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Replace the Cylinder or just the ring on a Saito rebuild?

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Replace the Cylinder or just the ring on a Saito rebuild?

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Old 08-02-2010, 08:02 PM
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BreakingPoint
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Default Replace the Cylinder or just the ring on a Saito rebuild?

A question for you fellow saito lovers like me. I have an older Satio 125 with a fair amount of use on it and the bearings have gone out in it and I'm in the process of replacing them. The question is, should I consider replacing the piston ring while I'm in there? The cylinder looks to be in great shape with no scratches. The motor still has decent power, so it may not be necessary, but thought I might be able to get a little more power back by doing a rebuild. Obviously the best practice would be to replace the cylinder and piston ring to get it back 100%, but didn't know if just replacing the ring would be ok, or will this only give a temporarily boost in power, with the cylinder needing to be replaced soon.

If only replace the ring, would I need to rough up the walls on the cylinder a little bit, or just slap the ring in it and go. Of course, I would need to do a proper 'break-in' again.

Any advice would be great.

Thanks.
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Old 08-02-2010, 08:10 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

If it's in good shape you just need to run some steel wool through the cylinder to clean it up a bit. Just removing any glaze that has formed from use. Brand new you don't really see any cross hatching like in an auto engine. Rebuild is a loose term with these engines. MOst people just replace the bearings and ring and some even replace the valve springs.
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Old 08-02-2010, 08:21 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

I just rebuilt my FA80. New bearings, gaskets and new piston ring. Cylinder was in perfect shape after a rub down with a clean rag and 91% isopropyl alcohol to remove the tiny bit of castor residue. I'm going to treat it like a brand new engine and take it through a full break in procedure.
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Old 08-02-2010, 09:18 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

If it currently has decent compression, do not take the cylinder piston apart

You can remove the Cyl/piston as a unit without taking the piston out of the cylinder

Just replace the bearings

For heaven's sake don't be rubbing around in the cylinder with any steel wool or 400 wet or dry paper. It is chrome plated on top of the aluminum cylinder

If you are going to replace the ring, just replace the ring. You don't need to be doing any so called busting the glaze procedures on the cylinder.

You will find that the new ring will seat right away.
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Old 08-02-2010, 09:52 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?


ORIGINAL: w8ye

If it currently has decent compression, do not take the cylinder piston apart

You can remove the Cyl/piston as a unit without taking the piston out of the cylinder

Just replace the bearings

For heaven's sake don't be rubbing around in the cylinder with any steel wool or 400 wet or dry paper. It is chrome plated on top of the aluminum cylinder

If you are going to replace the ring, just replace the ring. You don't need to be doing any so called busting the glaze procedures on the cylinder.

You will find that the new ring will seat right away.
How did I know you were going to say that????
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Old 08-02-2010, 09:52 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

If the engine is to be disassembled, and you have the bearings and ring handy, I just don't see the point of loosing the opportunity to change all stuff.
As have been said, the cylinder wall has a chrome plated cover, I do not know how thin or thick it is but I have done all my rebuilds with out sanding the walls, they are usually clean and I just clean the cylinder and lube it with 2 stroke oil.
Take care that the new ring seat at the same position as the old ring and that the piston stay in the same positio too.
Good luck.

Alfred.
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Old 08-02-2010, 11:41 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

On a Saito engine, to change the ring, you do not have to take out the crank shaft or anything

Just take off the carb and back plate, undo the four bolts and hold the jug on and you can lift the cylinder, piston, ring, and rod right off the engine.

You can do this anytime

You can also remove the crank and change the bearings without removing the piston from the cylinder and fouling up the seating of the ring
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Old 08-03-2010, 02:01 AM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

Mine had been "stored" at my dad's house in SE Texas for over 10 years. When I got it back last year the bearings were rough but not rusty. Probably could have cleaned and relubed them and been fine but I decided to replace them. Same with the piston ring and the valve springs. Gaskets and o-rings were a no-brainer. Because of all the work done it's going to be treated as if it just came out of the box for the first time. I'm really looking forward to getting this engine back in an airplane!
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Old 08-03-2010, 08:49 AM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

Thanks for all the replys! This has really helped. Some really good information here. I think I will go ahead and replace the ring while I'm in there replacing the bearings. I'm glad I don't have to hone / sand the walls of the cylinder any. The cylinder looks good and is still very smooth.
Any idea how long the saito cylinders last before they have to be replaced? I know on most other motors, like OS, there is a sleeve that can be replaced. Seems like at some point the diameter of the cylinder will get too big from wear. What's the best way to determine when the cylinder needs replacing?
Thanks
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Old 08-03-2010, 09:49 AM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

About 10 years ago I had an instructor that was working for Horizon doing the engine warranty work. He is the one that showed me how they used a oooo steel wool on cylinders to remove the castor glaze. Not honing or sanding, just cleaning. If a piston ring doesn't score the cylinder then oooo steel wool isn't going to harm it. I have only had to replace one sleeve and it was in a YS 1.10 that sucked up a big bunch of sand and was run again before cleaning. Other then that I haven't seen a cylinder or sleeve that required replacing from wear from running. They seem to last forever and a day.
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Old 08-03-2010, 11:28 AM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

The demise of the Saito cylinder will be bearing cage metal particles that get embedded in the piston and then scratches the cylinder when someone keeps running the engine with bad bearings. Even then, the engines do pretty good with a new piston and ring.

When the steel is embedded in the piston, it can eventually ruin the cylinder walls. When replacing the bearings and you lift off the cylinder/piston assembly from the crankcase, you should pull the piston down far enough to take a peak to see if there is steel stuck in it. Don't pull the piston down far enough for the ring to come out of the cylinder unless you are going to replace something.
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Old 08-03-2010, 03:57 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

Thanks everyone for the replys. I now feel a lot better about not replacing the cylinder. I ordered new bearings and a piston ring today. $40 in parts is not too bad of a price to get this motor running good again.

Thanks!
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Old 08-03-2010, 10:50 PM
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Default RE: Replace the Cylinder or just the ring on a Saito rebuild?

$40 is cheap insurance when you're talking about a $400 motor. Take your time, and if you have any problems there's plenty of help to be had right here on these forums. In fact, you might visit the Club Saito thread - but be prepared, it's up to 717 pages and counting!
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