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I have an unusual problem. Occasionally, the engine on my mower locks up and the starter is not able to crank it. I have to rotate the flywheel back and forth to free it up at which point the starter will engage and start the engine. It doesn't happen often but when it does, the starter won't budge the engine.

The engine is an 18 HP Briggs Vanguard. It has a new battery and solenoid but the starter is original. Any suggestions would be appreciated.

Check to make sure all connections are tight and clean. Particularly the grounds. If you have a three terminal solenoid the base is the ground and the starter is grounded through the bolts.

Georgia Boy said:

I have an unusual problem. Occasionally, the engine on my mower locks up and the starter is not able to crank it. I have to rotate the flywheel back and forth to free it up at which point the starter will engage and start the engine. It doesn't happen often but when it does, the starter won't budge the engine.

The engine is an 18 HP Briggs Vanguard. It has a new battery and solenoid but the starter is original. Any suggestions would be appreciated.

Click to expand...

Adjust the valves, fixed mine and several others, when the intake and exhaust valves get out of adjustment they will not dump the compression when starting which result in starter not able to turn over the engine on compression stroke.
Sonny

Thanks for the replies.

I've checked the electrical connections already. That's one reason I changed the starter solenoid. But the starter is original but it appears to be OK. When the engine cranks, it's at a fast speed, i.e., the starter doesn't appear to be dragging.

I'll check the valve adjustment and see if they're out. Is there a procedure somewhere with tolerance specifications for doing this?

Again, thanks for the help. I appreciate it. The sooner I can get this thing fixed, the sooner I can get my wife back out there cutting grass!

Georgia Boy said:

I have an unusual problem. Occasionally, the engine on my mower locks up and the starter is not able to crank it. I have to rotate the flywheel back and forth to free it up at which point the starter will engage and start the engine. It doesn't happen often but when it does, the starter won't budge the engine.

The engine is an 18 HP Briggs Vanguard. It has a new battery and solenoid but the starter is original. Any suggestions would be appreciated.

Click to expand...

Lawn Mower Repair Valve Adjustment V-Twin - YouTube watch the you tube video, .004 to .006 should be good for both valves.
Sonny

Excellent reference to the valve adjustment procedure. I'll try this procedure this coming weekend and let you know what I find. Thanks.

Just watched the video and its wrong.

He opens 1 valve to then adjust the other valve but thats not how you do it.

http://www.briggsandstratton.com/support/frequently-asked-questions/Servicing%20the%20valves/?body_0$tbKeyword=valves&selectCats=Troubleshooting+-+Repairs

look at section of adjusting overhead valves.

The reason its wrong is because the engine has a decompressor which you have to eliminate when adjusting valves.

Hey, thanks for the tip. Basically the difference between the video and the B/S instructions is you move the piston 1/4" off TDC then do the valve adjustment. I've checked the manual and the clearance is 0.004" for both the intake and exhaust valves for this engine.

Again, thanks the the tip.

Take a look at the gear on the starter it could be getting in a bind with the fly wheel

Sent from my iPhone using LMF

Thanks for the suggestion, I'll check to make sure the starter is not binding.

I adjusted the valves over the past weekend. Although I didn't measure them, they well all a little loose. I would guess they were around 0.008" to maybe 0.010". I adjusted them to 0.005" at 1/4" past TDC (I confirmed this was the proper procedure for my engine from the local B/S dealer).

Since I didn't have the problem with the engine lockup at each shutdown/restart, it may be a while before I can declare victory. We'll see.

Thanks again for everyone's help.

Well just when I was ready to declare victory, it locked up again. I must have had a dozen or starts on it when it locked. After I turned it off, it sat for ~ 5 minutes before I tried to start it. The starter couldn't turn it and it took me working the fly wheel back and forth before I could free it up. But once freed, the starter had no trouble turning the engine over.

I find it hard to believe then engine would hold pressure on that piston for 5 minutes. My mother in law was using this mower and had the same problem. When it happened with her, it sat for days before I was able to look at it. So I'm pretty sure even if it (the piston) held pressure for 5 minutes, I doubt it would for days.

I believe something else is going on. Other than this problem, the engine seems to run fine. Any other suggestions?