Home - Monday - Friday - Feb 16th - 20th 2009

I grew up one block from where my father was a mechanic. By the age of five, I could tear down a carburetor, and restore it back to some wondrous shape. No parts left over either.

I can not count the number of times I walked in and there Garfield was, repairing something under the hood. In Swift County, folks would tell me when he rebuilt an engine, it ran longer than the factory version.

In the humblest of my opinions, what he did is largely a lost art. I doubt there are more than fifty mechanics, that work for dealers, who have the facilities, and the knowledge to do what he did. In a metro of 2 1/2 million people, I am struggling to even find -one- place to bore my cylinder. I may have to send it out of state.

Imagine that ...

Lotsa pictures, some just a matter of record for me - so I know where something went.

Tech Note: In reality, the contrast of the images is a notch too high. But, that does highlight certain things that might be a bit harder to see in person. The engine is not really as crappy looking as some of the images suggest.

 

The Sacrificial Altar to the Gods of Horsepower and Noise. I decided to work on it inside, as it is cold outside. Jonnette raised no dummy.

 

Some of the Instruments of Terror. The Sherry in the bottle is for cooking and medicinal purposes. At least, that is what I claim on my 1040.

 

The engine.

 

This stub of shaft is used to hand crank the engine. The pawl in the crank, beat up the keyway pretty bad and the shaft is too large to get the pulley past it. I took a new file to it and cleaned it up.

 

I have a nice three jaw puller and it came in handy.

 

Note, the rust where the pulley was.

 

More images of record. Most of the lines/tubing have been removed.

 

Spin off two nuts and the Injector comes out. The Injector Pump is capable of 3000psi and the Injector opens at 2600psi. -That- is alot of pressure.

 

Images of record.

 

The valve area. On the right are the adjustment nuts where the pushrods, that go up and down, push up against the rocker arm supported by a shaft which open the valve which is closed by a valve spring. These are timed to the crankshaft to open and close exactly in the right moment.

 

The piston at BDC. Bottom Dead Center.

 

Part way up the cylinder.

 

At TDC. Top Dead Center.

 

The Cylinder Head. A Gasoline engine usually has a domed combustion chamber and somewhere around a 6.5 - 11 to 1 compression ratio. This engine has a 23 to 1 compression ratio and the chamber is flat. Gasoline engines use a spark plug to ignite the air/fuel mixture. A diesel engine injects fuel into the combustion chamber which, because of the high compression, the air gets really hot and the fuel explodes under that compression. The little pocket upper-left, is where all that happens. The fuel injector is held in place by the two bolts on the left side of the image.

Here is a link that describes how an engine works.

 

The Fuel Injector Pump. A complicated and very precise part. I have a new one waiting. The pump operates by a plunger that rides against a cam. The cam rotates, pushes the plunger in and the fuel is compressed. All this has to be timed to the crankshaft to deliver that tiny squirt of fuel at the proper moment.

 

Remember the exposed gear on the starter? This is the opposing gear on the flywheel. That's how the engine gets turned over for starting.

 

Flywheels usually have "Timing Marks" for the proper spots for TDC and Ignition etc. Here is the mark for TDC. The image below shows the position of the piston at TDC.

Ignition in most engines occurs before the piston reaches TDC. And there are marks on the flywheel for timing the injector. If the fuel was not ignited before the top of the stroke, the engine would be very inefficient. It takes time for the flame to propagate across the combustion chamber and the largest part of that explosion should occur as the piston is just a few degrees past TDC. This engine is timed at 30 degrees before TDC.

 

 

We have to get this hub off the flywheel. More than likely, there is more corrosion (Called "Rust" for our Calif Buddies.)

 

Another view. This puppie is hard to get at.

 

Warming a part with some gentle heat will expand it a little. This might break up the rust a bit, or simply make the part larger on the shaft.

 

Throw the puller on it.

 

Hub removed, now the nut. Takes a 1 7/8" socket. I will fetch that from my son Tom.

 

Another view.

 

While I wait for that, I will take the oil pan off. This is a wet sump engine. ie: The oil is contained within the engine in the pan. A dry sump engine, pulls the oil from an external reservoir and pumps it back after circulating it thru the engine. This engine holds three quarts.

 

The crankshaft. The piston, moves up and down in the cylinder bore. The connecting rod transfers that motion to the offset pin in the crankshaft. In turn that becomes rotary motion which ends up spinning the propeller. In a car, it turns the wheels.

 

I spoke of additional contrast. Here, the cylinder walls show pitting and a degree of rust. Looks alot worse here than in reality, but, these pits can be felt with your fingernail. Which, allows the hot gases to blow past the piston instead of being used for power.

I have a new piston, oversized by 0.020" and will find a machinist to bore the cylinder. Then, we will have better compression especially at the top of the stroke. The bottom image shows the corrosion where the rings work their hardest.

This is what I thought I would find on an engine with 350 hours, which is very low time, but thirty years old. Which, sat idle a whole lot of that time.

 

Now you can see where the connecting rod connects to the crankshaft.

 

The piston and connecting rod. It is hardly worn in and I will sell it on eBay for $35 or so.

 

Getting to be more bare.

 

The evidence.

 

-This- is a socket.

 

I jammed a piece of wood into the crankcase and the lobe of the crankshaft jammed into it. Then, I could stand on the wrench and crack the nut loose.

 

To get the flywheel off, I placed the hub back in, fastened it and cracked it loose.

 

Now for the other end.

The engine is really in two parts. The actual engine with crankshaft, cylinder, piston, valves and head. Then, the supporting things like valve cam, fuel lift cam, fuel injector pump cam, oil pump and so on.

 

Like a watch inside. For a small engine, the various parts are really massive.

 

The gear on the left, is mounted on the crankshaft. To achieve a 1:2 ratio of rotation, the gear on the right has twice as many teeth. The one dot on the left gear, the two on the right, are "Timing Marks". Used to make certain the "Timing" of the crankshaft and valves and fuel injector pump are correct.

 

I removed this shaft from the far gear, put a spacer under it, and popped this gear off the shaft that way by tighterning the socket screws. Kinda clever, I thought.

 

With that gear removed, now we can pop the crankshaft out of the crankcase. You can see an oil line from the oil pump that supplies oil to the bearing and shaft.

 

The plate contains the "Big End Bearing" and a thrust bearing. I have new ones for both plus the oil seal.

 

Ready to pull out.

 

This crankshaft is massive for a 300cc engine. Both gear and flywheel ends of the shaft are 1 5/8" in diameter. In a gasoline engine, these may be an inch or less.

 

Looking inside to the opposite end. Another bearing and thrust washer.

 

After removing the rocker arms, shaft and valves. These are the valve guides and I will press in new ones.

 

The valve springs, caps, retainers and valves. The retainers fit on the small groove at the end of the valve stem and jam into the cap.

 

The shiny part of the valve is what rests against the valve seat in the cylinder head. Looking carefully, one can see the corrosion. Not from wear, but age.

 

Another good view of the cylinder head and combustion chamber.

 

The fuel injector spurts a spray of fuel from this port.

 

On the opposite side, is a curious little hole. It is called an air cell. The small hole has a chamber behind it. About 5/16" in diameter and maybe 7/16" deep. At slower rpm's, as the air is compressed, it can go thru the hole in the chamber and reduce the compression a bit. At higher rpm's that will not happen as easily. I will have to clean this out just a bit.

 

Better images of the valves. I have new ones.

Now, to get things downstairs and do some righteous cleaning. Find a shop to bore the cylinder. Get 2-3 more parts from England and put it all back together.

 

Later ...