Carbon Build-Up - How to Minimize

[leeave96 490]

As I posted in another thread, i dread decarbing my Onan engines on my 520-H tractors.  The whole deal, while necessary at a service interval, looks like a pain in the buttox and fraught with potential snapped head or tin bolts.  Not such a bad service to do on a cast iron Kohler K or Magnum engine.

 

So my question is - what can you do to minimize carbon build-up in an engine in the first place.

 

I know there is lot of stuff you can pour in the gas, spray in the carb, etc., to reduce or eliminate carbon build-up.  What do you recommend?  Have you looked at a badly carboned engine (with head off), re-assembled, added gas treatment or sprayed into the carb the same and then taken apart to see the results?

 

Any tips, tricks, advice would be appreciated.

 

Thanks!

Bill

 

[Mr. 856 170]

im not sure what the right answer is but maybe its high octane fuel? Im talking AV gas. Not the crap we buy at the gas station. I havent run any tests on what seafoam or others will do. I think its just something we as small 4cyl engine owners have to deal with.

[Jake Kuhn 1,579]

Easiest way to clean carbon out is to rev motor up and keep reved up and slowly pour straight water in very slowley not killing engine. Water will knock carbon off everything in combustion chamber. Works very well on older cars as well. Black smoke will come out exhaust proving it.

[Wheel-N-It 2,976]

Another thing you can do is use Dextron 3 transmission fluid. Put about 8oz (or a little more) in a spray bottle. Start the engine and set the throttle to wide open. Liberally spray the ATF directly into the carb, not letting the engine cut off. The ATF has alot of detergents in it that will clean the carbon from the combustion chamber. After the process is over, shut down the engine and remove the plug. Look inside the spark plug hole. If it looks clean then all is well. If not then you will need to repeat the process, and keep in mind the combustion chamber was then totally carboned over.

[decksetter 50]

I use Seafoam. I mix it into all my tractor gas, it's supposed to be a fuel stabilizer too (but I still run premium). Every once in a while I spray some down the carb at half or full throttle with my engine cleaning gun that I got at Harbor Freight. It worked wonders on my truck pouring it straight down the throttle body slowly so I'm a believer.

[JackC 617]

I have some snake oil that I can sell you that works great.  

 

Other than that some use Seafoam.  Also keep the idle up at 1,200 or higher and run the engine at higher RPMS.

 

This is from the 520HC manual and note the use of MUST.  How many out there pay attention to that?

 

 

Engine MUST be operating at Full throttle

whenever tractor is in use. Using tractor while

engine is operating at less than Full throttle

may result in extensive transmission damage

as well as poor overall tractor performance.

 

Note comment about fuel containing alcohol. Ethanol is alcohol.

 

Do not use gasoline de-icers. Gasoline deicers

can cause internal damage to carburetor

and fuel pump parts. Do not use fuels containing

alcohol concentrations greater than ten

percent. Fuel containing alcohol may cause

poor engine performance and internal engine

damage.

 

How many have smoked the diaphragm in the fuel pump with additives?

 

An engine is like a wood stove.  The hotter you run it the better the combustion and the less carbon build up you will have.

[boovuc 1,090]

You nailed that......Jack. My 88 year old mother has a 1987 Plymouth Horizon that is driven a whopping 300 to 400 miles each year.

She always comments how it seems to run so much better after I drive it once in awhile. That is because I flog it and run it up past 3500 RPM and then punch the passing gear enough to blow the cobwebs out of it for a little bit. (If they would have waited a bit to buy back then they would have had fuel injection instead of that horrible Holly bult carb!

You can run an Onan as it should be run per the manual and use high octane gasoline and it will still carbon up. It's how quickly and how much build up you get when you don't. Many on this site have the Onan exhaust valve issues in the back of their minds and won't run their Onans as they should be run. (I was guilty of this as well).

In regard to the original post.......Seafoam them once or twice a summer but opening them up to decarbon and while doing so, adjusting the valves as the manual suggests is the best method of de-carbonizing and prolonging the engine's life. And it is really a help if you take pictures as you take the tins off this engine too! Some things need put on in steps!