Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

  • Announcements

    • Kent

      Sign In or Password Problems?   10/09/2016

      If you can't Sign In, you need to reset your password.  Use the Forgot Your Password link at the bottom of the Sign In screen, and the site will send you an email to reset it. If you have an AOL email account, use the Contact Us link at the bottom of the screen -- AOL is intermittently blocking email from the site.
    • Kent

      Feedback Please!   10/28/2017

      See News and Announcements forum.
Sign in to follow this  
patrician12

balance shafts?

Recommended Posts

patrician12
Why do you think some motors have balance shafts?Removal of them makes little difference on smoothness while running.I personally think they are there to act like wheel weights on a steam locomotive.Since it is cold and little yard work to do I have been tinkering.A 10 horse briggs w/o shaft and a 16 briggs with balance shafts I took apart to decarbonize and seat valves.Both have electric start.By accident I noticed that with their heads off and starters engaged and then released the balance shaft motor continued to spin much much longer on its own.I tried the experiment against a 18 hp briggs vertical no shafts with the same results.What do you guys think?

Share this post


Link to post
Share on other sites
MPH
From what I understand of it, the balance shaft or counter balanced I think they're called, were designed to offset the surge of the power stroke, by the wts helping to keep the crank rolling smoother to the next time the engine fires. This is kinda shown in your experment of the balanced shaft motor continueing to spin longer.

Share this post


Link to post
Share on other sites
B.Ikard
Many engines with 4 cylinders and less are equipped with balance shafts timed to oppose the inherent vibration created by uneven firing pulses-an effort to make the engine smoother at least that is the theory from the engineers desk. I have never seen a 6 and up cylinder engine with them. I just put together a John Deere four cylinder diesel with 2 timed balance shafts. My old Honda accord also has a balance shaft that is indexed to the crankshaft. I have a 12 hp Kohler apart with the balance gears (with worn bearings) that I am going to build into a 14hp for my 7012. After a lot of talking to several Kohler builders I am leaving the gears out when it goes back together. Supposedly it makes little noticeable difference and no change in engine life. I was suprised at all the Kohler hotrodder/puller guys out there,cant imagine an old cast iron Kohler turning 9000 rpms. I will let you know if it vibrates more than before Ike

Share this post


Link to post
Share on other sites
maxtorman1234
The balance gears in a Kohler make a huge difference when removed. I took them out of my 14, and I heard vibrations I never heard before. I think they're good to have in there, but i've been removing them.

Share this post


Link to post
Share on other sites
PhanDad
Pat, I agree the balance shaft weights act as "wheel weights on a steam locomotive". The engines with balance shafts have more weight rotating; the more weight, the more stored potential energy. The extra potential energy is turned into rotating kinetic energy until the friction finally stops the turning.

Share this post


Link to post
Share on other sites
papamerkle
Here's what happens when balance gears come loose in a Kohler:

I wouldn't put another balance gear(s) back in a Kohler again. I was lucky I was able to rebuild the motor. It has over 100 hours on it since the rebuild. Motor had around 5 hours on it when I took it to a plow day and hammer on it for the next 4 hours.

Share this post


Link to post
Share on other sites
Al
Hi, When we rebuild a Kohler with the balance gears, we ALWAYS put new bearings and retainer rings and shims in them. We also replace the shafts about 95 % of the time. These gears are timed to cancel harmonic vibrations in these engines and do make measurable changes in this area. The engines will run fine without them, but will have more vibration. They are of no value in a high reving pulling engine and should be removed. Almost all associations require STEEL flywheels in anything but 3800 rpm stock classes in order to get insurance. I was at my friends a while back and in the dyno room and saw a cast iron flywheel in a big bore 5 hp Kawasaki that exploded at 9100. His new cams and aluminum rockers he makes worked. He also makes aluminum billet flywheels with rare earth magnets for these engine. In this case he was just trying some new cam profiles he had developed and ground. Definitely resulted in major damage. Would have been bad news if anyone had been in the red line are on either side of the engine. Al Eden

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

×