920 piston has heat discoloration

[Whistler]

While doing a routine check on a used 920 Jonse , I noticed carbon buildup on the top of the piston so I pulled the cylinder and piston to do a carbon removal and noticed heat discoloration under the top of the piston(inside) and some in the area of the piston ports . Could this be from the piston carbon and also the exhaust port carbon ? I did a "search " but nothing came up . It is quite obvious that she was running hot . There was no scoring by the way . Thanks .

 

[bwalker]

Describe what the underside of the piston's dome looks like.

 

[HUSKYMAN]

A picture would probably be necessary. Was this a trade in? Sounds like someone had the carb adjusted a hair on the lean side

 

[bwalker]

If the carbon underneath the crown is solid black its normal. If it has ashy grey look it is a sign that it has been run very hot. As far as the carbon in the ports that is normal also with a high hour motor. If you used asynthetic oil you would probaly not be getting coked deposits like this.

 

[Whistler]

bwalker , the underside looks dark, almost black where the dimple in the casting is , turning lighter (light brown) as it goes to the skirt area . After removal of the rings , a purplish tint was noticed there also , in the base of the ring groove's . It should be noted that 90 degrees right of the top arrow , there is black discoloration on the edge of the piston where the ring grooves are . 180 degrees opposite , virtually none . This would be in the area of the piston ports . Its times like this I would like a camera as relying on my discription is vague at best . Sorry !

 

[Whistler]

Huskyman , The saw was not a trade in , it was just one I came across that had good compression and couldn't resist the temptation of a new (used ) toy . A guy has to play !

 

[bwalker]

Whistler,Thats completly normal. I would bet its got quit a few hours on it with dino oil. The deposits you are seeing are caused by the oil partially combusting when it come in contact with a hot part. Is this a epa muffler saw? That could be part of your problem as well.

 

[Whistler]

Yes bwalker , it WAS an epa muffler , that is what prompted the exhaust- port- carbon inspection . It had no snort of any sort . Thanks for the promising reply , much appreciated .

 

[Whistler]

Yes bwalker , it WAS an epa muffler , that is what prompted the exhaust- port- carbon inspection . It had no snort of any sort . Thanks for the promising reply , much appreciated .

 

[bwalker]

Open the muffler up and run a good iso egd synthetic oil and it should eliminate your problem. Maxima makes aproduct that will remove buildup you already have. I think its called power valve cleaner. I have found it works quit well if you use about 4 times the suiggested amount.

 

[Whistler]

bwalker . in my "search" prior to this thread I found that someone has proven Sea Foam to work as a combatant against carbon but it was vague as to mixing it with the gas or not . And I think it fair to assume tha t you DO NOT mix the valve cleaner with gas but use it by itself ,eh ? Also , was in the process of finding a Maxima dealer in my area > I use Husky or Echo mix but I can only assume that this carbon dillema was prior to my ownership . EPA , as you say . Bah ! Thanks again .

 

[tundraotto]

sea foam, slick 50, splitfire plugs, energy release...etc. = nonsense

synthetic oils = no carbon buildup

 

[bwalker]

If you read the msdfs on seafoam its easy to see why it will not work. Its basically kerosene. Which isnt to good for a two stroke.

 

[dstaton]

I found the MSDS for Sea Foam, but I couldn't seem to find the association to Kerosene. Where can I find the info?


Sea Foam components from MSDS:
1 PALE OIL 4229 40-60%
2 NAPHTHA 20 25-35%
3 IPA 125 10-20%

Is this similar to Kerosene?
Thanks

 

[bwalker]

Interesting. The last msds I read for it listed kerosene where the pale oil is now. This was a few years back though. Anyways, this msds is no better. I think they are reffering to a light vis oil when they say "pale oil". That would do nothing for deposits. Naptha is basicaly colman lattern fuel. That would also do nothing as far as cleaning goes, but it would lower the octane of the fuel. Your guess is as good as mine on what proprietary stuff is. My guess is a fuel stabaliser.

 

[dstaton]

Naptha is used in gasoline as a blending agent. (according to exxon). Pale oil is a straight Napthenic (sp) mineral oil. extremely low wax content, excellent solvency characteristics. IPA is isopropanol. All are petroleum distillates. Nothing else is listed on their MSDS.

 

[bwalker]

The only product I have seen remove crabon is Maxima pvc and it only worked when used in really high treat rates. With the ingrediants lyou have listed sea foam would probaly leave more deposits than it can remove. Being a good solvent has nothing to do with removing carbon. Gasoline is a good solvent also.

 

[johncinco]

carbon removal

Man I did a search on carbon removal and only three threads, and this is the only one that actually covers anything useful. Ben, you still say this is the only thing you know to get rid of existing carbon? ANybody else got any good ideas? I am cleaning up the 066 I got a week or so ago and the whole top of the piton is carboned up. I am rebuilding my mercury boat motor at the same time, and bought a used piston for it. When I bought it they sold me some stuff that is supposed to keep carbon from building up, and the guys there said to soak the piston in this stuff and it would take it off. it is made by OMC. Well I soaked it for two days, and the carbon was just as tough as when they pulled it off the shelf. I got it cleaned up nice with a brass wire wheel and it is on its way back together. I just dont want to have to take the saw apart to clean off the carbon.

 

[bwalker]

The best way to guard against carbon build up is to use a high quality oil and keep you morotr jetted properly. That said the only other product I have heard of that removes carbon besides the Maxima stuff is a product that omc makes. I believe you fill the cylinders with the stuff and let it soak and it supposidly removes the all deposits. I will call the company I deal with for my lodges outboards and ask if it works or not. I suspect not. Whatever you do dont take a brass wheel to your piston again. Its pretty easy to gouge/scuff the aluminum. BTW an a saw motor with a flat top piston you can remove crabon deposits from the piston crown with a razor blade. Just be careful not to scratch the piston.

 

[johncinco]

That OMC stuff is what I used and is soaking on the piston right now. I do not want to open up the cylinder if I do not have to, but will if I must. It is some pretty thick carbon buildup. This is a used saw I picked up, so I did not have it build up when I was using it, and having it build up is not a problem for me as I have been using the synthetic oil for awhile now. Some nut at the boat shop told me to put ammonia in the cylinder and let that soak. Ummm yeah, I think I will avoid that idea at least for now. I pretty much figured the brass wire wheel was not the best idea, but it did a fantastic job. I use it for a lot of my antique refurbishing work and have some experience with just how much pressure to apply.