QuestionQUESTION: First of all here are the specs: 18hp b/s 42A707, 1238-01,9703275A
I have this motor on a 46" mower. The motor when I got it, it was running but leaked oil and blew white smoke before shutting down. I found that there were bolts missing on the center block, there are 7 of them and was missing 4 (where the exhaust mounts). So I picked up another motor (19hp b/s) for parts and I broke the 18hp apart; this is how it went...
*I cleaned the sludge of old oil built up on the bottom half.
*Took off both sides where the spark plugs attach and cleaned carbon on both the rod/piston and side plate.
*I put two new spark plugs on.
*Replaced all three gaskets (each side and center).
*Bolted all of it back together using all 7 bolts in the center.
*Mounted it back on the frame and put all wiring back together.
*Added fresh oil.
I then try and start it and what I get is that it tries to turn over but does not. I will get about 3/4 of a turn and it stops and this will continue and it never spins a full revolution or strong enough to start it.
I put a splash of gas in the carburetor but still no difference
I have tried 2 different batteries, one being my wife's car, and still no difference.
I tired a second started from my 19hp parts mower and still no difference.
I disconnected the transmission and blade belt thinking that when I put the motor back on the body it was too tight but that lead to no difference.
So what am I missing?
ANSWER: Jeremy
Sounds like your timing is off. When you took apart the engine flywheel did you mark the position on how it was lined up to the crank shaft?
There is a key way on the shaft that should line up with he flywheel and the shaft check that first it may be the problem.
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QUESTION: I had taken the flywheel fan off but had not ever taken the flywheel itself off and it ran with the smoke and the leak so I do not think that it is my problem. Yet, I would have taken it off probably if I could have done it. I never could get the damn nut on top off. It would have made changing out the starters a heck of a lot easier.
The flywheel is quite rusty though; I wire brushed it, used some wd-40 on it, but not sure if I got it as good as new. Could the amount of magnetism produced have anything to do with it not starting?
ANSWER: Jeremy
The flywheel magnet must generate a sufficient magnetic field to start the chain of events in motion. A fair test is to hold the flywheel on edge with the magnet facing up. Place the blade of a 10" #3 (1/4") straight blade screwdriver against the magnet. Release the screwdriver. The magnet should have enough strength to hold the screwdriver straight out. If we pass this test, assume the magnet is OK.
Also Remember speed is a factor. The engine must be pulled over at a minimum speed of 250 RPM before the coil will even think about firing. Thick oil on a winter day or a heavy parasitic load may cause problems.
Rust on the flywheel magnets causes a loss of spark. Not true. A magnetic field does not care about rust. It has no effect on it.
A bright blue spark is best. A yellow/orange spark signifies weak ignition. Not true. Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap.
Laying the spark plug against the block and pulling the engine over can adequately test ignition coil output. Not true. The ignition coil will only generate enough output to jump the gap of the plug.
When under compression, the plug requires twice the voltage to fire. This check is not an accurate test of the coil and can be misleading.
An armature air gap that is too wide will prevent spark. Not true. Well, sort of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark providing the coil is healthy and the engine is spun over fast enough. A wide air gap, say .030" will ever so slightly retard the ignition timing as the magnetic field takes longer to build within the coil windings.
Ignition coils, particularly Magnetron™ coils, rarely fail. If one is suspect, perform the outlined checks exactly as mentioned. MOST IMPORTANT: Be sure to isolate the coil from the equipment wiring harness as well as the engine's wiring harness. That's right, unhook the ignition grounding lead from the coil itself and use the spark tester. Many a technician is fooled into replacing a good coil because the coil grounding lead was shorting out against a piece of sheet metal. DO NOT attach the tester to the spark plug for this test. The engine may start. Without the grounding lead installed, you won't be able to turn it off. If the coil is properly grounded to the engine block, engine speed is at least 250 RPM and the flywheel magnets are OK, there should be spark present in the window of the tester. If not, repeat the test double checking your procedure. Still no spark?
Then and only then, replace the coil.
Now for A final bit of trivia - All Magnetron™ Ignition coils have the manufacturing date code cast into the coil body. The coil manufacturing date will usually be within a month of the engine's date code. That's an easy way for you to tell if the coil has been changed before.
Hopefully This helps
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QUESTION: So per your description above; the magnet is good.
For the armature I adjusted that to the thickness of a business card.
I have bypassed all of the wiring and am going straight from the battery to the starter. I am focusing on one issue at a time. But have unhooked the ground you are talking about and that is how I have stopped it when running (leaking and smoking) by reconnecting it. I believe the coil is still good and I have cleared it all around the motor so it is not grounding out elsewhere.
It seems like there is too much compression. If I pulled the spark plugs and shot in some starter fluid in the chamber would that let if breathe a little better allow it to slide better?
The ground to the block? Is the block not grounded when bolted onto the frame?
AnswerJeremy
Take the plugs out and add some marvel mystery oil and then pull the handle a few times let it set for a day then pull the handle a few more times,this way you get lubrication on the cylinder wall.The block and the frame are the same ground.If it is hard to pull the rings may be sticking.
