56 Johnson 15hp Piston/Carbon question

[seawolf]

Hi what is the best way to clean carbon from the head of the pistons?

When I opened the cylinder head cover I noticed a carbon build up on the piston (head). It was to the point that it is flaked in appearance. There seams to be a very small (almost negligable) amount of cylinder scuff. should I try and take most of the carbon out or leave and run with seafoam or equivalant.

This is one of the first motors I have worked on and really don't know the extent of wear I am looking at. Is this normal or not? Is this build up caused by blow by and or pre-ignition? The carbon is black and build up is to the point it is somwhat flaked. Is this a sure sign that the rings are bad?

Any info would be appreciated.

 

[coolguy147]

Re: 56 Johnson 15hp Piston/Carbon question

seafoam basically one of the best products out there for this situation.

tasha has some of those instructions

 

[Silvertip]

Re: 56 Johnson 15hp Piston/Carbon question

If you have the head off the engine scrape the carbon off with a sharp putty knife but be sure you don't gouge the crown of the piston. After you've reassembled the engine, do the Decarb procedure (search the forum as its covered in great detail). If the head of the piston is carboned up, the rings almost certainly are too.

 

[samo_ott]

Re: 56 Johnson 15hp Piston/Carbon question

Yep, scrape it off. And post a pic if you can.

 

[wbeaton]

Re: 56 Johnson 15hp Piston/Carbon question

Make sure to use a new head gasket p/n 203247 and plane the head.