rcflyerds

When I converted my single-ring Ryobi 31cc recently I put on a larger carb and a Frank Bowman ring. I have just ordered what is supposed to be a twin-ring version to convert and have a question about the rings: Will it help to also get a ring(s) from Frank for this engine, and if so, should I replace both or just the top ring? My guess would be both, but I'm more of a plane guy than an engine guy, so what do you think? None, one or both? Thanks for listening. Dennis

Antique

My Feedback: (4)

We have run our race engines both ways, with two rings and with only one...No measureable difference..Some of the new chainsaws are now using only one ring...[8D]
The new G26 has only one ring...No one can say there is a performance problem with one of these...

captinjohn

Try just one Bowman ring. The ring groove that is not being used is a good place for some extra lube. One ring may mean less friction.....more RPM? Good luck. Capt,n

Volfy

My Feedback: (23)

Well, not all rings are the same. If it is the old single-ring Ryobi, it has a rounded profile and square ring gap ends. Leaked compression terribly. Upgrading to a Bowman ring for sure helped very noticeably. The new twin-ring Ryobi rings are pretty good, so differences are probably not as great, if any.

I bought a replacement set from Frank Bowman for the twin-ring Ryobi anyway. Ahh, what da heck... for the price, I'd say change 'em both and don't look back.

captinjohn

Volfy...The way I read his question....it is about a 2 ring engine?????

rcflyerds

Capt'n, Volfy, RCIGN1 -

Thanks all for your replies, and yes, my current question IS about a two-ring engine. I'm aware of the rounded-ring the single-ring engine had and why replacing it with one of Frank's rings makes a significant difference in compression. I haven't had my hands on a twin-ring version so far, so I don't know if they use the same rounded-rings as the single-ring version. My question then is, when I get my twin-ring engine, should I replace both rings with better ones from Frank, or should I just replace one (the top one I presume) and let the other ring grove handle some extra oil as suggested by captinjohn?

I've been monitoring these engine forums for some time now and have seen all three of you fellas appear quite a bit, and would just like to thank all of you for the time it takes to help the rest of us out. This is what makes the hobby enjoyable! Dennis

av8tor1977

My Feedback: (6)

If it were me, I would change both rings, and give it either run in time in the weedeater, or on the bench if necessary before putting it on a plane.

Good luck,
AV8TOR

captinjohn

Do not forget AV8tOR....he gives a lot of very good data also. So does a list of other good rc people. May we all be like brothers , like in the movie FIRST KNIGHT "Brother to brother. Yours in life and death" Take Care Capt,n

Volfy

My Feedback: (23)

I have already taken apart a twin-ring Ryobi. The rings are indeed much better than the old single ring. The conrod is still stampped steel but has much larger webbing. The ports are also different and may contribute more to the power gain more so than an additional ring. Curiously the "decompression" slits are still there. Still, for roughly $25, the Bowman rings are not a bad bet, IMHO.

Volfy

My Feedback: (23)

rdflyerds, I would take RCIGNS' opinions way over any of the rest of us weekend warriors. Ralph probably has more yrs tinkering with engines than I have lived since I pooped in my diapers.

rcflyerds

Capt'n, you're right on in saying not to forget av8tor - and sure enough he has already joined this thread. Thanks to ALL of you who grace these forums with your advice. Now, I have a few days wait till my engine gets here to ponder all this sage advice. It will be interesting to see how the twin ring compares with the single ring I already have. That one has one of Frank's rings, a muffler from JAG engines, and a larger carb from Peter Faith. It also has not been broken-in yet, so it will be awhile before I can do a comparison with the twin ring. And just to slow things down a bit, my wife of two weeks seems to think I should be spending lots of time with her (don't they understand how much fun all this engine stuff can be?). Thanks again guys.

Sky Viper

So, where/how can a guy (or gal) go about getting a Frank Bowman Ring?

Tom

av8tor1977

My Feedback: (6)

Thanks for the compliments guys... I just enjoy helping when I can.

AV8TOR

rcflyerds

Sky Viper:

Frank can be reached at [email protected] or 1-505-327-0696 ( 6pm to 9pm mst. weekdays) and the following address:
Frank Bowman
1211 N. Allen
Farmington, NM. 87401

Just let him know what engine you have and he will fix you up. Dennis

mikenlapaz

Somewhat related:
When cleaning up engines and the ring(s) are removed for de-gunking should they go back same side up as when removed? If 2 ring piston should they go back in same groove?

If the cyliner is replaced, change out of 'EPA slotted style older ' for non-slotted' , is it OK to just use the existing rings or should they get replaced if possible?

Got the cylinder and a set of Bowman rings but looking for the voice of experience before possibly needlessly commiting the spare ring set.

Got a hard starting 11hr total time, 'EPA slotted' Ryobi,w new WA 167A carb (new diapharms @10 hrs) & CH Ign.
After 11 hours of running (3.5 gallons +-) it has less compression than an used Homie 25 with identical setup. I'm thinking that part of problem may be the 'slot'......

av8tor1977

My Feedback: (6)

Mike,

Yes, it is important that the rings are reinstalled exactly as they were. They "wear in" at the location they were running. Also, for the same "wearing in" reason, used rings should not be used in a new bore. You need to go ahead and use the new rings. It wouldn't hurt to ask Frank exactly what finish he likes on the cylinder walls for the best breaking in of his rings, and apply that grit finish to your cylinder. Another hint; do not use synthetic oil for break in. It can glaze the cylinder wall and prevent the ring from ever breaking in properly. Result, blow by and poor compression. If you want to use synthetic oils that is fine, but break them in with a good quality petroleum oil first.

Good luck,
AV8TOR

mikenlapaz

av8tor1977
This is all news to me. Sounds like a honing process. Another tool to locate...Where can I gather more info on this?

av8tor1977

My Feedback: (6)

Hi Mike,

Well, the breaking, or wearing in, is an important process in a motor. If you examine even an apparently shiny metal surface with a microscope, it is really very rugged looking with peaks and valleys apparent. When two surfaces "wear in", these surfaces burnish to each other and kind of polish themselves. When this occurs successfully, the two parts are mated, and seal well to one another and further wear under ideal conditions, slows to almost nil.

The best surface for a cylinder, is a crosshatch pattern. If you look at one of your cylinders closely, you may see this pattern. The ideal crosshatch is with about a 30 to 45 degree instersection of the crosshatch lines. This is achieved as you said, with a hone. The hone is moved fairly rapidly up and down in the cylinder while spinning, and this creates the crosshatch pattern. The next thing to consider is the roughness, or grit used to make the crosshatch finish. Different types and compositions of rings work best with specific grits of finish, and the cylinder hones are offered with different grit stones (just like sandpaper) to accomplish this. Check with Frank Bowman to see what finish he recommends for his particular rings. Some rings like a very smooth finish done with fine grit stones, and others won't break in properly with such a smooth finish.

The cylinder hones themselves can be found at most auto or motorcycle parts stores and large tool outlets. Just make sure you find one that will go small enough as most of them used for auto use are too large. I have even heard of people using rolled up sandpaper to do the honing, and I suppose that is better than nothing. Frank might say that your new cylinder will have a finish that is fine with his rings, in which case you are home free. (Hone free??) But do remember that any time you install new rings in a used motor, you need to hone the cylinder, and that rings should always be replaced where they used to be when just doing a decarbon or cleanup. The honing process leaves very tiny metal grit imbedded in the cylinder and it is important to super clean the cylinder after honing and before assembly. I clean with a good solvent first, then a super good scrubbing with soap and hot water. Dry the cylinder well, and oil immediately with two stroke oil. (non synthetic) When a lightly oiled paper towel can be passed through the cylinder and remain white, it is clean and ready.

A little lengthy, but I hope this helps,
AV8TOR

mikenlapaz

av8tor1977 Thanks for the info. After reading last nite did some Googling on honing. Going to look tomorrow for a brake cylinder hone as it was mentioned as an option for small engines. Got the impression that one should just litely hone (break the glaze taking as little cylinder as possible.)
This had to be for the benefit of someone else Particularly the last source....Don't I wish!!


One reference that may help others: http://www.gov.ns.ca/nsaf/4h/manuals...gines/mech.pdf

Antique

My Feedback: (4)

Honing cylinders is only for cast iron blocks, not chrome plated aluminum cylinders...Think about it, if the chrome surface on the bore was rough the rings would always be wearign out...Cast iron rings would be no match for a rough hard chrome cylinder.......Chrome or Nikasil cylinders are not made with rough surfaces..The chrome is HARD.....The break in process is to seat the iron piston rings, not the cylinder..A rough cylinder surface would wear out the rings in short order...
I have some new, never used, cylinders here...NO sign of 45 or 60 degree honing, just super smooth chrome surfaces...
The chrome plated bores are very thin, so honing only makes the life of the cylinder shorter, just like ingesting dust and sand...

Antique

My Feedback: (4)

Honing cylinders is only for cast iron blocks, not chrome plated aluminum cylinders...Think about it, if the chrome surface on the bore was rough the rings would always be wearing out...Cast iron rings would be no match for a rough hard chrome cylinder.......Chrome or Nikasil cylinders are not made with rough surfaces..The chrome is HARD.....The break in process is to seat the iron piston rings, not the cylinder..A rough cylinder surface would wear out the rings in short order...
I have some new, never used, cylinders here...NO sign of 45 or 60 degree honing, just super smooth chrome surfaces...Don't believe it, go to a chainsaw store and look in the bore of a new cylinder...SMOOTH chrome or Nikasil, no hone marks...
The chrome plated bores are very thin, so honing only makes the life of the cylinder shorter, just like ingesting dust and sand...[
If you do get a hone at the auto supply and try to hone a cylinder, get a good grip on it, the hone will try to catch in the transer ports as it rotates...[8D]...
Only time I ever hone a cylinder I use a special hone that has small carbide balls instead of long abrasive pieces..When a chrome cylinder has had a piston stuck in it some of the aluminum from the piston gets stuck on the bore...Swimming pool acid on a Q tip dissolves the aluminum, and then running the hone through the cylinder makes sure the aluminum is all gone...The small carbide balls try to catch in the ports, but way less than a brake cylinder hone would...

av8tor1977

My Feedback: (6)

Hi,

Good info on the chrome or Nikasil bores. If you do have to hone these type cylinders, use the finest grit stones you can and go easy. The rings for these engines are designed to work with a very smooth, almost mirror like finish. The special hone RCIGN1 is talking about is generally called a "glaze breaker", and works especially well on two stroke bores. It looks like a bunch of carbide balls on wires, sticking out from the center part that chucks into the drill.

At the Rotax engine qualification school, they taught us to heat the bore before using muriatic acid to clean seized aluminum from the bore and it does seem to work better at removing all the aluminum than the old way of just applying it cold. I don't know how this might work on a chrome or Nikasil bore however, so try it at your own risk.

Thanks,
AV8TOR

mikenlapaz

Always good to have different opinions. It raises a few more questions.
Do any or all of the common makes (Ryobi, Homelite, Zenoah) have Chrome or Nikasil cylinders ? To me they look like finely finished Alum.?
I have a NIB Zenoah boreup 25.4cc cylinder, it shows no evidence of any 'crosshatch' in the cylinder.
I dug out Frank Bowman's cover letter, and got another viewpoint:

Antique

My Feedback: (4)

There are no aluminum cylinders that are not chrome or nikasil..
Using acid to clean the aluminum off the bore works OK cold, never thought about heating the cylinder..The acid doesn't seem to affect the chrome at all, but a good cleaning to get all the acid off is required....Rotax cylinders might have iron liners without chrome plating...
Light scuffing with fine paper is a good idea...The chrome is so hard you can't remove much...

av8tor1977

My Feedback: (6)

Hi,

Just to clarify, RCIGN1 and I seem to be on the same page and in agreement. Most of the weedies probably use an aluminum cylinder that is either chrome plated or Nikasil. (So far I haven't found one that isn't.) Other engines, and perhaps some weedies, use an aluminum cylinder with a steel sleeve for the bore. The difference for this discussion is in the treatment of the bore when replacing rings. The steel bores generally get a more aggressive finish and use different style rings than the chrome or Nikasil bores. (If you use "Chrome-Moly" rings your steel bore engine will also require a very smooth finish.) The point is, when an engine is run for a while, it gets a "oil glaze" on it that needs removed before running, and breaking in, new rings. With the chrome or Nikasil bores, this is done with either very fine stones and minimal honing, or as Frank Bowman suggests, with 4 to 600 sandpaper. Mikenlapaz, as I said, it is best to do what the ring manufacturer recommends for optimal results.

Hope this helps,
Take care,
AV8TOR