Measuring the Cylinder

It is too cold so I brought the go-putz engine 28M707 and the 31P777 into the house.  Now that they have warmed up I am going to take another shot at measuring the cylinders.  In this post I will only be dealing with the 28M707.

Nominal bore is 3.440.  Used gauge block to verify and lock digital caliper at 3.440.  Setup bore dial indicator to zero at the caliper setting.  A real pain.  Then verified the virgin cylinder wall below the piston travel.   It may be faster to set the dial indicator on the virgin wall.  Not sure.

Checking the bottom of the bore verified the setting of zero as 3.44.  The wear along the axis of the crank travel is .012 over so we will need to bore this one to .020 over.

The bore below the piston is consistent as expected and will allow the hone to follow the center of the original bore.

Lisle Cylinder Hone and Related tools.

Measuring GoPutz 's cylinder indicated that it needed to be sized up to .010 over. It took a long time to make the six measurements needed.  So I bought a Fowler Cylinder bore gage in addition to the Lisle boring hone. I also purchased #240   and #500  grit stone sets.   While I was at it I bought a better digital micrometer.

A boring hone should not be confused with a flex hone. The boring hone has the stones mounted solid to a rack and pinion arrangement that allows the hone to be precisely sized and expanded.

After reading the honing instructions I found out that I really needed a long reach micrometer to ensure the stones remain flat. 

My first idea was to hone the block in a tub of kerosene resting inside the parts washer.   Once I got it setup I found that there is a lot I did not like about it.

My plan B is to mount the hone in the drill press. This way I can set the speed using the belts and limit the stroke using the dept stop.  It does make recycling the kerosene harder  but that is a minor compared to what is gained.

To be continued....

Go-Putz has been started

The engine has been removed and torn down.  I have not removed the valves  which seem to be well seated.

The exhaust valve seemed a bit loose.

Found a plug gauge for briggs 5/16 valve guides on ebay for under  $10 with shipping.  It is NOS and a bit rusty in spots but should work.  Will use it to see if the exhaust valve guide on go-putz's briggs 13hp needs replacing.


Sunday, October 19, 2014

The plug gauge does not go in to the valve guide so it should be OK.
The plug gauge seemed large and I wondered if was the correct one but it is only .012 larger then the 5/16" specified for the valve stem diameter.

I measured the cylinder with snap gauges.  It seems every time I use these thing I need to relearn their proper use.  This motor looks to be well cared for. The insides are about the cleanest I have seen in an old briggs.    The cylinder out of round 0.0035 and taper 0.003 are not horrid but the larger dimension of the cylinder is too large for standard rings and both are too small for 10 over.

The cylinder needs to be honed to 10 over.   Looking at getting the Lisle LI15000 Engine Cylinder Hone.
    

Maybe a bit pricy for building a single engine  but  short of a cylinder boring machine it seems to be the only way to true up a cylinder.