Onan Generator Carbon Knock
 

I believe I have developed a carbon knock in my Onan Emerald 4000 generator. Has anyone else had a similiar experience and if so is there an easy remedy?

Re: Onan Generator Carbon Knock
 

Onan makes a carbon remover in a spray can I believe. I remember removing the heads on a 4.0 and scraping the carbon off. Ran like new.That was a pain for sure.

Re: Onan Generator Carbon Knock
 

You wont have much luck with the carbon spray. Its more for maintanance, Removing the head is a pain but its the only real fix.

Re: Onan Generator Carbon Knock
 

After you fix if you run some Lucas fuel treatment in every few tanks of gas this will help.I have a lot of rv buddies that swear by it. Just an idea

Re: Onan Generator Carbon Knock
 

I was hoping that I wouldn't have to pull the head, however that seems the concensous. I thought there may be a way to inject throught the intake some sort of liquid to breakup the carbon, like GM Top Engine Cleaner.

Re: Onan Generator Carbon Knock
 

Mark I had the same thing with my previous MH...tried a few different spays, gas treatments...didnt work...Had to pull the generator out and pull the heads off...PIA for sure...also I dunno if you can do it in the MH, it was easier for me just to pull it out....

Re: Onan Generator Carbon Knock
 

Mark, You might try some sea foam from napa. Start gen, and pour it into carb and stall out the gen. Alloy to set for between 20 and 30 minutes then restart. It will smoke alot but may loosen up and clean out your carbon deposits.

Re: Onan Generator Carbon Knock
 

Mark ,I,ve used the GM upper cyl lube for many years ,worked for us. Sprayed it in an let it set , i used a long flexable hose to get in further.
Spin it over spray, let it set, repeat .I always had the headgaskets but never did pull the heads .Running generater with no load on it seems to be the enimey.....

Re: Onan Generator Carbon Knock
 

Thanks to all who replied, I'm going to try the GM Top Engine Cleaner. I let you all know how it went

Re: Onan Generator Carbon Knock
 

I had the same problem. I thought is was a bad rod bearing or broken piston. When I took the heads off I found a smashed chunk of carbon on top of one of the pistons. I probably could have sprayed something through the spark plug hole to dissolve it but I already had the generator out and apart. I would try some carbon cleaner before taking it apart. You can try a marine dealer who sells outboard engines. They carry several different types of carbon cleaners you spray into the engine while running.