Pulled a second hand AX track motor down after driving for a year. Seems to have a knock.( maybe why it was for sale?) More so when hot... found what looked like bearing material in the screen when putting a Tuna can on. Knock was getting loader so I pulled it off the road before it blows and replaced the engine with a used 2.0l FI engine.. Running pretty good but no where near the power of the weber 2.0l with headers

Any how, I have the pistons and rods out and to my surprise the bearings and crank look fine for a motor with a few seasons on her:

https://www.dropbox.com/s/276lvb6nrq0yg9a/IMG_0895.mov?dl=0


What would be the next place to look mains or cam to cover? thrust bearing?

Cam thrust bearings are worn maybe so cam slides back and forth also hitting cam gear to oil pump bolts?
Does the cam move ??

You can only find the knock by using a measuring tool to determine the clearances in the main rod journals. If the rod piston pins are snug in the pistons, then it can really only knock at the crank end. I did have a motor once that did not have the proper shims behind the flywheel and it locked itself silly with end to end play. You could feel it in the clutch at some point as well. I would get the plastigauge out and measure the journals. They can be out of round but reading the bearings should give you some indication as well.

Cam gear to crank gear backlash? Piston tolerances against the barrels? Excessive end play on the flywheel? Valve seats coming out of place?

Checked the end play of the crank shaft today and it moves 0.009 to 0.010 with a large screwdriver prying up on the crankshaft and gravity pulling it back down. I may have swapped the flywheel on the other engine? I will have to split the case next for more inspection

And, the camshaft moves more that the crankshaft about twice as much (0.020?)

Here is a pic of the Thrust bearing for the camshaft. Note the missing babbit on one side (front) Single thrust
Click to view attachment Click to view attachment

here is a view of the crank, bearing and case:

https://www.dropbox.com/s/ynrblg4drx55t15/IMG_0900.mov?dl=0

https://www.dropbox.com/s/ut6yhu10hfub0x2/IMG_0901.mov?dl=0

Builders recommend using 2 of the cam bearings with the thrust surfaces (both case haves) if you've got a more aggressive cam with more spring loading.

53.9 cc heads
dished pistons
Single spring

From the paper work this looks like a 1.7 upgraded to a 2.0L 44 weber carbs. I changed the carbs out to 40 IDFs 32 (maybe it was 30s..Ill check my notes) Venturi 9had a flat spot on transitions and jetted to idle and run

https://www.youtube.com/watch?v=WKTNsrbUqvI

I believe you can here the knock here at 1:34 minute mark in the video above