tntatro 181 #1 Posted July 8, 2019 Hello, I have a K181 to rebuild and it is a standard bore. The bore measures at about 2.9405 and the max wear limit is 2.941. Also, there are light score marks that would not hone out with a ball hone. The pictures show the scoring on the front and back of the cylinder. Is a cylinder in this condition normally rebored? The last K181 I rebuilt had a similar bore and I didn't rebore it. I installed used piston (new rings) and used rod and the valve guides were a bit worn and that engine runs good but let's out a puff of blue smoke on cold startup. Also, the crank pin was worn to its max wear limit. This rebuild has many new parts and the crankshaft is good, I just have to decide whether to rebore it or not. I picked up a new standard OEM piston for $30 just because it was a good deal but wasn't sure if I should use it on this one. 2 1 Share this post Link to post Share on other sites
953 nut 58,697 #2 Posted July 8, 2019 If you plan to work it hard on a regular basis it would be reasonable to spend the extra money for machining and a piston with rings. If it is going to be used as a cruiser to go around the shows and haul a wagon load of grand-kids then that cylinder should do well for you. 1 1 Share this post Link to post Share on other sites
tntatro 181 #3 Posted July 8, 2019 That makes sense. I'm just rebuilding some engines I got a decent deal on. With this one I guess it's best to rebore because it's getting new bearings and everything. Share this post Link to post Share on other sites
squonk 43,013 #4 Posted July 8, 2019 These engines get egg shaped cylinders a lot. Best to have a machine shop check it 1 Share this post Link to post Share on other sites
tntatro 181 #5 Posted July 8, 2019 7 minutes ago, squonk said: These engines get egg shaped cylinders a lot. Best to have a machine shop check it It is out of round but not outside of the wear limits according to the manual. I just found a new Kohler .010 piston kit for just under $45 so I ordered it. This engine is getting an all OEM new old stock rebuild (piston, rod, bearings, valves and even gaskets and seals are OEM). I managed to find decent prices on NOS Kohler parts on eBay. 1 1 Share this post Link to post Share on other sites
moe1965 752 #6 Posted July 9, 2019 Not sure but I was rebuilding a boss 302 some time ago and the machine shop miked each piston for each hole or bore it was going into. Not sure if this would have to be the same for the piston you bought to match the proper clearance in the block on the tractor. I would not just put that piston in and hope for the best. Just my 2 cts 3 Share this post Link to post Share on other sites
ZXT 2,401 #7 Posted July 9, 2019 56 minutes ago, moe1965 said: Not sure but I was rebuilding a boss 302 some time ago and the machine shop miked each piston for each hole or bore it was going into. Not sure if this would have to be the same for the piston you bought to match the proper clearance in the block on the tractor. I would not just put that piston in and hope for the best. Just my 2 cts It's recommended that you bring the piston with you when you're having something bored, even small engines, so that the tolerances can be set up properly. Definitely a good thing that he bought the piston before taking it to have it bored. It may not be that critical being that its an OEM part, but I know that the tolerances on knock-off parts aren't always what they should be Share this post Link to post Share on other sites
tntatro 181 #8 Posted July 9, 2019 The local machine shop bores to spec. They did my first rebuild on a k241 and it turned out great so far. I asked if they needed the piston first and he said they just bore to spec. I ordered the parts from them so they probably checked everything. Seems to run perfectly. I'll be re boring this one myself and doing the valve seats. 1 1 Share this post Link to post Share on other sites
ZXT 2,401 #9 Posted July 9, 2019 4 minutes ago, tntatro said: The local machine shop bores to spec. They did my first rebuild on a k241 and it turned out great so far. I asked if they needed the piston first and he said they just bore to spec. I ordered the parts from them so they probably checked everything. Seems to run perfectly. I'll be re boring this one myself and doing the valve seats. How do you plan to bore it? Share this post Link to post Share on other sites
tntatro 181 #10 Posted July 9, 2019 I have a Sunnen AN cylinder hone. I practiced on a cracked block and a badly pitted block and now I think I can get pretty close. Share this post Link to post Share on other sites
squonk 43,013 #11 Posted July 9, 2019 (edited) 7 hours ago, moe1965 said: Not sure but I was rebuilding a boss 302 some time ago and the machine shop miked each piston for each hole or bore it was going into. Not sure if this would have to be the same for the piston you bought to match the proper clearance in the block on the tractor. I would not just put that piston in and hope for the best. Just my 2 cts Exactly. Every piston is different. You need the piston to be fitted to the cylinder. Pretty close might not be close enough. Edited July 9, 2019 by squonk 1 Share this post Link to post Share on other sites
tntatro 181 #12 Posted July 9, 2019 That's why you use a bore gauge and micrometer. Share this post Link to post Share on other sites
