Engine: 5.3hp Craftsman Eager One #143.434332 Lawn mower engine
Problem: Won't Start
The return spring on the front wheel drive gear box was missing, so I needed to order a new one. Thought I should replace the drive belt while I was ordering parts anyway, and I had the mower up on it's side during this operation. After reassembly, there was a new "clanking" noise. I thought that perhaps I had somehow disturbed the internal governor, so I dissasembled the engine, but could find nothing wrong. I'm now thinking that it was just the outside arm on the governor that was loose. Anyway, I neglected to observe the relationship of the timing marks on the cam and crankshaft gears, so assumed that I should line them up. Engine was resassembled, but now it won't start. Yes, I've checked for a spark, and yes, it is getting fuel. Now I suspect that maybe the timing is off. The manual for my HS 40 snowblower engine says that certain craftsman type carburetors WITHOUT governors, the camshaft timing mark must be advanced one tooth ahead of the mark on the crankshaft. Does anyone know if this mower perhaps has such a carburetor? I'm going crazy with this one; can someone please help?

Oh my word. You're in some pickle. First, the clanking noise was probably just a loose blade. As for timing, all mowers have governors. You can take the Sears ENGINE (143.xxxxxx for Tecumseh) model number, go to Sears.com, and view the IPL for the engine, and you can see the governore for yourself. To check valve timing, remove the cylinder head, turn the engine over SLOWLY and observe the valves. Just as the piston comes up on the exhaust stroke, the exhaust valve should be closing. As the piston achieves TDC, both valves should be open just a scosch (a bit). This period is called valve overlap. If they are open that little bit equally at TDC at the end of the exhaust stroke, your cam timing if off. A loose blade takes away a flywheel effect from the power impulses an engine has, (try pulling one over without a blade on it!) allowing the violence of the pulse to twist the crank herky-jerky resulting in a sheared flywheel key, and changing the ignition timing for the worst, creating a no-start condition, or in some cases a bad miss, or no power. BTW, unless you set the governor 100% in the wrong direction, a simple mis-adjustment won't affect it's ability to start, but may allow it to overspeed or fail to run-up to speed. I strongly suggest, you purchase a small engine repair manual, perhaps even for this series of engine as they have a wealth of info. in them. Torque specs. and sequences are indispensible when dealing with graphite gaskets and critical components.

Since you have already taken the engine apart, then it's likely that the camshaft is not timed properly to the crank. Might as well take it back down and check the timing marks to see if they are aligned properly. I would not worry about trying to look at the valves and figure it out, the only way to be sure is to check the timing marks.

Perform a static governor adjustment, make sure the blade is installed and is tight. I agree with the previous poster about the probable cause of the noise being a loose blade. I would also check the condition of the flywheel key.

If you go to the sticky post in the 4 cycle section, you will find links to download the service manual for your engine.

Thanks for the suggestions. Turns out that the manual that I have for the snowblower is the Tecumseh handbook for ALL 3-10 hp, 4-cycle engines, and covers my mower engine. So I have some reading up to do!
Stan1949

Stan, when I suggested you check valve timing by observing the valves with the head off, it was to save you the trouble of taking the pan back off. You can absolutely check the valve timing by observation of the valve overlap. Even being off one tooth is usually something you can pick up on, and an engine will usually run even when off one tooth abeit rather poorly. I played with cam timing 40 years ago, so I think I know what I'm talking about. The previous poster tells you how to download a service manual - an excellent idea and the price is right.

paulr44, where did you come from? checking the position of valve overlap is a great idea that I never thought of! Your ranking up there with 30year on highest level of knowledge on the board :P I can see this causing a riot, anyway I can recall my old go cart Motor used to run rough, turns out the cam was one tooth off just like you said. Always double check your marks!

Stan, when I suggested you check valve timing by observing the valves with the head off, it was to save you the trouble of taking the pan back off. You can absolutely check the valve timing by observation of the valve overlap. Even being off one tooth is usually something you can pick up on, and an engine will usually run even when off one tooth abeit rather poorly. I played with cam timing 40 years ago, so I think I know what I'm talking about. The previous poster tells you how to download a service manual - an excellent idea and the price is right.

I never said you did not know what you were talking about, but perhaps you might want to consider who your talking to. A novice will not be able to look at valves and tell whether they are in time or not, and may not be able to tell which one is the intake and exhaust. Baby steps, you can't expect that everyone will have the same knowledge as someone who has been working on engines a half century.

paulr44, what do you mean when you say "if they are open that little bit equally at TDC at the end of the exhaust stroke, your cam timing if off". I'm going to guess that you meant to say-"is off". But earlier you seemed to be trying to say that if one was just closing as the other was just opening, then the timing was proper. Which is it?
Thanks.

paulr44, what do you mean when you say "if they are open that little bit equally at TDC at the end of the exhaust stroke, your cam timing if off". I'm going to guess that you meant to say-"is off". But earlier you seemed to be trying to say that if one was just closing as the other was just opening, then the timing was proper. Which is it?
Thanks.

To Stan, I goofed in my typing - long day, sorry. If the valves overlap at TDC as I described, timing is correct.

To 30-year tech, you have a valid point. We can't assume other's know what we do. Easy to forget when you're deep into things.

To Justin, I come in peace. Thank you for the compliment. No walls here - 30yr tech seems to have been around the block too, and I've no intention of stepping on toes - we have a collective effort here, yes?

Paul

P.S. Rare, but have seen it: a severe backfire or loose blade making / allowing the crank to jerk (shockload) violently, resulting in splitting (or just moving it) the crank timing gear which then moves from it's correct position. Then the valves be out of time, and she a-no-startie. Only applies to pressed-on gears, not the keyed kind - never have seen one of those shear the key.

To Paul and 30Year: I've been on vacation and am just now getting around to looking at the mower. You were right so far. The key sheared on the blade adaptor causing a loose blade. I'm sure that was the source of the noise. Have not investigated the timing yet. I'll let you know.

OK folks, here's the deal. The timing was off, but it was the ignition timing, not the valves. The flywheel key had also sheared, causing the flywheel to spin on the end of the crank. I had such a difficult time getting the flywheel off when I dissasembled the the engine, that I thought I would be smart and apply a little anti-sieze upon reassembly. BIG MISTAKE! Apparently the taper is the main factor for absorbing the torque, and the key just keeps everything in the proper relationship. The anti-seize allowed the flywheel to move and sheared the key. Once it was out of position, the iginiton timing was off, and "she-a-no-startie". I just hope my local small engine shop has a new key so I don't have to pay Sears $6.95 shipping for a $.50 part.
Thanks to everyone who made suggestions.

The key is most likely (you can look it up yourself on Sears' website using the 143... eng. mod. number) is a 611004. The local mower shop would greatly appreciate it if you have the part number. The taper is responsible for holding flywheel in position; while the key is responsible for timing during assembly. Looks like you found the problem. You had good intentions with the never-seize LOL : )
Paul
BTW the blade was loose, so remove blade and inspect the HUB closely - often, locating pins often shear off, or keyways get wallowed out, or blade-holding flanges get bent, or blade bolts stretch --- any of which can cause another sheared flywheel key. Remember safety procedures first (plug wire off, gloves, etc.)