Riding mower repair

"Well, there's your problem!"

This is waaay out of left field for this blog, but I've spent the last week or so working on this project, so I figure I should describe it.

In the list few weeks, my engine in my ride-on power has been burning tons of oil. It would smoke a bit all the time, but after a while, it would bog down and unleash a massive cloud of blue smoke. I read some forums and things online to try to get an idea of what was happening. Many people said that it was caused by the crank case breather. I figured this would be an easy thing to try. When I went to the small engine store (Willamette Saw) they said that it was almost guaranteed to be the head gasket. Bummer. I came back the next day with the engine model number, and got a new gasket.

You can see the tons of oil swirling around in the air filter housing. What I think was happening is that the head gasket leak was pressuring the crankcase, which was causing the blower to expel lots of air and oil into the housing. When it overflowed, it would pour into the intake causing the huge smoke cloud.

It doesn't get much clearer than that!

Once I got all the covers and stuff off of the engine, the cylinder head came off very easily. It's painfully obvious that this was a blown head gasket, and that the combustion gasses were leaking into the crank case. It's bizarre how thin the gasket is in this location, and that it's really far away from any bolts.

Visible oil in the cylinder.

In addition to the obvious gasket leak, there was a ton of oil in the cylinder. There had to have been at least a table spoon of oil just sitting there in the cylinder. I mopped most of it up before taking the picture, unfortunately. Changing the gasket was really easy. It's important that you clean off all the old gasket and make sure that the mating surfaces are clean and smooth.


I know that it's fairly important to correctly torque the bolts when installing the cylinder head, and I attempted to find information online about the proper torque value. I read somewhere that it was supposed to be set to 55ft./lbs. It's not. Don't do it. That is a TON of torque. In attempting to install the bolts I realized this, and kept backing it off. However, one of the bolts broke anyway.

Hellooo down there!

I friend of mine insisted that I try to remove the bolt (yes, I was going to leave it), and lent me his ez-outs. It can be very difficult to drill into a hardened bolt, especially deep in a hole without destroying the threads. I saw a cool technique somewhere on the internet for drilling down the center of a bolt, so I used the opportunity to try it.

Center drilling a bolt

The trick to drilling down the center of a bolt is using a drill-press and a well-secured vise. Chuck the bit into the drill chuck, but upside-down, then lower it into the vise. It's easiest if you have an x-y stage type of vise.With the bit in the jaws of the vise, secure it. Now, chuck the bolt into the drill press and drill the hole. It's a kinda fun process. I did my best to keep the bit clean and lubricated.

Successfully center-drilled bolt

It should work great, it did for me. I also used a counter sinking bit to de-burr both sides of the bolt. Also, before starting this whole process, I ground off all the markings on the top of the bolt so the drill bit didn't wander around the surface.

Drill bit through the bolt spacer

Spacer installed into the bolt hole

As expected, the spacer fit the bolt hole perfectly, and the bit fit perfectly as well. I was ready to go! What could go wrong?


Well, crap. I hadn't anticipated that. There was no way I was going to get the drill chuck into that space. This sucks. I was hoping that I could get the bolt out without taking the head back off the block. But it became clear that there was no other way to do it.

Well, that's a bit easier to get.

With the head off, getting the bolt was trivial. That's nice. However, I had to buy another head gasket. Once the bolt was replaced,I was able to find the proper torque (220 in/lbs.) which is about 18 ft./lbs. This turned out to be just about perfect. The engine has some serious compression now! I also had to adjust the valve rocker clearance. Now the mower's running like a champ!

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