I have a B&S 16.5 OHV MTD Yardman that wil not turn over even though the starter and battery are OK. It will turn to a point and then stops. If I remove the spark plug it turns freely like it should. I know that removes the pressure in the cylinder but I don't know what could cause it to bind under pressure. Help!

thebriggsdude

Adjust the valves....... and go on from there.

http://faqs.custhelp.com/cgi-bin/faq...ted=1101860144

Techwriter

The valves need adjusting. This happened to me yesterday. With the plug removed, the piston at top dead center, and both valves closed, set the gap for the intake valve at .004 in. and the exhaust valve at .006 in.

newaukumdon

The engine has a built in compresion release that could be bad. Is there oil in the cylinder and could be causing a "hydraulic lock". Valve adjustment will be irrelevent because on the compression stroke both valves are closed and can not cause MORE compression the compression release holds the intake open a fraction to help crank, maybe adjusting is compensating for a failure .

Check and see if fluid comes out when cranking, clean it out and try again.

Techwriter

Perhaps there is another problem, but I had the exact symptoms. I replaced the battery, checked all wiring, and even took apart the starter and cleaned the brush contacts. When the plug was pulled, the motor would turn over fine. With the plug installed, the starter acted as if it didn't have enough power to turn the motor over. It would get to the compression stroke and bog down. My parts store owner suggested adjusting the valves as I stated in my earlier post. When I checked my valve gap, both valves were gapped around .008 in. I adjusted them to 4 and 6 and my problem was resolved. Perhaps with the gaps too wide, the valves were closing early causing more compression. I can't explain it, but I know it worked for me.

newaukumdon

Duh, I guess if the clearence is to wide the compression release would not work. . . I have to say though I have seen ALOT of these units and have never experienced an incorrect valve setting creating so much compression it won't crank. I have had manual start engines with incorrect settings kick back on the compression stroke.

Is it possible that when you removed the plug and cranked it, fluid was discharged?

Total waste of time BUT i bet if your clearences were set back to where they were. . . It would crank.

Just because I have not experienced it doesn't mean it can't happen. But pretty damn close.

newaukumdon

Oh Yea, I have had cams that were broke not allowing any valve travel and the engine still cranked.

thebriggsdude

Bought a briggs 16 horse I/C ohv engine maybe 2 years ago on a ayp (sears).... lmao, came with the valves mis adjusted and caught on the compression stroke almost every time.... could have fixed it myself...... sure.... but took it back, acted dumb and got a 18.5 intek powered one that had just went on sale that day... for a couple hundred more... :P which was a much better engine...

It happens.... valves go out of adjustment just a couple degrees and it will catch.., usually the first thing I recommend when they do catch like that... believe briggs recommends like every year or every other year they are checked and adjusted....

Zormo

Is it reccommended to use a threadlock after adjusting the valves and if so what type is reccommended?

thebriggsdude

wouldn't recommend it unless they keep loosening in a short period of time.