earlier this year. Turned out my piston got warped and had to rebuild the upper. Another member had a retainer pin slip and got into his cylinder causing poor high performance. You may want to have your shop guy crack open the upper just to have a look to rule that out as a problem.

lake effect · Post by **lake effect** » Thu Nov 28, 2013 2:43 pm

Very happy with the shop, after not finding the problem the first day, they called the home office in Chicago for advice. Genuine shipped a full engine rebuild kit plus other parts, due in later this week.

With the tech headed home for the holidays, the owner offered to take a used bike to the shop with me so we could look for the problem ourselves the old fashioned way, swapping parts.

A little while later, we'd confirmed good fuel flow, and went after ignition. The CDI swapped out with no change, moved on to the coilpack. Replacing the coil solved the problem, it was collapsing under load.

Bought a sparkplug and brought the bike home for the daughter. Thanks Vespa Marietta for making our holiday that much better!

Post by **jrsjr** » Thu Nov 28, 2013 3:57 pm

lake effect wrote:Replacing the coil solved the problem, it was collapsing under load.

Well, now we have a confirmed case of a weak coil in our archives. Thanks for the follow up and welcome to Modern Buddy! Good on Vespa Marietta for tracking that down and sorting it out! (Said the guy originally from Decatur, Georgia

)

lake effect · Post by **lake effect** » Thu Nov 28, 2013 4:31 pm

Knowing what the solution is, it's easier to describe the problem now.

Consider a very rough feeling rev limiter, not attached to any specific rpm. Uphill, it wouldn't carry me more than 10 or 15 mph, on the flat, it would stumble at about 30mph, downhill it would run all the way up against whatever limits the speed normally.

I'm guessing there's been discussion about the coilpacks...

viney266 · Post by **viney266** » Thu Nov 28, 2013 6:45 pm

Good to know, thanks for the info. suprised it was a coil, but anything can break!

Quo Vadimus · Post by **Quo Vadimus** » Fri Nov 29, 2013 3:23 am

Dear Quo, come back to this thread next year when the ice melts.

Yours always,

Quo.