estradajae

Hi everyone and specially Saito owners...

I friend of mine has an old Saito FA-91 and talking once to him..I told him if he would sell it....anyway I came across the engine and although it felt good I decided to open it and inspect it...oh my great surprise...the engine has many problems as shown in the pictures...But I would like to rebuild it anyway (taking it as a challenge!).

So ok, the problems are as follows:

1. Opening the backplate, I noticed that the engine ingested some kind of metal, I don´t know what since I haven´t found anything inside, but the conrod is chipped and the race inside crankcase too. (the bearing is shielded and felt " good" so I suspect it wasn´t the problem).

2. I opened the valve covers and right away one rocker arm pin fell off...the previous owner (not my friend) tightened it so much that it damaged the thread... whole valve cover was filled with dark oil (yes...alluminium powder aglutinated by oil)

3. The piston crown had a shinny line caused maybe by a stuck valve or maybe bad timing...but wasn´t damaged.
4. one valve retainer was broken.
5. And to make things worse a stripped glow plug thread....

Also the crankcase has one mounting flange broken just on the front screw hole..

The piston has small scratches but the ring looks fine as well as the cylinder walls (although it looks a little scratched but feels fine).
The crankpin/conrod fit feels a little loose (maybe a new rod here? or re-bush it??)


Tomorrow I´m going to see if a machinist can fix the glow plug thread for me, and if I can work out a solution for the rocker arm pin, maybe put also a brass insert..or make a new pin with a bigger thread...

For the other parts I would like to know what can I use from the current Saito versions? can I use the valve pushrods covers? valve retainers ?? Does anyone has anything that may help me with this and that would like to part with?

I appreciate your help and ideas here. I know it may not worth much doing this..but as I said, it´s kind of a challenge to me...and I may up end with a nice running engine =)

Sincerly

Jorge

proptop

My Feedback: (8)

When the rear bearing gets worn / loose, the bottom end of the connecting rod can rub the inside of the case. Perhaps the rear bearing in there now is not the original, and the damage occurred a while ago?

Maybe you can heli-coil the threads for the rocker arm pivot shaft?
Same for the glow plug threads.

earlwb

I would replace the crankshaft bearings as they are likely bad, even if they seem to feel OK. Like Dar Zeelon stated the rear bearing might have gotten too loose. Years ago one of my Fox engines when its bearings were worn down, felt OK cold, but when hot the crankshaft would move around front and back, etc. Saito FA-91 bearings for example: http://www.bocabearings.com/bearing-...er/saito-fa-91
Also RC-Bearings may have them too.
If you need to knowhow you replace the bearings: http://www.rcmodelreviews.com/bearings.shtml
Now if the bearings are a bit stuck, you may need to tap them out using a brass rod and a small hammer. heat up the crankcase and then tap them out. My brass rod developed a lip on one end, that is handy to snag the rear bearing with for tapping it out.

You can get a new piston ring from Frank Bowman.

The rocker arm...I would simply drill and tap for the next size larger screw size. You can alternate metric to SAE size and thus go up one slight size without getting the hole too large. You can carefully drill a small cup in the tip of a hardened screw. Of course one could make a new rocker arm out of a piece of steel too. Many years ago, I did something like that for a model engine using hand tools, it just took a long time and patience. Having a milling machine would have been much nicer way back then. If the screw head sticks up too high, yopu can cut it off and use a dremel cutting disc to cut a small screw slot in it. This is cool too, a extra long 4/40 set screw looks like it might work too and they have a small cup in the tip as well. http://www.palmerbolt.com/catalog.as...showprevnext=1
I haven't looked in one of my engines, so I forget if a 4/40 screw is too big or not.

If you damage a gasket, you can make one out of card stock. Just use a new X-acto knife blade and take your time.

You can clean it up some, as the valves may be a bit sticky. But I wouldn't try to really super clean it up as the old castor oil varnish and carbon may actually be helping it.

mike31

My Feedback: (67)

Donate it to a resell or thrift store and get a receipt for a tax write off. Use the money towards a new engine. Just my opinion. I destroyed my Saito 91 a few years ago and sent it back for repairs. Came back as good as new and runs fine. Didn't need to mess up the work bench or chase parts. Left more time for fun stuff like building a new plane to put the 91 into.

estradajae

I´m going to replace the bearings too, I do it normally to the engines I receive. Thanks for the tip, I already though about making new rocker pins, so I may get a couple of screws to see what happens.

to me the most important thing is to get the glow plug thread fixed, so stay tuned!


To Mike: No one here will buy this engine...I think not even me (o yes maybe if I get it very cheap)... and I really like fiddling with engines, as I said before...I took it as a challenge!

w8ye

My Feedback: (16)

All current Saito FA91S parts will fit the old Saito 91.

earlwb

Clarence Lee fixes stripped out glow plug holes. it is a very reasonable price too.
Send just the head $20 post paid

C.F. Lee
10112 Woodward Ave.
Sunland, CA. 91040
818 352 3766

The thread size is 1/4" X 32 tpi N.S.F.
You can special order a Heli Coil set that is 1/4" NFS or 32 tpi for around $85 and fix your own plug threads from McMaster-Carr

oskartek

I also agree with earlwb about sending the head to Clarence Lee for glow plug thread repair.
He uses a Timesert repair that is vastly superior to the Heli-Coil which does not really seal the thread
and can let compressed air leak around the glow plug, although the copper washer should seal the plug
the Timesert will endure a heavier torque load and will not fail as easily.
I have seen this in the past.


Happy flying, Oscar

estradajae

It would send it to Mr. Lee... but I don´t live in the USA, shipping from here is gold.

FentonFlyer

My Feedback: (11)

Wow, that baby has led a hard life and not worth fixing in my opinion.
I shy away from any engine that has plier marks on the drive washer. It usually says alot about the previous owners mechanical aptitude or lack thereof.

estradajae

Well I have some updates

I receive back the cylinder jug with a repaired glow plug thread....it cost me about 45USD...not cheap at all, but I could only find one place to get it repaired. The Helicoil people here didn´t have the 1/4x32 threads...and everywhere too had only up to 1/4x28 (Had to tell the people more than once that this thread actually exist, and still they didn´t believe until they took the glow plug and measured it with the thread gauges).
Finally found one machining shop that offered me to fix it (hard to find one that actually want to take the time to do it for you..since they are always "very busy"...) and I´ll have it with a threaded and loctited brass insert (which is better than helicoil).

For the valve rocker pin thread problem...I found that 5/32¨ bolts with an unthreaded section fit perfectly the rocker arm hole and bought some with a tap kit, so what I´m going to do is redrill and tap the rocker arm support on the head and the pin is going to be the bolt, I´m going to left about 2mm of threads and when I´m done I´ll cut the unthreaded portion to fit, and make a groove to tighten it...I hope this works!

So far I´ve cleaned the engine very well, the best I could with the things I have at home (altough the case darkened a bit) and changed the bearings.

So my hopes are on this engine!

Next is to " hone" a little the cylinder walls walls with light sandpaper...and then bring everything together with new o-rings.

It has been a lot of fun...and this remembers me why I like so much this hobby.

Here some pictures,

Saludos


Jorge

w8ye

My Feedback: (16)

Just clean the cylinder with solvent and a clean rag. Do not bother to sand paper it. You may do more harm than good

estradajae

Thanks Jim

I´ll just let it as it is...and it has lot of sense since it is an AAC cylinder.

cna91

Any idea what the size of the valve cover screws are? I seem to have had one vibrate out. Thanks guys.