January 1, 2016

Checking and decking a Classic Harley generator Shovel engine crankcase

Most of you know that I am quite extremist when it comes to engine ,tranny and a lot more,this time I will show something that is not done very often ,checking and correct if needed,the cranckcase where the bottom of cylinder bolt on, if it is not perpendicular to main axis and you leave like it is, you will end up with lots of problems.
I will talk a bit more about an 66 FL engine I am rebuilding now( my new project)
and since I have it completely apart ,and want to have it to be reliable and trouble free for a very long time I decide I will not leave anything overlook,at least I will try.
When the motor factory did there cranckcases machining way back then ,quality control was not important,some of the engines were encounting smoking problems,some were shaking badly,some were loosing a wrist pin to the cylinder side wall,just to name a few problems,but all could have been running really well if everything would have been done correctly.
Cranckcase in hands I decide to check the «decking», the part where the cylinder base seat on top of cranckcase, to make sure everything was set perfectly perpendicular to crank shaft axis,some would ask me why,reason I do this is, I did have this problem with my own 67 way back then,smoking problem as well as plug fouling and misfiring,so why not make sure everything was machine correctly from Motor Factory,not only the decking was not perpendicular but also the cylinders in the same axis so that was amplifying the problem and I would have also loose a wrist pins in a short while.

Here is another thread about cylinders problem,and to tell the truth I have never found one cylinders that is perfect,so they all need to be correct to be perfect.

from my blog on caimag.com


…to continue with the this thread….Here is the start on the vertical milling ,checking to see if head was set right with a double dial from Starrett,this will insure head is perfectly perpendicular to table,check on both side.

When you want to check the base portion of any cranckcase you need to make sure that everything is set up right and doesn’t move,so to do this I use an adjustable angle plate,that permit me to move up and down if case is not perfect,but before starting ,make sure angle plate is dial on the X and Y axis.
I use a special custom machine shafting, with the line lap bushing at the sprocket end plus an other custom made brass bushing on the pinion side,everything is machine with close fit tolerance in one set up on the lathe.then I use the dial on top of it,moving on the X axis,turn shaft several time so achieve and average(even with close tolerance with long shaft you could have a few thou off with this lenght of shaft )


You could see my set up on the angle plate with both pilot guide installed ,with the machine shaft protruding on the right side.

Dial on one end,move on the y axis also to get the highest mark on the dial,no difference in this case

When shaft was dial in to zero,time to check top of case,where base of cylinders sit on the top of case.,next few pics were done in the «x» axis,the «Y» axis has been dial in to the best I could with top surface,this was made as I set up thing with large C clamps.

Front cylinder surface

You can see several thou off mostly from the left side case,tappett block surface were also off by a few thou in the same position.

Here is the rear cylinders now, a little less on this one,but still need to be shave


So what can you do with that,I would say this need to be correct to ensure perfect perpendicularity to main axis,so time to shave surfaces…
Front cylinder after the little shaving ,took off .010 inch in all on both cylinders surface when I first touch it ,so the most that was taking off was .010 some spot almost not touching at all,took off .020 inch deep on both tappet surface,so I could drop the tappet block a little bit deeper ,I also use very thin gasket to help located the pressure hole farther away from tappet roller end,this keep oil pressure up a bit more

Rear one as I start machining,see on the top left corner and in the middle ,just barely touching,another very light cut and I should be good,to end up at .010 as the front cylinder.

But shit happen as they say,on my last cut the pneumatic draw bar decide to let the tool a little loose for a reason I still don’t know ,plunging on the gasket surface,not fun for sure ,but this cannot stay like that,Tig welding done time to redial again,this time on the top gasket portion,the cut was complete with only a few thou to go, but only after the welding was done.

Time to finish this surface with same carbide flycutter that gave me problems before.Here is the surfa«ce after welding and machining was done.

Just to make you think a little bit more ,I just add a picture of the rear tappet block surface as it was machine,you could see uneven gasket surface on the tappet,making the tappet rollers wear unevenly on the camshaft also…

here is the job finish.

I am sure most are not doing thing like I do , not many are even aware of this,it could cause very annoying problems,but when problem occurs with a completely new rebuild engine and you are wondering why your engine is not running as it is supposed to be ,then think of this.

I also had cylinders perpendicular problem with my 67 engine,and both cylinders need to be shave to achieve perfect perpendicularity,(they were off by .010 and .011 inch at the top,with case off by .004 inch all in same direction make it way off ) …to then a perfect running engine….and still running strong years after,without any smoking and plug fouling,hope you have enjoy this thread,Saddlebagrail

Filed under Engine & Transmission, Resources, Saddlebagrail's blog, Tech by saddlebagrail

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