what to clean pistons with??

[scottsgs]

Hi all.

I removed the head on my 81 GS850G. I noticed that the tops of the pistons are coated black what would be the best way to remove that carbon? I am not planning on a total overhaul, I just want to replace all the gaskets and o-rings to stop my oil leaks.

Thanks,

Scott

[TheCafeKid]

My manual shows using a flathead to do it, but they also show the piston OUT of the motor. dunno if you can accomplish this with it in. If you try it be carefull. Those crowns are thin, dont wanna gouge em.

[SabreJim]

I used a wire brush with rags wrapped around them so the carbon doesn't go in the cylinders. I also used a brush bit on the end of my cordless. It sholdn't cause dammage that I am aware of. The harder stuff its ok to carefully scrape off with a small scraper or large flat head. Obviousely you dont want to gouge the top of the piston.

I guess what I am trying to stress is that they are not as delicate as I thought your question implied...

[Nessism]

I recommend pulling the cylinders any time you pull the head so the base gasket can be replaced. Leaving the base gasket in place is false economy since it may leak once the clamp load from the head is released.

After the cylinder is off you can wrap the pistons in a rag and scrub the crown - not sure what is best but a fine wire brush should do the trick.

Good luck.

[RacingJake]

Sounds like your not going to pull the block off. So when your done with each piston use a wet dry vac to get anything between the pistons and cylinder walls out, or if the wife's not looking the house vac works good too.

[scottsgs]

what to clean pistons with??

Hi again,

I will be removing the cylinders once I figure out how to counter my own stupidity. That would be using JB Weld to stop an oil leak at the base gasket. I plan on replacing all the old gaskets and o-rings from the crankcase on up.

Thanks,

Scott

[spyug]

Somewhere in my Big Book of Motorcycle Knowledge (physical and online scrap book I keep of hints tips tricks and procedures) I recall a mention of oven cleaner as the chemical of choice. "Course I can't put my finger on it now but that stuff is so caustic it will likely remove any accumulation of crud.

I think I'd go at it first with a soft wire brush and scrappers ( gently) to get most of the lumps then dose them with the oven cleaner.

It might be easier to do with the pistons out of the bores and it sounds like you will be pulling the cylinders for a base gasket anyway so might as well make a proper job of it. I assume you'll be doing the head and valves while you're at it.

Good winter project. Keep us informed of how it goes for you.

Cheers,
Spyug.

[bwringer]

You definitely want to remove the pistons. New circlips are way cheap, and you can make a simple piston pin press tool using a small piece of PVC pipe, a length of 1/4" all-thread, and some washers and nuts.

Once the pistons are off, remove the rings, break off a hunk of one of the old piston rings, and use that as a scraper to clean out the ring grooves. Careful not to gouge in there.

(Yes, you do need to replace the rings, and lightly hone the bores. I suggest using a flex-hone -- it's dead easy and works beautifully. You don't need to overbore a GS850 unless you have a bazillion miles on the bike -- the larger displacement bikes tend to be much harder on their bores, but 850s don't wear out very quickly.)

There's not much that will dissolve carbon, and nothing I know of that won't risk damaging the aluminum pistons -- you have to physically remove it. I like to use WD-40 (a gallon is about $11, and I put it in a spray bottle) as a parts cleaner simply because it's very gentle to parts and hands and doesn't stink.

Use the blue (soft) Scotch-Brite pads saturated in WD-40 to scrub, scrub, scrub that stuff away. You might need to use the harsher green pads on occasion to get at particularly stubborn deposits -- just be sparing with them, and never use them dry.

Keep everything saturated with WD-40, and keep squirting the WD-40 to rinse off the field of battle. Avoid using the abrasive green pads on the sides of the pistons. Use bamboo chop sticks or some other hard wood implements if you need to dig in to carbon in those pesky valve pockets on the top of the piston.

Once they're nice and shiny, rinse and wash with a detergent-based parts cleaner (Wal-Mart's spray engine cleaner is effective and gentle) and warm water, then dry thoroughly.

[kingofvenus]

Get some Sierra Carbon Free, A good marine supply store should have it in stock. Comes in a spray can, a little pricey but it works great.

[Buddy]

Remove the pistons from the engine and soak them in a bucket of water for a couple days. When they're ready, shake briskly in the water, most all the carbon will just fall off. Use the factory end (not the rough end) of a broken ring to clean the groves.
This has worked for me many times.
Buddy

[rphillips]

Wouldn't try to remove the carbon unless you remove the pistons. The carbon isn't hurting anything anyway. If the carbon crumbs, from trying to clean a piston, gets down beside a piston or wedged on a ring, you could cause cylinder wall damage. Not likely, but why take the chance? wait till you pull the pistons & do it right. With the pistons out, clean the tops with a wire brush on a hand drill, won't hurt a thing, pistons are much tougher than a small wire brush. Probably just WD-40, diesel, or engine degreaser will clean the ring grooves. If there happened to be something that won't wash out, like said before, a piece of broken ring & gently scrape any crud from the grooves. Just my opinion

[lecroy]

One of my old manuals talked about using a hacksaw blade....

When the engine it running, you could shoot a little mist of water into the intake to clean them.
You could switch to alcohol and never clean them again. You could leave the carbon to increase the compression ratio and get better performance. I think my old Kaw tripple 2-stroke talked about this is in the manual...

[Clone]

Oven cleaner will erode the metal of the pistons. If you have the barrels off, remove the wrist pins and then put the pistons into a container of seafoam or Berryman's, it should make the carbon nice and soft, or an even cheaper route would be ATF.

[chef1366]

I use Berrymans. Remove the thick stuff first.

[spyug]

I was just looking at the XS forum this morning and one of the Gurus was answering a thread like this. He uses ordinary paint stripper. Let it sit 10 minutes and it will soften the carbon up enough to gently scrape off witha a plastic spatula....so he recommends.

Just passing this on for more info.

Cheers all.
Spyug.