MTD YARD-MAN RIDE 4145 - drive issue

[harrym1byt]

We have had a few issues with this over the years, all of which I have managed to solve except this one.

It has seven speeds plus the 'handbrake' on a setting lever on the right. It normally drives the wheels fine, unless I try to use the faster speed settings or so it seems. What happens is it will then drive for a while then the drive seems to just stop. Engine continues at the same speed, but no forward progress. If when this happens, I press and release the footbrake, normal forward progress resumes. It seems that anything I change (forward/reverse, speed) also causes normal progress to be resumed.

I'm finding it difficult to diagnose, because obviously it doesn't happen except when sat on it, when it is impossible to see what is going wrong.

Your ideas and suggestions please?

 

[harrym1byt]

I've just checked the drive belt, replaced last year and all seems well. No tension on it in P, tension applied at 1, pressing brake pedal releases tension. The only oddity (maybe) is that there is a lot of tension on the speed lever from P up to around 3 or 4, but not much between 4 and speed 7. This is with engine off and the rear end of the machine raised up in the air to be able to see below.

 

[harrym1byt]

A little more progress in trying to work out how it works, but none with regards to the problem...

From the top again..

Its difficult to be able to see very much, due to its drive system being close to the ground, but there is no obvious fault...

It has 7 speeds of progress, set by a control which has P then 1 to 7. P applies the brake and releases the tension on the v belt.

The drive is via two V belts, one from the engine to the middle dual pulley, then one from that to the diff at the back. The dual pulley is controlled by the above mentioned drive speed control, which allows the pulley centre to move up and down to form a variable gear ratio - rather like a moped or a DAF variable gear drive, except the highest gear ratio is set by the 1 to 7. The pulley centre part is like two shallow cones shapes, back to back, so as the diameter which one belts travels around increases, the diameter for the other belt decreases. The 1 to 7 just limits how high a gear is available and hence the speed.

The foot brake, applies the brake and also releases the tension on the V belt, just as for P.

The engine runs at a constant speed set by a throttle control.

Now for the problem...

It drive around happily, then drive is slowly lost. Press the clutch /brake and it continues again to drive for a while further - which suggests the belt is slipping. However the belts are like new and as near as I can tell the spring applied tension is correct. Obviously its impossible to see what is happening, because it only happens when on the move. There is no sound as if the belt is struggling for grip, it just stops moving and the drive feels good and solid once fixed temporarily by pressing the brake pedal.

 

[Fish]

You just have something a tad rusty on the vari-drive setup. Once moved from "P", the belt should always remain tight, and the next time you drive it, move through the gears without depressing the pedal, the belt tension is what makes the gears move.
The double sheaved pulley moves up and down to mimic "Gears", so you need to get under there and see what is hanging up when you move the pedal.