TheSamba.com :: View topic - Right way to clean the piston rings/lands/cylinder?

Sat Jun 11, 2016 8:54 am

So, I keep adding to the stuff I'm doing on the engine before reassembly. Yesterday I decided I would like to pull the pistons out of the cylinders, and ensure there is no crud in the lands, possibly clean the cylinders (no honing) and rings and reassemble, ensuring the ring gaps are all out of phase. So I borrowed a sweet compression ring tool to reinstall them.

Anyone have suggestions on how to clean? Brake cleaner OK? The cylinders have absolutely no lip. So it looks like just a clean and inspect thing. I was not planning to pull the rings off as they seem delicate - just solvent and brush and look for any particles - especially in the sieve-like oil ring. Are they, or can I just manhandle them off?

Thanks.

Sat Jun 11, 2016 9:01 am

a broken ring is great for scraping out the lands. just watch your eyes when breaking them.

Sat Jun 11, 2016 9:08 am

I'd just buy a new set of rings while you're there.

My ring lands were so dirty it took some good work, and overnight sitting in the parts washer with rings removed, to get them all cleaned up.

I used my set of snap ring pliers to carefully get the rings out without putting too must stress on them. Careful with that oil control springy one, it is easy to squash and bend wrong.

Keep the orientation right, there is a face up / face down!

Sat Jun 11, 2016 9:11 am

With new rings, then I'd have to hone the cylinders so they properly seat though, right?

Sat Jun 11, 2016 9:26 am

If you pull the pistons out of the cylinders after the rings have seated, it is unlikely that they will seal properly when reinstalled. Get new rings and deglaze the cylinders. It is neither expensive nor difficult.

Sat Jun 11, 2016 10:06 am

What he said ^^^

Just buy a dingleberry hone and do a quick run to deglaze.

Sat Jun 11, 2016 12:18 pm

Break in of new rings after re-assembly is just as important as the honing and ring replacement, so don't ignore this critical element. Essentially, proper ring seating depends on loading the engine and varying rpms. Equally important is deceleration or "trailing throttle" running. If you use a rough hone, (not necessarily recommended, but a cheap hone leaves no options), then the "window" for ring break-in is larger. If you use a truing hone with a fine grit (eg Sunnen CK-10), then the break-in window is smaller, but the cylinder dimensions are better controlled.

In either case, the engine needs to be loaded in 4th gear, initially at low to medium-high engine speeds (say, running at full throttle from 2,000 rpm up to, say 4,000 rpm) initially, and after each acceleration, permitted to slow down, in gear, with a fully closed ("trailing") throttle. Repeat a few times. Do not drive at low load and constant speed! Drive after the initial loaded-to-trailing throttle events using varying speed. Then repeat the whole process going to a higher rpm, say 4,500 rpm. Now change the dino oil you cleverly used instead of synthetic oil, which will impede ring break-in.

If the final hone was very fine, then your ring break-in is complete. If the final hone was rough, do the above again with your clean oil.

There is hard evidence of the above process being appropriate. See just one excellent article (with lots of pics) here: http://www.mototuneusa.com/break_in_secrets.htm

In karting, with nikasil cylinders, the standard ring break-in was to install the rings dry into a dry cylinder and load the engine heavily on the first few seconds of running. A compression test would then reveal how successful the break-in was. This is not recommended for a 4-stroke street engine, but it illustrates the importance of maximizing the gas pressures forcing the rings against the cylinder wall on initial ring installation/replacement to achieve a perfect ring seal. With a cast-iron bore, you only get one shot at a perfect seal. The reason is that the honing ridges need to be cut by the rings, not bent over, which is what happens when the engine is not run under a load to force the rings against the cylinder walls. The rings are also cut in this process, which is part and parcel of how the ultimate sealing is achieved. If a cylinder was properly broken in and is still round and true, it is possible to break in new rings without even honing the cylinder, but the loading of the engine needs to be heavy and immediate. This will rarely achieve the level of ring sealing that is possible with a fresh truing hone of the cylinder.

To clean the ring grooves on a used piston, soaking in carb cleaner, gasoline or even biodiesel can often do most of the work, followed by a solvent-resistant plastic bristle brush. Only use a broken ring if you have carefully dressed the broken edge of the ring on a fine grinding wheel. Scratching the ring land bottom is a no-no.

Sat Jun 11, 2016 12:34 pm

best bet is solvents and a stiff plastic brush. Id shy away from scraping the grooves with a broken ring, the hardest thing that should be used is a piece of hardwood. the soft aluminium piston ring grooves are easily scratched by rough cleaning such as with a broken ring or any other metal thing. once scrathed, the ring groove is ruined. the ring groove diminsions and surface finsh is critical for proper ring fit and seal. so only use something no harder than wood or a plastic bristle brush. no broken rings, screw drivers files etc to clean the grooves.

Yes as stated by others, once the rings have been pulled, best to hone the cylinders a bit. also make sure the ring to groove gap is correct. this can be checked witha feeler gage, but use care that the gage is not going to scratch or gouge the soft piston ring grooves, they are a critical surface.

Use nothing hard to clean the grooves please!!!!!!!!!

good luck

Sat Jun 11, 2016 12:55 pm

A ring groove cutter works wonders.
Gets all of the garbage outa the ring groves fast, clean, & easy.

I'd also use a ball hone to clean up the bores ,& leave a nice cross hatch in them.

Sat Jun 11, 2016 1:04 pm

Great advice here.
All that work to have it fail or have rings not seat.

We use an ultrasonic cleaner for jobs like this....no scrapping, period :!:

Sat Jun 11, 2016 2:26 pm

Nice stuff - you guys are spending all my time! And money! Heh.

Doug

Sat Jun 11, 2016 3:09 pm

I found a nice Snap on ring land tool at a garage sale for $5.00.

Nobody had a clue what it was, or what it did.
I remember using this tool back when I was working for Triumph / BSA.

It has 4 bits on the working end which can be used for different land widths.
The tool is nothing more than a U spring, that applies the right pressure to the bit into the groove.

It knocks the snot outa the grooves easy, usually with one swing.

Sat Jun 11, 2016 7:48 pm

Terry Kay wrote: A ring groove cutter works wonders.
Gets all of the garbage outa the ring groves fast, clean, & easy.

I'd also use a ball hone to clean up the bores ,& leave a nice cross hatch in them.

Id not use a cutter when all that is needed is cleaning. a cutter could scratch the critical ring groove surfaces. only soft stuff should be used for cleaning this.

Sat Jun 11, 2016 11:03 pm

Ordered the rings today. You guys r killing me!😊

Sun Jun 12, 2016 12:41 am

So, any suggestions on which BRM ball to get? Size, grit and abrasive type? Thanks in advance.

DougM