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48 H mag timing

K

Kippster

Member
I've timed this engine by the book several times. The mag has been rebuilt (new coil, condenser, points, cap, rotor, coil cap, re-timed) by a reputable shop and has HOT spark. Engine was rebuilt two years ago and has excellent compression. The carb has been cleaned and rebuilt and is set so the engine runs beautifully, has excellent power and will idle nicely. The internal timing of the mag is right on. However despite all of these things, it is still a bugger to start by hand. No electric start currently. Would the fact that the engine has flat top pistons make a difference in where the engine should be timed?? Thanks yall. Kippster
 
Can you here the impulse click when you turn it over? The purpose of the impulse coupling is just for that reason. You should here a distinct "clink" noise when it's turning over.
 
Spark should occur at or just barely after TDC. (no kickback against the starter or the hand crank)
Our family of H's (5) start great with about 1/3 throttle and no choke. Cold temps require just a bit of choke for a few seconds. Some are magneto and the others are battery ignition.

Does your Super H have a intake manifold or carburetor gasket leakage? With the engine running at idle, take a small propane torch(no flame) open the valve so propane is flowing, and pass the tip near all gasket joints listening for RPM changes indicating an air leak.
 
No intake leakage. Checked that too. Impulses are snapping good and solid. Those were checked when the mag was rebuilt. Thanks for the suggestions~~!!
 
I noticed you did not state plug wires, if one or more are bad the rest is work is to no gain. After wires I would change out plugs to AC brand, I have found them to be more reliable for me when used on magnetos. Make sure your not using a resisor plug as that will diminish the output.
 
your mag on that tractor is made to fire on TDC make sure the rotor is pointed at the tower on the cap when it fires. Make sure #1 is at TDC and both valves are closed. You mite need to remove #1 plug to make sure and it wouldnt hurt to remove the tappet cover to make sure both valves are closed when the impulse fires if the rotor is off even one tooth it will make a difference. There is no advancing of the impulse on those mags it just fires on TDC or will be trouble getting it to start.
 
How many yrs have you had timing those mags they are ment to fire on TDC then when engine is running they advance 32 or so deg.
 
Plug wires are new copper core wires. Plugs are Champion NON resistor. I think D18 IIRC. I could be wrong. Thats what was in the tractor when I bought it so thats what I put in it when I replaced them along with the wires. I've heard some bad stuff about champ plugs and mags. Have to try the AC plugs. Which ones do you recomend? Thanks so much!!!
 
Rotor is pointed at #1 when mag fires. I was using the marks on the crank pulley to determine TDC not the ol' drinkin straw method like grandpa taught me. The pulley marks would be wrong with the flat top pistons. Dumb mistake!!! UGH!! I'll give the old method a try and take into account that there is no impulse advance. Thanks Gene.
 
Hold your hand over the throat of the carburetor while a helper hand cranks the engine and see if there's good suction on your hand. You need good suction to pull that gas into the engine.
You may want to install a primer bulb so it squirts that atomized fuel into the air stream.

Your impulse coupling needs to be snapping so you get that hot spark when hand cranking. We had 10-20's and 15-30's and they started easily by hand cranking. We even used them in cold weather for hauling manure and sawing wood. If your H has a fully charged battery you can convert that mag to a distributor by using the points and condenser in the mag and installing an auto type coil. You would need to remove the wire from the mag's coil to the points and connect the hot wire from the new coil to the points. I would also check the magnets in your mag using a screwdriver to make sure they have good magnetism. It should attract that screwdriver with a lot of effort. Hal
 
Type of piston has nothing to do with it. Step heads will give higher compression. You can use the pulley mark to confirm TDC provided nothing else is wrong. Should be able to pull the crank while using a light to look at the #1 cylinder. You can tell when it is at TDC with a little practice. As to the mag, you install it at TDC with the rotor pointing to #1 in the the distributer cap. The rotor is set just before it trips, not after. Rotate is until you feel resistance, then install the mag. When you have it in put the coil against the block, pull the coil wire out of the cap and hold it close to the nut on the side, rotate the mag away from the block until it trips, at the same time you should see a spark. You can then rotate the crank 360 degrees and the pulley mark should be inline with the pointer. Start without the choke, or no more than a couple of pulls on the crank, the tractor floods very easily, which may be your problem.
 
Flat top makes no difference now if you have FireCrater type I-H did say you need a dist so you could have advance for starting. I found that out the hard way then talking to my buddy he said you need a dist. It wouldnt start with the mag but put a dist in and it would fire rite up. Changed it several times to prove it to friends who said i was full of it. Then later my friend told me about the factory directive explaining the procedure. Other hi-domes will work with a mag but the RED POWER ones have a higher dome and they wont.
 
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