WM drive belt question

[Jim_Rogers]

I'm in the process of changing a broken brake strap and I see that my drive belt is separated into two pieces, split right down the middle by the v-grooves in the pulleys. As you who have woodmizers know it's a one piece snow mobile belt.
I was wondering if I should replace it as I have nearly everything else apart.
As I have one on hand and assuming all of you will tell me to replace it now, I'm replacing it.
Can anyone give me some tips on how tight this belt should be?
And how do you tighten it correctly?
Thanks
Jim Rogers

[Tom]

First of all, since you have it all apart, you are probably right in changing it. I wouldn't change it only because it split the backing and made two separate belts though.  

I ran for years using separate belts and they pull fine.  The only reason for  connecting the two is so that they pull evenly.  It's hard to get two separate belts to tension the same.  I found that, although they are better, the "tied together" belts don't always tighten together either.    Keep your old belts for spares.

The way to adjust the belts, as I was told, is to make sure that they slip freely when disengaged and  have about a 1/2 inch of play in the center when tightened.  About the same way you would tighten an alternator belt.

The confusing part is the interaction between the drive belts, the brake, the handle and the throttle.  I'm speaking from a 1990 vintage LT40 but I'll bet the general philosophy is the same for the newer mills.

The engine idle is controlled by the brake-strap adjustment.  The brake strap should be adjusted such that the handle (on the older side-pull machines) will be at 10 o'clock when the brake is engaged and the power belts disengaged.

When the handle is pulled, the engine is throttled up and the brake is released as the power belts engage.

If your engine is idling too slow, look for adjusting the brake, not the carburator linkage.

There is a metal plate furnished with newer machines that keeps the "power belt" from jumping off of the engine pulley when disengaged.  I had to make one when I installed the new, single-backed belts.    I found that the separation of the two belts was helped along by the rubbing of this metal on the back of the belt while idling.  

Another thing that helps to cause the separation is the wearing of the belt.  as it wears, it runs deeper in the pulley groves and the belt contacts the pulley which separates the backing with its knife edge.

I guess one should keep in mind that the pulley wears too.  When the grooves wear, the belt has to ride deeper to make contact with the sides of the V channel.   This could cause separation of the belt too.

If your belts continue to slip, a worn pulley is the place to look.  Because the belt has to ride lower in the groove, it may be bottoming out before the sides of the V can make contact and you will not be able to tighten it enough no matter how hard you try. (the grooves on the blade wheels will do the same thing.  If you put new V belts on the bandwheels and you haven't much sticking up over the top, then don't expect them to last as long as when the wheels themselves were new.)

[Jim_Rogers]

Tom:
Thanks for your advice.
I have the new drive belt(s) in place and the new brake strap in place also.
I've had to adjust my turn buckle to make the drive belt looser as it was so tight I couldn't lock the clutch handle.
And I have the brake strap right so that I can stop the belt correctly.
The problem I'm having now as you have mentioned is in the engine idle. But not a low speed at high speed.
I usually run it at around 3550 and it's running around 3150 now, due to the fact that the throttle linkage isn't being pulled enough.
What do you change to improve this?

I was loosening the linkage bracket at the engine to shift the cable to pull it more, is this right?
My threads on the other end of the cable are all the way to the end of the shield part.
Jim Rogers

[customsawyer]

if i remember right you tighten the belt with the cluch engaged and you should be able to move the belt about a half inch with 24 lbs of pressure but i don't have my manuel with me right now so i'm working off of my mind which slips sometimes too

[Tom]

Jim,
Going to the throttle linkage is the very last thing you want to do.  I was told to leave it alone unless there was some catastrophic maladjustment, like I bent the mill or something.

If the throttle isn't going to the speed it was set, then it means that the clutch handle isn't going all the way down or the linkage is out of sync with the clutch handle.  Perhaps you need to pull the handle all the way through and then adjust the linkage.  At this point I think a call to WM'ers customer service might be in order to make sure that you get everything Sync'ed back up.

It sounds like you have most of the problem solved already.

[Jim_Rogers]

I put a new blade on and brought it up to tension so that I could run everything as normal at every idle position.
The low idle was ok and the high idle was off.
I have a tach on my mill so I know my numbers well.
I adjusted the cable bracket at the engine to get to high idle and that worked ok.
But it threw the low idle off. I adjusted the cable at the spring at the frame and that fixed the low idle.
I do understand about not changing things at the carburetor.
I've been down this road more than once.
And I sawed up a log afterward with the customer standing right here. And all went as it should.
Seemed to even have more power? Maybe my belts were slipping and I just didn't know it.
Thanks for all your advice.
Jim Rogers

[woodmills1]

Mine is a 93 so when I redid the brake starp it was a drill and refit new design.  At that time I noticed the separated drive belt so ordered a new onw.  For info I still have the new one and have just now heard the squeek of slippage.  I think I will tighten the drive and still not replace the separated belt.

[MemphisLogger]

Me thinks that you have to use the single backed belt.

If it separates, one belt will surely not have the same tension as the other and it will slip under load.

Tom, thanks for the thoughts on the brake strap and low idle--I never thought of that--duh.

For a couple of weeks last summer, I didn't seem to be able to get full revs in the cut and I couldn't figure out why. I fooled with the governor and throttle and rebuilt the carb all to no avail. Then when I'm sawing on a slight incline the clutch lever pops up in the middle of a cut. I look to see why and find that one of the adjustment bolts is turned so that a "point" of the nut is hitting the pivot rod and keeping the clutch handle from fully camming over. turned the nut to a flat and my reves came back--duh.

I love figuring out how to run machines--I wish I'd learned how to read manuals  :P  

[Tom]

Scott,
I sawed a lot of wood with two drive belts.  That was before we were enlightened to the single backed belt.  I think they call them Power belts or something like that.

The trick to using multiple belts is to try to buy "matching Pairs".   Look at the serial numbers of the belts and buy those that are in sequence with one another.  The chances that they came off of the same piece of bulk stiock and the same machine at pretty much the same time is pretty good and insures that they will tighten together.

[Kevin_H.]

We are running two seperate belts on our drive, I put them on a couple of months ago and have not had a problem yet...I will say I think it is easer to put on two seperate belts than the combined.

[sparks]

We use a wide double belt to allow more HP to transfer to the blade. 2 single belts are never exactly the same size so you do not get equal torque on them.
When replacing the belt you make your engaged adjustment first. 7/16 deflection at 25lbs of force. How do you know what 25lbs is, it a pretty good push to make it move 7/16". Verify the the clutch enhancer is in the correct place. This is the rod mounted to the engine, near the engine pulley, below the drive belt. It should be a 1/16" away from the belt when engaged. After all this, then you adjust the brake strap. When the brake is adjusted properly you should be able to walk the belt off the drive pulley almost all the way without getting it off.

[Jim_Rogers]

On my 94 LT30HDG24 there is a bracket near the drive belt after you remove the engine drive pulley cover.
In the past I used to measure from this piece of bracket to the belt first, then add the 7/16" to get the total distance from the bracket.
I went to K-Mart and got a fish weighing scale from the sporting good department and used it to pull on the belt until it read the correct number of pounds. At that weight I'd measure with a ruler and see if I had the correct distance.
I didn't do that this time, but maybe I will, and I probably should have.
I remembered this after I had all the covers back on the machine.
It seemed to run alright today but the clutch lever was a lot harder to pull down then last week.
I probably should check my settings.
I understand about how to set the brake strap once the belt is the right tension, and how to check how loose the brake strap should be to not let the drive belt fall off the main shaft drive pulley when the brake is on and the engine is running.
What I had trouble with on Saturday was the correct way to adjust the throttle linkage once both of the other two things were done (first the drive belt tension, then the brake strap tension).
When I first started my mill the engine ran at the correct low idle rpm, but not at hight idle. Then I adjusted the cable bracket at the top end of the cable to increase how much the cable would pull on the throttle linkage under the air filter. Then I set the high idle by bending the small bracket with a pair of pliers. But by changing where the top end of the cable was secured it changed the low idle speed.
By adjusting the actual position of the spring on the bottom end of the throttle cable where it attached to the frame solved that problem.
And I currently have both idles correct again.
It was getting dark and the customer was standing there waiting for his order to be finished so I could deliver it with my trailer as they were planing on building the building Sunday.
So, I didn't got threw all the proper procedures as I should have to insure that everything is correct, with the installation of the two new belts. But I probably should.
Thanks for all your advice.
Jim Rogers