Torque Converter engages, but weak?

[Swaffy]

I have kind of an odd issue here and I am baffled. I've been able to solve other issues with my bike but not this one.

I have a normal torque converter on my MB200-2. After riding it offroad for a while my clutch didn't seem to engage as strong. It has weak acceleration but it will hold its speed after speeding up. Here is what I noticed:

The clutch will "grasp" against the belt and the friction will accelerate the bike. But I noticed the belt doesn't do the conversion thing where the belt widens on the clutch and thins on the driven pulley. The belt stays in the same shape no matter the speed.

This is the only video that I can find that shows how the belt is supposed to change:
https://www.youtube.com/watch?v=OQmfQHSAHvg

My belt does not widen at the clutch and narrow at the driven, it is pulled fairly tight (no wobble) same as my chain, but not too tight to cause restriction.

I also changed the clutch boot springs to softer springs, the clutch began to rub the belt (engage slightly at idle) so I new it would grab the belt better, but again the belt didn't widen on the clutch like it was supposed to when I opened the throttle on the road.

Any suggestions? Maybe it is the driven? (the image shows the part I refer to)
image of driven

 

[capguncowboy]

I would guess that either your belt is worn or you need to disassemble, clean and lubricate your driver unit. If you do end up cleaning/lubricating the driven unit, use a dry lubricant to help prevent dust buildup.

 

[Swaffy]

I would guess that either your belt is worn or you need to disassemble, clean and lubricate your driver unit. If you do end up cleaning/lubricating the driven unit, use a dry lubricant to help prevent dust buildup.

Sounds like I will be cleaning up my driven pulley then, I did see some black junk in there but didn't think anything of it (normal buildup from offroading) and I need to buy that pointed C-clip remover tool again.

I have dry moly which I can use, which specific part needs the dry lube? I don't want to put it on parts that need friction...

 

[danford1]

Here is video I found that shows you how to put it back together. Sadly it doesn't show you how to clean and lube it though.
Danford1
[video=youtube;kmGY0qsgW4Y]https://www.youtube.com/watch?v=kmGY0qsgW4Y[/video]

 

[TheDullCarbide]

It sounds like your driven is locked up. Take it apart, clean it, lube it VERY lightly, and make sure the spring is okay.

A tip for assembling it, set the pulley on the ground (preferably an old rug), step on the cam plate with the heels of your boots, and put the retaining ring on. That's a GY6 trick that's helped me tons. :thumbsup:

 

[capguncowboy]

Once you pull the driver apart, you can lubricate everything inside that housing without prejudice. The flyweights need to be lubricated so they can slide against the housing. That's what makes it wider. It's important you use dry lube inside this as well. A lot of heat is generated inside during use. If you use grease, it'll become fluid and make a huge mess when it comes into contact with dust, or slings all over the inside of your TAV cover.

Maintenance is key on these torque converters. You have to clean and lube them pretty regularly, especially if you're riding off road. Check your belt for wear too. I try to keep an extra on laying around in the event i need to change it

 

[Swaffy]

Maintenance is key on these torque converters. You have to clean and lube them pretty regularly, especially if you're riding off road. Check your belt for wear too. I try to keep an extra on laying around in the event i need to change it

Update: I cleaned up the driven pulley, checked the clutch disk/boots. Original springs (normal tension) back on the boots. I squeezed the driven pulley in and out to make sure it was sliding and it slides well. Still the belt does not widen at the clutch and I am not sure what step to take next.

Perhaps I should order a new belt? It isn't very old... I think. I can try my old belt but it's slightly narrower. Might be worth a try anyway, I guess.

 

[RPH]

Try changing which hole the driven spring goes in

 

[Swaffy]

Try changing which hole the driven spring goes in

Thanks for the input, I am currently trying to get the cap taken off the driven to release the spring, I wanna check the spring in case it's warped, also the spring was in the center hole which I wanted - but I can try the other holes.

 

[jeep2003]

it could also be the driver clutch not fully expanding

 

[TheDullCarbide]

Thanks for the input, I am currently trying to get the cap taken off the driven to release the spring, I wanna check the spring in case it's warped, also the spring was in the center hole which I wanted - but I can try the other holes.

I would try revving the engine without the belt. The driver sheaves should close smoothly and completely. If it's not the driven's fault, the pins in the driver weights could be bound. When I had that problem, I drilled out the holes in the weights and pressed in Teflon bushings.

And if the driven can completely open and close by hand, that's not the problem. Are all the black plastic cam slider thingies present in the driven?

Also, what's the number on your new belt? Is it longer than the old one?

 

[capguncowboy]

it could also be the driver clutch not fully expanding

That's what I had originally suggested. I still think that's what is causing it

 

[Swaffy]

I would try revving the engine without the belt. The driver sheaves should close smoothly and completely.

I will try this tomorrow, it's almost 11 PM right now. Thanks for the suggestion. I did see the clutch closing on the belt so it crossed my mind that either the belt got worn down or the clutch is not squeezing the belt hard enough or the belt is too narrow.

it could also be the driver clutch not fully expanding

If it's not the driven's fault, the pins in the driver weights could be bound.

That is possible, I looked at them briefly, but I will take a closer look at the two rods.

And if the driven can completely open and close by hand, that's not the problem. Are all the black plastic cam slider thingies present in the driven? Also, what's the number on your new belt? Is it longer than the old one?

All the 6 driven pulley tabs are present, slightly worn. Chinese 669 belt, it fits snug between driven and clutch so it isn't floppy. I put on my original (old) belt today and the engine revved with 0 acceleration (no clutch grab) and my newer belt is a similar width but is able to be grabbed by the clutch and accelerate. Perhaps a wider belt is needed? I don't know which one to try, though. And what brand, need something well built.

 

[TheDullCarbide]

Chinese 669 belt

:confused1: A quick search shows that that's a symmetrical GY6 50 belt. The correct Comet belt is a 695 with an asymmetrical V-angle. I'm thinking belt at this point. Get this: https://www.OldMiniBikes.com/replacement-belt-comet-203589a.html

 

[Swaffy]

:confused1: A quick search shows that that's a symmetrical GY6 50 belt. The correct Comet belt is a 695 with an asymmetrical V-angle. I'm thinking belt at this point.

My original belt is asymmetrical Qinjiang VS 669
Newer belt is asymmetrical Yameige 669 28 16

The rods of the clutch weights move freely, actually quite loosely so they should not be binding up.

I will try a Comet belt and see how that works.

 

[TheDullCarbide]

My original belt is asymmetrical Qinjiang VS 669
Newer belt is asymmetrical Yameige 669 28 16

The rods of the clutch weights move freely, actually quite loosely so they should not be binding up.

I will try a Comet belt and see how that works.

Before I criticize the belt length again, is this on a TAV, or some other type of 30 series setup?

 

[Swaffy]

Before I criticize the belt length again, is this on a TAV, or some other type of 30 series setup?

Whatever the stock torque converter is on the MB200-2, the Comet belt fits pretty well. As an update, the belt grabs really well to the point I nearly did a wheelie, but still the belt doesn't widen on the clutch at full throttle. Maybe this has to do with the fact that I went from the smaller (original) sprocket to the bigger sprocket 50 tooth on the rear wheel? I was thinking that if the sprocket was larger, there is a lower top speed, thus maybe the belt wasn't at a high enough speed to change shape. I dunno. I might mess with the driven pulley settings again on the spring.

 

[Raskin]

I got a 52t sprocket on my mb200-2 and it is still too high geared to fully ramp up on the driver. I see i need a bigger sprocket..I am going to get a 60t and i know i have to change the driven spring to the tighter offroad setting because i noticed on my ct200u it goes into high range faster coz im running a 16" tire.

 

[Swaffy]

I got a 52t sprocket on my mb200-2 and it is still too high geared to fully ramp up on the driver. I see i need a bigger sprocket..I am going to get a 60t and i know i have to change the driven spring to the tighter offroad setting because i noticed on my ct200u it goes into high range faster coz im running a 16" tire.

Putting a larger sprocket on your rear wheel means lower top speed and higher torque to the wheel

 

[Raskin]

Putting a larger sprocket on your rear wheel means lower top speed and higher torque to the wheel

Yes but when your belt on the driver gets higher up it makes ratio higher to rear driven so top speed drop not necessarily as much as one would think.The relationship changes effect outcome.