R5 runs rough

My cousin's Twenty-Two idles very smoothly so I'd suspect that if your R5's behavior is not a fuel-related symptom, then maybe there is backlash in the magneto drivetrain?

Have you tried valve adjustment or looking for a weak valve spring?

good Luck

Biggastractor

Fairly simple to do a compression test on a spark ignition engine. I don't know what pressure to expect but lok at the spread between cylinders.Also look for wear in the governor and linkages it doesn't take much to cause a flutter.
Cheers WF

I'd suggest closely observing the interaction between the loping and the throttle rod action between the governor and the carburetor. This to try to determine if it's a gov or carb problem.
If I remember right edb has addressed this previously and sometimes wear on cam lobes (?) in the gov were the problem. If the owner didn't didn't want the expense of a gov rebuild sometimes a slight increase in the idle speed would 'cure' the loping.

Daron

Thanks for the tips. I have adjusted the valves twice. The valve springs appear tight but I am not too experienced in determining if a spring is loose. After adjustment the observed engine behavior did not change.

I'll check the compression for uniformity across the cylinders - any idea on what the pressure should be? I'm guessing at least 90-100 based on my other older gas engines but none are as large as the R5.

I'm guessing if it is the governor I'll see some erratic or intermittent movement on the governor that is causing the carb to hesitate, surge, sputter... I'll check this. I've had gov issues on some other tractors and those issues presented a little different than this but it is worth checking. The R5 has more of an intermittent/irregular sputter. Usually I have traced this to a fuel supply issue, carb float issue... but none of this has helped so far.

Neil - "backlash in the magneto drivetrain?" How can I run this down? I dread a little messing with the mag on the R5 - kinda of a pain getting this beast adjusted but I'll give it another try if you have some advice on this topic. I was so relieved to get her running the first time around (she was dead as a doornail when I pulled her off the trailer) I left well enough alone once I got her running. It took about 1.5 years to get everything together to get her breathing again.

Thanks for all the sage advice to date!!!

Hi ravenenv,
Caterpillar does not work on the year of manufacture but by Serial Numbers as several upgrades can be carried out in any given year and thus Serial numbers are critical to ensure we give you correct info or indeed you were to try and order the correct parts for either a pre or post updated S/No changed item.

For example the early machines had Ensign carbs and later ones had Zenith--I stand to be corrected on this for at least the R5 as I am quoting from my grey Operator's Instructions Book for R5, Thirty-Five and Forty Tractors, Form No 30610, Dated  10/52.

Maybe check the flat anular shaped screen, as used in the Ensign carby machines, or the small EDGE screen--later fuel pumps--if still fitted-- in the fuel sediment bowl of the fuel pump--the small spaces between the discs can clog with crud and also solidified fuel, from sitting dry, and so may need to be moved apart or it is probable that you may need to dismantle the stack to clean the gaps properly--often carb cleaner will not do the job properly if still stacked tightly.
If you have a Zenith Carby there is originally also a screen in the union fitting at the float chamber entry on the carb. so any restrictions at these screens can cause the symptoms you describe.

Cheers,
Eddie B.

Hi Ross, to be clear I'm just putting possible causes out there. But if it is mag backlash, you can check by turning the distributor rotor back and forth to see how much "slop" there is. I've seen situations before where there is gear chatter that clears up with a small increase in RPM, such as in a Roadranger transmission when idling. Doesn't happen on all of them but some do. I drove a Hino once that had a 13 speed and it chattered like a schoolgirl at idle but with the same transmission in my Kenworth, there was/is no chatter - same transmission, same idle speed. If this was the issue (and it may not be), then likely changing out parts is the only way to solve it. I would check the possible causes that Eddie and others suggest first because they have a simpler solution.

SN on the dozer is 4H725. It has a Zenith K6 which I think puts it later in the 1937 production year (unless someone swapped carbs some point in the past). The carb and fuel pump have been cleaned/rebuilt in the last year but I will go back in to check all the items Eddie suggested - I might have missed something or more crud may have surfaced. The fuel tank is clean given I pulled it, acid washed it... but you never know. It is also easy enough to go into these fuel-related items . If no improvement I'll check the mag as Neil suggests.

It actually runs pretty well - I push some big material with it. Just this intermittent cough/sputter annoys me 😞

Also anyone got an idea what the numerical oil pressure should be on an R5 at operating/working rpms once the engine oil is hot? I have an after-market gauge on the engine that shows 15-20 once the oil is hot and I am working at mid-range rpms. This is normal for many tractors - not sure about this engine.

I'll keep ya'll posted on my progress - thanks again for the tips.