The difference in the wear marks on the spacers might be due to using different alloys if they are aluminum (as it appears to be).  If there's some hammering going on 6061-T6 might be a bit soft, and upgrading the spacer to 2024-T6 or 7075-T6 would help resist deformation.

6061-T6 95 Brinell
2024-T6 125 Brinell
7075-T6 150 Brinell

or make a steel spacer.  4140 annealed is 197 Brinell.

Last night I was pondering the completion and start up of the engine today.  I had primed the oil system yesterday - but I got to wondering about the cylinder and piston skirt.  I had not really applied a lot of oil to the piston this time, as I was trying to keep from getting oil all over the place while working with the engine in the frame.

So - I did something weird.  I filled the engine block up with oil - enough oil to bring some oil up into the bottom of the cylinder.  It took about 2.5 gallons.  I made a small level gauge that fit in the oil fill hole.

This is the piece I made to check the level.  It goes in place of the filler plug and the clear tube stands upright.

The new oil pressure gauge arrived and I put it in.

I pushed the bike outside and put a couple gallons of fuel in.

When I hit the starter button it fired right up and felt very responsive to the throttle.  I looked for oil leaks and saw nothing - but I felt a bit of wind under the fuel tank.  When I was putting the rear valve inspection cap on I had disconnected the breather hose - once I put it on the wind was gone.

I went for a ride around 2 of our county blocks - a bit less than 5 miles.  The cylinder head temperature seemed to stabilize around 213 at the 30 mph I was riding.  With the other piston it would run around 240 degrees when I ride 50-60 mph.  The engine ran very smoothly - it will be interesting to see if it runs this smooth on premium pump gas once I give up using the race fuel.  There is a bit of a bumping/rattling noise from the piston that is most noticeable at idle - it is not awful and doesn't sound like anything is coming apart.

The oil pressure is absolutely scary!!!!!!  At startup it was around 10-15 psi at idle and when revved it would approach 50psi.  As my ride went on and the engine started to warm up the oil pressure got down to zero anytime the rpm dropped below 2,500 rpm.  While I know there is oil moving around in the engine - it is not a warm fuzzy feeling to see that gauge on "O" so much of the time.  The engine is rated for 30 weight oil in the manual - but it sure doesn't make you feel good.  The last time I put in a cam in this engine I ran 30 weight break-in oil and it worked fine - I just was ignorant of the fact that the oil pressure is so minimal in this engine.  I am going to reread DragBikeMike's oil thread and see what his baseline was when his oil system was stock.

Perhaps I need a thicker oil - or it is time to put my overdrive oil pump gears in this bike!  (I wanted to run it stock first to see what was going on before I made the change).

Mike:

Yep, that oil pressure is surprising low!  I agree that this engine has been operating just fine for the last 18,000 miles without me knowing that the oil pressure is not measurable - ignorance is bliss!  The ball and roller bearings really don't need pressure - they need flow.  However - you would think that some kind of a psi reading would be necessary to make some flow, also the cam bearings would benefit from having some psi available!

The compression tester I have is a screw in model.  I ran the test again this morning after my 5 mile run - it is now up to 220 psi, and increase of 12.

I am running the stock cam tensioner spring inside the new plunger I made.  I have allowed 2mm of movement.

A few years ago I made a primitive tool to hold the clutch basket while loosening or tightening the clutch basket.  It is ugly - but is still works!

I started the bike up and the oil pressure seemed to be a bit higher when the engine was cold.  At 3,000 rpm the oil pressure was right around 20psi.

I went for a 15 mile ride and got up to a steady 60mph on the way home.  I would have expected cylinder head temperatures to be around 240 on this ride - but it never got over 220.  It appears the piston is running cooler.

Once the 30 weight oil got fully warmed up the pressure was 10psi at 3,000 rpm.  It dropped to zero at idle as it did with the stock gears. Perhaps with the 30 weight oil the #120 bleed is just too big.

My next change will be to remove the clutch cover and drill a hole in the filter housing and tap it - so I can change the bleed screw (jet) by just removing the filter cover.  Also I have discovered the current location using the screw hole for the seal retainer puts a hole at the bottom of the filter cavity - this allows the oil filter housing to empty whenever the bike sits.  If I make the hole higher the oil filter cavity will not drain.