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Blown Kohler with 450 hours

Discussion in 'Mechanic and Repair' started by furball3, Oct 2, 2005.

  1. Smalltimer1

    Smalltimer1 LawnSite Bronze Member
    Posts: 1,223

    These engines are designed with a 10% safety zone of rpm's above 3600, meaning the max safe rpm (surge, not continuous) is around 3960rpms, so it should have been well within that range. However Exmark's specs seem to be off and I personally would think that Exmark should be held responsible for overrating/revving that engine.

    I've seen some of the older engines that were rated at 3200rpm, but never and stock engines rated above 3600.
  2. furball3

    furball3 LawnSite Member
    Posts: 59

    I spoke to someone at Exmark today. He advised me to take it to a dealer to have the engine looked at. They will decided if it was abused or kept in good shape. If(when) the decide it was kept in good shape they will contact Kohler and advise them that there was some latent defect in the engine. From there Kohler will hopefully offer to sell me a new engine at a reduced cost. Both the dealer and Exmark rep agreed that the engine should not have blown with so few hours.
  3. The landscaper

    The landscaper LawnSite Senior Member
    Posts: 845

    I may have a new 25hp kohler if your interested
  4. tshank

    tshank LawnSite Member
    Posts: 201

    Don't let 'em rawhide you. There have been thousands of Kohlers that have run at 3750, no load, as standard practice, some with 3000+ hrs.
  5. Jman

    Jman LawnSite Member
    Posts: 217

    Running the engine at 3750 no load won't hurt a thing at all. There are different spec Kohler twins running at 4000 rpm. The engine speed is determined by the manufacturer of the equipment to get their blade tip speed correct, with the gearing of the belts and pulleys.
  6. MarcSmith

    MarcSmith LawnSite Fanatic
    Posts: 7,157

    I had a kohler 16 go on me. it was the one with the slap stick oiler. the slapper on the bottom of the piston rod broke, before it overheated and blew. I was fit to be tied as it had about 10 hours on the engine... Kohler was saying that it was installed imporpely, no oil, ect. but then I showed them pics of the slapper broken with no heat marks on it but the reast of the assebly had scorch marks from being over heated, they relented. But they did make me pay a mechanic to install the second engine....if i wanted it covered under warranty.....

    Good luck...
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Sorry Sir but you are dead wrong on this one, Engine Manufacturers design THEIR engines to put out X amount of HP at X amount of RPM's so THEY decide what the proper RPM should be run at on THEIR engines and enter this spec. in THEIR Service Manuals as MAX rated RPM, If this rated RPM is exceeded by the Equipment Manufacturer that can release the Engine Manufacturer of any liability for any engine failures due to Not following THEIR RECOMMENDED RPM setting. If the Equipment Manufacturers done their homework right they could get their blade tip speed right without exceeding the Engine Manufacturers RECOMMENDED MAXIMUM RPM rating.
    It was only stated that a engine ran over the Mufacturers Rated RPM could have been a factor to the short life span of the engine.

    I do agree that 3750 no load will not hurt a thing Because once the blades are engaged the RPM will drop back down to the rated RPM range. As for different spec. engines having different RPM ratings I agree also, But in my 14yr. stint as a Service Technician I am yet to see a 4000 RPM rating in any 4 cycle lawn mower ENGINE Manufacturers Service Manual.

    Now with that said, What it all boils down to is; If one cares about getting the maximum life out of their equipment engines it's BEST not to exceed the ENGINE MANUFACTURERS RECOMMENDED RPM range.

    Have a good day all.
  8. Jman

    Jman LawnSite Member
    Posts: 217

    Well apparently you've never gone to Kohler's Idle and High speed setting book, form # TP-2514. Also it is in Kohler's microfiche set on card MISC. 3 (purple header). If you go to page 20, on paper, or grid F06, on fiche, take a look at spec number 68630, it is for a model CH25S Kohler engine. Idle speed should be set at 1400, the high speed setting is 4000 rpm. Every engine is SPEC'd for the manufacture based on what they want, they calculate the percentage horspower dropped for the rpm change. If you look at that form you'll see high speed settings from 2800 to 4000 rpm. I don't know how a technician could possible set rpm without knowing what it should be.
  9. TLS

    TLS LawnSite Fanatic
    Posts: 7,940

    I'm with Jman on the RPM issue. Pleanty of Kohler V-Twins running 3-5K hours running 38-3900 rpm. RPM's don't kill.....not unless you go crazy.

    But back to the main problem.....furball blew his engine.

    First red flag is the noisy lifter issue. Who replaced the lifters? Hydraulic lifters rarely just go flat w/o a cause (dirt, etc).

    Second, if it's a 23hp Kohler on a LAZER Z it is a HORIZONTAL shaft engine, not VERTICAL. If your is VERTICAL, you have a Lazer Zhp...NOT a Lazer Z.

    Was everything that was disassembled with the lifter change replaced properly? I would think this would be the cause of the problem.

    Second possiblity would be the oil pump. Not enough oil pressure and not enough oil gets to lifters....makes them sound flat. Not enough oil pressure,....KABOOM on the rest of the engine.
  10. VegetiveSteam

    VegetiveSteam LawnSite Senior Member
    Posts: 297

    Most equipment manufacturers DO have their engines built to a specific RPM by the engine manufacture. Like Jman said, that is why Kohler and to my knowledge all other engine manufactureres have the RPM information charts and list RPMs by specification number. The only exception to this would be if the manufacture is using a BASIC spec engine. Also, on a Kohler Command twin if the engine is overspeeding you're going to pump up the hydraulic lifters and float the valves before you throw a rod in most cases. I won't say that it can't be done but it is very hard to do. Given the right condtions with low or dirty oil you could probably throw a rod if you tried hard enough by overspeeding. So that being said I really doubt RPM's had anything to do with FURBALL3 throwing a rod. With over 300 hours on the engine about the only thing that could cause a failure like that would be lack of oil to the connecting rod. Bearings get looser with time not tighter so improper clearence shouldn't be an issue. Loose rod bolt? If there is a loose rod bolt at that many hours then somewhere along the line this engine was run low on oil and overheated. A loose rod bolt from the factory would have shown up long before 300 hours. So ruling those things out our next question is why there was a lack of oil? Was it low on oil? Was it run at an extreme angle? Did something go wrong with the oil filter or oil cooler if so equipped? Did the welch plug come out of the oil pump?

    Anyway with a hole in the side of the block the best minimum repair would be a short block. By the way. What is the spec number of the engine?

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