Help resurrecting an old cub

[footprints]

This is my first post here and I would like to thank the forum for all the work that has been done here to help other cub owners. I purchased a dead cub 2 weeks ago and this site has been an invaluable tool thus far but Im at an impass and need help. I will briefly bring you up to speed before on whats been done so far to the cub. I bought it from a guy who bought it this year from an estate auction where it apparently sat in a barn for 8 years. The motor was stuck and the PO said he got it unstuck and checked the valves and it was all good, just needed wires, tuneup etc. This was not the case. No compression on #4 due to rust, trash and water running into the engine while setting outside at his house with no protection. I replaced the bad/stuck valve using information from here. Changing #4 exhaust valve with the motor in the tractor is no day in the park especially without a spring compressor but I did it!

Got motor back together but crankshaft pulley is chipped and I could not find TDC because I believed it was broke off the pulley. I used the timing procedure from here where you look in # 4 and watch the valves to find TDC. I did so and then checked the distributor to find it had broken gears/bent shaft and wasnt working properly. Removed old distributor and the gear housing just behind it to reveal the 2 notch disk behind the governor. I replaced the whole unit ( distributor and gear housing ) and rebuilt the distributor before install. I noticed scribe marks on round disk were lined up cut outs on governor drive like I have seen on cub online magneto timing video on youtube. I then installed distributor in to gear housing and lined it up to #1 on the cap. I then hot wired the coil and backed the distributor back past #1 and turned it forward until in fired and locked the distributor down. I then tested all plugs laying out on the head and turned engine over to verify firing on each plug, all good. I attempted to start the engine and still no firing. i SLOWLY MOVED THE DISTRIBUTOR BACK AND FORTH while trying to crank just in case I was a few degrees off and still nothing.I did find the TDC mark on the crankshaft after this and rechecked everything and my timing was wrong.

I used the valve watch procedure on #4 again and after the exhaust closed and the intake started to open it took about half a turn of the crankshaft to bring the crank TDC to the pointer. I pulled the distributor back out and set it roughly where #1 on the distributor cap was. I did not use the procedure to set the distributor before it reached number 1 and turn it until it fired and lock it down. I figured I was close enough to get it to fire here and would adjust once it was running. It still isnt firing. My compressions run 60, 70, 80, 100 but I read on here not to trust those values on engines that had been setting due to buildup. I have been trying to start the engine with starter fluid because I did not want to put gas to it until I was sure of the firing, however I dont feel anything is getting to the cylinders and Im considering going back and resetting the distributor to spark at tdc and pour gas in each cylinder and then put the plugs back in and try. Any other advice, I'm at a loss here

[Cecil]

OK do this. Remove #1 plug. Place your thumb over the hole and turn the engine until you feel pressure. with a light look into the cylinder and make sure the piston is at TDC. Line up the rotor with the number 1 tower and replace the cap. Check that the firing order is correct. 1,3,4,2. Get a can of cheap carb cleaner (I get mine at Walmart) and spray some in the carb while turning the engine. It should at least fire. Most of the time it will run a few seconds on the carb cleaner. Let me know how you make out.

[Eugene]

Compression tests, dry then wet on all 4 cylinders?

Could remove the air cleaner hose, hand over carburetor throat, check for suction.

[footprints]

Compression tests were dry. I will try the thumb pressure test tomorrow instead of watching valves and set to tdc timing mark once pressure is felt on #1. Firing order is 1342 now and was wrong on old distributor. I read somewhere the rotor should be set at 10 oclock and not 12 o clock when setting up the static timing with the coil/ distributor setup, is that true or should I stay with 12 o clock or go back and hard wire the coil and turn the distributor by hand until I get spark with the engine setting at tdc and lock the distibutor down when it fires?

[Eugene]

Compression tests with a compression tester. Record the answers and post back.

It's neither 10 or 12 o'clock position for the distributor rotor if distributor is correctly installed.

Down load the operator's manual. It has photos of the correct distributor position. Lot of good information at top of page.

You need to time the distributor to the engine, then time the spark. Several steps involved.

[Jim Becker]

A couple points I didn't see mentioned yet:

1) Put a couple squirts in each cylinder to do a wet compression test. The oil will also help the compression to get it to start. Another squirt into each cylinder after the test won't hurt either.

2) When rotating the distributor to set the timing, rotate it counterclockwise (viewed from tractor seat). This is opposite the direction you rotate a magneto. If you rotate the wrong direction, you will have the points closing at TDC rather than opening. Timing will be way off.

[Eugene]

Prime the oil pump before starting the engine?

[challenger]

I will comment briefly on some things I noticed beyond the great posts already offered. I want to emphasize the one made by Eugene, however, about priming the oil pump because it is so critical before starting up a Cub engine that has been sitting for an extended period of time.

You said you replaced an exhaust valve. Did you set the gap at the lower stem end after install? This needs to be set at
.20 -.25.

With regard to ignition timing, Cecil’s thumb test is a sure way to know you have the #1 piston on compression stroke but it will be hard to hit top dead center exactly on the piston. If you have located the TDC mark on your pulley and know you are on the compression stroke, use the fan to rotate the engine crank slightly backward or forward until the pointed peg near the crank pulley exactly lines up with the TDC mark on the pulley. Note that there may be two marks on the pulley. If your pulley has two marks, TDC will be the second mark on the pulley in its normal rotation past the peg. If you are unsure about the pulley markings, I have used a wire through the spark plug hole to sense when the piston is at TDC.

The # 1 post of the distributor cap is usually marked on the outside of the cap. The #1 post should sit at about 10 o’clock when looking at the outside of the cap if the distributor has been properly installed into its housing. The rotor tip on the inside of the cap needs to be facing this #1 post on the inside of cap when the points open. If it is way off, the distributor may need to be pulled out of the housing a short way, the shaft rotated and replaced a time or two until you have the rotor pointing to the #1 distributor post at about 10 o’clock. You can do the fine tuning from here by slightly rotating the distributor forward past the # 1 cam lobe to permit the points to close and then slowly rotating the distributor back against the normal rotation of the cam until the points just break open and spark occurs.

[Jim Becker]

The #1 post should sit at about10 1 o’clock when looking at the outside of the cap if the distributor has been properly installed into its housing.

[challenger]

Jim,
Thanks for the catch. I'm still having trouble reading time! The old brain went in neutral on that one.

[Eugene]

You said you replaced an exhaust valve. Did you set the gap at the lower stem end after install? This needs to be set at .20 -.25.

Typically .013" to .015". All valve stem lifter gaps needs to be the same.

Check you owner's manual for the correct gap for your engine.

[footprints]

Ok here is the update from today. Got #1 to tdc by verifying compression then watching for piston to rise to the top. I did in fact find out the timing mark is broken off the corner of my crankshaft pulley. STill wouldnt crank. I backed distributor slightly counter clockwise past number one heading back to #2 then made the coil hot and rotated until #1 plug sparked. STill would not crank. I now realize from a previous poster that I should have gone past #1 on the distributor and then turned counterclockwise until spark at plug. I have not tried that yet.

I went ahead and put my hanging gas bottle to the carb today and pulled started the cub behind the truck. It would fire and run as long as the truck was pulling it. I did notice oil and water mixing so I pulled the head off again and did a much more thorough job of cleaning and re-installing everything. I followed cub manual headbolt tightening sequence and went to 55lbs instead of 45 lbs just because I was worried that perhaps I didnt get them truly tight enough last time considering all the rust in the threads. I also used the air ratchet to run the bolts back and forth with penetrating oil to clean up the threads and it appears all it well with the new head gasket now.

I cleaned up all the moisture and test fired all the plugs before trying to start again. All are new but # 1 plug had stopped firing and #4 was weak. Replaced both plugs and tested spark again, all good. Tried to start with starter, getting white smoke out the exhaust but no real firing. Pulled cub behind truck again, runs and sounds good but will cut off as soon as you push the clutch in. Did a compression check after re-installing head with a little moisture build up and penetrating oil in the cylinders I was getting a consistent 80-90 psi across all cylinders with about 8 cycles of the starter.

Right now I am thinking I need to go back and let the distributor be past #1 on the distributor and back it up counterclockwise until it fires since I did it opposite of this which would make my firing too early.

[footprints]

BTW, my #1 on dist cap is setting at about 1 oclock. I set the firing of #1 to be exactly at TDC by watching the piston, verifying compression stroke, making coil hot, using hand crank and fan belt to move engine back and forth and having plug to fire exactly at TDC on #1 ( no mark to look at on my pulley, just watched piston ). I will do as suggested next and rotate distributor past #1 and back it up ( counterclockwise ) until I get spark and try that. Of course TDC here will be based on observing piston at top of cylinder during compression stroke since I do not have a tdc mark on my pulley.

[challenger]

Eugene,
Thanks for the correction on the tappet clearance. While setting clearance a little on the high side is acceptable, those numbers I gave were way too high in anyone's book.

Footprint,
I could not get my first Cub started for the longest time and the problem was as simple as the spark plug wires being crossed. Strange things can happen when you are in a hurry. Do not just eyeball the wires, hand trace them from each distributor cap port to make sure they are connected to the correct cylinder spark plug. Number 1 distributor cap wire to # 1 cylinder, moving around the cap to the right, # 2 wire goes to number 3 cylinder and so on around the cap consistent with firing order, 1342.

[footprints]

Thanks. I will re-look at that again. I have even pulled them out of the cap once and re-ran each one individually to make sure I had them in order, but I have taken the plugs in and out probably 50 times and probable should retrace my steps again.