Good method for cleaning piston tops ?

[pearljam724]

I removed my head on my 550 due to a minor head gasket leak on my left cylinder. Upon looking at the pistons, my right one is fairly carbon fouled. While the other 2 are pretty clean. Until, I get a chance to work over the carbs, I'm assuming the right cylinder carb is running a tad rich. Can't tell by running the bike though, as it runs great. Anyhow, I tried spraying the tops with degreaser. Followed by smearing a little oil on them and very lightly scraping them with a flat head. Being cautious, not to scratch them. That didn't work too well. I'd like to clean all 3 of those pistons well, including the domes before I reinstall the head. Anyone have a good method to completely remove the carbon, without removing the cylinders ?

[aslsmm]

try oil eater, ive never done this so it's not a tried and true method, just a thought.

i use oil eater to degrease and remove carbon. i would get the piston to a position where it can hold fluid on top of it, then put some oil eater on it, let it sit over night. then put the piston to top position to drain all the fluid, it should come off easily with a wire brush. thats how i clean my hard to clean parts. besure to clean the oil eater off with gas or it will oxidize the nutz out of your piston and or cyl. over night should be fine, just clean the oil eater off when done.

[Alan H]

Might not be carb, could be extra oil on that pot (or the SRIS from the next pot along).
Personally, if it's running OK, I'd leave it alone.

[Pete O'Dell]

elbow grease works well I find combined with either wire brush, emery or wire wool or a combination but elbow grease can be in short supply these days

[Flywheel]

This method is from my youth working on dirt bikes. Soak the top of the pistons with Liquid Wrench (I used the squeezable oil can not the spray). Lightly scrape with the rounded edge of a hacksaw blade. Hacksaw blades bend just enough where you can get a nice angle on the scrape.

[Fritz500]

I spray the piston top with de-greaser and let it sit for 15 minutes then use a fine stainless steel brush (it is about the size of a toothbrush). Gets 90% of the gunk off very cleanly. I then scrape the remainder off with a piece of hardwood shaped like a chisel. Never scratched a piston.

[T350guy]

I use combustion chamber cleaner..awesome stuff.

[pearljam724]

I use combustion chamber cleaner..awesome stuff.

Where, might I find this ? I guess I'll have to try a few of the suggested methods. I might try dropping some Berryman's carb cleaner onto them too. The stuff that comes in a 1 gallon can.

[oldjapanesebikes]

I might try dropping some Berryman's carb cleaner onto them too. The stuff that comes in a 1 gallon can.

I wouldn't recommend Berryman's - it will ruin the seals if you get too much in the cylinder.

As was mentioned earlier, normally elbow grease and a fine wire brush works fine - you can soften the deposit if you wish with a bit of a mineral spirit of your choice (Varsol, penetrating oil, WD40, etc), along with the use of the round end of the hacksaw blade as a scraper. Easy-peasy !

[GT750Battleship]

Hi,what sort of mileage is recommended for doing a top end decoke ?
I try to do the baffles fairly regularly,not that they are all that bad when I check...modern Synthetic two stroke oil seems to help !
Cheers,
Roger.

[Fritz500]

I looked at the pistons in my T500 at about 13,000 and they weren't too bad, I cleaned them anyway. The seals are shot so I imagine they were worse than normal.

[T350guy]

I use combustion chamber cleaner..awesome stuff.

Where, might I find this ? I guess I'll have to try a few of the suggested methods. I might try dropping some Berryman's carb cleaner onto them too. The stuff that comes in a 1 gallon can.

Any automotive shop or a Marine shop.
Spray it.let it sit , wipe off.
Also I have used it on my 77 GT 750 last fall when I bought it..Rings were stuck.Gummy from sitting.
Spray in the chamber. let sit for 10 minutes..fire the ol gal up..Did this about 3 or so times.
Pulled the pipes off and squeaky clean inside. Compression back up to normal.

[oldjapanesebikes]

....what sort of mileage is recommended for doing a top end decoke ?

Using current day 2 stroke oils, much much less than back in the day assuming the engine is in good shape (seals are good). I'd actually be tempted to say, next to never but I'm sure someone will jump in to correct me

[pearljam724]

....what sort of mileage is recommended for doing a top end decoke ?

Using current day 2 stroke oils, much much less than back in the day assuming the engine is in good shape (seals are good). I'd actually be tempted to say, next to never but I'm sure someone will jump in to correct me

It also depend how rich or lean someone's carbs or oil pump is adjusted. It also depends greatly on how someone rides. If you ride around at constant low speeds or someone allows there bike to idle a lot. It would have to be much sooner than not.

[oldjapanesebikes]

It also depend how rich or lean someone's carbs or oil pump is adjusted. It also depends greatly on how someone rides. If you ride around at constant low speeds or someone allows there bike to idle a lot. It would have to be much sooner than not.

Well, I did say the engine had to be in good condition, so in addition to having good seals, proper set up also follows eh ?

Its true that the style of riding will have an impact, but one of the issues back when these were new was lead in the fuel which left loads of deposit, as well as the common practice of using whatever oil was available in the injector tank. Even with the current practice of ruining fuel by adding ethanol, just about any modern fuel has significantly better detergents than fuels available in the 1970's and 1980's - couple that with modern low ash oils specifically designed for 2 stroke injector applications and deposits generally will be minimal as compared to 40 and 50 years ago. And pre-mix is different eh ? Lots of engine idle and slow running with pre-mix systems will lay down loads of deposits.