My neighbor put too much oil in his coleman 10HP brigs. engine. It ran for several minutes and locked up and spit oil out the exhaust. Now it cranks very hard. I am trying to help him fix it if possible. What kind of damage could have been done?

didnt try very hard simple search pops up a few thousand sites also colemans site offers same http://powermate.en-manuals.com/d-pm0545305-03.html

I recommend starting with the basics. a lot of generators will not start or quit running if they are low on oil. check to make sure the oil level is correct before doing anything to the carburetor.

It depends the model# I have a 10 hp 19G412 and it holds is 1 3/8 quarts

Hi Jim, sae 30 mineral oil for all Briggs engines. Regards Phil.

take out the jets , and run small wire through all holes .should fix your problem

Simply unbolt it...nothing sp[ecial there remove the bolts that hold the generator to the engine housing the remove the bolts the hold the gen to the frame (if any)...REMOVE GENERATOR

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

20:1 that's 1/4 pint to a full tank of fuel.

Intake and exhaust valves need adjustment. Intake .004, exhaust .012.
look for wear or loose rocker arm bolt before adjusting valves.

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

If you have fire coming out of the carb, then your intake valve is stuck open. Take the head off, and as you turn the engine, tap on the valve with a plastic screwdriver handle to make it go in, then turn it more to push it back out. If you need to put a light coating of oil on it, so be it. Keep doing this until it's freed up, then put it back together.

You need a quart of regular old SAE 5W30 motor oil with detergent.
The engines on these generators are more or less the same as a lawn mower.
Don't forget to service/change the air cleaner when you change the oil, that should keep your generator producing full power.

Regards,
Carl