ORIGINAL: Chancho

W8ye,

As promised here’s the report on the cylinder and an update on the repair.

It took a while to get all the parts between, RC-bearing, RougueRC and my LHS. I ended up changing the front and rear bearings, jug, piston and piston ring. I saved my new valve springs and tappets for later. I just couldn’t justify the swap. (If anyone has a periodic maintenance table for these items or suggested hour engine run time to change, please share.) The valves cleaned up and are tarnish free now. I was able to carefully reuse the cam box gasket. I just ran the engine this afternoon and everything went just fine. After running an just under an hour in accordance to the manual and a mixture of others techniques, I felt that the new rig was seated pretty well and she’s ready for an airplane. As usual the idle sits nicely and scoots right up on command. “Very satisfying.� I am not anticipating any problems with this engine. This engine ran good before I crashed and with the new innards and jug I’m expecting the same performance from the rebuilt engine as the original.

The jugs were actually quite different. I want to comment about the 115 jug and the “New� 125 jug. Though my 115 went back in for service, as you are probably aware from the other thread, the jugs appear identical. The only difference I could tell between the 115 and the 125 is that the exhaust and intake ports are smaller on the 115 than the 125. They use the same piston and rings. The only difference is a 2mm stroke that must be made up in the crank and case. Now I’m wondering what would happen if someone put a 125 jug on a 115 engine? Bigger ports – more power? (It’d require a modified intake pipe, etc.) Hmm... Or maybe the 115 is designed to be more efficient and you really won’t see much power increase, if any. But from what I can tell, it’s totally possible.

OK… back to the difference in the old and new Saito 125 jugs;

- The exhaust port wall thickness measures 2.34mm from inside thread to outside wall on the old and 3.07 on the new.
o That is a substantial amount of meat increase for those of us who tend to use our muffler as an auxiliary landing device from time to time…
- The intake side of the casting has been cleaned up. There is no longer the extra casting material as you can see this in attached picture.
- The fins are larger diameter and have been redesigned all around. There appears to be room for better cooling and more airflow around the cylinder. The diameter of the top widest fins is 50.75mm on the new jug and 48.92mm on the old jug.
- Glow plug; the Glow plug on the old casting was offset more to the exhaust side. While on the new jug it is more centered, though not exactly between the valves.
- Internally the valve seats have been redesigned and it appears there is room for more fuel air mixture. However I can only observe and this may be only an illusion, but based on the new cuts in the casting around the valve seat – it’s cleaned up inside compared to the old jug.
- The new jug weighs a tad more. (Sorry I forgot to write it down.)

Sorry to ramble on so much, but this is pretty exciting for 125 owners who may be looking at a new jug in the future. I really give the engineers at Saito a lot of credit for cleaning up this casting, big time. I believe part of launching the new Saito 115 was to piggy back the budget to have a new shared jug design for the 125. It was a beautiful engine before and the new casting makes it look all that much sexier. Only Saito knows all of their new design features, but again, good job to our buddies in Japan.

A few hobby shops who still have the older jugs and possibly Horizon may not like me publishing this, but if I were to order a new jug and received an older one, I’d send it back and ask for the newer Jug!!!

Thanks again, all, for sharing the knowhow for taking on this job. I’m that much more endeared with these engines after a teardown/overhaul.

Happy Flying!

ORIGINAL: djsdog

OK, I also tore down my first Saito alllllllllllllll the way down. I read somewhere last year to heat the case to get the bearings out and so I did and they did. I wrecked this engine but not straight into the ground so a freind will check the crank for me. Lots of questions come to mind:

1) Wouldn't stainlees bearings be better if everyone is having corosion problems with bearings?

From what I understand the stainless resist corrosion better than the plain steel bearings. Stainless steel is softer than the plain steel bearing. I and others have had problems with stock Saito bearings. From what I’ve read, pretty much any bearing you put in after stock will be better. My personal tastes are to use the cheep steel bearings at $9 from RC-bearings.com. I plan to change them either on a periodic maintenance schedule or annually.

2) What is the best way to get the new bearings in?

Look up bearing change on youtube. There are a few people who’ve taken some time to put some great videos up on bearing changes and have really helped me thru my first change a few months ago. But specifically, if you heat your case in the oven your bearings should drop in. Some people will put their new bearings in the freezer and then drop them in.

3) I noticed the new bearings (Saito's at the LHS) have seals on them, are these to be removed for lubrication.

The front bearing is sealed and the rear bearing is caged - open. You want the seal so oil doesn’t leak out the front.

4) How do I time the engine, (Ithink the book that came with the engine may tell)?

The manual will show you how to set the timing. There is a dot on the cam that needs to line up with TDC. Some people use a razor blade or something of the sorts to hold the cam in place while to drop it over the crank for alignment. I’ve reassembled and ran the engine just fine after assembly and haven’t had any timing issues a few people have posted. It just feels weird dropping the cam in place and assuming everything lines up when assumedly 1 tooth off will affect timing, etc.

5) Use gaskets with no gasket sealant or use sealant?

It sucks having to buy a new gasket set when you only need a few seals. But the cam case seal is a spacer for the gears to align. If you use no seal or any other method you may be asking for trouble. It is a precision fit. I however have reused a cam box seal that was slightly torn in a few places (as normally is the results when removing the case). I just wiped a small amount of red high temp RTV around the old gasket and reassembled – no leaks – but again, anything out of the manufactures spec and we may be asking for trouble…

6) Any tricks to the pushrod replacement?

I can’t say on this one. I’m surprised no one ripped on me while in a prior post I am showing the pushrod tubes assembled backward. The lip on the tube actually goes on top toward the valve cover. Also the push rods should be pointier side up. I have mixed my rods up during reassembly and haven’t noticed any difference in performance. Obviously you’ll have to retime your engine after reassembly so this should take care of any differences. I don’t think it makes a difference if you mix up the push rods.

Enough for now HELP!!!!

ORIGINAL: w8ye

What is your current problem?

ORIGINAL: cman_25

Oh yes and thanks to, w8ye for the reply on using the razor blade to line up the cam shaft, BUT it does not work on the Saito Fa-180 it has cam followers that have shoulders, and are installed while the cam gear is out of the housing. So it makles it impossible to use the method you described.

But thanks SOOOOOOO much for your time and information.