Part of Kohler's engine test lab includes spin-testing flywheels.  Each flywheel is properly installed to a clean, dry, motor-driven-and-monitored shaft, then hand-torqued just like the manual instructs.  The flywheel is mounted into what resembles a large safe with very thick walls and a big door.  RPM is then run up to the point of burst.  They need to survive at least 2X the normal rated speed of 3,600 RPM.   

   After bursting, everything that still stays on the shaft is out of balance and the lab floor will shake as the speed comes back down. When the door is opened, there will be a pile of broken parts with magnet bits stuck all over the inside of the chamber.  All flywheels pass the 2X3600 mark -- 7,200 RPM -- and many of them hit 10,000 RPM. 

   Anytime a new flywheel is developed, whether for a new engine or as a new flywheel design for a current engine, it gets qualified/tested. And anytime a modification is made to an existing flywheel, it gets qualified/tested. 

   Many Kohler engines are set to run 3750 no-load speed.

   Keep in mind that lubricating the tapers or using an impact wrench to torque a flywheel are always bad ideas.  Broken flywheels result from lubricating the tapered shaft or over-torquing the flywheel bolt/nut. But properly hand-torquing a stock Kohler flywheel on a clean, dry taper will safely allow in excess of 5,000-6,000 RPM.   

   As noted above, this is Kohler's flywheel-test information.  I'm still trying to get information on Tecumseh, Briggs, Kawasaki and Honda flywheels. 

   Now, having said that, and having watched Knoot's video, I need to say that the Kohler we ran to 5,700 RPM did not have any counterbalance mechanism inside, just a well-balanced crank, rods, pistons and cam.  The Tecumseh V-twins being raced don't have counterbalancing mechanisms, either, but I don't know what RPMs they're producing.  What I saw on Knoot's Briggs video looked like the oscillating counterbalance weight self-destructing, and the oil that came out of the crankcase looked quite dirty and black, which would tell me that the internals had a lot of wear from the dirty oil.  This may have helped contribute to the self-destruct.  What was the RPM at the point of disintegration? 

   And Paul keeps mentioning "insurance companies and a 3,650 RPM maximum."  Which insurance companies?  Would a stock Kohler running it's governed 3,750 RPM be uninsurable?  Maybe the insurance companies are using outdated information from when the flywheels included the cast-in cooling fins.  The new unfinned flywheels with separate plastic fans can safely spin much faster, as Kohler's tests -- and my own experience -- prove. 

Respectfully, 
Rodney 

Heymowers, 

   In the Driveline section, there is a post entitled "Getting speed out of Drive Shaft Mowers?" and one of the questions was about tweaking the governor to get more than 3600 RPM from the engine.  One of the Replies cautioned about going beyond 3800 RPM.  Allow me to share an incident from a factory service school:

   In February of 1999, I attended the Kohler Engine Level 2 Factory School in Kohler, Wisconsin, and on Thursday afternoon of the 5-day school, the class was given two Command 25hp V-twin engines to "do with whatever you'd like."  Since in our shops, we only see an engine needing repairs after it's been damaged, we decided we'd run one wide open and the other without oil.  For the wide-open engine, the instructor wired the governor open, set the engine stand outside (just in case), and started it up.  The tachometer read 5700 RPM -- for 45 minutes!  It never missed a beat, and would have run faster but the valve springs began floating, so 5700 was its maximum RPM-- well above the "recommended" governed 3600-3800 RPM.  Even with the factory muffler, the sound was impressive!

   Engine RPM limits are dependent on keeping with the design engineering of a maximum metal stress in a stock engine of 2,500 feet-per-minute (FPM) of travel, with allowable momentary speeds of 3,500 FPM.  An engine with a 3" stroke will travel 6" per revolution.  This engine turning 5000 RPM is at the 2,500 FPM industry-acceptable limit.  And with the precision manufacturing and materials of today's engines, these stresses are even more controlled.  An engine with a  2.75" (2-3/4") stroke can run over 5400 RPM to reach the 2500 FPM limit.  The stroke on the CH25 Kohler engines we maxed out is 2.64" which, at the 2500 FPM stress limit, is 5,681 RPM. 

   This applies not just to Kohler engines, but to all engines -- Tecumseh, Briggs & Stratton, Kawasaki, Honda, etc.

   Hope this helps. 

Respectfully, 
Rodney Rom 
Rom's Reworks 
Butler, MO
   

Victor, 

   I'm attaching the pictures of the shift-shaft extension I made for the Kansas City customer.  It isn't that difficult to do. 

   Photo 1 shows the parts I used to make the extension.  The piece of square stock and the two short spacers on the right side of the picture are only for aligning and assembling the extension.  The 1/4"-28 SAE All-Thread in the center is what will hold the extension to the transaxle shift shaft.  The shift arm in the lower-left corner can be any shift arm -- you will be cutting off most of it, only keeping enough to weld the long spacer tube to.  The U-shaped piece at the top-left is the original Murray shift yoke. 
   The long shift shaft is 4-1/4" longer than the standard 820 short shift shaft.  With the 1/4" thickness of the shift arm, the long spacer will need to be 3" long (See NOTE 2 below).  I used a piece of 7/8" ID by 1-1/8" OD (1/8" wall) mild steel tubing -- it was what I had in my stockpile.

   Photo 2 shows the extension parts aligned, ready to weld.  Since the key stock has to extend beyond the bottom and top pieces to keep them aligned, the short spacers go around the extended key stock so all three pieces can be clamped with a long C-clamp for welding. 

   Photo 3 shows the parts welded together.  The key-stock piece is critical in keeping the transaxle shift-arm and the Murray shift-yoke squares aligned for proper shifting alignment.  Once welded, the key stock can be removed. 

   And Photo 4 shows the extension installed on a new 5-speed Peerless 820-001B made-for-Murray transaxle.  This will also fit the 6-speed 820-040 transaxle, but the 820-040 has a 3/4" input shaft instead of the 5/8" input shaft used on Murrays.  Actually, it will fit any 820 with the short shift shaft, if you have another 820 you want to use on your Murray. 

   NOTE 1:  When installing the 1/4" All-Thread into the transaxle shift shaft, the 3/8" square hole in the Murray yoke will allow unacceptable slop at the top, so you'll need a shouldered bushing in the square yoke hole to keep the All-Thread from moving around.  I cut off a short piece of a Kohler Flywheel Fan Spacer, P/N 24 112 04-S, from a Kohler Command engine to make this bushing (See next thread in this Post).  Unfortunately, this Spacer is obsolete from Kohler, so unless you have a junk Kohler in your boneyard, you'll need to come up with your own spacer.  A flat washer, lock washer, and nut will finish the installation; I'd recommend a Nylock nut. 
   And I use blue Loctite on all the threads for security. 

   NOTE 2:  The 820-037 long-shift-shaft made-for-Murray transaxle also used a tall input shaft that extended the 5/8" pulley-mount section one inch (1.0") above the input-shaft post on the top cover.  This was to keep the transaxle pulley aligned with the engine and idler pulleys with the extended mounts for the axle housings and the mower chassis.  Using a standard short input shaft 820 on a Murray lawn tractor will work fine, and will allow the 3"-long extension tube to put the shifter exactly where it needs to be.  If you are using the 820 on a Murray garden tractor, you will need to use a 4"-long extension tube and the taller input shaft.

Respectfully, 
Rodney Rom 

Knoot, 

   "Will the stock transaxle hold up?" 
Probably not for long.  Recommended input RPM is 2000.  Beyond that is tempting fate, especially since there are very few DANA repair parts or replacement transaxles left out there. 

   "Is there anything I need to do to make it tougher?" 
Replace it with a Peerless 820.  Higher-speed final-drive gearsets are available for the 820s that allow your axles to turn faster without overspeeding your input shaft. 

Respectfully, 
Rodney Rom 
DANA Certified
Peerless Gear Master Technician 
Rom's Reworks 
Butler, MO 

Heymowers, 

   Butler, MO, has a 3/8-mile oval dirt track that's been dormant for the last few years due to an ownership issue, but it's being refurbished for racing this season -- hopefully -- as Old 71 Speedway.  How would I be able to present mower racing to the new management?  Who would be good contact people for USLMRA, ARMA, or other organizations?  I'm still trying to find contact information for the track -- they have new signs out, but no contact numbers. 

Respectfully, 
Rodney Rom 
Rom's Reworks 
Butler, MO 

DBS, 

   Check out this post -- http://www.heymow.com/index.php/topic,32459.0.html .  It gives a picture of the 700 transmission mounting dimensions, from which you can make a plate. 

Respectfully, 
Rodney Rom 
Peerless Gear Master Technician
Rom's Reworks 
Butler, MO 

Bobby, 

   Just re-read this post and all its responses.  Did you ever finish this project?  How did it turn out?  Glad you decided on an 820 transaxle .

Respectfully, 
Rodney Rom 
Rom's Reworks 
Butler, MO 

Not able to send pic at this time and may be approaching this project with the wrong equipment. The transaxle I have isn't the one that came with the mower, but the bolt pattern is the same. Murray chassis . As I mentioned, it is a Peerless 800 series and I have locked the axles.
The  intent is a drag mower.

 

Skip, 

   If you want to have a successful drag mower, your 800 transaxle would be considered "the wrong equipment."  You need an 820 transaxle -- all heat-treated cut steel gears; all needle and ball bearings on the internal shafts (no bushings); 1"-diameter axles; high-speed final-drive gearsets available so you don't have to over-rev your input shaft; and the 820 has the same mounting as the original transaxle in your Murray and your current 800, for a "bolt-in" installation. 

   Is your shifter between your legs or on the right fender? 

Respectfully, 
Rodney