M-600 Bobcat Variable Speed??

Dubbya Are · May 19, 2015

Just bought an old Bobcat M-600 and there seems to be a problem with the variable speed ... the drive pulley won't push the belt all the way to the top of the pulley and therefore won't pull the belt down inside the driven ... the driven pulley seems to be moving on the shaft with no problem .... pulling the control lever back will open the drive and let the belt ride high in the driven ... I known it's working but it act's like it's only closing the drive half way ... Maybe a problem with in the variable speed hydraulic cylinder?? Any thoughts or help would sure be appreciated.

leonard j. etta · May 19, 2015

You may try and loosen the three spring loaded bolts and/nuts on the driven hub,they only need to tight enough not to have drive
belt slip,if this does not help,then the hydraulic activated cylinder needs new rings and seals.

leon

Dubbya Are · May 19, 2015

Thanks Leon ... I have loosened the three nuts to the end of the bolts and it still just runs both pulleys half way .... I'm thinking the cylinder also ... pretty sure the driven will open as it should ... the grease zerk is broken off and I' haven't got it backed out yet... may need some good idea's for removing it also.

Bob · May 20, 2015

In addition to many other potential problems, if the belt is worn (width) or stretched (length) or simply the wrong belt things ain't gonna work as they should.

Dubbya Are · May 20, 2015

(quoted from post at 22:33:08 05/19/15) In addition to many other potential problems, if the belt is worn (width) or stretched (length) or simply the wrong belt things ain't gonna work as they should.

If I take the belt off shouldn't the drive pulley close by using the cylinder (high) ..... I assume the spring on the driven is what opens the drive pulley when pressure is release on the cylinder (low) .... I've run it some and see no slippage with light work.

IowaJohn · May 20, 2015

Try lifting the bucket up and letting it down with the lever pushed ahead the hyd pump may be a little weak. Also watch when you replace the grease zerk, I can't tell you where to turn the spring in relation to the zerk, but if it's in the wrong place it'll shear the zerk off again when it compresses. I think if you know about this you can figure it out.

Dubbya Are · May 20, 2015

(quoted from post at 07:08:31 05/20/15) Try lifting the bucket up and letting it down with the lever pushed ahead the hyd pump may be a little weak. Also watch when you replace the grease zerk, I can't tell you where to turn the spring in relation to the zerk, but if it's in the wrong place it'll shear the zerk off again when it compresses. I think if you know about this you can figure it out.

When I push the variable will it stop (slow) my lift cylinders? I know it will pop a bucket full of dirt right up and the lift and tilt are both quick empty .... When it stops raining here in Mo. I'll give this a try.
The zerk is in the middle of the coils ... If I can get the old one out I'll move it closer to the pulley and coil (I think?) ... Thanks John.

IowaJohn · May 20, 2015

Get the bucket up in the air I'd say 5-6 feet then push the lever forward and let the bucket down, have the engine running fairly fast. I do it all the time with my 610. It's the only way I can get the belt to the top of the engine/drive sheave. hope this works and gets you by. If not I'm not sure if the inside of the drive sheaves are the same on a 600 and a 610.

Dubbya Are · May 20, 2015

(quoted from post at 09:49:38 05/20/15) Get the bucket up in the air I'd say 5-6 feet then push the lever forward and let the bucket down, have the engine running fairly fast. I do it all the time with my 610. It's the only way I can get the belt to the top of the engine/drive sheave. hope this works and gets you by. If not I'm not sure if the inside of the drive sheaves are the same on a 600 and a 610.

I tried this and still couldn't get the variable to top of drive ... didn't make any difference I don't think, still about half way is all she'll do.

IowaJohn · May 21, 2015

A question for you when you get it to 1/2 way does it stay there or work itself back to completely open/slow down? Just taking a guess here if the speed stays the same and doesn't slow down on it's own. I'm wondering if there is a ridge that's gotten wore into 1 of them or both stopping either of the sheaves from moving completely either the front opening or the back 1 closing. Or you've got a problem with the cylinder that runs the drive sheave. As far as the belt being wore/loose that's only a problem when the drive sheave is completely open and there is no tension on the belt, mine is loose right now until I speed it up then the spring up front holds it tight. 1 last thing before I close and maybe you've already checked this is there something stuck in the spring keeping it from compressing?

Dubbya Are · May 21, 2015

Haven't felt the pulleys to see if there smooth or not ... but just looking they seem ok ..... I've had the driven pulley pushed wide open so I know it's not stuck at least and I haven't run it enough to know but I think the belt stays where it stops?
I'm now thinking that when the drive pulley cylinder or the actuating spool get so much pressure that they are bypassing instead pushing the drive pulley closed ... just guessing

... I'm open to ALL thoughts ... keep em coming as I'm stumped

Dubbya Are · May 21, 2015

Finally got it working ... not real sure what fixed it ... I ran the driven pulley in out a few times by hand and tried to grease it best I could by hand ... I did add a little more pressure to the control valve

I took it out to the drive and ran it at high rpm pushing the variable speed to high and it stared working and now is working the best ... Thanks to everyone for the help ... not sure what cured it ... maybe the extra pressure (3/4 turn clockwise).

Here's picture of the grease zerk location we talked about on the driven pulley in case anyone else needs to know.

IowaJohn · May 21, 2015

Great and thanks for the idea on turning up the pressure. I'm going to give that a try on mine.

M-600 Bobcat Variable Speed??

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