Rubuilt 1961 cub max rpm?

[Shadow_storm56]

Just out of curiosity what is the max safe rpm on a 1961 farmall cub? The red ones... :p This one had the engine rebuilt so all of the rings and I think even the pistons were replaced, it sat for quite a few years and took a bit of work to get going but I looked inside and although the valves are rusty the bores are pristine. It was set at around 2000rpm and my other 1971 yellow cub seems to run at around 1900 but it was never changed or rebuilt. The red one runs much cooler from the extra air flow and I ended up turning it up to around 2150-2200 rpm and it runs just fantastic. So my main question is basically is there any reason I can't run it at this rpm or would it potentially damage the trans or somthing else? Also keep in mind this was read using a cheap laser tachometer....my good one went missing so I am not sure the accuracy but I atleast know that the one is running faster than the other but alot.

Oh also on a side not both of my Cubs need a new rear main, one leaks when the tractor gets working hard and the oil gets thinner. Oddly enough the red one leaks when the oil is cool and once it gets hot is seals right up.... so that's weird eh? I think it'll be a winter projecr but I am curious how big of a nightmare it is to change that seal. I recently got a sudden fasination with these old little tractors even though we had them for years and years but I never really did much to them. My father did most of the repairs to them actually, they are a nice tractor for cultivation I find.

[inairam]

The RPM was adjusted though the years of the engine from 1600 very early to 2400 for the later cubs to increase the HP rating of the tractor. (Some boat applications of the engine were higher) Max torque is the same at 1600 through the years

The stationary engines used in power units and balers and the like, which was the same as early cub ones, with the same cam and flat pistions, were running at 2500 RPM and the later ones as I said were at 2400 using basically the same governor as the stationary, but different carb and manifold. The cam and the pistons and the rods were changed in 1968 and not really related to the later RPM increases in the 1970s

You can safely run at 2000 -2100 RPM. I have a few cubs set up at about 2300. Most of my work is mowing where the added RPM helps a great deal. IF you are not mowing all of the time I would keep it at 2000-2100 as a max.

[Shadow_storm56]

Both are used for cultivation so ill keep it in the range you stated. Interesting that they ramped up the rpm alot in the later years. Thanks for the info

[tnestell]

You can safely run at 2000 -2100 RPM. I have a few cubs set up at about 2300. Most of my work is mowing where the added RPM helps a great deal. IF you are not mowing all of the time I would keep it at 2000-2100 as a max.

I can only run 1800 rpm using my Woods 59 because I kept breaking the castors running in 2nd at 2100 rpm.

[inairam]

You are breaking castors because your deck it too low for the field condition not because you are going too fast. I set my decks high for 4-6 cut min. I have mostly pasture field not lawn lots of ruts.

I like the Woods 42 and the c-2 in part because they do not have casters.

[Glen]

Hi,
Below is a page from the 1959 Cub operator's manual with specifications.

It says the maximum engine speed is 2016 RPM.

http://farmallcub.com/rudi_cub/www.clea ... age-45.jpg

The 1965 operator's manual says 2000 RPM.

The maximum RPM of Cubs from the beginning at serial number 501, to serial number 192113 was 1800 RPM.
The maximum RPM was raised at Cub serial number 192113, to 2000 RPM.
It was 2000 RPM until the longstripe Cub came out during 1975.
The operator's manual for the longstripe Cub says the maximum RPM is 2080 RPM.

You have to split the Cub behind the engine to get to the rear crankshaft seal.
Then remove the clutch, and flywheel.

The engine rear crankshaft seal is held by a soft metal retainer.
They have talked many times on here about the rear seal retainer.
They say the oil seal available nowadays may not fit the retainer the Cub has. Some seals fit loose in the retainer.
The new seal might, or might not, fit tight in the retainer the Cub has.
Member tst on here machines used retainers, and installs a seal with a slightly larger OD, so it fits tight in the retainer.
You can write him a PM if you want to buy a retainer and seal.

Below is the Cub service manual, it has lots of info. It has a section about splitting the Cub.

http://farmallcub.com/rudi_cub/www.clea ... index.html

Be sure to wedge the front axle pivot when splitting a Cub. It can tip over without wedging it, there is more weight on the left side.
You will need to make them from wood.
Hammer them in tight, and be sure they aren't hitting at the small end, that would prevent them from being tight in the pivot.
Check them some during the work to be sure they don't come loose.

Below is a pic from TM Tractor of the seal retainer.
The 2nd pic is the wedges.

[inairam]

Hi,

It was 2000 RPM until the longstripe Cub came out during 1975.
The operator's manual for the longstripe Cub says the maximum RPM is 2080 RPM.

I should have been clear - the numbered cub engines the 184 with the c-60 wa 2300-2400 RPM

[Shadow_storm56]

Wow thanks for all the info! I won't have time to split them until winter time but it's nice to research how so I'm ready when it's time. I hadn't thought about it tipping over so thanks for that tip . I find cubs such interesting little tractors, my one was leaking hydraulic at the little seal by the reservoir. I was like oh good I need a new seal, I decided to try tightening it up and did so about 1/16th of a turn and now it dosen't leak a drop.