73 cub loss of power, timing issues

[Jonross51]

I recently did a in frame engine overhaul on my 1973 ih cub.
Replaced the valve guides, new valves, pistons , rings, rod berrings, exc,
I have done everything by the book that it says to do and it still is not running right. I have gapped the valves the way the book says and it still has a loss of power and runs like crap. I’m to the point to here I do not kno what else to do. Can someone please point me in the right direction….?

[Stoffregen Motorsports]

Timing issues? Did you have the front timing cover off? Did you remove any of the timing gears? I just went through this with my 1950 Cub. Somewhere along the line, someone removed the governer and installed it a tooth off. This kept the distributor/magneto from having enough timing advance, as the unit was clocked all the way over to the end of the slot in the magneto housing, with no more adjustment left.

It's also possible to get the cam timing a tooth off. That would also hurt power.

[Matt Kirsch]

On a 73, the timing of the governor is not really a concern. That only applies to magneto ignitions, and by 73, IH had long since stopped supplying magnetos in general production. You can turn the distributor a full 360 degrees where a magneto will only turn a few degrees. Being a tooth off on the governor will only affect the final position of the distributor, something that's only of concern if you are incurably obsessive comulsive.

An in-frame overhaul is quite the extreme measure to take for "runs like crap." Even a slap wore out engine can be made to purr like a kitten as long as there is nothing catastrophically wrong like a hole in a piston or a burned valve. It just takes tuning.

What have you done to the timing? Have you confirmed fuel flow to the carburetor?

[Jim Becker]

Does it run like crap the same as before the overhaul or is this new running like crap? What, if anything have you done to the ignition system and carburetor?

[Glen]

Hi,
The ignition timing is an important thing that affects the way the engine runs. If it is wrong, the power can be less.
A 1973 Cub probably has a Battery Ignition unit.
The Cub service manual says to set the Battery Ignition timing using a timing light, you didn't say if you did that.
Below is a page from the manual showing the timing marks.
Mark 1 should be aligned with the pointer at slow idle speed, about 500 RPM.
Use only the pic and the words under it, they are talking about other things on the page.

http://farmallcub.com/rudi_cub/www.clea ... -01-43.jpg

[Jonross51]

I have placed new pistons and rings and new valve guides and valves and springs. I did all of this because the highway compression I had was 70psi. I gaped the valves at what was specified at .015. Fuel flow is fine. Still spits n sputters now runs worse than before I did all of this. I put it in gear and try to drive it and it has no power and will not pull. I am lost as to what to do at this point

[Eugene]

Ignition wires installed on wrong spark plugs. Ignition not in time.

After tripple checking the ignition, conduct compression tests.

[Jonross51]

I did not take the timing cover off or adjust any timing gears

[Eugene]

I did not take the timing cover off or adjust any timing gears

There is quite a bit more involved in ignition timing than matching up the crankshaft and idler gears.

Four folks have indicated an ignition timing problem.

[Glen]

I sent you a PM, you get to it at the top of the page.

The round part of the Battery Ignition unit, the distributor, turns, to adjust the ignition timing, to make it earlier, or later.
That is what is involved with the info I posted above in my other post.
A Cub is timed in a similar way to cars and trucks in the past, that had distributors, the distributor turns, and then is tightened again to keep it in 1 position.
It only takes a small part of a turn to make lots of difference in the timing.
That is part of a tune up.
You didn't say if you have ever used a timing light to time a car or truck engine before.
If I was there I could time it for you.
Below is a pic of one from online. They have some that are low priced, between $20 - $30.
It connects to a battery, and to 1 spark plug wire.
You point the end of it at the timing marks with the engine running, and it lights up where the engine is firing.

[Don McCombs]

It would be helpful if you answered Jim Becker's questions.

[Jonross51]

Mr glen, thank you for the info, and the pm. I have replaced the points, wires , plugs , the entire electrical system is new, I wish there was a video on how to time the ignition on you tube but oh well. I’m thank full that there is people out there willing to give advice to a young person like myself who struggle from time to time

[ricky racer]

As others have said, the symptoms you've described can be cauesd by incorrect timing, incorrect ignition point gap, fuel blockage or low compression.

Low compression could be caused by a sticking valve or worn cylinders or cylinder components. A quick compression test will indicate or negate poor compression as a cause.

Ignition timing can be checked with a timing light as Glen suggested. If you don't have a timing light, you may be able to borrow one from your local auto parts store. I also suggest you recheck the ignition points for proper gap. (Tip, for checking timing, dab a spot of white paint on the timing mark on the front pulley and also the tip of the pointer)

Let us know what you find after making these check and we can move on from there.

[Gary Dotson]

Since we don’t know what sort of “runs like crap” you’re dealing with, the best we can do is stab in the dark. You mentioned that you replaced all the electrical in the distributor, it’s possible you may have gotten a bad condenser, it happens from time to time. Also, double check your point gap, an incorrect gap can “run like crap”. New points often have a corrosion preventive film on the contact surfaces, burnishing them with a piece of brown paper will remove it. By all means, get your hands on a timing light and figure it out, it’s not difficult or complicated.

[tst]

I would 1st check to see if you have good compression after your rebuild, make sure firing order is correct, check the advance weights in the distributor to make sure they are free and springs are good