4 cycle lawn mower engine question

[Judy and Dave G]

Thanks for all the help and hints that you don't know you have given us!

Here's our question(s). We have a Craftsman power propelled lawn mower. Bought in 1995. Only been run for maybe 3 hours tops. So everything still even looks new. Took it out, cleaned it up, drained it, tightened it, etc. But it won't start. Ordered a solid state ignition and put it in. Dave thinks the problem may be a clearance problem but there are no specifications in the owner's manual. This mower was from back when everything Sears sold, had only Sears' name on it. So we don't know the engine manufacturer. The mower is Sears model #: 917.376340 and the engine Sears model #: 143.966500. This is 6.5 hp engine takes plug RJ19LM.

Dave is trying to find out the specification for clearance between the magnet mounted on the flywheel and the solid state ignition. When the clearance is set at 2 - 3 thousandths, the mower would not start. When the clearance is set at 17 - 18 thousandths, it starts, runs rough and fouls the plug. Of course, at this time, he isn't really sure this is the problem. So if anyone has any other ideas, please?

Hope there is someone out there who can help with this. Even if just to help us identify the engine, or if there is a standard for clearance that might work?

Thanks again for all your help. We really appreciate the time it takes to give it.

Judy

[Tony Hwang]

Hi, Timing? Try to advance it. By moving the module against the direction of rotation of crankshaft. Little by little at a time. Tony

Judy and Dave G wrote:

[Bob M.]

The engine is most likely a Tecumseh engine. They specify an air gap for the solid-state ignition module of 0.0125 inches between the core and the flywheel. The timing is NOT adjustable.

The 143. engine number is not listed in the info I have, but many numbers around it are.

[Zack]

Judy and Dave:

You said it won't start but you said nothing at all about testing the coil and spark plug to see if they are working.

Before you remove and readjust anything you must do a standard set of tests in the proper order.. First off I would make sure the control levers where in run position and not the stop position which usally grounds out the coil. Next I would remove the spark plug and hold the plug wire about an 1/8inch from the motor block and have some one crank the engine over. If you have spark the next thing to do is put the coil wire on the spark plug and ground the metal part of the plug body on the frame and again crank the engine over looking for a nice blue spark at the plug. Next leave the plug out and have someone crank over the engibne while you hold you finger tightly over the spark plug hole and if it blowes your finger out you probably have enough compression for the engine to run. You next step is the fuel supply system and it is almost certainly plugged with varnish deposits that can oinly be removed by disassembly and cleaning no short cut here.

Just last week a mechanic friend of mine couldn't get an industrial mower going but finally traced it down to a broken found wire under the machine that was ground out to the frame. He found it by removing all the wires running out of the engine and it started immediately, as soon as he hooked them up again it wouldn't.

Lots real good mowers to be had a garage sales because people don't know how to trouble shoot simple problems.

Good luck

Zack

[Conase]

HOW LONG was the fuel in it ????

Bought in 95, run total of 3 hours, "took it out and DRAINED it" ........

Drained what - oil, gas, both ?

Sounds like a clogged carb to me.

How long was what was in it - in there ?

++++++++ Someone mentioned timing. Depending on the motor that is often affected by HITTING A CURB OR ROCK and slighly shearing the KEY at the flywheel.

Newer motors usually have ALUMINUM keys vs STEEL like the old ones.

[glen]

[Stormin Mormon]

Very likely clogged carb. Give it a little shot of ether on the air filter and see if it runs for a couple seconds. If so, take the carb apart and clean it out.

Most likely either the main jet is clogged, or the float is sticking.

[Anon Ymous]

IF the no-start problem persists, pull the flywheel, the little aluminum key that locks the FW to the shaft may be distorted or sheared which will throw the timing way off. you can change everything on the motor and it still won't start if the key is a little bit off, it should be perfectly square.

And most engines will start if you space the gap with an ordinary matchbook cover.

Backyard mechanics at it's best, Good Luck , Byrd