If it was left without any preventative maintenance
it is going to be damaged.
Be very very gentle when you start rocking it loose. Also, remove the carb and the reed valve cage. You will be able to see the big-end bearings. The center main, upper and lower bearings will also be accessible. You will be able to see the crankshaft and judge the condition.
The Enduro is supposed to run on 50:1 oil
mix, and its the same bearings as the Leisure model that is 100:1. If you were running 50:1 of TCW3 grade oil you could be OK.
Best case, you slowly rock it free and it runs for another year or two, but it will be rough. Many of these have recovered like this, but they never sound great again.
Worst case, its a new crankshaft assembly with bearings.
It is possible to push the center bearing pin out and replace the CM bearing, but, in my experience, the push fit is a one time deal, a re-fit can work but you run the risk of both big end journals wanting to be next to each other not 180 degrees apart.
To remove the carb.
Remove the stop lanyard.
Remove two screws and remove the plastic resonator. Remove fuel
hose using a long or needle nose pliers. Disconnect the choke linkage by rotating the white plastic catch and then withdraw the Stainless Steel
linkage. Loosen the throttle linkage set screw, and then put motor
and open the throttle, the link will fall out. Place back in N. Undo the two 10mm bolts and withdraw the carb. Remove the small hose on the reed cage. (This is a reverse pulse hose to snap the reed shut) Undo the 3 x 10mm monel bolts and withdraw the reed cage using the slots provided to lever it with a flat screwdriver. Inspect reed valves and retainers for rust.
Use a flashlight and inspect the crankshaft and bearings.
Use 50/50 mix of kerosene or diesel
and TCW3 outboard
oil to liberally and I mean LIBERALLY rinse the entire mechanism while rocking it free. You need to allow it to rinse the rust away from the journals and not allow the rust flakes to re-attach in a good area. I use a spray bottle and approx a quart of liquid. It will drain out of the exhaust ports
, place a receptacle under the prop.
While doing the above, of course spray into the spark plug
holes as well.
No tools are required to add the force required, if you cant do it by hand, do not add torque. Its easier to remove the start cowl by loosening 3x 10mm monel bolts, and you can leave it hanging on the "In gear start protect cable"
When you get it started again, treat as for running in a new motor, details in owners manual.