1972 whirlwind push mower

A broken pushrod can indicate an engine with out of sync valve timing. It may be that a piston slapped an open valve snapping the pushrod...neither one is good, you may need to tear this one down.

4 stroke engine, no fuel oil mix.

IGNITION COIL BAD PULL WIRES OFF BACK AND HOTWIRE OR REPLACE IGNITION

The paper air filter will now be soaked with oil, remove the filter completely, remove the spark plug and crank the engine to evacuate any oil above the piston, clean/replace the spark plug and re fit, top the engine oil up if low, now attept to startbthe engine with the filter still removed, once it starts it will smoke heavily until it clears the oil in the bore.

Hi goldengear...

Make sure you have installed the blade on the right way, if it is installed upside down then it will "beat" the grass instead of cutting it and make a terrible cut, also make sure the blade is good and sharp.
The rough running may be due to trash in your carburetor, I would advise to clean your carburetor and also check you fuel tank for trash, water,etc. if there is any trash,water,etc in there then you need to also clean the fuel tank.
Do one more thing and check/clean/replace your fuel filter if you have one.
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Piston clearance is .002. The push rods can be straightened, be careful not to crush them. It's also not critical that they are perfectly straight. Not sure about the year, Honda actually didn't create "model years" until 1972. They used a letter and # designation (for example, 68-71 CB 750's are K1) until the changed something about the bike.Good luck!

did you replace you diaphrams or just clean them, does it have a float bowl or just diaphram? sounds like during all you cleaning you did'nt adj the tab to the needle, therefore diaphram is not opening needle which is not giving gas to the carb. tab should be flush with carb body and when you push on it needle should move to open and let fuel in, good Luck

I tried the website for manuals but no luck. I called the toll-free # 1-800-282-2886 and got a rep right away. I gave him the model and s/n (lower bottom on the back side) and he walked me thru it. For the model I have, there are 3 screws to remove - With the vacuum upright and standing facing it - there is on on the right and one on the left of the bottom cover and one on the left side near the hose intake. Remove those to get to the belt. I ordered the belt with him too - althought the belts were cheap ($2.99 for 2) the shipping was $8. If this didnt help - call the 800# - they were great.