Intek, 17 HP, uneven cranking speed

Gumby83 said:
I did have to siphon the oil out of the dipstick tube because the drain plug is seized and it didn’t seem worth the time/effort to get it out because the engine had just run so well.
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No issues doing this. Fluid evac is such a time/labor saver.
Gumby83 said:
Now, it’s cranking unevenly like it’s out of time, and after 5-6 revolutions it snaps off a near-deafening backfire in the full choke position.

The plug is damp with fuel but not wet, so I don’t think it’s flooding to the point of hydro-lock.
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Investigate the carb needle/seat. Pull the oil stick and smell for gas. If you smell gas, repair the needle/seat and dump the oil several times. Gas will dilute the oil into a water like viscosity. Stop running the engine until you confirm this tip.
Gumby83 said:
Pulling the air filter and it’s obvious that pressure is escaping into the intake as well.
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Possible notorious Intek head gasket blow out. If so, recommend lapping the head and block where the head gasket sits. Use a solid copper head gasket. Some hi tack head gasket spray wouldn't hurt either.
 
1.De-carbon the engine
2.Valve lapping job
3.Smell the oil stick
4.Possible stuck open intake valve

Sounds like several issues. Need to go over the entire machine.
 
Auto Doc's said:
Key looks good,

Leaking into crankcase should be slight leakage past the rings and that would usually be expected, but if you loosen the oil fill cap and it blows the dipstick out under pressure, there is a blown head gasket at the push rod area between the block and the head. You can pull the valve cover to verify this.
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I think I may have already (albeit unintentionally) confirmed the head gasket - or possibly a valve guide/seat issue.

I didn’t have time to share the details earlier, but when I did the leak down test, I already had the valve cover off per StarTech’s suggestion to have the rockers loose to ensure the valves were closed.

The leak was much louder at the valves/top of head - a couple of times I held the valve cover over the head just to listen for leaking at the dipstick tube and the noise level there was much lower (sounded like normal ring leakage).

I didn’t have time to find the actual source but either way it sounds like I’m pulling the head.

Thanks again.
 
slomo said:
You would be wrong. Under the full mark, nope. Over full, nope. Right on full is a win. Check oil level prior to EVERY mow.
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As with any other engine, I add an amount of oil that’s expected to be close to capacity after draining the crankcase, but always re-check the oil level after running the engine for a few minutes after the initial fill, and adjust the level as needed.

Since siphoning was the method used, I didn’t expect the crankcase to be drained nearly as much as it would’ve been had I pulled the drain plug. At 1.5 qt capacity, 1 qt. was a reasonable amount to use for the initial start.
 
Gumby83 said:
As with any other engine, I add an amount of oil that’s expected to be close to capacity after draining the crankcase, but always re-check the oil level after running the engine for a few minutes after the initial fill, and adjust the level as needed.

Since siphoning was the method used, I didn’t expect the crankcase to be drained nearly as much as it would’ve been had I pulled the drain plug. At 1.5 qt capacity, 1 qt. was a reasonable amount to use for the initial start.
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Put it ON the FULL mark PRIOR to every mow or starting the engine. Oil is cheap, engines not so much.
 
Gumby83 said:
Confirmed today the head gasket is at fault. We’ll see how it runs after re-assembly.
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Don't forget to lap the head and block. De-carbon everything while she is open. Pull the valves out and clean the back sides. Do a valve job with grinding compound.

You don't simply toss on a new head gasket and call it good. Or I don't anyway.
 
The shiny spot is from the heli-coil that failed.

It had somehow threaded its way about halfway into the cylinder, but held its coiled shape and was just making contact with the piston at TDC.

The piston isn’t scratched or scored or otherwise damaged - it basically just cleaned off the carbon in that one spot.
 
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