Compression Valve

[chauke]

I recently purchased a Yanmar 1500 tractor. When I was doing some reading up on starting/operating a tractor since it is my first tractor, I saw a Youtube video where they used the compression valve when starting the tractor. When I checked out the tractor before I bought it the previous owner didn't use the compression valve when starting it, so I just assumed it didn't have one. However, later I noticed it did have one and mentioned it to the previous owner. He didn't realize it even had one. It seems like I should use this when starting it from now on. However, I am concerned that since I don't know the last time it was used, if I do start using it could it fail so it would be stuck in the "exhaust valve partially open" position and then I would be unable to start it.

 

[jaxs]

I'd be skeered to touch it.

 

[Jerry/MT]

I recently purchased a Yanmar 1500 tractor. When I was doing some reading up on starting/operating a tractor since it is my first tractor, I saw a Youtube video where they used the compression valve when starting the tractor. When I checked out the tractor before I bought it the previous owner didn't use the compression valve when starting it, so I just assumed it didn't have one. However, later I noticed it did have one and mentioned it to the previous owner. He didn't realize it even had one. It seems like I should use this when starting it from now on. However, I am concerned that since I don't know the last time it was used, if I do start using it could it fail so it would be stuck in the "exhaust valve partially open" position and then I would be unable to start it.

It's something you can use for a start in cold weather. I have one on my Kubota M4500. It located in a position where you have to open the battery compartment to get to it. The Kubota Work Shop Manual and the operator's manual don't even mention it so I doubt it was ever used. I tried it several times but I rarely use it. It would check it out and consider using it for cold weather or low battery starting.

 

[rScotty]

I think you mean "decompression", not "compression valve". And I believe what you refer to is the control - usually a lever or knob on the dash that you could operate (pull) when cranking the engine. It's a control that holds the exhaust valve open on one or more cylinders whlle the starter is cranking the engine. It reduces engine compression and is useful for weak starters or cold weather. But if your engine starts without it just ignore it.

If you do want to use it - and you might in the winter - there is an adjustement for how much it opens the exhaust valve and also you need to check that the cable that operates it allows the exhaust valve to return to the proper position with freeplay when the engine is running.

good luck, rScotty

 

[chauke]

Thanks for all the replies! Yep, I meant decompression valve (control). I live in Alabama so it rarely gets really cold and just bought a new battery so I think it should be fine not using when I start it (unless I do crank it up when we do have a cold snap). Thanks again for all the info b

 

[Vigo327]

To me, its one of the things you want to move every once in a while whether you need to or not, just to make sure the linkages or cables don't seize in place.

I use mine frequently, for no good reason. I just let the engine spin up to cranking speed before pushing it back in and the tractor starts easily. If that was the only way i could get the tractor to start it would be a sign of a problem (it is not cold here in South Texas..) but i just use it to lessen the demand on my battery while cranking. If one had no battery or starting system or fuel system or compression issues, in other words nothing wrong, you would essentially never NEED to touch it, thus the reason lots of them get seized in place or owners don't realize they exist.