Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

Sign in to follow this  
427435

7790 oil burning

Recommended Posts

427435
As I've previously posted, I bought this tractor for $220 this summer knowing that it used oil. It blows lots of blue smoke and goes from full to add in about 2 hours. So I tore it down yesterday and found some interesting things. First, the cooling fins were totally blocked with grass and oil. Second, the oil ring on the front cylinder was completely worn flat. Third (and very surprising), there were no score or scuff marks on either the cylinders or pistons!! Right now, the cylinders are at a machine shop to see if just honing is necessary or if re-boring will be needed. There was very little wear noticeable running a fingertip over the cylinder ring area vs where the rings don't run. As pistons are about $200 more EACH than just rings, guess what I'm hoping for (although I doubt it will be). Here's a picture.
[img] http://i160.photobucket.com/albums/t178/427435/DSCN1030.jpg[/img]
A son and 2 grandsons on Old Smokey!!
[img]http://i160.photobucket.com/albums/t178/427435/AarontheBoysandOldSmokey.jpg[/img]

Share this post


Link to post
Share on other sites
UCD
The cause of your problem was the grass in the cooling fins causing it to run hot. i talked to a lombardini engineer a couple years ago. I told him my engine had over 5000 hrs on it a conservative estimate. he asked about how it started and compression. I told him it started on second or third time over, even in cold weather with a heat lamp as the preheater didn't work. I also told him all this tractor did was blow snow, I never mowed with it. He told me that was the reason the engine has lasted so long was because I did not mow with it. The grass clipping get in to the fins and people didn't clean them causing the engine to run hot taking the temper out of the rings causing them to burn oil. He also told me when looking at a use engine that was not running in a tractor to pull the exhaust manifold off and rub my fingers inside of the manifold ports. If it was black and dry it was a good engine. If it was black and oily the engine had bad rings and low compression. I bought a used engine and checked it that way. It was a good engine and went into a friends GTHL-17 that had a blown KT17.

Share this post


Link to post
Share on other sites
427435
That's what I thought happened also. What still is surprising is that it got hot enough to do take the temper out of the rings but not score up a piston/cylinder.

Share this post


Link to post
Share on other sites
427435
Update. The machine shop said there's only .001 wear so no need for spendy new pistons. The rings are still $100 per piston!! The machine shop wanted to know if the rings would be moly or cast iron (changes how he would hone it). After a couple of calls, got an engineer at Kohler that says they're cast iron. Rings should be here in 3-5 days and the cylinders should be done tomorrow. Maybe I can get it done before winter is over and use it on the snow thrower!!

Share this post


Link to post
Share on other sites
crankyyankee
Nice tractor!!! I am using the snowthrower now and its awesome!! You will love it ..I think someone on here uses the mobil 1 and has very good luck with the engine longevity. I use rotella diesel for now. The mobil one is probably better but i dont know what type of mobil one he was using..I think it was UCD?

Share this post


Link to post
Share on other sites
427435
quote:
Originally posted by crankyyankee
Nice tractor!!! I am using the snowthrower now and its awesome!! You will love it ..I think someone on here uses the mobil 1 and has very good luck with the engine longevity. I use rotella diesel for now. The mobil one is probably better but i dont know what type of mobil one he was using..I think it was UCD?
Thanks. I plan on using Mobil 1 5w-40 diesel oil. There are stories about not breaking in with a synthetic, but I've never understood the logic of that, and I have a car in the garage that came from GM with Mobil 1 in it.

Share this post


Link to post
Share on other sites
UCD
The logic for not using synthetic for break in oil is that it is supper slipery and takes a long time for the rings to wear in to the cylinder wall. The same for chrome or plasma rings as they are harder than the cast iron rings.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×