Power unit

Sun Jul 21, 2013 9:53 pm

What is the difference between the engine in the tractor and the one used in the power unit? Ray

Re: Power unit

Sun Jul 21, 2013 10:15 pm

The main differences that I am aware of are all external, carb, flywheel, radiator. There are probably more.

Bob

Re: Power unit

Mon Jul 22, 2013 7:04 am

Governor is different, too, I believe. Basic "short block" is the same. Ed

Re: Power unit

Mon Jul 22, 2013 8:46 am

How is the governor different? I have had many power plant engine governors apart. see no difference. weights are the same.. Just wondering cause I have heard this before. Been doing cub engines for 40 years. am I missing something?

Re: Power unit

Mon Jul 22, 2013 9:43 am

Clark Thompson wrote:How is the governor different? I have had many power plant engine governors apart. see no difference. weights are the same.. Just wondering cause I have heard this before. Been doing cub engines for 40 years. am I missing something?

I have heard it. never dissected one, to see if it was true. My power units run, as power units,not in cubs. Ed

Re: Power unit

Mon Jul 22, 2013 9:49 am

The governors are the same except I believe the weights are different to give a higher RPM.

Re: Power unit

Mon Jul 22, 2013 9:56 am

I think Cecil is right. In looking at the 1954 parts catalog for the Cub, the part # for the weights is 351 778 R1. In the thresher/baler parts manual that has John Puckett's name on it, the part # for the weights is 351 891 R1.

Bob

Re: Power unit

Mon Jul 22, 2013 11:01 am

As has already been posted, the weights in the governor are slightly lighter giving higher rpm. You really have to look close to tell the difference though. The problem with this set up on a tractor is that you have very limited selection in the mid range position of the throttle. It goes from idle to full speed in a shorter move of the lever, which if all you do is mow or ride around, is ok, but doing things like plowing, cultivating, or driving in parades you need those other engine speeds. I put one on the cub I took to the Tug a couple years ago, but when I got home I took it off because I did not like it for regular use. My loader cub has a power unit engine in it and I left it's governor alone since you do not normally use that many different throttle settings to be critical using a loader. Most of the time it is either wide open or idling, very little use in between.

Re: Power unit

Mon Jul 22, 2013 11:22 am

I have a governor off a power unit installed on my 1976 mowing cub. I havent noticed any problems selecting RPM range. I can make any cub engine run at any rpm up to 3200 RPM and still be able to slect any rpm .. I have a old junk power unit with the governor still on it. Soon as I have time I will compare the weights..

Re: Power unit

Mon Jul 22, 2013 11:29 am

I could still select different ranges, but they were in wider steps.

Re: Power unit

Mon Jul 22, 2013 8:38 pm

Thanks guys I just bought this for the carb and the head but after I got it home and looked it over a little I think will see if it will run it is mounted on a two wheel trailer with a saw RAy

Re: Power unit

Mon Jul 22, 2013 9:31 pm

The limited experience I have had with them they do not have near as much wear as a typical cub engine, but if you are going to use it much, I suggest putting new rings in. the one I put in a tractor went from good compression to smoking like crazy in only a few hours. When I tore it down the cylinders had hardly any wear, but the rings were worn badly. the bearings had pieces of babbit coming out, so I gauged it and purr standards back in, all has been great since.