proptop

My Feedback: (8)

Do the .82's have valve seat inserts? I don't think they do...but if they do, maybe one is shifting and allowing the compression leakage?

Might also be a slightly tight valve guide? It seems o.k. when cool, but as it heats up, the guide grabs the valve stem and makes it hang up a bit?

brewski

Can anyone tell me the part # and/or where to get a intake manifold for a fa 120? I ordered one for the "S" which looks like the right part but the threaded nut that goes into the head is to large. Thanks in advance.

freeonthree

My Feedback: (1)

I see there is a Special, and an S. Are they the same thing ? I don't see a plain FA 120 on Horizons site.

RVM

I didn't change anything from where Hobbsy had it set. He's got way more experience than I do and I wouldn't dare second guess him.

I have tried two different fuels. A brand-new, fresh bottle of 25% Omega is what I used today.

I know it isn't rich. I can tune a Saito better than most people I've flown with

I am 99% sure it is hissing from the intake and exhaust valves.

Thanks for all the input guys!

freeonthree

My Feedback: (1)

Thats what it is all right... leaky valves. Im afraid your going to have to pull the cylinder and remove the valves and clean everything up good to get er back to correctness. Simple job really, and actually fun to do. It took me about an hour to do my 72. Those little valve spring retainers are tiny ! I had to stack 2 pairs of reading glasses to do it... lol I lapped my valves with colgate toothpaste (not the gel) , worked good ! No hiss at all now... My leakage was constant though, not just when it was hot.

w8ye

My Feedback: (16)

RVM,

If your valves are OK and do not "hiss" when the engine is cold, Then the everything is OK. Just use it.

I think your awareness has increased with all the attention you have paid recently to Saito engines?

Jim

RVM

The valves don't have much compression at any time.

Hmm, I am not sure what I would have become aware of recently.

I would just run it, except it doesn't run. :/

Darklotus

My Feedback: (4)

Lap the valves... Go out buy some valve lapping compound, or use some of the other suggestions people have mentioned here. I used graphite powder on my 72, and it worked great. Compression, in any state of the engine, was completely gone. Now it runs like new out of the box. Its cheap, and easy to do. If it doesn't work you only wasted a few bucks and a little time.



James

freeonthree

My Feedback: (1)

Yeah, and you'll have a lifetime supply of valve lapping compound. I used toothpaste, but I think next time I will use the fine automotive compound. It took too long using the toothpaste. I was just trying to be gentle because the valves and seats are so tiny and fragile looking. It sure would be easier if the cylinder heads were seperate from the cylinders though. Actually, thats my only gripe with these little engines, but im sure they have a good reason for building em this way.
I was just thinking... I wonder if maybe pulling the valve covers and putting some of the marvel mystery oil over the rocker arms and valve stems would help his situation. Maybe he needs a little oil on the stems to keep thing moving freely, if thats what is binding up under heat. It does seem possible to me, and tomorrow im going to remove all my covers and do that to mine. Couldn't hurt, thats for sure...

proptop

My Feedback: (8)

I think I would pull the jug and remove the spring retainers and springs any feel for any drag or anything unusual through the range of motion of the valves...then pull the valves out and inspect the stems for unusual signs of wear with a jewlers loupe or strong magnifying glass, etc. looking for scratches, burrs, etc. and check the valve guides closely too. If it's a low time engine, the valves should drop right through the guides because (hopefully) the keeper (valve lock) slots don't have any displaced metal yet.

When re-assembling, I usually use a little Comet or Bon Ami mixed w/ light oil for a lapping compound, and just do it lightly and only for a few seconds because if there are no bronze/ brass seats, you don't want to wear away the thin coating on the seats.

freeonthree

My Feedback: (1)

Maybe the toothpaste was a good idea then, it sure was a slow process though... Even this fine grade automotive lapping compound I have here may be a bit rough on the seats. Not to mention the fact that for a flight or two, I had minty fresh valves. lol

proptop

My Feedback: (8)

Something freeonthree said made me think about the rocker arm pivots too...maybe try loosening the screw in rocker shaft a turn just to see if it isn't pinching or binding the rocker when tight?

Ya don't suppose it could be a lifter hanging up in the lifter bore do ya?

proptop

My Feedback: (8)

Yeah...the toothpaste is rather fine and takes a while, doesn't it?!
I have some fine 1:1 automotive valve lapping compound, but I thought it was too coarse, so I rummaged around until I saw some Comet and thought (light bulb went off over the head) that if I mixed a tiny bit of it w/ some 3-in-1 oil it would work well...and it does.

brewski

I think the "S" and special are the same thing. I just can not find parts list for a FA 120. I dropped mine and it hit on the carb and broke the intake manifold. Don't do this! Shame on me for mishandling such a treasure. Now if I could just find the right part to get her back in the air.

Hobbsy

My Feedback: (102)

Here is Robert's engine turning an APC 14x6 at 9,200 plus with his muffler and IronBay regulator, then his engine turning 9,400 plus with a TurboHeader and no regulator. There were no valves hissing when it was here. William Robison cautioned people over and over about polishing the valve seats on the AAC Saitos, you can easily remove the chrome that serves as the seat. I cleaned Roberts with a Q-tip and they came clean easily.

w8ye

My Feedback: (16)

The 120S was a complete redesign of the 120. It is unlikely for a individual part to be interchangeable between the two.

However, the new cylinder assembly will fit on the old crankcase. But then you have to use all the upper stuff for the new cylinder.

Insanemoondoggie

Thats for that info Ed, I seem to draw the noobies at the field, must be becuase I are one lol. and was looking for away to get them involved more.
I`m new to Club Saito, just got a 56 to replace a ST GS40 in my goldberg clipped wing .40 Cub. Can I rotate the carb assembly around 180 degrees putting the carb linkage on the same side as the muffler? On my Magnum 52 you can but I could`nt find it in the manual for the Saito, and figured this is the place to ask.
Going to break it in on the test stand today, I have 10% Coolower or 5% Omega, which fuel would be best ?
Thanks ahead of time.

--------------


It wasn't long ago that many clubs would have sessions once or twice a year where building and covering would be demonstrated for all to see. I have seen such sessions convert ARF flyers into real modelers in no time. What seems impossibly difficult can be made doable by a newbie with just a little instruction.


Ed Cregger
[/quote]

w8ye

My Feedback: (16)

RVM,

I must have missed the part where you said it wouldn't run at all?

Your valves could just be gummed up around the stems and seats. Remove the rocker cover and squirt some fuel through the valve springs and then turn the prop several revolutions to move the valves up and down?

Birman

Here is a bit from Bill Robison's Saito notes on grinding the valves.


ABC/AAC identification, o/haul inspection
Now to your FA-120.

First, look at the cam cover. Do the cylinder fins reach out over the cover, or does it look like the cover can be taken off with the cylinder in place? With the fins out over the cam box you have the ABC engine, the small fins are the AAC cylinder. The ABC version has bronze valve seats, OK to lap the valves. The AAC cylinder has hard chrome seats, plated on the base metal aluminum. Do not lap the valves in the AAC cylinder. If you grind the plating down, it will flake and the cylinder will have to be replaced. Use a pencil eraser (a big one) and spin it on the seat if it needs cleaning, chuck the valve in your Dremel after you clean the seats and use the eraser again to polish the valve. If the valve leaks after this, replace it. Install new valve springs, they lose their tension after a period of time, and they are cheap.

rajul

My Feedback: (58)

Download link for Bill Robison's Saito Notes, for those that need it

http://www.ssrcc.org/General%20Files...Nov%202006.doc

N1EDM

My Feedback: (2)

Thanks for the link to our website, rajul. It should be noted that those notes are from November 2006. Is there a more recent version? I had never gotten around to asking Bill if there were - I guess we all thought he'd be around forever.

If there are more recent notes than November '06, please let me know (and please send a copy or a link) and I'll post them and send out the new link.

Thanks,

Bob

w8ye

My Feedback: (16)

Bill Robison once said (and Birman says above) that you do not lap the valves on a AAC Saito. The valve seats are just chrome plated aluminum. If you cut through the chrome, you have ruined the whole cylinder.

Correction:
I originally posted this as a thought without reading what had been already posted. However, someone had beat me to the thought.

Jim

RC Specialties

Hi Jim,

In an earlier post you referenced the SAI50GK93 velocity stack from Horizon. The codes show it fits Saito's up to the 91. Is there another for the 1.00 or is this the one used by everyone?

Jim

freeonthree

My Feedback: (1)

Call Horizon, and speak to them directly. You may be out of luck. I have a 45 here that needs a cylinder (2 of the mounting ears busted off), but their not available any more either... I just keep watchin ebay now. Maybe someday...
Maybe you can put a 120 S cylinder on it...

w8ye

My Feedback: (16)

Saito only has three velocity stacks for the singles. There's one (SAI50GK93) that Saito sells for the engines 45S up through the 91S. There's another that comes on all the 120S and 150S from the factory. Then there is the one for all the 180's and 220's.

We have been using the little one (SAI50GK93) which was originally intended for the 50 on the 100 and 125 also.

I have two 100's with these velocity stacks and the 100's seem to work great. I do not own a 125 so I cannot share any first hand experience about the 125. I do not own a 62 or 82 either.

The problem with this small venturi is just that, it's small and originally intended for the 50. When you mate one up to the 100 the hole through the throttle barrel is as big as the velocity stack's I.D. But due to the spray bar taking up some of the surface area of the venturi, the small velocity stack still works.

All the engines, 45S through 125, have the same bolt spacing for the carburetor hold down, therefore, the velocity stack will bolt to any of the intermediate series engines.