Does removing carbon buildup increase your compression?

[ChainLightning]

This might sound stupid, but I had a mechanic tell me this. He said that he did it on a few saws that had low compression. Said that by removing the carbon buildup from the ports, top of cylinder, and cylinder walls it will boost up the compression by a bit. Then he said to scotch brite the piston and cylinder until they shine. I don't see the logic behind this.
I was talking to him about one of my XL-12s haveing low compression. I told him that I was gonna order some new rings and he told me to not waste my money. Anyone ever try this!?!?

 

[Macman125]

In all reality Removing the carbon from the top of the cylinder would reduce compression. You are making more airspace. Which = less compression.

 

[Macman125]

Not that carbon is a good thing. At least make sure the exhaust port is clen. But as far as the top of the cyl is concerned. I wouldnt take the trouble of removing the carbon from it. You probably are not going to see a gain.

 

[ChainLightning]

In all reality Removing the carbon from the top of the cylinder would reduce compression. You are making more airspace. Which = less compression.

Makes sense. I did not know tho if this was one of those "magic" fixes. I remember hearing stories of people using detergent oil in older engines that have been ran with non detergent oil their whole life. The detergent oil would eat all the carbon out and reduce compression and they would smoke like hell.

 

[tdi-rick]

All he's done is either free the rings up or installed new rings for his compression increase.

If he really believes removing something from a piston crown or chamber and increasing volume increases compression, well, I'll be polite and say nothing at all but he isn't a mechanic.....

 

[half_full]

All he's done is either free the rings up or installed new rings for his compression increase.

If he really believes removing something from a piston crown or chamber and increasing volume increases compression, well, I'll be polite and say nothing at all but he isn't a mechanic.....

freeing up the rings is likely the best explanation. A slight scrub on the cylinder walls might help seat the rings too.
Getting the carbon out can't hurt in the long run.

 

[PARTSWOODCHUCK]

Makes sense. I did not know tho if this was one of those "magic" fixes. I remember hearing stories of people using detergent oil in older engines that have been ran with non detergent oil their whole life. The detergent oil would eat all the carbon out and reduce compression and they would smoke like hell.

Run a good oil at the right ratio and tune the saw up, the carbon buildup will take care of itself.:msp_smile:

 

[CTYank]

freeing up the rings is likely the best explanation. A slight scrub on the cylinder walls might help seat the rings too.
Getting the carbon out can't hurt in the long run.

Havven't run into it myself, but my understanding is that chunks of chamber carbon can act as low-grade diamonds, cutting grooves into piston. No thankew!

 

[Macman125]

Havven't run into it myself, but my understanding is that chunks of chamber carbon can act as low-grade diamonds, cutting grooves into piston. No thankew!

I have seen alot of engines 2 stroke and 4 that have been carboned up and the cylinders have been smooth as glass.

 

[Macman125]

Piston too.

 

[nmurph]

Removing carbon will slightly lower compression, but removing it also improves the fuel charge ignition.

 

[fearofpavement]

Removing carbon will slightly lower compression, but removing it also improves the fuel charge ignition.

It also reduces the chances of pre-ignition/detonation occurring.

 

[Big_Wood]

I recommend doing what J.J does if you have low compression. stuff a piece of bubble gum in the plug hole then heat the top of the cylinder with a torch. the bubble gum will melt and harden to the top of the piston while maintaining the perfect squish always. he has sold a lot of saws he did this to and they still run with no complaints from the people who purchased them

 

[Macman125]

It also reduces the chances of pre-ignition/detonation occurring.

Only if you had high compression to begin with.