Buddy max speed 20 mph

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Steve77
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Posts: 9
Joined: Sun Nov 27, 2022 11:36 pm

Buddy max speed 20 mph

Post by Steve77 »

Hello,
Our 2-stroke Buddy 50 was converted to 70 CC years ago and ran to 50MPH for years. Recently, it started stalling after twisting the throttle to full speed. I would need to shut it off, then restart and it would run fine again as long as I didn't twist the throttle wide open. I could ride all day to 45 MPH with the throttle at around 90%, but again, if I twisted to 100% it would stall soon after.
I replaced the fuel filter and lines with clear parts to assure I was getting fuel, then I cleaned the carb, changed the ignition coil and wire and changed the ignition module. I cleaned the air filter and spark plug which all looked well. None of these things worked. So I ordered a new reed valve and I also needed to replace my starter switch assembly on the handlebar so I got that too. When the parts arrived a week later I installed the new parts and found that the scooter wouldn't go over 20 MPH. Unfortunately, I had not tried to start and run the scooter just before I changed the reed valve and starter switch assembly, so I put the old parts back on; but it still will not go over 20MPH. So then I re-installed the old ignition coil, no improvement. Then I re-installed the old ignition module, but still stuck at 20MPH. I cleaned the carburetor again, still limited to 20MPH.
I removed the throttle cable from the handlebar so that I could be sure it pulled to 100%; then I rode while pulling the throttle cable. It still only goes 20MPH.
I am lost for ideas now. I thought that maybe there was a wire plugged or unplugged that limits speed but I can't find any discussion about that.
It is all strange that it was a 50MPH scooter then it suddenly only goes 20MPH with the throttle at 100%. The RPMs do not sound like they are going as high as they used to, but it does sounds smooth.
Any suggestions?
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az_slynch
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Joined: Wed Sep 12, 2012 4:56 pm
Location: Tucson, AZ

Re: Buddy max speed 20 mph

Post by az_slynch »

Hi!

Sounds like you've looked at a lot of things to speed up the scoot. I don't believe the Buddy is electronically governed; known restrictions to the scoot are mechanical in nature. I just have a few suggestions:

- Compression check: It's making enough to run, but is it healthy?
- Crankshaft seals: You'll have to look behind the variator and the stator plate, but you may find evidence of oil leakage. If it's an older scoot with higher miles, these might be leaking. That can affect primary compression.
- Variator: Your troubleshooting doesn't mention looking in the CVT case. If it's been a while, maybe the transmission isn't variating properly? Make sure the belt and rollers are within specification and check that your driven pulley/clutch assembly is lubricated and that the pins and slots on the sliding sheave aren't damaged.
At what point does a hobby become an addiction? I'm uncertain, but after the twelfth scooter, it sorta feels like the latter...

Seriously...I've lost count...

Seven mopeds ...that's still manageable...
sc00ter
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Joined: Sun Mar 30, 2008 9:17 pm
Location: Norfolk VA

Re: Buddy max speed 20 mph

Post by sc00ter »

If the compression is in spec then I would wager a bet on something going click, bang or boom in the CVT. My old pre-bug would get "stuck" around 25-30mph because the torque driver pin guides were worn slightly oval. Never fixed it, I could blip the throttle and it would un-snag most of the time.
Check the rollers as well while in there.
Neil82
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Posts: 83
Joined: Tue Feb 01, 2022 11:57 pm
Location: Denver

Re: Buddy max speed 20 mph

Post by Neil82 »

Could it be a partially blocked main jet?
2022 Buddy 170i
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tenders
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Joined: Mon Dec 03, 2018 1:08 am
Location: NYC area

Re: Buddy max speed 20 mph

Post by tenders »

It could be a carb problem but I would get into the transmission first and rule out all potentially dirty/sticking/glazed/worn parts. Suggest having a replacement belt and rollers on hand in the likely scenario that you decide to replace them.

By the way, if you’re using stock 7.5g rollers with that BBK you’ll really like 7.0g sliders.

Edit. I recently solved a similar problem with my friend’s BBK-equipped Buddy, which like yours had run great for years. There were a few things out of kilter that you’ve probably avoided: the hose clamp on the petcock wasn’t close enough to the petcock to properly clamp on the nipple, so it was possibly restricting fuel flow. I replaced the fuel and vacuum lines with translucent Tygon and there was a lot of air visible in the fuel line - turns out that is not material, nor does it matter if the fuel filter has a lot of air in it.

The scooter was taking what seemed to be too long getting to top speed on a flat road, struggled going up a long steep hill, and occasionally surged, stumbled, and stalled while going uphill. But it ran pretty much fine on the flat.

It felt very much like the engine was getting a limited fuel supply or was running out of gas when taxed. So I bent the carb float up a few degrees (up, being relative to the level when installed, not necessarily as you hold it in your hand while bending). This, I surmised, would allow a larger reserve of fuel in the float bowl, and would open the needle valve earlier and faster as that fuel was depleted, allowing more fuel to flow into the carb when needed. I do think this helped a bit but cannot explain why the engine had run so well for several years with the BBK without needing that adjustment.

What made a huge difference was cleaning things up in the transmission. I’d replaced the rollers and belt a few months ago without doing much else in there, but when I went in again I noticed the bushing tube that the variator slides back and forth on had a bit of gunk on it so the variator wasn’t necessarily moving smoothly. There was a lot of dust in the clutch and around the inside of the clutch bell, which I blew out with compressed air, and I cleaned and sanded the inner surface of the clutch bell and the clutch pads with 100 grit paper.

The fixed the situation completely, and gosh does that thing giddyup uphill with the BBK. I strongly suspect the clutch was sticking as it approached and got into “high” gear, making the scooter slow to get to top speed, lugging the engine when stressed uphill, and as the scooter speed slowed uphill the clutch was slipping, which caused the surging. Eventually high gear and low speed were what were causing the engine to stall, and fuel supply ultimately had little or nothing to do with it.

Perhaps this is your scoot’s issue too.
Last edited by tenders on Thu Feb 09, 2023 3:50 pm, edited 1 time in total.
Steve77
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Posts: 9
Joined: Sun Nov 27, 2022 11:36 pm

Re: Buddy max speed 20 mph

Post by Steve77 »

Thank you all for the advice. The scooter I am working on is my daughters who lives in Miami, but I have returned to my home in Gilbert, AZ before I could look into your suggestions. As soon as I return to Miami I will look at the CVT and engine seals behind the varistor.
I will update this post as I go through the list of suggestions.
Steve77
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Posts: 9
Joined: Sun Nov 27, 2022 11:36 pm

Re: Buddy max speed 20 mph

Post by Steve77 »

I have realized that there is no voltage going to the auto choke, so it stays on all the time. This explains why the speed is limited. Does anyone have a pictorial of the harness that shows where the power should come from to supply the choke? I have taken a couple feet of tape off the harness trying to find where the problem originates, but someone must have a real pinout description.
Please let me know if someone can help with this voltage issue.
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