Riding mower wont start. Flywheel turns full turn and stops.

William2146 · Aug 22, 2012

Ok, I checked the valves and they are good. The decompressor seems to be working. I saw the valve move slightly but not 100% sure it was that or me twisting the motor to far and starting on the intake or exhaust stroke. Any other ideas. I seem lost since it started fine before I put the new flywheel on.

chance123 · Aug 22, 2012

Did you loosen the ign coil at all? I ask because sometimes the OD of the flywheel gear, you "must" loosen the coil to remove the FW. If so, loosen the 2 bolts that secure it and move the coil the FURTHEST "away" from the flywheel and slightly tighten them. Then rotate the flywheel so that the magnets are centered just under the coil. Take any business card and place it between the flywheel magnet and the coil. Loosen the 2 coil bolts, and the magnetic force will draw the coil to the flywheel magnet. Then tighten the 2 coil bolts, rotate the flywheel and the business card will fall out giving you your coil to flywheel clearence. It's not totaly accurate, but I have been doing it this way since the 60's with never a problem.

Rivets · Aug 22, 2012

I would check the size of the positive battery cables. Companies have been putting larger gauge (smaller diameter) wires on to save money. This creates a high resistance which means less power available to the starter. I recommend 6gauge wire for both battery to solenoid and solenoid to starter cables.

William2146 · Aug 22, 2012

I didn't have to move the solinoid to replace the flywheel but checked the spacing with a buisness card just to rule it out and it didn't change the problem. Also, not sure exactly what gauge wire there is on the battery and starter, however I had no problem starting the mower untill after I replaced the flywheel.

chance123 · Aug 23, 2012

William2146 said:
I didn't have to move the solinoid to replace the flywheel.

I assume yopu meant "the ign coil"

pugaltitude · Aug 23, 2012

Something to do with this flywheel.
What happens if you remove the coil, keep the plug in and turn engine over on the starter?

Could the alternator under the FW be dragging?

Is there 2 much oil in the engine?

DaveTN · Aug 23, 2012

pugaltitude said:
Something to do with this flywheel.
What happens if you remove the coil, keep the plug in and turn engine over on the starter?

Could the alternator under the FW be dragging?

Is there 2 much oil in the engine?

Just a thought but do you have the correct flywheel? One that is slightly different could cause the intake, compression, firing, exhaust cycles to occur at the wrong time. The flywheel will fit but it won't work. Hope this helps. Dave

24Karat · Jan 29, 2017

pugaltitude said:
Check your valve clearances.
Valve Clearance | Briggs & Stratton

If ok then the decompressor on the camshaft could be broken and not allowing engine to turn past conpression stroke.
A decompressor lets excess pressure out of engine to allow starting.

Inlet should be 0.003"-0.005"
Ex should be 0.005"-0.007".

So here's the kicker for me. I have a similar issue with my Craftsman B&G 21HP motor. It won't turn past 1/2 but if I have my Dad manually hand turn it past while I'm turning it over it will start. Could this be the decompressor too? I've already replaced both intake / exhast valves and rods thinking that was the problem.

Riding mower wont start. Flywheel turns full turn and stops.

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William2146

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chance123

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Rivets

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William2146

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chance123

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pugaltitude

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DaveTN

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24Karat

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