GY6 Variator Question

[Brother Turtle]

My son's Hammerhead GTS 150 broke the belt. When we opened it up, we found that the belt had disintegrated. Below is what's left of it. In the variator , we found that the plastic coating on the rollers had melted and stuck to the aluminum. I had planned on changing the belt and rollers, but now I need a new variator as well. Any ideas on what would cause that much heat to melt the rollers? When I put that belt on, it was very tight, so it shouldn't have been slipping.

 

[landuse]

I am not too sure about gy6 belts, but generally belts shouldn't be too tight. Could be that you had the incorrect belt, and that was causing a lot more friction than if it were looser

 

[itsid]

slipping belts can be caused by "insufficient" throttle
there's always a range of rpms where the clutch is just partly engaged and slips,
you need to get over that transition (clutch starting to engage -> clutch fully engaged)
as quickly as possible in order to keep the belt as vital as possible.
The hot belt then heats the variator which softens the roller coating and
after a while it looks like what you hold in your hands.

You don't happen to have limited the throttle (or pedal for that matter) in order to slow your kid down considerably [likely to seduce mom's demand for 'not too fast!'], have you?
in case you did.. THAT is the direct result.

Another cause would be too steep of an inclination to climb
and/or too heavy of a weight to carry
(say increeased rear wheel diameter and running at or beyond the loading capacity...)
If your boy packs six or seven of his best friends inside occasionally you can be rather certain it's been overloaded

You can likely clean the variator plate with acetone..
just allow it to soak in for a few hours and take an old toothbrush for the then sticky residue.

While at it, clean the clutch side as well.
it might look almost as bad (maybe glazed by now, lightly sand it or if that fails replace the shoes)

Take care that the gear ratio (rear wheel size as well as sprocket ratio) is okay,
and that the throttle isn't limited to get the motor to rev up to it's full potential.
And if you stay below the max capacity the now fully restored CVT (clutch, belt and variator)
should be able to move your son and his kart for a good amount of time reliably

'sid

 

[Brother Turtle]

Thanks for the comments. I don't have the throttle limited in any way. It runs wide open. He likes to do most of his riding on a mud track , so he spends most of the time running high rpms to drift around the turns. But not really much steep hill climbing.

 

[itsid]

mud..
more knee deep tarpits
or slightly wet roads?

the former is a problem, a sink hole is the exact same thing for the go kart as a steep hill
(just way shorter) it's the climbing angle that does the worst things (low speed lots of rpms)

A muddy(wet or dirty or both) CVT belt slips..
Soooo yeah I know it's fun but it's not exactly "intended use" and thus might be cause for "accelerated wear"

I#d say clean everything up, fix the rollers and the belt..
check (and fix where necessary) the clutch shoes as well.

Make sure gear ratio (incl wheelsize is according to the manual)
And see if that makes any difference... (keep CVT clean! check and clean often)
if it doesn't, cut some fun sprinkles off your boy's donuts
(or live with the high maintenance levels if you can)

It might help to increase gear ratio (also helps braking traction btw )
and/or reduce wheelsize on the back (which is -as mentioned- the same thing)
Or thinking about increasing the torque the old fashioned way (getting a big bore kit)

Also there are several "tuning" rollers for gy6es out there IIRC there are also lighter ones which increase engagement rpms and thus torque by a hair or two..
Not an expert on those engines soooo check what others have to say about such.

'sid

 

[JTSpeedDemon]

No offense, but this is why I'm not too keen on sticking a torque converter on my kart. So much more complicated. True I would probably utilize my torque and horsepower better, but to me, having to manage the belts and pulleys and whatnot just seems like it outweighs the benefits. I might consider upgrading from a drum clutch to a disc clutch though.

 

[itsid]

No offense, but this is why I'm not too keen on sticking a torque converter on my kart. So much more complicated. True I would probably utilize my torque and horsepower better, but to me, having to manage the belts and pulleys and whatnot just seems like it outweighs the benefits. I might consider upgrading from a drum clutch to a disc clutch though.

And now I want to see how you are able to remove the CVT from a gy6 engine...
(jeez kid that was a brainfart of yours)

Oh btw if two variable diameter pulleys and a belt are overly complicated for you,
it tells us something about you
that you might not want us to know
And this now is the correct location for the "no offense" platitude

*giggle*

'sid

PS Tune in next wheek,
when we see JTSpeedDemon running in terror from the complexity of a three speed gear box...

 

[Tpdingo]

No offense, but this is why I'm not too keen on sticking a torque converter on my kart. So much more complicated. True I would probably utilize my torque and horsepower better, but to me, having to manage the belts and pulleys and whatnot just seems like it outweighs the benefits. I might consider upgrading from a drum clutch to a disc clutch though.

I've run my TC/30 in the snow, rain, drifting in the rain, literally getting it wet from a garden sprayer....usually the centrifugal force from it revving right up to 3600rpm gets engagement back pretty quick. The rain has never effected it and nor did the snow....only the garden sprayer.

And 'sid.....HAHAHA the 3 speed comment is killing me .

 

[JTSpeedDemon]

Also the cost...
I'm just a poor boy...
Is ever so true here, I literally work on my kart under the eve of the back porch, sometimes sitting on a bucket, oftentimes in the dirt dust and leaves. Also, because I'm quite the penny-pincher, I borrowed Permatex No.2 and black spray paint from a car friend of mine to save money. I haven't worked on my go kart for a while though, since my foot has a mysterious major bruise. So yeah. $100 here for a torque converter seems sky high to me. I would love to build a shifter kart someday though. To me, a torque converter just doesn't seem to have enough benefits for me to want to work on it. I would be very willing to work on a three speed gearbox, though!

---------- Post added at 10:37 AM ---------- Previous post was at 10:35 AM ----------

Fun note: That 'car friend' of mine has a one of a kind Datsun 240Z with a black lower body and Ferrari air vents behind the front wheels and dual carburetion. His daily driver is a fuel injected Datsun 280Z.

 

[Tpdingo]

$100 here for a torque converter seems sky high to me.

1: A clone TAV costs 50-55$...not 100.

2: If you look around...I found my entire kart with a T/C 30 for 50$. Motor, cable, seat, and I was done. I don't have any money to work on it...so I did as cheap as possible.

 

[tgus3]

No offense, but this is why I'm not too keen on sticking a torque converter on my kart. So much more complicated. True I would probably utilize my torque and horsepower better, but to me, having to manage the belts and pulleys and whatnot just seems like it outweighs the benefits. I might consider upgrading from a drum clutch to a disc clutch though.

I have bought several tcs and they're completely worth. only cost 50 bucks on eBay and are actually quite simple to assemble and maintain.

I got what felt like a gain of 3 times more torque from it even tho lowered my top speed about 2-3 mph.

 

[itsid]

Yeah.. but this is NOT about TCs it's about a gy6 CVT

And while the two are certainly siblings,
this is not the place to discuss the pros and cons of a TC on an industrial engine..
THERE IS NO FRICKING POINT!
Move that discussion to some other thread!

OP is stuck with his CVT since it's an integral part of his engine.. period

'sid

 

[Brother Turtle]

When I tried digging the melted plastic and rubber rollers out of the variator, I scarred up the roller pockets. So I found a new one on ebay for $25, so that what I'm gonna get.

 

[ghost civic]

I had 2 bikes, both with 50cc 2 stroke motors putting out nearly identical power. One had a 2 speed automatic wet clutch, the other a normal scooter style CVT. The one with the CVT had better takeoff, midrange and top speed.
I've also had a 5hp mini bike with cheap clutch that couldn't match the speed of either 50cc bike. Having some "gearing" is worth any hassle. And the mini bike clutch required oiling, cleaning and if it got wet while riding could slip and overheat.
I will take a CVT any day.

 

[Brother Turtle]

I ordered the new Gates belt, a new variator, and new rollers, I’m trying to install them and can’t get the belt on. I watched a video and the guy was able to hold the rear cluctchpulleys open and stick the belt down in there. That gave plenty of slack at the variator end. But I can barely move my clutch pulleys with both my hands. I can pry it apart with a screw driver. But how do you fix it so that it moves freely?

 

[Snaker]

I ordered the new Gates belt, a new variator, and new rollers, I’m trying to install them and can’t get the belt on. I watched a video and the guy was able to hold the rear cluctchpulleys open and stick the belt down in there. That gave plenty of slack at the variator end. But I can barely move my clutch pulleys with both my hands. I can pry it apart with a screw driver. But how do you fix it so that it moves freely?

Some of the GY6 belt changing video's are misleading on this. Some CVT cases are shallow and the pulleys are outside of the case and can be left in place for a belt change. Other CVT cases are deeper. I have a GY6 150 in a cart and I have to remove both pulleys to change the belt. Even then the driven pulley won't spread freely. Your spreading and twisting against the contra spring. The two pulley nuts are crazy tight from new, pretty much require a impact which I'm not fond of doing. These CVT's absolutely demand regular maintenance, or you will end up with a pile of it in your hand. Always look out for rollers flat spotting. There should also be a air filter in the front snorkel of the CVT cover that will plug up in the dirt and causing overheating.

---------- Post added at 03:25 PM ---------- Previous post was at 02:54 PM ----------

Just wanted to make a couple comparisons between GY6 and Comet type CVT's. GY6 engine and gearbox cases are one-piece so center to center distance and pulley alignment are a non-issue. That also means its all set up for the spec'd belt. The GY6 pulleys and belt are smaller then the Comet parts. Notice the drive pulley moveable sheave in the hand of the photo in the first post, its around 5" diameter. The Comet type has the drive pulley perform a "clutch function". The GY6 has an actual centrifugal clutch riding on the driven pulley. The obvious difference is that the Comet type belt only spins at engagement and above rpm's. The GY6 is spinning anytime the engine is running, even at idle. One thing that this does is puts the engagement abuse on the clutch pads instead of the belt. The GY6 CVT is enclosed with the exception of cooling vents. It relies on mechanical cooling from the fan blades on the drive pulley fixed sheave and on the airflow design. There usually is a air filter in the front snorkel that needs to be cleaned. For some reason the manufactures and dealer/vendors don't seem to advertise this. I do think the GY6 system that was designed for a scooter weighing maybe 1/3 as much and riding on pavement is near its limit in a off road cart. That said I bought mine new in 2010 and put it to lots of run time and abuse. But I have probably opened my CVT up and serviced it maybe 20 times in those 8 years.

 

[Snaker]

I forgot to mention that a shredded belt just about guarantees that the roller flyweights are no longer in position and there is debris in the driven pulley. Ya gotta pull both pulleys apart.

 

[Brother Turtle]

I knew my rollers had flat spots when I put the last belt on it. But I didn’t have any new ones. I put it back together and let him ride it. I guess that is a lesson learned. But now I have a new variator and rollers with a new belt. The clutch looked good so I cleaned it and reassembled everything I guess we will see how this does.

 

[ghost civic]

when I had to put a belt on a gy6, I had to put it over the rear pulley, pull it toward the variator while letting the wheel rotate...that allowed the belt to work it's way down into the rear pulley, giving the slack needed to slide the belt onto the variator's shaft. I could only slightly budge the rear pulley open by hand, but pulling the belt while letting it rotate allowed the pulley to open up as it would during operation.

 

[Brother Turtle]

A few weeks ago, I installed the new variator with new rollers and the new belt he has driven it twice and the new belt broke yesterday. What should I check next?