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Discussion Starter · #1 ·
Hi everyone,
My Briggs engine locks up when trying to start.
Can rock it back and forth a bit on the starter and sometimes get it to run. Engine runs perfectly.
Tried to adjust the valves to what I thought were correct settings but still fails to turn over much before it locks on compression. Adjusted valves closer and it will not start.
There is no decompressor on the camshaft, Is this normal?
What could be the problem? I even ordered a new camshaft and it still came with no decompressor?
Hope someone can help please.
 

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You should mention the model number so others know what size/style of Briggs you are working on.
If there is no CR on the camshaft, it may be there is a slight bump on one of the cam lobes that just 'tickles' the valve a smidge, whenever it rotates, performing CR functions, but not enough to affect operation at higher rpms. FWIW.
Might want to inspect the lobes closely, and/or watch for a valve to do a slight bump/jump/wiggle on the compression stroke.
Even so, you should check your battery resting voltage, hopefully being above 12.5V, check voltage at the starter cable terminal when cranking, s.b. above 10V, and check across the starter relay,or at the starter relay starter side when cranking. Bad terminal connections, worn relay contacts or loose cables can cause stalling as can a battery that is undercharged or has lost capacity. One other check is to use jumper cables connecting an auto/truck battery to either the mower battery, or to ground and the battery terminal on the starter relay. If the battery is weak or the starter worn and drawing too much current, the auto battery may help, and indicate is is nothing about a CR, but is starter/relay/battery/cable related.
tom
 

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Discussion Starter · #3 ·
You should mention the model number so others know what size/style of Briggs you are working on.
If there is no CR on the camshaft, it may be there is a slight bump on one of the cam lobes that just 'tickles' the valve a smidge, whenever it rotates, performing CR functions, but not enough to affect operation at higher rpms. FWIW.
Might want to inspect the lobes closely, and/or watch for a valve to do a slight bump/jump/wiggle on the compression stroke.
Even so, you should check your battery resting voltage, hopefully being above 12.5V, check voltage at the starter cable terminal when cranking, s.b. above 10V, and check across the starter relay,or at the starter relay starter side when cranking. Bad terminal connections, worn relay contacts or loose cables can cause stalling as can a battery that is undercharged or has lost capacity. One other check is to use jumper cables connecting an auto/truck battery to either the mower battery, or to ground and the battery terminal on the starter relay. If the battery is weak or the starter worn and drawing too much current, the auto battery may help, and indicate is is nothing about a CR, but is starter/relay/battery/cable related.
tom
Thanks for your reply, the model number is 406777-0503-E1 as mentioned in the post subject.
I will check the new camshaft against the old one. The new one came with new followers so maybe the old ones are worn down thus not providing enough opening.
The battery is new.
Cheers
 

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I not saying this is your issue. I had a starter that tested good on the bench with power applied but would not turn engine fast when installed. I took the starter apart and one of the magnets had broken and dragging on the armature.
 

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Discussion Starter · #5 ·
I not saying this is your issue. I had a starter that tested good on the bench with power applied but would not turn engine fast when installed. I took the starter apart and one of the magnets had broken and dragging on the armature.
Cheers but I have already swapped starter motors, same problem.
Does anybody know what the correct valve clearances are for this engine?
 

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Cheers, Yes the info I got was 1/4 inch past tdc. Maybe that is the problem?
1/4" is the official number I guess, just make sure you're there or a hair more, roll it forward a little and measure again. Also (and I've done it), make sure you're past TDC and not BTDC.
 

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Discussion Starter · #10 ·
1/4" is the official number I guess, just make sure you're there or a hair more, roll it forward a little and measure again. Also (and I've done it), make sure you're past TDC and not BTDC.
Cheers, I’ll def do that when I put the new cam and followers in. Thanks for your tip!
 

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Did you happen to see a forest around here? Can't see it for all these dang trees...
Sorry. Missed that right in front of me.
tom
 
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