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I have a craftsman LT1000 with the briggs 17.5 31C707 engine. Flywheel was turning really slow while trying to start, so I figured it needed a valve adjustment again. Adjusted the valves twice and no changes. Flywheel spins freely with the plug out. What could be the problem?

The compression relief part of the camshaft could be broken.

Does it turn slow or kick back? Turn it backward against rotation until it comes back to compression and see if it will start.

MParr said:

The compression relief part of the camshaft could be broken.

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very common on that engine.

hlw49 said:

Does it turn slow or kick back? Turn it backward against rotation until it comes back to compression and see if it will start.

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When I hold the key down it doesn't budge, slowly turns, then lurches forward and repeats the cycle. I just did the valves and both rods seem to be opening the valves. I'll have to wait until the morning to get back at it

dahyippur said:

When I hold the key down it doesn't budge, slowly turns, then lurches forward and repeats the cycle. I just did the valves and both rods seem to be opening the valves. I'll have to wait until the morning to get back at it

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Remove the spark plug. Put your thumb over the spark plug hole and turn the engine by hand until you feel compression. Then stop and reinstall the plug and wire. Now, get on the mower, choke it and try to crank it.

I also have 2005-purchased LT1000 with the Briggs 31C707 engine. By early 2010s I also have issue of slow cranking, kept adjusting the valves, getting the battery checked or replaced, kept the battery on a charger.

Then in 2013, apparently while mowing the weeds in the pasture, I developed an oil leak somewhere and the oil leaked out, destroying the engine. I ended up buying a replacement 31P677 0912G5 engine online which was a couple more hp and also had a spin-on oil filter, and it was very easy to install. Since then, I no longer need to do the battery charger thing and have not needed to do a valve adjustment either. So basically the new engine took care of several issues.

dahyippur said:

I have a craftsman LT1000 with the briggs 17.5 31C707 engine. Flywheel was turning really slow while trying to start, so I figured it needed a valve adjustment again. Adjusted the valves twice and no changes. Flywheel spins freely with the plug out. What could be the problem?

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What stroke were the valves adjusted on specifically? There are 2 TDC spots on a 4 smoke engine.

Watched the valves today and didn't see any bump for compression release. Seems like it'll start reliably if I turn the flywheel to the end of the the combustion stroke by hand then turn it over. Hopefully I can make it to the end of the season

Cam part numbers are 793880 or 84005207, either one will work. (just changed part numbers

Good luck. Hope the governor/oil slinger didnt take a lick. Last three camshaft ACR failure took out the governor and it took me a month to get three governors and still havent seen any Briggs OEM camshafts. I had to use junk after market camshafts just to get the customer's mowers going.

Scrubcadet10 said:

Cam part numbers are 793880 or 84005207, either one will work. (just changed part numbers

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Not sure if I should order a cam, or find a whole new motor somewhere

It sounds like the compression release mechanism. Have a Load Test done on your fully charged Battery. Don't jump it from a running vehicle. Set valves Cold at the correct TDC. Check Manual for lash/gap.

I just had that issue, and the magnet in the starter housing were broken. Pulled starter off another unit I had here and works great now!

Whatever you do do not bang on the starter it has ceramic magnets and you will break them and ruin your starter.

did you check you valve clearances if not mine was 4 intake 4 exhaust thousands

if we read back we see the OP did not have an ACR bump when he watched the valves.

slomo said:

What stroke were the valves adjusted on specifically? There are 2 TDC spots on a 4 smoke engine.

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Gord Baker said:

It sounds like the compression release mechanism. Have a Load Test done on your fully charged Battery. Don't jump it from a running vehicle. Set valves Cold at the correct TDC. Check Manual for lash/gap.

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crawford111 said:

did you check you valve clearances if not mine was 4 intake 4 exhaust thousands

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I set the intake to .004 & exhaust to .006. I usually set one valve while the other is open, is this bad practice?

dahyippur said:

I set the intake to .004 & exhaust to .006. I usually set one valve while the other is open, is this bad practice?

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that's usually the way i do it... no one's ever complained.

dahyippur said:

I set the intake to .004 & exhaust to .006. I usually set one valve while the other is open, is this bad practice?

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If your ACR on the cam took a dump.... I wouldn't run that engine at all. Those lil pieces will cause more damage ...... It does pay to tear it down and replace the the cam instead of swapping to a new engine ..... I have sold many of cams for those model engines.....

Boudreaux In Eunice La. said:

If your ACR on the cam took a dump.... I wouldn't run that engine at all. Those lil pieces will cause more damage ...... It does pay to tear it down and replace the the cam instead of swapping to a new engine ..... I have sold many of cams for those model engines.....

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I agree...a replacement used engine could have the same issue in the near future and also could have had poor maintenance.

Boudreaux In Eunice La. said:

If your ACR on the cam took a dump.... I wouldn't run that engine at all. Those lil pieces will cause more damage ...... It does pay to tear it down and replace the the cam instead of swapping to a new engine ..... I have sold many of cams for those model engines.....

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Boudreaux!? how in the world are ya? good to "see" ya...

Scrubcadet10 said:

Boudreaux!? how in the world are ya? good to "see" ya...

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Hey Hey There Scrub , I said hi to you about a month ago or so Guess you didn't see my reply to a problematic but simple fix people were making a big deal over ...

Boudreaux In Eunice La. said:

If your ACR on the cam took a dump.... I wouldn't run that engine at all. Those lil pieces will cause more damage ...... It does pay to tear it down and replace the the cam instead of swapping to a new engine ..... I have sold many of cams for those model engines.....

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This engine was not treated well before I found it. I put on a new head, lapped the valves, replaced broken push rods, and rebuilt the carb a few years ago. Idea of a new machine or a new engine is pretty appealing at this point

dahyippur said:

This engine was not treated well before I found it. I put on a new head, lapped the valves, replaced broken push rods, and rebuilt the carb a few years ago. Idea of a new machine or a new engine is pretty appealing at this point

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In that case new machine or new engine at least. Could be fixing one thing after another on that engine.