Buddy 50cc suddenly lost power and wont rev past idle speed.

Meis · Post by **Meis** » Sun Feb 05, 2017 12:29 am

I would like to get some help with this thing. About 3 days ago I was riding (the buddy is my daily now and I ride around town at about 150 miles a month) and i turned left at an intersection after riding for about 5 minutes after startup. I hit no bumps or anything whatsoever and i turned slowly as i was sitting at the red light waiting for a protected arrow to turn left. Mid way through the turn the scooter lost all power... It was still running but I would turn the throttle and it would try to rev up and then sound like it was hitting a fuel cutoff (or a rev limiter). I have a tachometer installed on this thing and the revs would go from about 2,000 to 3,200 and then it would just rev bounce and not rev up any more.

Assuming that something was clogging a carb jet, I pulled immediately into the gas station on the corner and started pulling it apart in the parking lot. (I carry a few essential tools just in case lol). While pulling the carb out i inspected the throttle cable and it was working properly. All electrical connections were good and all vacuum lines and fuel lines were good as well. After pulling the carb out and apart i saw no blockages. I pulled the jets and blew them out but they were not blocked upon initial inspection.

I put it all back together and it started right up but same thing... it will idle all day but not rev (or hit some limiter) once throttle is applied. I shut it off and started it back up and gave it throttle while starting it and the Scooter roared to life and as long as i gave it throttle it would rev. the moment i released the throttle it would bog down and then do the same no rev/limiter thing.

So i started it up again and gave it the beans, full throttle the whole way home just controlling speed with the brakes and i was able to get it home.

I thought about it and thought maybe the exhaust was clogged or something so i pulled the exhaust to inspect and it seemed fine... I had a Stage 6 pro-rep exhaust sitting for when i do my 72cc kit along with some ignition upgrades and carb jets so i went ahead and tossed that on just to verify. While i was at it i pulled the carb and cleaned it out 100%. I replaced the jets with the same size pilot and an 85 main jet just new, just in case.

It started right up but did the same thing....

anyone have any ideas what the issue may be? Reed Valve? Piston rings went kaput? Im kind of stumped on this one

Thanks for the help!

babblefish · Post by **babblefish** » Sun Feb 05, 2017 8:08 am

I had a similar situation with my Blur, could not rev pass 6K. Turns out it was a vacuum leak in the CV slide diaphragm (that round, black rubber thing under the CV cover). A vacuum leak here will not allow full travel of the throttle slide, thereby limiting the engine's RPM. The lip of the diaphragm was not sealing correctly in the groove in the carb's body. I fixed it by applying some rubber safe grease (silicone based) around the edge of the diaphragm before assembly. You may have the same problem, but just in case, examine the diaphragm carefully under a bright light for any pin holes or cracks.

sc00ter · Post by **sc00ter** » Sun Feb 05, 2017 3:32 pm

I would also check the float height and make sure the float does not have a hole (taking on fuel) or warped. Stator issue? They fail with no warning sometimes. Last I would pull the transmission apart and look for anything weird. Problems like this are hard to diagnose over the internet but those are my 3 ideas for a quick check/in that order.

BuddyRaton · Post by **BuddyRaton** » Sun Feb 05, 2017 6:04 pm

I would suggest checking the stator. More than once I have thought I had a carb problem that turned out to be electrical. I have the cleanest SS180 carb...got a bad new condenser.

Sometimes electrical components will fail when warm and under a load. I would do a search for how to check the stator and pickup with a VOM. . I know what the correct readings are for a Vespa but not a Buddy 50.

I'm pretty sure it is on here somewhere. Try the tech library and keep us updated.

az_slynch · Post by **az_slynch** » Sun Feb 05, 2017 6:45 pm

The Buddy 50 has a cable operated slide carb, so it's not likely to be a CV diaphragm issue.

The running at WOT but not low throttle reminds me of a plugged pilot jet. Look at the exploded diagram for #12; pull that jet and clean not only it but the passage it screws into as well.

Stator could be a possibility. Just worked on a friend's kitted Zuma. Only made spark when the engine was already warm. Had to warm the block with a heat gun or a torch before it could spark and run.I replaced the stator and CDI in a shotgun approach and it ran fine. Checked the old parts; the CDI box is probably fine. The stator was likely the culprit, as I found a cold solder joint tying the charging coil to the CDI lead. It tested poor continuity cold, so I'll probably resolder it and keep it as a spare.

jickel · Post by **jickel** » Mon Feb 06, 2017 3:37 pm

Sounds ignition related to me. Have you replaced the spark plug? It's possible your plug gap is too high and you're blowing out spark. That would be the first step and then I would go further down the line if the problem persists. Coil-->CDI-->Stator.

Meis · Post by **Meis** » Mon Feb 06, 2017 10:13 pm

new twist,

I took the carb off again and cleaned it 10000% still no changes. If i give it full throttle while i start it it will rev, once i let off the throttle and it idles it will not rev up again. if i shut the bike off and restart it at full throttle it will rev... but once it returns to idle it will no longer rev... i can do this over and over again

Meis · Post by **Meis** » Mon Feb 06, 2017 11:11 pm

https://youtu.be/747x2nmHlcQ

Here is a video of the issue for a little more clarity

sc00ter · Post by **sc00ter** » Tue Feb 07, 2017 4:22 am

Does the rear wheel spin freely? That sounds like a transmission issue to me. Had something similar happen when a roller failed (shattered) and would get caught behind the variator, then break loose then jam again. I stink at tuning carbs and hate trouble shooting them, but it could also be a bad needle not letting the carb transfer form idle to W.O.T. Have had that happen also. Now make sure stuff it tight and thread locked as the Zuma's will push 13,000 RPMs. What fun they are!

Meis · Post by **Meis** » Tue Feb 07, 2017 5:50 pm

The rear wheel does spin freely if i start it at WOT. if i start it normally the RPMs dont rise to the level that would spin the rear wheel

sc00ter · Post by **sc00ter** » Wed Feb 08, 2017 4:05 am

It only takes a few minutes to remove the transmission case. Take a look and see if there is a part or foreign object floating around in there. If all looks good then lets check the ignition system. Swap the spark plug first. Still does it? If so, check the plug boot. On our Zuma's they crack at the cap and cause a loss of power "kinda like" what you are dealing with. Looks good/no damage/cracks/fits tight? CDI next. Though I have never seen one go bad, it needs to be checked. You Tube has how-to's on the test procedure. Checks out as good? Stator is next. Again, You Tube has your how-to. Again, its hard to diagnose a problem over the internet but this is the order I would go in if mine did what your scooter is doing. Good luck and keep us posted.

Meis · Post by **Meis** » Thu Feb 16, 2017 6:45 pm

sc00ter thank you so much for that!

I opened the CVT cover and it is clean and debris free. The plug that was in it was producing great spark but in the name of science I put a brand new one in there anyway. no changes at all. The Coil tested good and produces a bright spark so im sure that is fine. Checking resistance across the CDI checked out good as well. The stator itself checks out too but the pickup coil only read 114 ohms of resistance and 0.1 to 0.2 VAC while cranking. I think I might have a bad pickup coil. what are yalls thoughts?

Meis · Post by **Meis** » Mon Mar 13, 2017 1:20 am

Okay, so i finally managed to pull off the reed block and inspect the reeds thinking that might possibly be an issue. I was a little sidetracked putting a new motor in my 2010 VW GTI so the scoot had to sit for a little bit. The reeds were intact and appeared to be in great condition. Because they were out, i pulled the reeds off, flipped them around and then reassembled the block before putting it back in just to be safe.

It was a really nice day outside today in Texas so i figured what the heck, I will just go ahead and put the 72cc Polini kit on. So I did just that. Pretty straightforward process too. got it all buttoned back together and i started it up and it immediately roared to life. It had no issues idling or running with the new kit on so i let it warm up for a few minutes and then took it for a spin. It ran flawlessly up until the end of my street where it started doing the same rev hang issue...

I just ordered a new stator pickup coil... I really hope that's the problem... The old one tested just BARELY outside the low end of the recommended resistance values so we will see.

Meis · Post by **Meis** » Fri May 26, 2017 8:58 pm

!!!!!Resolution post!!!!!!

Okay so it has been a while and to be honest the scoot went to the back burner for a little bit but I got it fixed and would like to give a huge thank you to yall for the assistance in troubleshooting!

Seeing that my pickup coil wasn't in the acceptable range of resistance, I got a new one and wired it up. After that I couldn't even get it to turn over... I'll attribute that to the fact that I had to splice it into the existing harness in place of the old one instead of repinning it into the harness plug connector.

So I decided to splurge and get an all new stator that comes with the pickup coil and harness all the way up to the plug. I got that in no problem and fired the scooter. It started right up and then did the same thing..... so clearly that time was wasted. I was a little bummed because my electrical diagnosis pointed to the pickup coil...

So I figured what the heck and just bought a new CDI box despite the face that it tested within the normal ranges for resistance. It came in. I installed it. I started the scoot up, and now it runs flawlessly!

I just wanted to take the time to write up a reply to show a resolution to an issue that had me scratching my head!

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