K181 rebuild

[bwcollins 1]

Hey guys, I have a 1977 B80 that was running decent but blowing puffs of white/grey smoke during throttle changes. The plug would have oil on it after a while but run.There was no smoke when just normally running. The piston had no cleaned off area near the edges that would indicate a lot of oil being burn. When I pulled the piston the oil ring appeared to be stuck and not moving freely. I measured the cylinder and came up with the attached measurements. My predicament is that I really don't want to machine the bore as the crank and everything else looks good, valves just need re lapped. Would I be ok with just new piston/re ring instead of a bore. Cylinder is in great condition just appears to be glazed? Opinions? Options? I have no money in this tractor so I don't want to dump a bunch into it right now when I have others. 

[gregg'shorses 77]

Download yourself a service manual here      http://kohlerengines.com/manuals/landing.htm                                         page 8 says max wear limit   2.941"

Edited June 10, 2016 by gregg'shorses

[Shynon 7,435]

My  cylinders are bored to fit a piston, that is why a machine shop will not bore a cylinder without a piston (if the do it without a piston I would find a different machine shop). In my opinion putting in a new piston without boring the cylinder will not fix your problem. You could possible hone the cylinder if it is not out of round and install new rings but in the end it will not last as long as a fresh engine. Total cost for a complete engine kit and boring is less than $200

[bwcollins 1]

If you look at the numbers bottom of cylinder is good, and just more worn in middle.... I was pondering a hone and new rings but wanted some opinions 

[953 nut 51,464]

If you were to hone the cylinder and put in a new set of rings it would be an improvement over what you have, but can't say how long before you would be wishing you had done it right the first time. If you will just be putting around at shows and in the yard it would probably be OK, but if you plan to work it I think you would be a lot better off to go with the over-sized piston. 

[oldredrider 2,547]

IMO, Since you say the oil ring was stuck, and the measurements you gave are "within tolerance", and you don't want to have it bored, give it a good hone and new rings. It should serve you well until it does need to be bored and a new piston...just run a good quality oil in the meantime. Let us know what you decide to do and the outcome. 

[slammer302 2,154]

I've just put a new piston and rings in Kohler k181. On a no name wheel horse 8 4speed. It seemed to work just fine.

[bwcollins 1]

Any opinions on an .003 piston in this build? Versus boring the cylinder, or stock piston/rings?

[953 nut 51,464]

6 hours ago, bwcollins said:

.003 piston

Typicality over-sized pistons com in .010, .020, .030 and .040. The cylinder needs to be concentric around the piston through the entire stroke. Most cylinder wear takes place about half way down due to the forces applied by the crank shaft and connecting rod. If you don't plan to have the cylinder bored then hone it, use the standard piston and a new set of rings. 

[squonk 38,842]

I don't know what machine shops are like in other areas but around here if I took that block in to have it checked they would want to bore it. They have to guarantee their work  and don't want to take chances on anything. Again if it's a put around at shows /yard tug you could probably re-ring it. But if it's going to be your everyday mower/ snowplow, at least take it to a shop for their opinion.

[slammer302 2,154]

12 hours ago, bwcollins said:

Any opinions on an .003 piston in this build? Versus boring the cylinder, or stock piston/rings?

.003 over piston rings sets can be very pricey. No one aftermarket is making them 

[953 nut 51,464]

Here are a couple of reference pieces that ma be handy to have.

Kohler_Guide_To_Engine_Rebuilding_19890900.pdf

Kohler Single Cylinder Engine Specs _ Torque Values and Sequences for Fasteners _ Identification & Torque Settings of Most Commonly Used Grades of Bolts (1) (1).html

[bwcollins 1]

Jut to add, This tractor is not going to be my main tractor, its just going to supplement my 310-8 and i was just hoping to get it freshened up. I didn't notice much oil consumption before other than normal for an all original 77 engine... I just don't want to take the crank and bearings out when they seem good to go, Still torn on what to do, but thanks for the tips so far,

 

[JPWH 5,295]

I'm am not a motor builder but after just finishing a k181 rebuild if I were in your shoes I would do a total tear down and check everything. Not much more work and then you know exactly what you have. Then you can make your choices without any assumptions or guesswork.

Jay

[prondzy 3,867]

You are already at your max out of round in the top (this is where your oil is blowing by. Honing and deglazing cylinders does not fix out of round. Looks like you need to rebuild, (trust me you won't regret the investments in your backup tractor). But it kinda sounds like you have made up your mind about the complete rebuild.

[bwcollins 1]

Just an update, I am sure it will irritate some of you guys but it just boiled down to being curious on how long it would last without a bore. I also cleaned up, re lapped, and adjusted with valves a bit too. 

 

I will re bore the next time but I just put a cheap Stens piston and rings in it, It only smokes slightly on a throttle change, and mowed my 3/4 acre the other day with no noticeable change on the dipstick and went up and down my ditches without a hiccup from the little 8hp. Running 30 weight oil but may switch to 40 to see if it changes it. Thanks for the advice, You guys give the textbook answers however I have rebuilt several kohlers prior to this but they have all been in spec.... so I wanted to see what would happen!

Edited June 26, 2016 by bwcollins
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