Ym220 with low compression

[peatpatrick]

I purchased my tractor about a year ago for a very low price off CL. The electrical was so bad I removed the harness and have started over, I'm pretty adept at electrical stuff though. A month ago I was mowing and as I was going up the first hill it died and I couldn't get it started back up, it has always been very difficult to start though. I towed it back to the shop and finally did a compression test: cyl 1=400psi, cyl 2=200psi, cyl 3=400psi. I don't think I have any valves stuck open and judging by the blow-by I think my rings are bad. also I've had no noticeably mixing of fluids. I'm going to take the head off soon and explore. Any suggestions on what to look for or other tests to do before i remove it? should I try and open up the lower half too? I haven't looked to see how hard it is to remove the oil pan, but if the rings are bad I'll have to figure it out right?
Thanks
Pete

 

[winston1]

Yes, the pan will have to come off too. From your blow by and low compression I think you have pretty much diagnosed your main problem. The 220 is a sleeved engine. You will have to wait until you open it up to know just how far you need to go. Head condition, sleeve condition, bearing and crank condition, all that will have to be looked at. Probably get some better advice from some of the more knowledgeable contributors.

 

[kenmac]

You will have to wait until you open it up to know just how far you need to go.

pretty much sums it up. May as well do a complete rebuild once you'er in there. head, rings, bearings,etc,. if you take a short cut, you may have to go back in at a later date

 

[peatpatrick]

My wife and I just a baby so I've been unable to work on the tractor. I started the dis-assembly and so far it looks better then I would have thought. Or at least the gasket was in good shape. Should I do anything to the head or just clean it and continue? I was considering Lapping the valves and putting new seals on and also maybe taking it to a cylinder head shop to be checked over.

I'm expecting then that my problems came from the bottom half, I think my pistons will have broken ring journals when I get them out tonight.
One question though, Can Hone first and then take my measurements in the cylinders? or do I need to measure first?

 

[winston1]

You can measure before or after. You are not wanting to hone enough to remove metal. Just enough to put cross hatching on the liners. Can't tell much from your picture. Do you have a ridge at the top of the liner that you can hang a finger nail on?

If it were mine I would give the valves and seats a good inspection keeping them in order, use a straight edge on the head to make sure it is not warped, and install new valve stem seals. If all looks good I wouldn't take it to the shop. I am a cheapskate and sort of trust my judgement on head condition. So you will have to determine what would be good for you.

 

[peatpatrick]

Thanks Winston1, that was the advice I was hoping for on the head.
The cylinders do have a very slight ridge at the tops, I can't tell yet if its the metal or just carbon build up, thus the honing question. I will try a gentle cleaning and check for the ridge with better light this evening.

 

[winston1]

As Cardoc has advised before he prefers a dingle berry hone if one is available. Might read his post #s17 and 18 in this thread explaining why. http://www.tractorbynet.com/forums/yanmar/281240-ym-1700-head-gasket-2.html

Got to thinking about it Cardoc. I am hoping you understand I am just repecting your advice and passing it on. Hope you don't mind.

 

[peatpatrick]

Okay so this morning before work I got the pistons out. #2 was in pieces and the cylinder wall is equally as bad

Pistons 1 and 3 looked fine with the slightest of burnished edges on the rings and bearings (will replace anyways)
But the cylinder walls look rough, Should I even bother measuring them? or just spend the extra $$ to replace?

They all have a slight ware ridge at the top, very slight though, its hard to feel but I can see it with a light from underneath.
I'm breaking the bank.... my wife hates me

 

[winston1]

Replacement of the liners would be great, but at nearly $90 ea you may have to look for a new wife.
No doubt, even going as conservative as possible you are going to end up with a pretty good total. If you fix it right now it should last your lifetime if taken care of. Makes me wonder if someone has used ether in starting with the broken piston lands.

I don't know if you have a manual or not. I can help you with tolerances and so on if you need.

 

[kenmac]

buying used is like a opening a box of chocolates. You never know what you're going to get. We've all been bitten (I know I have).Like Winston says. If you bite the bullet now and repair it right, It will last you a life time:thumbsup: