Box Stock

Wear and tear

MoreHP68

MoreHP68

Member
I started another thread a few days ago "just a question". Anyways long story short I asked if the stock internals could handle high rpm situations..... Well I heard what sounds to be a rod knock and it turns out it could barely handle its own rpm. Take a look. And keep in mind that this engine has only been run for a total of 2 hours. Brand new!
 

Attachments

  • IMG_20220529_114118409_HDR.jpg
    IMG_20220529_114118409_HDR.jpg
    87.4 KB · Views: 61
  • IMG_20220529_114030689.jpg
    IMG_20220529_114030689.jpg
    67.2 KB · Views: 61
  • IMG_20220529_114021838.jpg
    IMG_20220529_114021838.jpg
    62.2 KB · Views: 60
Get your calipers out and measure the rod journal for roundness. Not many are round at all. Good enough for tilling your garden at 3650 rpm but a lot need an extra .001 clearance in the rod for higher rpms.
 
mike97760 said:
Get your calipers out and measure the rod journal for roundness. Not many are round at all. Good enough for tilling your garden at 3650 rpm but a lot need an extra .001 clearance in the rod for higher rpms.
Click to expand...
No roughness, just visual scratches.
 
Did you clearance this engine properly?

A few months ago I started rebuilding my built Predator and found similar wear on the piston and cylinder wall, only not as severe. There was also some wear on the rod bearings.

Turns out my piston to cylinder wall clearance was like a 1/3 of what it should have been. I’m guesting that’s what caused my damage.

As for the rod damage, maybe not enough oil clearance, or the crank pin is out of round, could be the oil you’re using. I always use straight up 10w30, maybe I’m wrong in using that though.

This engine is stock right?

If you were running high compression or a lot of timing without using proper fuel you could have experienced some spark knock, which could’ve caused the rod damage. I think that may have been what caused my rod bearing damage.

I’ll post some pics of my engine damage when I get the chance.
 
Here is another picture of when I was building. I could also smell some gas in the oil when I drained it.
 

Attachments

  • IMG_20220529_114742586.jpg
    IMG_20220529_114742586.jpg
    122.6 KB · Views: 27
Smelling gas in the oil is bad. It gets there through the intake, so the scuffing could be coming from the gas washing the oil off the cylinder walls . Either running too rich or the float sticking and causing it to flood
 
271mac said:
Smelling gas in the oil is bad. It gets there through the intake, so the scuffing could be coming from the gas washing the oil off the cylinder walls . Either running too rich or the float sticking and causing it to flood
Click to expand...
I just installed a makuni, my last carb was a real piece. The engine wouldn't run and idle smoothly without running rich. I could tell it was rich because when I turned the gas lever to off the engine would start to rev high.
 
You must log in or register to reply here.
Back
Top