Briggs and Stratton, valve lash

[StarTech]

Oh it is so much easier to adjust each valve independently in my opinion instead have to hunt up the extra tools. I just turn until one is fully open and adjust the closed valve rocker.

 

[CWatters]

My understanding is that the B&S has an extra little centrifugal widget that opens a valve at low rpm to decompress the engine to make starting easier. Apparently it only opens the valve a tiny bit, because if the valve gaps are slightly too big it doesn't open it at all and it becomes hard for the starter to turn it over. It's worth spending time adjusting them to get them spot on. Took me a few attempts because the gap changed when I tightened the locking.

 

[bertsmobile1]

All Single cylindre inteks, he outer nut is the adjuster and the inner grub screw is the locking device
There are a lot of You Tube videos showing it the other way round because the poster is a brain dead moron with a massive ego
Twins can go either way
If the adjuster is over the pushrod then it is grub screw to adjust & nut to lock
If the adjuster is on the mounting stud then the nut is the adjuster & the grub screw is the lock .

 

[m610]

The valves are adjusted. They were actually really close to where they should have been.

With the spark plug out, I cranked and the motor spun fine. After I put the spark plug back in the motor would barely turn. The mower has a new battery and starter. I made sure the battery had a full charge by leaving it on the charger for a few hours, then tried again. No change. The motor barely turned. It was too dark to continue so I'll look a little deeper tomorrow.

 

[bertsmobile1]

Jump directly from the battery to the starter + terminal and to a good ground near the starter ( I use the oil drain plug )
If it spins normally then investigate battery leads terminals

 

[CWatters]

With the valve cover off turn the engine over by hand. Check the intake valve (I think) for a slight movement just before TDC. If no movement then it looks like broken decompressor. Think it's needs a new camshaft to fix that.

If you need to use the machine sometimes it will start if you manually rotate the engine backwards against compression then try starting it. This gives the starter a bit of a "run up" to clear the next compression stroke.

 

[m610]

Thanks for the suggestions. I cleaned every electrical contact, including the grounds, then shorted the starter cable straight to the battery, and the engine cranked great, for the few seconds I gave the starter power. I thought the problem had been solved. When I tried to crank it again the starter would engage but the engine would not turn. I put a wrench on the crank and turned it myself, and every other rotation was much more difficult than the others. I turned the crank past that point again and fired the starter, and the engine turned twice and stopped at that difficult spot again. Too much compression once the rings got a little wet with oil and/or fuel? (If I ever get this thing cranking again I'll measure compression.) Not enough starter? The battery is rated for 330 CCA, which is considerably more than what I have on my Craftsman riding mower/tractor.

I tried the run-up idea, turning the crank until just past the difficult spot, and that didn't help.

 

[CWatters]

That really sounds like the decompressor isn't working. I'd have the valve covers off again, recheck valve clearances and look for the little extra lift when turned over by hand.

 

[m610]

The intake valve does not do the tap dance, so yes, it looks like I'll need another cam. Per the video, it looks like a very doable procedure. I'll let you all know how it goes.

Thanks for the tips, and the video is fantastic.

Mike

 

[CWatters]

Another good vid..