Briggs 19.5 hp motor won’t operate past half throttle / overly rich

[Baymee]

On the Briggs website it states that if the timing marks line up, it's not important where the piston is. It will not usually be at TDC. News to me. Anyway, the crank gear and key are good and carb and cam on order.

 

[Baymee]

Regarding the ipl above, there is no spring shown; but the service manual shows one. Anybody have a part number on this ?

 

[StarTech]

StarTech and ScrubCadet10, could THAT cam gear rotate on the shaft and cause this faulty cam timing? Or someone got it off by mistake? I see one lobe splined up a bit. Those lobes shouldn't move unless stripped.

slomo

If Cam gear rotate on the shaft then the ACR pin won't be centered up on the intake lobe and possibly be broken off. BUt from image the lobes are in the correct positions according to the camshaft I just looked at.

To me the closest lobe, (intake?) Looks worn more than the other

That is the exhaust lobe that is heavy worn. Still not as bad the one I just recently replaced on an Ariens ZTR. They case harden but once that case harden area wear though it is soft and will wear quickly. BTW save that ACR components from that worn out camshaft for later use.

As for piston position I will double check that in the morning as I got governor and oil pump coming in late today for a 310000 series engine. I just haven't paid that much attention as to the piston position on these engines. But I think it should be at TDC and if so then the matching crank gear key is probably damage but I will know for sure in the morning where the piston is position with the timing marks lined up.

 

[slomo]

Normally when you advance cam timing, you build more cylinder pressure. Gives you more low and mid punch torque.

slomo

 

[StarTech]

Okay got the answer to piston position by actually looking at an engine here that I know is running okay after a lockup oil pump. It is down (about a third to half of the stroke) like shown pass TDC.

Regarding the ipl above, there is no spring shown; but the service manual shows one. Anybody have a part number on this ?

Not all the Nikki carburetors have that spring. More don't than does.

 

[slomo]

Guess the engine manuals have no specifics on the piston and cam timing marks?

slomo

 

[StarTech]

Slomo, The question was piston position when both camshaft and crankshaft gears are timed. I can see why if is the way it is as it make changing the camshaft a lot easier without have to disable the valve train otherwise. On these it is a common thing to change out the camshaft due to ACR failures.

The service does the markings including the piston marks:

The notch or arrow on the piston and “MAG” on the rod (B) must face the same direction. When installed in engine, the notch will face the flywheel.

 

[Baymee]

Installed the new cam. The piston is not at TDC, it's position is still like the picture showed. Ran for half hour test.

Thanks all. I'm glad it's running well again.

 

[Scrubcadet10]

Great news!!!