Piston and Cylinder scoring on my LTD :(

[shizznats]

So with the new forum and all, I'll recap my situation and my recent unfortunate findings in my 81 LTD engine to see if you guys have any advice...

I picked up a 1981 LTD 440 for $100 off craiglist a few months back. It sat outside for about 4 years straight so it needed a lot of work. I took out the motor and got to work on it. First thing I did was remove head and cylinders to inspect everything. There was some gunk and carbon buildup which I cleaned up and then replaced the cylinder base, head, and intake gaskets amongst a few other things. After that, I had some trouble with the carbs but got everything sorted out and last week I had the engine running. I was running on premix since I wasn't sure about oil pump, but did the output test and oil pump checked out. Also put water in the cooling system and confirmed the thermostat opens up water pump works. Everything was going great. That is until I noticed water seeping from the cylinder base gaskets on the exhaust side >..< Today, I took everything apart and couldn't believe what I found... pistons, on the intake side, were scored... the right one actually has a flat spot on it which you can even see in the picture below. Exhaust side looked alright; just some browning. Cylinders have slight scoring... there are a few spots I can feel with my fingernail... again, worse on that right hand side. I have no idea what caused this as I was running on 40:1 premix the whole time I was working on the engine and test running it.

Based on all this, what advice would you guys give me? I'm guessing pistons are beyond saving, but do I need new cylinders as well? Thanks in advance!

[gixxer6]

Did you change the crank seals when you had the motor apart?  If not, change them. 

Being that you had a coolant leak around the base gasket, it would be safe to assume you were also leaking air.  This would make it run lean, and could cause this damage. 

[shizznats]

Thanks. We did change the crank seals but we didn't do a good job with the cylinder base gaskets so it's our fault they were leaking. At this point, based on what you see in those pictures and what I described, what would be our best option? The cylinders have some scoring that can be felt with a fingernail but I know that since these are chrome plated cylinders, reboring/honing is not possible or very expensive. Can we leave the cylinders as they are and just change the pistons and rings? If we do just put new pistons in there, would it be better to leave the old rings (assuming the end gaps are to spec) since they are seated to the cylinders, or is it better to put new ones? Only reason I ask is with new rings, the cylinders usually have to be honed so the rings seat properly and I'm not sure we can do that...

Any advice is much appreciated. Thanks!

[gixxer6]

IMO, at a minimum, change the piston and rings.  I have lightly honed chrome cylinders with success. 

Don't use any sealant on the base gaskets when you put the motor back together. 

[jimvw57]

The key here is "lightly honed" If there was decent compression before you pulled it apart, you could get away with it but you might want to start watching for replacement parts..

[Trucker]

carefully use "the works" toilet bowl cleaner to take any aluminum off the walls where its scored and then check for grooves

[shizznats]

Is this like muriatic acid... is it as effective? I've heard of some people using liquid plumber but most say muriatic acid is the way to go

[Trucker]

It has muriatic acid in it.

[ChaChi]

I have talked with several snowmobile guys in detail about the cast iron bores that a lot of these LTD's seem to have been fitted with over the years and although it will work for a while cast iron bores and cast iron rings really aren't a good  idea in an LTD... From the factory I believe they came with a chrome bores and cast iron rings...

Although others may disagree from what I've been told by people in the business for 20 plus years, you want chrome bore/or nikasil with cast iron rings or a cast iron bore with chrome rings... If anyone has a source for chrome rings for an LTD please post it up as my local supplier is no longer in business and would love a new supplier...

I agree with everything else said, good crank seals are a must and the new ones don't seem to last like the originals did, because the originals had a metal wall while the new ones are plastic. LTD's are very picky about how they get put together... I really don't like the bolted on head, especially reusing bolts many times... I would recommend going and getting some copper washers for the head and follow the torque spec to a T! Re tourquing the head is also a good idea after a heat cycle or two!

If you really want a two stoke to last run an EGT gauge! They're not cheap tho!

Good luck!

[jimvw57]

On Invaders, the head and cylinder studs will stretch over time. This can let the acorn style nuts used bottom out and it will appear that they are torqued tight but they are only tight to the top of the studs, and the cylinders are not tight. Adding a thick washer will help this from happening (more room  inside the nut)

true about the chrome rings on a steel bore or steel rings on a Nikisil (or chrome) bore.

[gixxer6]

Here is the info about ring compatibility.  This is from Wiscoe's website. 

All Wiseco rings can be used in cast iron, nickel ceramic platings (Nikasil), boron composite, and Electrofusion bores.
CAUTION: Unless otherwise noted, Wiseco rings can NOT be used in chrome plated bores. Engine damage will occur.
*CSM & CDM rings are designed to be used in chrome bores.

CSM:  Nodular iron, phosphate coated, internally notched
(for use in • Chrome Bores)
CDM:  Nodular iron, phosphate coated, internally notched
(for use in • Chrome Bores)

[Interceptor398]

Cast iron rings for chrome bores!

[shizznats]

Thanks for the replies! The cylinders turned out to be ok, so I bought these aftermarket pistons/rings and put them in the engine today:

http://www.ebay.com/itm/120817720787?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Not sure what the rings are made of, but they were black which I thought was interesting. The problem is that I'm only getting 90psi of compression on each cylinder when I should be seeing closer to 120 or 130. Is it normal to see low compression after putting in new pistons/rings before running the engine? (I put plenty of oil on cylinder walls and pistons/rings) Thanks!

[Interceptor398]

Not sure about the Ebay listing showing John Deere and LTD together. I'n not aware of any John Deere sleds that would use the larger rist pin of the 81-82 LTD?  As for compression it should go up after they seat.

[shizznats]

Yes, the title is a bit misleading but I found out that those pistons do indeed have the larger wrist pins. They were identical to the old pistons I pulled out and fit perfectly. The part number is 8072 for these pistons. I believe they are the only aftermarket pistons for the LTD out there.

Good to hear about the compression.. going to start her up in a few days. Is there a certain break in procedure for these engines that I should follow? Thanks!