Getting really annoyed now [CVT malfunctioning?]

[Rat]

So to cover the basics first:
Comet 30 series clone, 6" driven, 6-15/16" CD, and a 203589A comet belt.

The extent of my driver trouble shooting so far:
Cleaned the fixed sheave spindle, cleaned the inside and out of the slider bushing, lighty hand polished/buffed the slider, reverted to stock spring (this one came with a red iirc it equal to a Comet green) tested all spring hole positions including 2 I added myself (one on each end of the original 3)

The issue if (it's actually an issue) is it wasn't opening at all with the yellow spring in the softest setting (almost the same as red in the hardest) and only opens by about half way even at 35mph.

Someone tell me WTF I am not thinking of or am overlooking.

2.50-18 tires (aprox 24" outer rolling diameter)
9/36 gearing (4:1) because the 48t would not line up for anything, and the 56t made for a wheelstander.

 

[BrownStainRacing]

So to cover the basics first:
Comet 30 series clone, 6" driven, 6⅞" CD, and a 203589A comet belt.

The extent of my driver trouble shooting so far:
Cleaned the fixed sheave spindle, cleaned the inside and out of the slider bushing, lighty hand polished/buffed the slider, reverted to stock spring (this one came with a red iirc it equal to a Comet green) tested all spring hole positions including 2 I added myself (one on each end of the original 3)

The issue if (it's actually an issue) is it wasn't opening at all with the yellow spring in the softest setting (almost the same as red in the hardest) and only opens by about half way even at 35mph.

Someone tell me WTF I am not thinking of or am overlooking.

2.50-18 tires (aprox 24" overall diameter)
9/36 gearing (4:1) because the 48t would not line up for anything, and the 56t made for a wheelstander.

Imho, tire is too tall for that 4:1 gear, it's gonna take more then a 208 to pull that on a mini bike with a 24" tire.

The 6" driven is .9:1 when it gets to high.
So your 4:1 is actually 3.6:1. That's gonna take a HELLAVA engine to pull that gear with a 24" tire. It's gonna take some power jus to get it to go into high.

I know what you say about "wheel pop", let's see what throttle assembly you have.

Mini bikers always complain about wheel pop with these clone style engines and t/c's.

The stock throttle assembly was designed to work at a steady constant rpm, not up and down throttle like we use on minis and karts.

The throw is too short on the stock throttle assembly. There's almost nothing there between idle and WOT

A 1/4 twist of the grip, goes from idle to WOT, that's where you are getting wheel pop.

Theres throttle assemblies made to increase the throw for the twist grip or pedal.

The yellow spring is a power robber. The deeper you drive the belt into the driven, the more power it takes to keep it going. We all run out of power eventually.

I dont use the yellow spring any more, unless I need to take power out for the rider. And thats usally a non gov'ed build that somebody went too far on.

Or a 280# rider with a stock 196, 6" driven and 5:1 gear with a 19" tire, it won't be fast, but it'll pull weight up a hill.

I live in east tn, we drive up hill more then we drive down hill, , and I still don't have to use that yellow driven spring.

Another thing I like to do is add stall to the driver.
It'll give you more throttle control, and won't be so snapping from a dead stop and more time to react to the wheel pop.

It will give you more rpm on the high side, if you have the tune for it.

Don't expect a 9k+ rpm gain on the high side jus by adding heavier driver springs, 300-400 is a normal gain.

I'm 200#, if I had a mini with a 24" rear tire that had a 208 I would run a 7" driven, red spring in the farthest hole clockwise (least resistant) a 30 series driver with aluminum weights, 3000 rpm springs, and 6.66:1- 7.2:1 gear.

Mph is not important,..... but climbing hills to get my a$$ back home is.

 

[Rat]

I know what you say about "wheel pop", let's see what throttle assembly you have.

Generic Twist grip throttle pulling a 24mm Koso PWK Keihin copy carb.

A 1/4 twist of the grip, goes from idle to WOT, that's where you are getting wheel pop.

1/2 turn from 1200Rpm idle to WOT and it only took whiping it to 1/3 of its range too quickly to stand up.

I live in east tn, we drive up hill more then we drive down hill, , and I still don't have to use that yellow driven spring

SWVA, I know... I'm Noreast of Bristol.

I'm 200#, if I had a mini with a 24" rear tire that had a 208 I would run a 7" driven, red spring in the farthest hole clockwise (least resistant) a 30 series driver with aluminum weights, 3000 rpm springs, and 6.66:1- 7.2:1 gear.

6'2" and about the same. I've considered using a 7" driven but some armchair professionals said that there's no belt that fits 6⅞ CD on a 30 series with anything but the stock 6"... I didn't give a Sh!t enough to debate ir pursue it seriously.

I asked about it potentially malfunctioning simply because the driven doesn't want to open at all and wont go past half if it does.
I have had this thing bone stock minus governor wound up to the extent that the driven sucked the belt into the sheave rivets with the stock spring in its tightest hole and shredded it apart with 10/36 gearing more than once (not in the mountains though)!

This is a relatively new issue that cleaning and a light polish isn't fixing.
FWIW it also pulls just as hard up a steep inclines with the 9/36 as it did with the 9/56 the only difference is that it obviously doesn't get there as quickly, and does so at a lower rpm without the wheelstand on take off risk.

There is no lack in torque or power here because I started with a high torque winter engine to begin with (LCT Husqvarna Snow)

 

[panchothedog]

The belt that you mention with the number ending in 89 for your 6" driven, the 7" driven uses the belt ending in 91. Sold by OMB Warehouse and Go Power Sports. It works with the standard 6&7/8" O. C. 30 series set up. Don't think I have ever seen it for sale on Amazon. Only the 89. I don't buy my belts on Amazon anyway.

 

[Rat]

The belt that you mention with the number ending in 89 for your 6" driven, the 7" driven uses the belt ending in 91. Sold by OMB Warehouse and Go Power Sports. It works with the standard 6&7/8" O. C. 30 series set up. Don't think I have ever seen it for sale on Amazon. Only the 89. I don't buy my belts on Amazon anyway.

Thanks for that information, Ill check fleabay no doubt... OMB and BMI both have a store there anyway.
Now if I can figure out what is making the damn thing jam up currently I'd be a bit happier.
Would general wear on the slider bushing or the aluminum front sheave hub cause a bind issue? There's very little play in the parts spring off unloaded, but there is a little bit

 

[BrownStainRacing]

Thanks for that information, Ill check fleabay no doubt... OMB and BMI both have a store there anyway.
Now if I can figure out what is making the damn thing jam up currently I'd be a bit happier.
Would general wear on the slider bushing or the aluminum front sheave hub cause a bind issue? There's very little play in the parts spring off unloaded, but there is a little bit

Yea that 203591 is the belt I use with the 7" driven. I use only bando belts on minis with 7" drivens.
I give my old ones to my son, he's NEVER bought a belt,

Comet Torque Converter Belts | Go Kart Drive Belts

Go Kart Belts and Mini Bike Belts. American Comet Torque Converter Belts, Go Kart Drive Belt Catalog: Genuine Comet 30 Series Belts, CAT99 Belts, 20 Series Belts, Comet 40 Series Belts, 44 Magnum and 500 Series Belts. Comet Torque Converter Belt Charts.

www.gokartsupply.com

When you say "jamming up", you mean the belt is stuck in the driven???.

I'm sure you know about "pre loading the spring", right.

 

[BrownStainRacing]

@RLS_Underground
If you do go to a 7" driven, make sure you trim the cover a lil more for the belt.

It'll wear a slot in the plastic on deceleration and eat the sides of the belt.

 

[JimD]

With the floating sheave off the engine check the clearance under the belt. I like to have the thickness of three business cards. You don't want it tight and you don't want it sloppy. Sloppy it slams into engagement which will shorten the life of the t/c. You said yours unit was a series 30 and your center to center was 6 7/8" which would tell me looking at Comet's chart that the belt is to tight a belt and would have to go to far down into the driven unit. I am just basing this on information you gave. I am trying to attach Comet's belt chart but having no luck. I tried opening it up but don't know if it is there or not since I cannot open it and double check. Not good with computers --too old and have little patience.

 

[Rat]

When you say "jamming up", you mean the belt is stuck in the driven???.

I'm sure you know about "pre loading the spring", right.

When I say jamming up I mean the driven sheave won't open past half where it used to open far enough to eat the belts with the rivets.

Im not an idiot, and this is absolutely a new issue and I don't run a cover at all. I've got a rail on it that keeps my leg off and jeans out if the driver.

You said yours unit was a series 30 and your center to center was 6 7/8" which would tell me looking at Comet's chart that the belt is to tight a belt and would have to go to far down into the driven unit.

Idk it might have been a bit tight but it's broken in and fits fine now. It's just loose enough that I can grab the belt and rotate it in the sheaves, but still way too tight to even try popping it over the driven (remove the belt without removing the driver).

Aside from not being the cheap Chinese version it's the same belt that it came with new minus the /5959 Manco reference which are too big anyway

 

[JimD]

I have no clue what you mean by "it's broken in now" . Max-Torque only dealt with symmetrical belts because they are easy to measure when it was time to replace them. I can only give good advice on symmetric belts but I can try and do a little cross over help for what it is worth on an asymmetric belt. Both belts would measure 3/4" (.750) at the top of the "V". when the belts gets down to .600 it is time to think about getting a new belt because it will drop down to far inside the driven unit and get locked up preventing the sheaves on the driven unit from closing. The belt number you gave 203589 doesn't fit a 6 7/8"CD it would be too tight and you would have to open up the driven you so you could get the belt on which is not a good idea.

The next belt down #217248 would be a better choice and it would only be a little loose by 1/32 which is better than too TIGHT. Again this is just some advice from a guy that made torque converters but we did not make the nice bolt on the engine style that Comet produced and then the China copies flooded the market. The belt on the driven unit should be on the top of the driven sheave and you never open up the driven to assist getting the belt over the driver with the floating sheave off the crankshaft. If you have to do that, that tells you immediately you got the wrong belt it is too tight.

 

[Rat]

Just more for more reference and re measured with driving face off and got 6-15/16 which is no doubt more accurate than the eyeballed 6⅞

 

[Rat]

If you have to do that, that tells you immediately you got the wrong belt it is too tight

You ABSOLUTELY misread what I said!

IF THE BELT IS SO STRETCHED YOU CAN REMOVE IT BY SIMPLY SLIDING IT OVER THE DRIVEN WITHOUT REMOVING ANYTHING ELSE THE BELT IS DONE....

ReRead!!!!

What I meant by broken in is that it is not stiff and trying to retain the packaging shape (smashed and folded in half) it is is pliable and moves freely in the sheaves by hand with the engine off... which it wouldn't be able to do if it was too tight.

Also stop focusing on the sheaves NOT closing... THAT is NOT AN ISSUE... the issue is again for like the 5th F★CKING TIME is the sheave not opening. I've over stretched 2 belts and cleaned this thing multiple times trying to figure out what the bind is being caused by when previously the driven would iopen until the belt was all the way down in the rivets being eaten and slipping in the process

 

[Rat]

At this point getting a 7" and the needed belt seems like my best course of correction because NONE of you are providing any useful information because you are too busy focusing in issues you've concocted but do not actually exsist

 

[Rat]

I kept poking at it piece by piece... it seems like maybe the issue is/was a bit of belt dust making the bushing on the driver prevent the slider flyweight hub from closing, which would make it seem like the driven wasn't opening properly.

I'm going to take a quick burn to see if cleaning everything down to the shafts and relubricating by comet parameters happens to be the magic bullet.
Either way I'll probably get a 7" driven and corresponding belt although I'm also thinking it might be time to just get a 40 series because Bone stock was already at the upper limit these 30's are meant to handle.
Also something note worthy because diameter means more than the physical tooth count, I run a ProTaper PT415MX chain, so my 36T sprocket is significantly larger with ½inch pitch than some sissy #35 chain based crap.

[EDIT] It pulls harder now, but 40mph just isn't enough ground speed to open it up... it's not a lack of RPM, it's not a lack of function, nor power at this point, it's a total lack of straight open road. I did test it unloaded and was able to reach full open at around 4600 rpm at the tach if that tells anyone anything significant.

 

[Snaker]

Very confusing thread.
Different lingo being used, lot of sidetracking, hard to tell which pulley is being referred to at times.
Here's my take on the various names I've heard used with these CVT's:
Drive - Driven
Driver - Driven
Primary - Secondary
Clutch - Clutch
Torque Converter - Torque Converter
TC - TC
Variator - Clutch
Variator - Driven
Engine - Gearbox
Little pulley - Big pulley
And probably many more

I'm in the fog with about 75% of this one.

If all the tire size and gearing and other stuff was in place both before and after the problem, then all that should be ruled out.

Adding extra holes to(I assume your referring to) the driven pulley only goes so far.
You can have the spring get too loose on one extreme and get spring binding on the other end.
I suggest putting that spring in a original hole at least while troubleshooting this

If you can slide the belt around in the pulley's, that sounds suspect to me.
Usually the driven has enough contact to grip the belt by itself and not let it slip.
I'm not sure on that one

Your photo #161958 drive pulley
Can't tell if that is a too wide side gap or reflection
I haven't found a Comet spec on that side gap, but a similar design by Polaris runs a spec of .020" IIRC.
1 to 2 business card thickness
As mentioned, too small a gap and you don't get proper disengagement
Too big a gap and the movable sheave has to move excessively to engage and slams too hard.
It also uses up some the upshifting range and may not pull the belt down into the driven far enough.
I did get confused on that comment about a gap under the belt? In the drive pulley?
The belt should go down to the bottom of the drive pulley onto the boss, bushing or whatever, at least in the CVT's I've worked with any ways.
With the exception being the GY6 style, but that's a different animal.

Always remember that it's the belt sides being squeezed by the sheaves that drive these CVT's, not the tops or bottoms
And that one of these components will be the mechanical stop for upshifting and possibly the other is the mechanical stop for downshifting.
In you case, you have to find out which component is being the mechanical stop, and why it changed

 

[Rat]

Adding extra holes to(I assume your referring to) the driven pulley only goes so far.
You can have the spring get too loose on one extreme and get spring binding on the other end.
I suggest putting that spring in a original hole at least while troubleshooting this

Yeah, I added one to each end of the original 3, currently have the driven spring in the tightest original setting.

If you can slide the belt around in the pulley's, that sounds suspect to me

Engine off, it takes a bit of wiggle to get it sliding but the point was mostly that the it's not too tight despite the "wring number" "too small" cowing I got. It's the same belt number the damn thing came with on it just better quality.

Your photo #161958 drive pulley
Can't tell if that is a too wide side gap or reflection
I haven't found a Comet spec on that side gap

Oh it's side gap and it was that bad new. It's like the sheave hub is a bit too wide because the first thing I notice was that the bronze bushing seemed awful narrow.
I've learned to feather the throttle to get moving so it doesn't slam.

The belt should go down to the bottom of the drive pulley onto the boss, bushing or whatever, at least in the CVT's I've worked with any ways

It does ride the bushing, I was referring to the slack. It's just a 30 series clone and it would probably just be best to replace the sheaves if it continues to act up.

 

[Rat]

The belt number you gave 203589 doesn't fit a 6 7/8"CD it would be too tight and you would have to open up the driven you so you could get the belt on which is not a good idea.

The next belt down #217248 would be a better choice and it would only be a little loose by 1/32 which is better than too TIGHT.

Try this on for irony.
Due to how much gap was between the belt and movable driven sheave at rest, I tested a theory due to the flyweights having asymmetrical faces...
In flipping the flyweights to see if I had done so previously during a routine clean and lube, it stuck the sheave to the belt just tight enough to grip and the starter can't even roll the engine over without the whole bike wanting to roll with it.

GO F★CKING FIGURE... seems to me that's how someone in China the got the wrong size belt for the C.D. measurement (which is 6 15/16) to fit and still function.

Still looking at probably swapping to 7" driver most likely after the new year.

 

[Rat]

So probably the final update to this thread, got it working properly... FDR got adjusted again