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Discussion Starter #1
I bought a used garden tractor a couple weeks ago. And I'm trying to get it running. I'm not sure that i'm doing the compression test properly. I took both spark plugs out and connected my tester into one hole. I cranked the engine over, and nothing. No reading. The needle dances around slightly on zero. Then I checked the other side. Same thing. Zero. Does this sound right? Does it matter if I have the carb and intake man. off the engine? Shouldn't I get something on the gauge? I haven't used this compression gauge in years. Maybe it's broken. Maybe I should buy a new one and try the test again. I really, really, really hope I'm doing something wrong and the engine is still good. My smoking hot deal isn't feeling so hot anymore.
 

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If I'm not mistaken the B&S twins have compression release to aid in easier starting. If so, you're not going to get a good compression reading at starting speed as the exhaust valve remains slightly cracked open at slow rpm. Once it starts and the rpm picks up the exhaust valve will operate normally.

Try the thumb/finger over the spark plug hole test. With the engine spining (via electric starter or just by hand) you should "feel" your finger or thumb get slightly sucked down on the intake stroke and it should get slightly pushed off the hole on the exhaust stroke. If you feel this then it's safe to assume the valve train is operating, if not theres a problem.

Some models of B&S engines had a problem with the push rods bending and/or loosening up to the point where they don't operate the rockers/valves.
Your Intek should be an overhead valve engine so you can easily take the valve covers off to observe the valve operation. Any problems with the valves will be clearly seen.

Gasoline engines need a fuel air mixture, compression and a spark to run.
Test and verify that each works before you go to deep.
Good luck
 

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It sounds like your doing the compression test correctly,technically the throttle should be at wide open to get a good reading,having the intake off would be ok also.You should be getting something on the gauge,if your not,I'd check the valve train but it seems unlikely that neither would be working but anything is possible.
 

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If you look in the briggs manual they say to use a diff. compression tester. Or a leak down tester. I think they tell you more anyways. You will know were the leak in. You might be able to make one all they are regulator manafold and two gages . the first gage reads the supply( as supplied by the regulator ) psi 80 psi and second reads the pressure in the cylinder (or the amount of leaking. Any thing above 60psi is passing. ( thats a aviation standard) You can here were the leak is . Briggs tells you how to do the test in their manual . You need to hold the crank on tdc ( and I do mean hold) of compression stroke. If you have the piston on tbc it wont move but if you a little off it will, care must be taken. I make sure it their with 10 psi and slowly add air. good Luck . if you find leaks on the valves check the adjustment???If thier to tight they leak and to loose and you will have trouble cranking the engine over.
 

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Put the plugs in. remove the plug wires. SPin the engine by hand clockwise as fast as possible...If you can make it 2 revolutions without encountering major resistance, you have either a pair of broken rods, a broken cam holding the valves open, or some other unforseen failure.

If you feel resistance, do a leakdown test...

OR

Remove the engine shroud, leave the plugs in, remove the wires, whip the flywheel counter-clockwise as sharply as possible. If it snaps back when it hits compression, you have enough compression to run. If it just spins and stops...you have a problem.
 

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Discussion Starter #6
Ok, today I tore into my tractor engine. I figured if it was no good I wasn't going to hurt anything by tearing it down piece by piece to find out what went wrong. I unbolted the engine and put it on a stand. Turns out both aluminum intake push rods were bent. They had fallen off their seat in the rocker arms. Volfandt, I did that thumb in the holes thing. I was getting compression. Thanks for the tip. I'm still not quite clear on how the compression principle works. I ordered new push rods, a new set of gaskets for the covers and a carburator rebuilt kit. Is there anything else I should rule out before I put this thing back together?
 

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Well, the exhaust pushrod should me steel, not aluminum.

Pushrods can rub on the guide plate and wear over time, valve guides can creep up and block the rockers, causing the pushrods to bend...that's about it on these engines.

Considering the pushrods had failed, and your gauge showed no compression, but you haee air movement, I hope it didnt break or bend a valve.
 
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