Searcher60 209 #1 Posted May 5, 2017 I am replacing the piston while rebuilding my K-341, because it is worn .001 below the minimum specs that Kohler says are required to maintain the required 003-.005 cylinder wall clearance. My old .020 piston measures 3.764. Now, the new piston, both Style C, measures .002 smaller than my old worn out piston at 3.762. So much for Communist Chinese junk. You people put this junk in your rebuilds without even checking it for size, and the Commie bastards know it. Guess I have to pay $300 to get a piston from Kohler. Kohler don't even make them any more, and neither does Stens. Not sure where to go from here. Maybe my machine shop can knurl it up to size. Comments? 2 Share this post Link to post Share on other sites
WHX?? 51,825 #2 Posted May 5, 2017 Not quite sure what yer beef is about here Searcher ...Don't like it don't buy it I guess??? Share this post Link to post Share on other sites
Searcher60 209 #3 Posted May 5, 2017 1 minute ago, WHX11 said: Not quite sure what yer beef is about here Searcher ...Don't like it don't buy it I guess??? I don't have a beef "here". Problem is one doesn't know until after they buy it and it is shipped half-way across the country that the parts are not up to specs. size wise. My beef is that they send junk over here because they know they can get by with it because Americans are basically ignorant stupid. Share this post Link to post Share on other sites
WHX?? 51,825 #4 Posted May 5, 2017 Agreed searcher..let's not help them out and keep our calipers close...and send back the stuff that doesn't measure up. 1 Share this post Link to post Share on other sites
oldredrider 2,553 #5 Posted May 5, 2017 The last piston I got was .002 undersized. Not a big deal because the cylinder was getting bored. I didn't mic it prior to boring, but my machinist let me know for future reference. 2 Share this post Link to post Share on other sites
953 nut 60,166 #6 Posted May 5, 2017 You bring up a good point, that is why it is important to have the parts in hand prior to having the engine machining done. Know that is not the case here as yours was already done. 3 Share this post Link to post Share on other sites
oldredrider 2,553 #7 Posted May 5, 2017 Searcher, since the K-341 is such a great engine, you may want to consider having it sleeved and put back to the original bore, or to match bore of the piston size. 1 Share this post Link to post Share on other sites
Searcher60 209 #8 Posted May 5, 2017 That seems to be my only option, my bore is perfect according to the Kohler manual and machine shop, but, it does not fit the Communist made smaller new piston I have. 1) I can exchange this new .020 piston for an .030 piston, and have my block bored to fit the new .030 piston. 2) I can put the old piston back and live with it being .001 under spec.. This would also require buying $95 Genuine Kohler rings as I cannot find any Communist junk rings for this piston. 3) I can find a .020 NOS Kohler piston with rings, and hope that it is the size that their literature says it is. Cost $275 plus shipping. Share this post Link to post Share on other sites
Searcher60 209 #9 Posted May 5, 2017 1 hour ago, oldredrider said: The last piston I got was .002 undersized. Not a big deal because the cylinder was getting bored. I didn't mic it prior to boring, but my machinist let me know for future reference. That's about where I am. The new .020 piston is about .003 under the minimum new size listed in the Kohler manual for a new piston. If I use the new piston, I would have .008 piston to cylinder wall clearance. Kohler says .005 maximum. It sucks. Share this post Link to post Share on other sites
WHX?? 51,825 #10 Posted May 5, 2017 1 hour ago, Searcher60 said: $95 Genuine Kohler rings Where you buying your rings.. I just got a genuine Kohler .030 set for $14.95 & free ship. Seller was kleen1dog on that popular auction site. By mistake I had ordered a aftermarket stock size from Pats small engine.and while they might have worked they were no where's near the quality of the Kohlers. VinsRJ has a youtube where he dissects the quality of aftermarket kits. Share this post Link to post Share on other sites
6bg6ga 272 #11 Posted May 7, 2017 (edited) Going to throw something into the mix here. This is an aftermarket piston, correct? Ever think of contacting the manufacturer and seeing IF they figured the thermal factor in. In other words SOME piston manufacturers some pistons don't come to their true diameter/size until warmed up. I for one would have no problem putting that engine together. I would start it and let it run and I don't think you would hear any piston slap BUT if you did hear something I would bet when the engine warmed up the noise would go away and the fit would be right. Some of the newer alloys some of the newer aftermarket pistons are designed for thermal expansion. If this bothers you have your machinist knurl the piston skirt and this will bring it back into spec. You can do this on a lathe. Just support the skirt. Edited May 7, 2017 by 6bg6ga 3 Share this post Link to post Share on other sites
Searcher60 209 #12 Posted May 7, 2017 I have emailed the piston manufacturer and have not heard back yet. If that is the case, then how does a machine shop know how much clearence to allow when boring? There is no info that comes with the piston. Tomorrow, I will probably attempt to call the manufacturer. That call ain't going to be cheap, $3.47 per minute. When i restored vintage cars and motorcycles, I ran into this kind of crap all the time. The Taiwanese and Chinese are very capable of manufacturing a piston to any size someone wants, but not for the money that American greed suckers want to pay. It cost more to maintain tighter tolerances, and with the much cheaper, much larger tolerances, they are going to error to the smaller size to prevent returns. That is why I now have all my measuring tools. I am also going to attempt to get a genuine Kohler piston tomorrow. These situations are all about profit, money, greed, and laziness. Sure, I can stick it in the hole, but I want it right. I ain't playing these BS, anti-American, communist, Wall St. greed, blood sucker games. Share this post Link to post Share on other sites
6bg6ga 272 #13 Posted May 8, 2017 GM has used cam ground pistons in engines for years. I especially remember the ones used in the 1994 -1997 Z-28 LT-1 engines. Most engines were noisy when cold until fully warmed up. I'm sure you all have formed an opinion but like I said I'd put it together with a slight knurl on the piston. I would double check the piston to wall clearance because most aren't capable of using measuring tools without making a mistake. Share this post Link to post Share on other sites
Fordiesel69 271 #14 Posted May 8, 2017 One thought here, using the Chinese junk works as long as your machinest measures the parts and sizes the bore correctly to match. If you are just slapping the piston in, you may not have a good fit. I would just get the .030 china piston, and have the cylinder bored to fit it perfect. Get rod checked and crank machined if needed. Run a great diesel SAE30 or SAE 15w40 every 25 hrs, not an hour more, and you will never have to rebuild again. The china alloy does hold up well. 1 Share this post Link to post Share on other sites
Butchc 2 #15 Posted May 8, 2017 Hi, new to this site but I operate a shop and have been using the aftermarket parts from Rotary for years without issue, probably 30 K series overhauls out and running. You guys are correct in that the aftermarket pistons will at the least be on the small side of the OEM spec and some run under but it has never been a problem with me because in my experience the bores wear more than the pistons and need to be oversized anyway. I would get a 030 piston and have the block bored/honed to give proper clearances. Will still be cheaper than an 020 OEM piston and you will have a better job due to the new bore. 1 Share this post Link to post Share on other sites
Searcher60 209 #16 Posted May 8, 2017 The ring end gap with the new .020 rings is over .030, slightly more than the old rings. Those old rings have a lot of hours on them. Share this post Link to post Share on other sites
aHorseofCourse 261 #17 Posted May 8, 2017 The Chinese kits are very tempting but you get what you pay for, just like everything else. I just rebuilt a Briggs twin and spent a lot of extra time and a few more bucks finding oem parts. But you know what, it went together without a hitch. Worth the extra time and money in my opinion. Plus most of them were made in the good old USA! 1 Share this post Link to post Share on other sites
6bg6ga 272 #18 Posted May 9, 2017 On 5/5/2017 at 5:47 AM, 953 nut said: You bring up a good point, that is why it is important to have the parts in hand prior to having the engine machining done. Know that is not the case here as yours was already done. Probably the best post here. even if using what you consider to be sub standard parts. Rule of thumb in my neck of the woods is to take the piston in with you so the cylinder can be bored and fitted correctly. Its easy to blame China for cheap parts but in the end the owner the purchaser of the parts is the one responsible. Note here* If I were the one boring the cylinder I would have insisted on having the piston. Maybe your little machine shop is good and maybe it isn't but one cardinal rule has been violated in my opinion. As to ring comments.... I've used ring sets in small block chevy engines that were in excess of $100 per cylinder. Always fitted correctly and only marginally better than a cheap TRW set. You need to remember its not a high RPM engine and cheap simple cast irons rings will work fine. I don't think anyone has dyno tested a one cylinder engine and found a drastic increase in horse power as a result of higher dollar rings. If you do come across an article on this please do post it. 3 Share this post Link to post Share on other sites
Butchc 2 #19 Posted May 9, 2017 On 5/7/2017 at 4:37 PM, Searcher60 said: how does a machine shop know how much clearence to allow when boring? There is no info that comes with the piston. Kohler provides manuals on line free of charge. The K series shop manual is here http://resources.kohler.com/power/kohler/enginesUS/pdf/tp_2379.pdf K-241 clearance with new bore and piston should be .007-.010 I shoot for .007 myself. As they said, have your 030 piston in hand and the spec and take both to your machine shop.. Share this post Link to post Share on other sites
Searcher60 209 #20 Posted May 12, 2017 Today, I ordered a genuine Kohler piston, rings, and rod. I just do not believe that the aftermarket parts are up to the same quality level as the genuine Kohler. That being said, the aftermarket parts will no doubt function. But, how long will they last in a working tractor, how much oil will it burn, and how much extra noise will it make? I may do another thread comparing the differences in weight of each component, and size, Kohler vs. aftermarket. To create a YouTube review video of aftermarket parts based on looks and the type of wrapping paper is basically worthless in my opinion. 2 Share this post Link to post Share on other sites
6bg6ga 272 #21 Posted May 12, 2017 Unless you are capable of figuring out the alloy type and a lot of other factors in my opinion your spinning your wheels. If you want to talk car pistons I've used GM, TRW, Johns and a number of others. The only thing I can say with 100% certainty is buy forged. The weight of a specific piston doesn't necessarily have any bearing on how strong it is or how long a life it may have. Piston fit/clearance is a major factor. To be blunt I have spent $800+ on a set of high performance rings and $1600+ on pistons only to have very very little difference in both power and durability. You need to look at it with the idea its a simple little garden tractor engine not something running an 1/8 mile in excess of 300 mph. 1 Share this post Link to post Share on other sites
Searcher60 209 #22 Posted May 12, 2017 56 minutes ago, 6bg6ga said: Unless you are capable of figuring out the alloy type and a lot of other factors in my opinion your spinning your wheels. If you want to talk car pistons I've used GM, TRW, Johns and a number of others. The only thing I can say with 100% certainty is buy forged. The weight of a specific piston doesn't necessarily have any bearing on how strong it is or how long a life it may have. Piston fit/clearance is a major factor. To be blunt I have spent $800+ on a set of high performance rings and $1600+ on pistons only to have very very little difference in both power and durability. You need to look at it with the idea its a simple little garden tractor engine not something running an 1/8 mile in excess of 300 mph. You need to to look at it with the idea that the only thing free in this world is bad advice. To think that we can get something for nothing is what we all want to so despertly believe, but we are lying to ourselves. When I restored antique cars and motorcycles, I dealt with camshafts that were not hardened properly and parts that were not sized correctly. To have to deal with an engine were the camshaft lobes turned to s--t in a few thousand miles, in an engine that I had thousands of dollars tied up in is a lesson that I will never forget. And then there are the parts that were simply machined the wrong size and would not fit. And, don't tell me it's the oil, or I didn't break it in properly, because I paid to have it hardness tested. It flunked a hardness test with flying colors. Do you even know the process used to harden a camshaft? You never dealt with automatic transmission aftermarket parts made backwards. And, I doubt you have personally experienced ebay manipulating feedback to keep sales up for high volume sellers selling questionable parts? I look at it as a job that I do not want to do twice. The bad part of this whole deal is that for a few bucks more, we could have aftermarket parts as good or better than OEM. But, the greed based sellers just don't give a rip, because they realize 1 cent is all it takes to loose a sale in America. You answer your own question when you question if I am able to determine the alloy type. Well, the odds are that the Kohler piston has the right alloy, and that we do not have a clue what the aftermarket piston alloy is. Also, regarding the weight of the aftermarket piston and connecting rod, weight is important due to the counterweight on the crankshaft and engine balance. The ideal situation for me me would be to have the cheap s--t for the tight wads, and for $10-50 more, the better parts that were put through some sort of quality control for people like me. Parts that were as good as OEM or better, and when I put a micrometer on them, they measured what the book says they should. 3 Share this post Link to post Share on other sites
6bg6ga 272 #23 Posted May 12, 2017 Well, friend it would seem that your an expert. If that is the case you should have known enough not to buy anything but kohler. I'm somewhat amazed that with your vast experience you managed to purchase as you would call it cheap communist junk. Also, with your experience I'm sure you would be able to balance the piston and rod combo to come up with the same weight as the Kohler parts or alter the counterbalance weight. Quote: Today, I ordered a genuine Kohler piston, rings, and rod. I just do not believe that the aftermarket parts are up to the same quality level as the genuine Kohler. That being said, the aftermarket parts will no doubt function. But, how long will they last in a working tractor, how much oil will it burn, and how much extra noise will it make? I may do another thread comparing the differences in weight of each component, and size, Kohler vs. aftermarket. To create a YouTube review video of aftermarket parts based on looks and the type of wrapping paper is basically worthless in my opinion. I would think that since you have had such a problem with soft camshafts, parts made backwards, and parts of incorrect size you would stoop so low as to once again purchase parts not made in the U.S.A. but rather communist china. Sir, in my opinion you may very well be your worst enemy. You talk about checking the alloy and making comparison between weight between the Kohler parts and your Chinese parts. I for one would like to read a detailed report from your lab. Share this post Link to post Share on other sites
Searcher60 209 #24 Posted May 13, 2017 2 hours ago, 6bg6ga said: Well, friend it would seem that your an expert. If that is the case you should have known enough not to buy anything but kohler. I'm somewhat amazed that with your vast experience you managed to purchase as you would call it cheap communist junk. Also, with your experience I'm sure you would be able to balance the piston and rod combo to come up with the same weight as the Kohler parts or alter the counterbalance weight. Quote: Today, I ordered a genuine Kohler piston, rings, and rod. I just do not believe that the aftermarket parts are up to the same quality level as the genuine Kohler. That being said, the aftermarket parts will no doubt function. But, how long will they last in a working tractor, how much oil will it burn, and how much extra noise will it make? I may do another thread comparing the differences in weight of each component, and size, Kohler vs. aftermarket. To create a YouTube review video of aftermarket parts based on looks and the type of wrapping paper is basically worthless in my opinion. I would think that since you have had such a problem with soft camshafts, parts made backwards, and parts of incorrect size you would stoop so low as to once again purchase parts not made in the U.S.A. but rather communist china. Sir, in my opinion you may very well be your worst enemy. You talk about checking the alloy and making comparison between weight between the Kohler parts and your Chinese parts. I for one would like to read a detailed report from your lab. Good points. Regarding the camshafts that were were being sold for the engine mentioned above. Many suppliers were selling camshafts with their name on the box. However, everyone of them were using the same camshaft blanks, one made in Turkey and the other made in China as they were the only ones available in the entire world. Also, those who were grinding the inferior hardened blanks would have been able to tell that they were not hardened properly if they were experienced, or cared. Knowing what I know now, if I had to do it all over again, I would have had a company like Crane cams manufacture a "key" from the blueprints from the original manufacturer. The price for the key and first camshaft would have been about $2000. This would have been a top quality camshaft. What I had to go through to clean up the mess from the soft camshaft, $2000 would have been a bargain. Now, the piston that I needed for my Kohler has been discontinued by Kohler. After studying the after market parts, I went looking for the Kohler piston that I needed. I found one that a parts supplier had on the shelf. Soon, we are all going to be using aftermarket parts because genuine Kohler parts for K series will no longer be available. No doubt that Kohler Is discontinuing these parts at least partly due to demand not being what it would be, because of the cheap, communist government subsided aftermarket parts people are flocking to. This is also driving the price up due to the lower volume of the genuine Kohler parts. There is no way any American company can compete with the government subsidized cheap Communist Chinese junk. With the costs associated with manufacturing anything in America, there is no way any American company can manufacture a piston at low volume for what the Comies do. But, the Comies cannot manufacture a piston to Kohler specs and sell it over here for what they are selling their junk over here for either. So, you go right ahead and keep buying cheap Communist junk. Quote Share this post Link to post Share on other sites
6bg6ga 272 #25 Posted May 13, 2017 Searcher60 First of all I don't purchase Chinese engine parts. I will purchase the cheap regulators because they seem to function correctly. I probably would not have purchased a piston and rod in the first place. I probably would have looked for a used piston and rod if needed and bored and sleeved my cylinder. If I had purchase the chinese junk I would have been smart enough to have the piston in hand before boring the cylinder. Almost 50 years of building toys taught me a long time ago not to bore without having a piston to check the fit and clearances. Your vast experience should have taught you not to purchase it. I suggest you either figure out a way to make it work or scrap it. 1 Share this post Link to post Share on other sites