Mixed up engines.


We bought a handful of new engines a while back and also got a couple engines in a sellout deal at some point. I've since gotten them mixed up after a year and a half of sitting around at the shop.

Pulled one apart today assuming it had never been run.

Combustion chamber black
Piston surface black.
Residual oil only in crankcase.
Darker amber oil
Very little residue in crankcase
Still had governor, carb, tank, and stock exhaust.
Spark plug missing
Stock airbox missing but I may have pulled it off a while back to compare carburetors. Can't remember.

My questions are these.

When the manufacturer test runs these engines, do they run them long enough for soot/black to cover the piston and combustion chamber?

What have you guys seen when pulling apart new engines from the box?

I fear I may have an engine that has been run in a box stock class for an unknown amount of races. It's possible that it came from the sellout deal.



The valves definitely have carbon.
The only reason I pulled the head was to lap the valves.
Looks like I'll be using this head because I've got time invested in it from lapping at this point. Maybe I'll take the guides off of a new head and install on this one.
I've never removed and reinstalled guides before. Are there any concerns with that?
Would I be better off lapping valves on a new head instead?


Dawg 89
Why would you change the guides ?
An engine thats been ran a little had the valves touched up then an inspection . Would be a good engine .
The old adage - If it Ain't Broke Don't Fix It. Still holds True.
Carbon as in hard carbon deposits 1/32 ths thick or just black soot ?


I'd call it hard deposits.... on the stem/filet.
I agree with if it ain't broke don't fix it, I just don't know the history of usage.
The cam could even be aftermarket for all I know. It's important for me to stay true stock internals per rules and spirit of the rules.
I'm very inexperienced with these engines as far as markings and identification. I'm also very limited when it comes to accurate measuring tools. That's why I am concerned with using the unknown.


Dawg 89
Ten 4. Hard deposits on the stem would indicate some usage beyond factory startup. With governor intact and all , personally I think you will be alright . You could get a factory cam to put in if needed for peace of mind .


Good point about the governor.
It spins pretty free too.
To your point also the oil level sensor was still in place and wired.
I'm thinking now that I'll slap a new stock head gasket on it, install the known stock cam and carb from my previous engine, and go racing.
We run air filter adapter, header with governor removed along with stock carb jetted and stock flywheel, stock timing. 10.8's.
After this conversation I figure that this engine hasn't seen any of the abuse near what I'm about to give it.
My previous engine would turn 5400-5500 on the stand at which the valve float would occur. Though I never turned that much rpm racing.

Another question for those who know better than I.
Should I swap the magnet out of the flywheel for one that's not so rusty?
Coil is also rusty as well.
Not crazy rust.... just surface.