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Buddy brought me a late 70's Troy Bilt tiller with a 5HP Briggs motor. Rod was broken, so I put a new rod in it and put it back together. He fired it up while I was away, and I think when he did it was low on oil (the crankcase gasket apparently leaked, and when I tore it back down there wasn't much oil in it). It ran for a few seconds and when he tried to engage the tines it died and now won't start.

I tore it back down and put new rings in it (cylinder walls look smooth, no gouges or scratches) and put it back together and it won't do anything.

Timing key on crankshaft/flywheel looks fine.

Timing marks on cam and crank are lined up.

I put a compression gauge on it and got 30LBs, which I know is low.

Given the above information, what should I be looking at? I know it is not recommended to bore/hone these engines, and since I don't have a local machine shop that isn't really a cost effective route anyway.

Valves seem to be opening and closing properly, but I guess I need to pull muffler and carb and check clearance. Just doesn't make sense that it would be valves given that it did start briefly.

Has strong spark, but will barely pop if I pour gas directly into spark plug hole and then reinstall plug and turn it over. Backfires out of both intake and exhaust (and when I say backfire I mean barely putts). Again, that says valves to me.

Anyone have any guidance they can offer? This is my first Briggs tear down. I've rebuild a couple of Honda ATV engines so figured this would be a cinch, but now I'm about ready to toss it.

Harbor Freight has a bolt on engine but it does not have a provision for the reverse pulley on this Troy Bilt, and he really wants to keep the reverse if possible.

Thanks

10 to 1 that the intake valve isn't closing all the way. Remove the head and see if you can turn the valves by putting your thumb on them while in the closed position and twisting them to see if they turn.

I'll try that here shortly. Thanks for the suggestion!

When both are closed I cant turn them. Piston at top dead center. Piston goes down, exhaust valve opens, piston goes up to tdc again and both are loose, back down intake opens. Isnt there supposed to be slack in the valves at tdc on the compression stroke?

I was getting 30psi of compression, and someone mentioned to make sure the push rods didnt get mixed up. I swapped them out and now only have 10psi so guessing I had them in right the first time.

You originally said a 70 tiller and I was thinking L head briggs, but when you were talking about push rods, now we are talking OHV. If OHV then turn the piston until it is slightly past TDC with both valves closed, and set the clearances at .004-.006 and see what happens.

Sure sounds like a compression problem. You said you installed rings. Did you install the right rings? and installed them the right way? are the valves adjusted? how are the valve seats? Just recheck your work.

reynoldston said:

Sure sounds like a compression problem. You said you installed rings. Did you install the right rings? and installed them the right way? are the valves adjusted? how are the valve seats? Just recheck your work.

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Rings were OEM for std size piston (I didn't replace the piston) and were installed per instructions that came with them.

I honestly haven't ever messed with an engine this small, so wasn't sure how to adjust rods. The valve seats look ok just eyeballing them; no pitting or obvious roughness to them.

I'm not even sure if I'm using the right term when I say push rods. The engine is a 130292 3016. What I'm referring to as push rods ride above the cam and push the valves up, so to me that's a push rod.

Thank yall for the replies. Hate to give up on it but need some direction so I'm not wasting my time.

jeepwm75 said:

Rings were OEM for std size piston (I didn't replace the piston) and were installed per instructions that came with them.

I honestly haven't ever messed with an engine this small, so wasn't sure how to adjust rods. The valve seats look ok just eyeballing them; no pitting or obvious roughness to them.

I'm not even sure if I'm using the right term when I say push rods. The engine is a 130292 3016. What I'm referring to as push rods ride above the cam and push the valves up, so to me that's a push rod.

Thank yall for the replies. Hate to give up on it but need some direction so I'm not wasting my time.

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What You can do if the engine is together is a called a leak-down test. With the valves shut you put compressed air in the cylinder through the plug hole. This will tell you where you are losing your compression.

What you are calling the push rods are what we call tappets. Tappets ride on the cam and can either push a valve open, or push on a push rod to open a valve.


I would second the leak down test to find out where you are loosing compression.

reynoldston said:

What You can do if the engine is together is a called a leak-down test. With the valves shut you put compressed air in the cylinder through the plug hole. This will tell you where you are losing your compression.

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I've heard of it. How does one tell where the leak is? I'm guessing watch where the air comes out?

jeepwm75 said:

I've heard of it. How does one tell where the leak is? I'm guessing watch where the air comes out?

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Rigged up an air fitting on the plug hole. Shot some air down in the cylinder with both valves closed and the cyl at TDC.

Oil came gushing out of the fill hole. Guessing that points to bad cylinder, and these aluminum deals aren't bore/hone friendly right? (not that I have a machine shop close by who could do it anyway)