M600 variable speed

[Kilroy2k1]

I had the chance to pickup a M600 for parts that i needed for my M620. The owner had issues with the hydraulics, drive issues and poor starting. After further inspection I really think this unit is too good to scrap. I've already sorted out most of the drive problem which needed the clutches backed off and new seals in the variable speed pully.
The var speed pully is run off the hydraulics with a lever by the seat and when i move it the pully only closes up about 1/2" and will not close any more. There are no more leaks in the system with the new seals, the springloaded side of the driven pully slides free and the hydraulics will lift a bucket of dirt, albeit a little slow and jerky..
Anyone familiar with the 600's var speed system? Is there a pressure relief in that part of it or could it just be bypassing inside the var speed valve?
Tom.

 

[M600-Des]

Hi Tom, Oddly enough I spent yesterday rebuilding my M600's var speed system after reinstalling the rebuilt engine! I'm going to do what I most dislike in others and answer a question when I don't really know the answer ... I don't know if there is any kind of bypass system but I'm going to ask the obvious question - Was the M600 jacked up (wheels off the ground) or moving when you shifted the speed control lever? Naturally the drive belt can't compress so for the pulleys to close the pulleys need to be turning (I know, I know: Make a small hole in the top of the egg and create a vacuum!) Other thoughts: did you have oil in the hydraulic delivery pipe before installation (I'm thinking trapped air might take time to clear making the action poor) Also did you grease the two halves of the pulley? (Grasps at straws!) Good luck, Des p.s. I'm off out now to complete the last tasks and then fire her up for the 1st time in 2 years – it's minus 10c here (Austria) so lets hope it's a quick job.

 

[Kilroy2k1]

Hi Tom, Oddly enough I spent yesterday rebuilding my M600's var speed system after reinstalling the rebuilt engine! I'm going to do what I most dislike in others and answer a question when I don't really know the answer ... I don't know if there is any kind of bypass system but I'm going to ask the obvious question - Was the M600 jacked up (wheels off the ground) or moving when you shifted the speed control lever? Naturally the drive belt can't compress so for the pulleys to close the pulleys need to be turning (I know, I know: Make a small hole in the top of the egg and create a vacuum!) Other thoughts: did you have oil in the hydraulic delivery pipe before installation (I'm thinking trapped air might take time to clear making the action poor) Also did you grease the two halves of the pulley? (Grasps at straws!) Good luck, Des p.s. I'm off out now to complete the last tasks and then fire her up for the 1st time in 2 years – it's minus 10c here (Austria) so lets hope it's a quick job.

Thanks for the reply, Yes I did try it while moving, made no difference. I'm sure there is a little bit of air in the system but it should still build up to pressure once its compressed. I gave it a very good cleaning and greasing before final assembly so its well lubricated.
From the research I've been doing there are a couple possibilities I can come up with. There is a max pressure relief valve in the speed control assembly that may be leaking or blocked open and bypassing, or the pressure coming off the lift/aux valve is bypassing internally before getting to the var sleed valve.
I'm behind the 8 ball on my 620 restoration and this 600 just seems too good to scrap for just a few parts so while the 620 is in pieces I'd like to use the 600 to clear the driveway for the winter. I just need to sort these couple of minor issues and I'm set for winter. once the other machine is done then I just might restore the 600 as well.
Thanks and hope your installation goes well
Tom.