K181 hone cylinder or leave it?

[Rustyred 63]

Hi all,

 

Simple question. We have just taken apart our Kohler 8 horsepower k181s engine. The cylinder looks beautiful with no scratches, it's shiny, and smooth as glass.

 

I have heard that it's good if there are some fine horizontal scratchings from honing in the cylinder to allow for oil to pass the piston rings for good lubrication. However, if the cylinder is as smooth and perfect looking as the one I have would you hone it or would you not?

 

Thanks for your advice. Rustyred

[oliver2-44 10,377]

If it is polished like glass that indicates there has probable been some metal wear i.e the original honing fine scratches have been worn off to leave a polished cylinder.  The amount of wear on the cylinder needs to be measured.  If you don't have the tools to measure the cylinder, take it to an engine machine shop or a friend that has the tools.  see the spec's for a k181 in this link http://www.smallenginesuppliers.com/html/engine-specs/kohler/k91_K141_K161_K181_K241_K301_K321_k341.pdf

[KC9KAS 4,744]

@Rustyred I have to agree with @oliver2-44. He gave you very good, sound advice!

[Rustyred 63]

Okay thanks for your advice.

 

I have a very precise digital caliper. Would that work for measuring the cylinder? Or is there a special tool for getting further down inside the cylinder?

[W9JAB 156]

Simple fix, use a "glaze breaker" to the cylinder,

fit a new ring set and put it back together.

The new ring set will require some fitting (cutting/grinding the open ends.)

The rings should seat quickly, and last a long time.

You can always go the full route, boring oversize, 

with oversize piston and rings.

but if the cylinder is in reasonable good shape it is not necessary.

[rmaynard 15,935]

I use a ball hone to break the glaze and put a nice cross-hatch on the cylinder. A smoothe cylinder will burn oil.

[squonk 42,610]

You need a cylinder bore gauge to check for out of roundness and taper. If the bore is out of wack to much, all the honing in the world won't fix it. Take it to a machine shop and have them check it.

[oliver2-44 10,377]

2 hours ago, Rustyred said:

Okay thanks for your advice.

 

I have a very precise digital caliper. Would that work for measuring the cylinder? Or is there a special tool for getting further down inside the cylinder?

 

When a cylinder wears it leaves a "eidge" of unworn area at the very top.  Unfortunately A dial caliper will onty measure that unworn area at the top.  

[953 nut 58,061]

The best measuring tools in the world will not do you much good if you are not proficient in their use. A cylinder bore gauge needs to be held exactly perpendicular to the cylinder wall and the slightest variation will give you an erroneous reading.

You can get a good idea of the condition of the cylinder by removing the piston and removing it's rings. Compress the top ring and insert it into the cylinder and use the piston to "square it up" at the top of the cylinder then measure the end gap of the ring. Use the piston to keep the ring square and move it about a quarter of the way down the cylinder and check the end gap at this point; also shine a light from below and look for the slightest light leakage past the rings (out of roundness check). Repeat this process at one half and three quarters and bottom of the cylinder bore. 

If there is any light leakage past the ring you have an out of round condition. If the  measurement of the end gap changes at all this is an indication of cylinder bore wear. In either case a hone won't do the trick and you would be well advised to take it to a small engine machine shop for proper measurement.

 

Edited August 27, 2017 by 953 nut

[Rustyred 63]

Ok.  Measurements have been taken. We took them at the top the metal and the bottom of the area that Rings run in. We took eight measurements at each level and averaged them. All the measurements were at the factory minimum. They have not even worn down toward the max limit. There is no light leaking through the Rings and cylinder.

 

Still, the cylinder is smooth as glass. What would you do? just leave it given that the diameters are at factory spec? Or put any other type of surface on it? Like honing?

 

Secondly, given that the measurements are what they are what do you bother replacing the Rings? Or just leave them after cleaning?

[briankd 819]

i always run hone thru cylinder to put crosshatch back in if it smooth the rings won't seat and will burn oil. least that is what i was told. last couple engines i done k181 and k301 i sent em to machine shop 40 bucks they checked em out bored them if needed  and honed all i done was put them back together. always install new rings if you pull the piston out cylinder better insurance now then latter when it has blowby and burns oil

[artfull dodger 440]

You need to measure at the very top, middle and bottom of the bore, NOT the bottom of where the rings ride, but the very bottom of the bore.  This is done in an cross pattern, ie twice in each location to check for roundness or lack there of.  A piston will "egg" shape the bore at the lowest point the piston rides over time.  This causes piston slap and other issues you do not want.  If the bore is out of spec anywhere, either in the roundness or bore diameter.  The block will need to be bored oversize and the machine shop will tell you how much so you can order new piston head.  They will then bore to match that piston head. This is the correct way of doing it.  In order to bore, the block will need to be bare, ie no bearings or valves installed.  So your are in for the full overhaul at this point.  Inspecting and grinding valve seats, lapping them back in, new seals everywhere ect.  Head inspection for flatness and if warped, it will need machined.  Half assing an engine overhaul is ust a waste of money and will bite you in the backside pretty quickly. Since you do not completely understand what your doing, get the Kohler engine book for the K series, its not expensive and will walk you thru every step to properly overhaul one of these.  From proper piston ring install(making sure the end gaps do not line up ect) to exactly how to measure that bore.  even tells you to the tools to have on hand.   P.S.   I have 30 years experience in small engine work on both gas and small diesel.    Mike   Oh yeah, if done right, there is NEVER a need to do anything to the new piston rings.  Rings are sized to common bore sizes, std(standard) and over size in several increments.

Edited August 27, 2017 by artfull dodger

[953 nut 58,061]

4 hours ago, Rustyred said:

measurements at each level and averaged them.

Oil burning and loss of power is not a mater of averages, it is a mater of weakest link causes problems! @artfull dodger is right on.

take some time and read and heed this thread.

This manual should help too.

Kohler_Guide_To_Engine_Rebuilding_19890900.pdf

 

[artfull dodger 440]

He needs to either download or purchase the Kohler K series service manual if he wants to do a correct and proper job on his engine, bar none.  IMHO its a book that should be in EVERY GT owners library if they own Kohler powered models.  It has everything from carb base settings, carb rebuild steps, engine rebuild and inspection steps, torque values and sequences for all the engines as not doing it correctly will allow head gaskets to blow again along with warping the head.  The book is invaluable to even someone who untill recently, made a life out of working on and fixing lawn mowers.  I still have all my books, Kohler K singles, twins, Magnum series, Command series, Courage series, B&S of all vintages, Onan, Wisconsin, Tecumseh, Clinton and Kawasaki gas.  Then I have Yanmar, Lombardini, Kubota and 6.2L/6.5L Detroit diesel service manuals.   Hard to set a computer on top of an engine in the bright sun light, but a book is worth its weight in gold more times than not.  Ok, off my soapbox.       Oh yeah, do not forget to check the camshaft end play with a dial indicator.  So many techs do that, then wonder why the engine knocks at mid RPM, also known as the "kohler knock".  Its the cam slapping back and forth in the block as it needs a shim kit from Kohler to return it to spec

[ohiofarmer 3,333]

I have a K-series 14 HP that measures out of spec even with the piston still installed, so I know I am in for the the great unknown at the unseen bottom of the bore. The bore appears as smooth as glass.The Kohler service guide mentioned above mentions additional things about the bigger engines with the counterweight that should not be overlooked. All this information is helpful in that it might serve as a checklist when discussing things with machine shops.Some of the piston is eroded away and it appears that it may be because the path of detonated fuel from the spark plug in the head traveling toward the bore sort of washed away the portion of the piston above the top ring

 

 It is very helpful that you guys have posted what to watch out for in rebuilding engines, but it is a bit scary to someone like me who has never done it before

 

 I am wondering if I would be better off having someone else do the assembly who has all the measuring tools needed to properly do the work, or just find an engine that is not as worn out as mine. I presently have installed a really nice 12 HP K series borrowed from a tractor that I tore down for a full repaint, and maybe i would be better off trying to find another nice motor . It just might make sense from a cost standpoint.

 

 I only paid $200 for the tractor,deck, and front blade, and the rest of the machine is in nice shape, so all is not lost

[Sarge 3,464]

Look around your area for engine machine shops and ask around at mower dealers - they will know who does quality rebuilds and uses OEM Kohler parts and will stand behind their work . We're lucky here as we have a shop that has been rebuilding Kohler engines for over 50yrs and never had a reputation problem . You get it done right , or they won't do it and ask you leave , now...!

 

Their is no real modern replacement engine the same physical size/weight/torque range of the Kohler K series engines , they are worth saving now before parts become completely obsolete and you're stuck with having to bastardize the tractor to fit a different brand/type engine . The only other engines available with the high torque curve and physical size are single cylinder diesels - their price tag will warrant rebuilding that Kohler the right way , the first time .

 

Sarge

[953 nut 58,061]

4 hours ago, ohiofarmer said:

 It is very helpful that you guys have posted what to watch out for in rebuilding engines, but it is a bit scary to someone like me who has never done it before

 

 I am wondering if I would be better off having someone else do the assembly who has all the measuring tools needed to properly do the work

Buying the tools to do it correctly could be expensive if you are only doing one engine. Check around to see if a local Community Collage or vocational school has an engine rebuilding class you could participate in. They would have all the tools and a knowledgeable person to guide you.

[Searcher60 209]

I believe that it is now necessary to always check behind your machine shop. Things ain't what they used to be. Not sure why honing is being discussed. Always hone not matter what, or the rings ain't never going to seat. I found out the hard way.

Edited August 29, 2017 by Searcher60