need better belt

[Newoldstock]

I am running a PIX belt on this bike.

Not impressed with the speed at which it has worn.
About 15 minuts was its life.

Since all new Comet belts apear to be Pix and I am using Pix anyways does anyone have any NOS 91 belts for the yerf dog?

Message - Old Mini Bikes Photo Gallery

 

[Newoldstock]

Anybody feel free to chime in on your belt thoughts
Closer examination of the belt in question and the stretch does not seem like all that much compared to a new one.
But new one is clearly tighter on the clutch kit.

New clutch maybe an hour of tuning and scaring the shit out of myself.
30 primary 7 inch 30 sec on a Yerdog jack shaft with the 91 belt.
9 - 54 final drive ratio.

Bronze busing shows a lot of wear already ( not expected, but I have been doing a lot of tinkering on the stand )
The hub driver is showing some wear too.
Inner clutch face and driver weighs are polished up like a new shiny penny.
From that I conclude they are moving smoothly and no binding.
Everyhing apears to be functioning perfectly.
I was careful to make sure there was the correct amount of slack on the belt before I started so this has realy suprised me.

Clutch engages at around 2200 rpm as desiged.
Clutch has fully transitioned to high ratio before 3500 rpm depending on load ( this is early but I have plenty of power on tap )
Engine and clutch kit continues to excellerate and pull to 4200 rpm ( looking down the belt apears to be climbing out of the primary clutch ).
At that point I am out of road and its time for a brake test.

Everything is well lubricated with moly dry lube and the belt is correct for this clutch combination ( same as yerdog kart )

 

[Newoldstock]

Well I wonder why this has not been discussed before?

Some thoughts of my own.
That brass busshing is too short!
The surface finnish on the shaft is not the best.

Here is the interesting bit now.......
Prior to 1994 these primaries used some spacers to adjust the belt clearence.
The clutch opens too wide in my opion I may be able to machine off some material to make the primary both stronger and less likely to beat the shit out of the bushing like mine has at high load.

Maybe I don;t need a bushing at all and could just make a steel replacement, highly polished to reduce belt wear.....

 

[Neck]

TAV I? Where is the belt wearing, sides? inside? is it symmetrical or asymmetrical?

 

[Newoldstock]

30 series.

Not TAV

30 primary asymetrical and a 7 inch 30 series secondary

Everything is inline as it shoudl be checked and double checked.
But the belt took a shit kicking.
I honestly think I have a low grade belt.
PIX made in India.

However I noticed some other things like the way the clutch faces closed up once the belt was worn and I confess to throwing a little more power at this than 8 HP.
But this is not a TAV-1 or TAV-2.....
Same system as used on the Yerfdog karts.

I bought a TAV-1 from BMI a few years ago and used Comet belts with no issues.
I think about 50% of my problem is belt.
But now that I look at the way things fit together and the amount of excess movement in the moving face and the deleted belt spacers on this new version I'm starting to wonder if maybe there's room for some fine tuning here.

Has anyone else had the clutch faces close up far enough on a worn/stretched belt to cause idler bushing damage?

Oh.
Where is the wear?
Worn out.
Slight cupping in the centers of the belt as it has crept up and started to come out of the primary clutch when fully closed.
Removed belt.

 

[packmule62]

go to www. belt palace.com i got good service and great belts get the kevlar reinforced belt they also have comet original parts

 

[gpxsrxracer]

Anybody feel free to chime in on your belt thoughts
Closer examination of the belt in question and the stretch does not seem like all that much compared to a new one.
But new one is clearly tighter on the clutch kit.

New clutch maybe an hour of tuning and scaring the shit out of myself.
30 primary 7 inch 30 sec on a Yerdog jack shaft with the 91 belt.
9 - 54 final drive ratio.

Bronze busing shows a lot of wear already ( not expected, but I have been doing a lot of tinkering on the stand )
The hub driver is showing some wear too.
Inner clutch face and driver weighs are polished up like a new shiny penny.
From that I conclude they are moving smoothly and no binding.
Everyhing apears to be functioning perfectly.
I was careful to make sure there was the correct amount of slack on the belt before I started so this has realy suprised me.

Clutch engages at around 2200 rpm as desiged.
Clutch has fully transitioned to high ratio before 3500 rpm depending on load ( this is early but I have plenty of power on tap )
Engine and clutch kit continues to excellerate and pull to 4200 rpm ( looking down the belt apears to be climbing out of the primary clutch ).
At that point I am out of road and its time for a brake test.

Everything is well lubricated with moly dry lube and the belt is correct for this clutch combination ( same as yerdog kart )

Too many variables here, and not seeing it in the flesh makes this hard to make a diagnosis. First off, dont use ANY lube, no moly, nothing. I know comet used to sell lube, but dont use it. Any lube with any oil on it instantly attracts dirt and any debris. Plus any lube that gets up on the belt will start to slip and ruin the belt, even a little bit. Ok, now from the pic I saw that you posted the link to, it appears that the belt has too much slack. One unfortunate flaw with a TAV setup is center to center distance adjustment, or lack of...that sucks, so much performance is lost when you cant adjust center to center. Next question, are you useing both the same style asymmetric or symmetric and not mixmatched? They must be the same. Next, clutch offset. Question, can you adjust your secondary sheaves to be closer together or farther apart? If you can, you can tighten your belt slack up and get it running alot better. Ive messed with alot of different snowmobile cvt or belt drive systems over the years, set up drag sleds, trail sleds and I also have a TAV I just got recently...im gonna be messing with that soon, but what I see so far, I dont like the lack of adjustability. Really, when it comes to a belt drive and doing what you need it to do, and work like it should, you would need something like this >>> Complete Jr. Dragster Company this, or something similar from a different company, properly setup, would put a comet tav setup to shame instantly, it would smoke it! But the cost is a huge factor...these setups run in the 700 dollar plus range unfortunately.

 

[Newoldstock]

Been thinking about this a lot....

I am going to make some new bushings longer than the OEM parts.

Here is my theory.
AS the primary closes up there is not enough suport for the moving sheave. When it does come in contact with the bronze bushing there is too its hammering the brass and causnig me wear.
Slack as the unsuported section of clutch beats on the bushing it comes in contact with
The bushing is too loose.
.010-015 loose. I need to tighten that up.
There was a design change to the 30 series drivers to make them cheaper.
I know understand that these deleted shims were actualy the same diameter aas the bronze bushing and suported the moving sheave as it moves in so its less likely to smash up the soft brass bushing.
Surface finnish on the fixed side where the bushing rides to not smooth at all and needs to be polished to reduce wear.
Some parts inside could be dressed and machined to tight up the tollerences.

On the adjustment side.
I may use a higher engagement spring.
I will use yellow secondary spring.
I will increase my rear sprocket from 54 to 60.

I am probably going to detune my engine.

This was a race bike but I have to pass on the racing this year.
I could tollerate the way it eats parts. Its plenty strong enough to race.
I could finnish a course even with its quirks.

Lube fit and alignment.

Lube is Crown dry moly.
This does not attract dirt.
Cleaned with contact cleaner and relubed as needed my TAV-1 was never any trouble at all!

Fit/Aligment.
Perfect.
Using the corect blets and spacing as per comet spec.
It may look very odd but this is esential a yerfdog kart grafted to a Baja mini with a clone.

May consider your sugestion and slot my jack shaft plate and add some jack bolts to spead the the C to C and compensate for wear and stretch.
But I think I need to get a proper Yerfdog/Kartco/or Comet belt made in the USA first to see if thats going to wear longer.

I wanted to run a 340 on this bike but I could not afford one.
Better would be a JR drag clutch but thats a lot of money too.

I went cheap hoping the gearing and 7 inch 30 series secondary would function well enough to give me some advantages with a less powerfull engine.
Then I built a more powerful engine......

 

[Newoldstock]

More info:
Here is the Yerf Dog 3200, several version of this kart.
All used the same dirver, driven and jack shaft.
The only difference is I have swapped the drive sprocket to the other side.
I power the right side of the rear wheel instead of the left as built by Baja.
http://www.yerf-dog.com/manuals/3202_D.pdf

 

[Neck]

This is kinda weird, my 3/4 TAV II uses a bushing, but my 1 inch does not. So let me get this straight, your belt has cupping on the inside diameter where it rides on the bushing?

 

[Newoldstock]

Does this help?

Message - Old Mini Bikes Photo Gallery
This is less than an hour of use.
Belt us toast now. Narrow and actualy apears to be a little longer......


Bushing looked like it was hit with a chisle in lines parrallel to the shaft.
Some wear can be seen on the moving parts in the primary.

Look a the cord....
See the side is not flat like the new one on the left.
The belt wore out funny and I think its because it rides too high inthe driven pully at full speed.
I think that happens because its worn out and stretched.

Hammered up bushing and wear on the moving sheave and other parts seem unrelated to the belt.
Just weak design, and I was not very nice to this thing.

OK looking at the belt guys....
Have any of you ever reduced one to this condition just under hard excelleration and tuning?
Honestly I was loading down the engine to break it in and tuning my carb.

All together this is maybe 12- 20 passes up and down the street never exceeding 4500 rpm.
Over two days I guess.
1/2 hour each time maybe 45 minuts.

Tach only tells me I rolled over an hour not exact minuts and I was not paying that close attention to the number of pulls.
I was taking plug reading and setting my carb, monitoring the engine ect....

 

[Neck]

Can you see which pulley is doing the chewing? Or where the pile of rubber is being deposited? Or are they both eating it?

 

[Neck]

I ran my belt ass backwards for three races and multiple rides on my eight horse one inch TAV and didn't do that much damage, and I could feel it jerk and slip as I rode it! your belt should be riding deep in the driven at high speed, not up high, and if it's stretched, let's just say I haven't seen a vee belt stretch and not tear in my 35 years as a mechanic. Something has got to be causing abrasion to the belt. Are the shafts parallel?

 

[joekd]

More info:
Here is the Yerf Dog 3200, several version of this kart.
All used the same dirver, driven and jack shaft.
The only difference is I have swapped the drive sprocket to the other side.
I power the right side of the rear wheel instead of the left as built by Baja.
http://www.yerf-dog.com/manuals/3202_D.pdf

If you need any actual pics of this setup I have that same kart in my garage. The TAV is on the 3rd motor swap and has been perfect since day one

 

[Newoldstock]

Sure snap some shots maybe there is something I have missed

 

[Newoldstock]

Major rethink and retool in progress.

Dam bike turns money into smoke and noise faster than my wife.

 

[bwt]

I knew what the problem was as soon as you said that you looked down and the belt was riding out above the top of the driver sheaves. When that happens, the sides of the "teeth" of the belt are riding on the rounded edges of the sheaves. This will destroy any belt in a short time and produce the wear you are seeing. The top of the belt should never come closer than about 1/16 of an inch below the top of the sheave when working properly. I had the same thing happen to me with a tav2 30 series. It didn't matter if I ran a comet or a pix belt. To fix it, I had to slot the backplate engine mounting holes so I could increase the center distance between the driver and driven shafts because I couldn't buy a shorter belt. You may also want to check the driven clutch and make sure it isn't opening too far, as this will cause the same problem. By the way, I am running this on a modified clone making around 12 HP and I haven't had any belt problems since.

 

[Newoldstock]

Thank you bwt.

I will look into that.
I am riught now trying some things to cure than belt creep and slotting is one of them.
I also thought a lot about what you waid about the 7 inch secodnary opening too wide and plan on trying to adjust that as well.

 

[Newoldstock]

I am going to pull the secondary off the bike this evening and see exactly what I would need to do to prevent it from opening any more than it does.

Or maybe the solution is simply the Yellow spring from Comet....

Any more thoughts guys?