150cc GY6 scooter lost top speed

Battercake · 06-01-2024, 03:20 PM

For a couple months now, I've been trying to pin down why my scooter, which would usually go up to 62 MPH if I so desired, will usually only go 51 now. This problem began at the same time I had to replace the carburetor diaphragm, so naturally the assumption was that something was affected by that, and a wild goose chase ensued. But this week I had the cover off the CVT and noticed grooves in the variator pulley. I wouldn't have been concerned had they been near the top, but these grooves are only about two-thirds of the way up on the pulley.

I assume my next step is gonna be to remove the variator pulley and see what's going on behind it. Any advice is appreciated!

sc00ter · 06-01-2024, 05:50 PM

How many miles do you have on the Wolf? What miles are the transmission service suggested? If it was sudden I would check:
Carb diaphragm is it has one. My Buddy 125 has one and they get pinholes in them and make the scoot run weird. Then ensure the new one is seated correctly.
Valve check. My scooter stays pretty set between valve checks. Exhaust can be a tad snug between checks but it'll still run good.
Spark plug check, since you should pull it when checking valves. Also, plug color can tell you how the motor is running. Ashy white=lean. Dark black/wet=rich.
Exhaust for leaks. Plug the end with a damp rag while running. It should stall. Also check for obstruction, kinked pipe or carbon build up.
I just rebuilt my transmission at 8000 miles. I did the following:
New belt.
New V-slides.
New Rollers. Old ones looked good, no major flat spots.
Re-grease torque driver, inspect springs, gently sand glaze from clutch shoes. All good.
Clean bell.
New reduction box oil.
Finally, is you engine oil at the correct level? Over-filled can cause power loss.
My Genuine Buddy 125 has the best health care a scooter can have. I'm very meticulous about services and keeping it clean. But things will fail without warning.
Keep us posted on your progress.

Battercake · 06-02-2024, 02:47 PM

Quote:

Originally Posted by sc00ter

How many miles do you have on the Wolf? What miles are the transmission service suggested? If it was sudden I would check:
Carb diaphragm is it has one. My Buddy 125 has one and they get pinholes in them and make the scoot run weird. Then ensure the new one is seated correctly.
Valve check. My scooter stays pretty set between valve checks. Exhaust can be a tad snug between checks but it'll still run good.
Spark plug check, since you should pull it when checking valves. Also, plug color can tell you how the motor is running. Ashy white=lean. Dark black/wet=rich.
Exhaust for leaks. Plug the end with a damp rag while running. It should stall. Also check for obstruction, kinked pipe or carbon build up.
I just rebuilt my transmission at 8000 miles. I did the following:
New belt.
New V-slides.
New Rollers. Old ones looked good, no major flat spots.
Re-grease torque driver, inspect springs, gently sand glaze from clutch shoes. All good.
Clean bell.
New reduction box oil.
Finally, is you engine oil at the correct level? Over-filled can cause power loss.
My Genuine Buddy 125 has the best health care a scooter can have. I'm very meticulous about services and keeping it clean. But things will fail without warning.
Keep us posted on your progress.

That's a lot of questions, but I appreciate your thoroughness. I'll answer what I can.

The Wolf has 6400 actual miles. I've misplaced the manual at the moment. The diaphragm is brand new and perfectly seated. I just checked the valves and they were exactly as you said - the exhaust had worked itself a little tight but they weren't bad. The spark plug looks normal grey, not white or dark. The entire exhaust has been fiddled with repeatedly with no change in performance. The belt is still original with no noticable loss of width or fraying. Engine oil and gear oil have both been regularly changed and are at proper levels.

I have not torn into the variator or clutch because I wanted to solve one problem at a time and until this week I didn't think that might be causing this one.

sc00ter · 06-02-2024, 08:50 PM

Belts are usually good for around 8000 miles, some will say 10,000. Meansuring a belt is a PITA, so if it's in question just replace it. I save the old belt as a back-up and write the mileage on the old belt with a Sharpie. Never hurts to have a "Oh crap!" spare for emergencies.

You could do the Sharpie line trick on the variator and see if its fully engaging, but then again, if the scooter is restricting itself then the line trick might not go according to plan. If it did the power loss suddenly I would guess going into the transmission and ensuring the V-slides aren't broken/worn/hanging up. And, peek at the rollers for flat spots. It's slightly possible a torque spring may be worn out but at 6000 miles I doubt it. The 3 clutch springs will break sometimes but again, rare at your 6000 miles. I will say this, burnouts will tear a CVT up! So if you do them every now and then like my dumb butt then its possible its trans related.

I hate those stupid diaphragm carbs. Every time I go into one I end up going back into it again! My diaphragm seating skills suck!

Nothing else is popping in my head at the moment.....
Again, keep us posted!

Battercake · 06-05-2024, 09:55 PM

I looked in my journal and noted that this problem surfaced at 3760 actual miles. I just did the Sharpie diagnostic, and it looks like I've got a good 6 millimeters of pulley going to waste here. I'm too busy this week to take the variator off, but I will when I can and check the rollers and ramps. I guess I've been running the piss out of this thing thinking the problem lay elsewhere.

sc00ter · 06-05-2024, 10:56 PM

Slightly off subject. I had a Suzuki Burgman 200. It started to slowly suffer a speed loss and would get a bit wonky on the top end. I pulled it apart and found noticeable wear on the variator faces at around 3000 miles, both fixed and the side that contains the rollers. Suzuki wanted mad dollars for a new assembly so I found a used assembly on ebay. Gently used ebay variator suffered the same fate at around 3000 miles as the original one. Turns out the variator faces were not hardened correctly. We have a metals lab at my job and I compared the drive face hardness (or rockwell rating) to a found technical spec from Yamaha. I luckily found a Malossi variator that worked great, I just had to replace the fixed face at every 3000 miles. Thankfully Suzuki lowed the price of that wear item part. Maybe they knew of the problem? That scooter made me hate Suzuki and I'll never buy one of their products again. Impress me with the base/entry level model before I buy a high end model.

I honestly suspect something transmission related as mentioned above. So if everything looks good then you may wan't to consider a performance variator.

06-01-2024, 05:50 PM	#2
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 552	How many miles do you have on the Wolf? What miles are the transmission service suggested? If it was sudden I would check: Carb diaphragm is it has one. My Buddy 125 has one and they get pinholes in them and make the scoot run weird. Then ensure the new one is seated correctly. Valve check. My scooter stays pretty set between valve checks. Exhaust can be a tad snug between checks but it'll still run good. Spark plug check, since you should pull it when checking valves. Also, plug color can tell you how the motor is running. Ashy white=lean. Dark black/wet=rich. Exhaust for leaks. Plug the end with a damp rag while running. It should stall. Also check for obstruction, kinked pipe or carbon build up. I just rebuilt my transmission at 8000 miles. I did the following: New belt. New V-slides. New Rollers. Old ones looked good, no major flat spots. Re-grease torque driver, inspect springs, gently sand glaze from clutch shoes. All good. Clean bell. New reduction box oil. Finally, is you engine oil at the correct level? Over-filled can cause power loss. My Genuine Buddy 125 has the best health care a scooter can have. I'm very meticulous about services and keeping it clean. But things will fail without warning. Keep us posted on your progress.
	0

06-02-2024, 08:50 PM	#4
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 552	Belts are usually good for around 8000 miles, some will say 10,000. Meansuring a belt is a PITA, so if it's in question just replace it. I save the old belt as a back-up and write the mileage on the old belt with a Sharpie. Never hurts to have a "Oh crap!" spare for emergencies. You could do the Sharpie line trick on the variator and see if its fully engaging, but then again, if the scooter is restricting itself then the line trick might not go according to plan. If it did the power loss suddenly I would guess going into the transmission and ensuring the V-slides aren't broken/worn/hanging up. And, peek at the rollers for flat spots. It's slightly possible a torque spring may be worn out but at 6000 miles I doubt it. The 3 clutch springs will break sometimes but again, rare at your 6000 miles. I will say this, burnouts will tear a CVT up! So if you do them every now and then like my dumb butt then its possible its trans related. I hate those stupid diaphragm carbs. Every time I go into one I end up going back into it again! My diaphragm seating skills suck! Nothing else is popping in my head at the moment..... Again, keep us posted!
	0

06-05-2024, 10:56 PM	#6
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 552	Slightly off subject. I had a Suzuki Burgman 200. It started to slowly suffer a speed loss and would get a bit wonky on the top end. I pulled it apart and found noticeable wear on the variator faces at around 3000 miles, both fixed and the side that contains the rollers. Suzuki wanted mad dollars for a new assembly so I found a used assembly on ebay. Gently used ebay variator suffered the same fate at around 3000 miles as the original one. Turns out the variator faces were not hardened correctly. We have a metals lab at my job and I compared the drive face hardness (or rockwell rating) to a found technical spec from Yamaha. I luckily found a Malossi variator that worked great, I just had to replace the fixed face at every 3000 miles. Thankfully Suzuki lowed the price of that wear item part. Maybe they knew of the problem? That scooter made me hate Suzuki and I'll never buy one of their products again. Impress me with the base/entry level model before I buy a high end model. I honestly suspect something transmission related as mentioned above. So if everything looks good then you may wan't to consider a performance variator.
	1