Did you set the valve clearance with the piston 1/4" PAST TDC?

I set the valves with one valve open, one valve closed, then vice-versa. How do I accurately measure the piston 1/4" past TDC? Thanks!

Find TDC and then rotate until the piston drops 1/4". Use a straw, screw driver, chopstick or whatever you want in the spark plug hole to measure a 1/4" drop in the piston. Then set the valves.

one thing- could it be that the battery wires have corroded inside the wires and now are not transferring the power well? do a resistance test, and replace if in doubt. Just a thought

I set the valves 1/4" past tdc using a scale. Actually, they were spot-on at .003". The engine still has mad compression; I can barely rotate it by hand. I'll dig deeper into the starting system, battery cables and perhaps swap a starter from an I/C 20hp twin that I have here (more torque). We'll find it.

If the Int is set at .003 and the Exh at .005 1/4 inch drop past TDC, then most likely you have a bad cam, being the compression is high. Remember looking at the head with the cover off, the intake is the bottom valve and exhaust is the top valve.

Briggs changed the cam design for the 18's and 18.5's too, if memory serves. Make sure/verify battery cable clean/tight connections at both ends both positive and negative. Also include any engine grounds.

Briggs doesn't publish a spec for compression on these engines.

This sounds like the EXACT problem I have. JD dealer says it is the valves.

The most common cause of this is valves needing adjusting as said above, however, here is a fair number of these engines put out that had soft cam lobes which wore down giving the exact same symptoms as valves needing adjusted. when you adjust the valves, note the amount of lift, movement, of each valve.

Walt Conner

Well I did set the valves once again, hooked up my commercial charger to the battery, and she roared to life! I have another Briggs 17 I/C OHV that was a pull with a broken connecting rod. I found a small spring at the bottom of the crankcase which was part of the unloader on the camshaft. I robbed some parts from a 14.5 and have a rotating assembly. I'll let you know how this one goes. Thanks again for all of your replies.

"I set the valves with one valve open, one valve closed, then vice-versa. How do I accurately measure the piston 1/4" past TDC? Thanks!"

They should both be closed.

i haven't opened it up yet but what does it take to adjust the valves?

Not by the book valve ajustment (.25 inch past TDC)but it worked for me when by the book didnt. Watch video.
Now my tractor turns over easy.

Here is a link that might be useful: valve Ajustment

Hey guys like to add my 2 cents and maybe get some help. Mine is the 18hp ohc,wont turn thru the comp stroke with a known good battery,starter good and all connections good,set the valves at .004 1/4" past tdc. I understand you should see a slight decompression coming off the cam just b4 tdc. I have no movement in the pushrods whatsoever. Suspecting bad cam. How do I get to that? Anyone know where I can access a disassembly/shop manual? Im kind of over my head here. Doing favor for my neighbor. He says go for it but I would like some kind of instrucions. Thnx

Compression release isn't working