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Author Topic: Saito 72 needs work  (Read 5246 times)
Bill Barber
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« on: February 08, 2012, 03:45:06 PM »

  Our club the Valley Circle Burners had a large scale control line P-38 with a Saito 72 donated to the club . Both need some work to get flyable again but the model would be perfect for club demo's . The Saito seems to be frozen and I know nothing about four strokes . The Saito has been modified for control line . My question is do I send the motor back to Saito or is there someone who specializes in repairing four strokes ?
      Bill
« Last Edit: February 08, 2012, 04:13:48 PM by Bill Barber » Logged

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Mike Callas
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« Reply #1 on: February 08, 2012, 09:39:25 PM »

Hi Bill,
Jim Kraft might know.
I am rebuilding a 56 right now.
I would think it could be dis-assembled and cleaned first. Then the replacement parts ordered thru Horizon.
I bought a ring, valves, valve springs, bearings, rod and gaskets for around $120.
Is there another motor involved here? I thought the P-38 had 2.

Mike
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Bill Barber
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« Reply #2 on: February 08, 2012, 09:57:49 PM »

   Mike your right the P-38 has two motors , but this semi scale version has one in the central pod . This a big model
that's been sitting for a while . The club plans to fix both plane & motor .
 So I should disassemble the motor myself
and replace parts as needed ? May ask for your help as I get into this project .
    Bill
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Mike Callas
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« Reply #3 on: February 08, 2012, 10:53:49 PM »

Bill,
Lets do it! What could go wrong?
http://www.horizonhobby.com/products/72-aac-with-muffler-new-case-rr-SAIE072B
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Jim Kraft
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« Reply #4 on: February 10, 2012, 08:08:51 AM »

Bill; I am with Mike. I think you can do this with maybe a little help. The first thing I would do is take a heat gun to it to warm it up and see if you can free it up that way. That generally works for me. I have worked on a few for the R/C guys at our club, and there are only a few things that are very difficult. Removing the valve keepers and keeping them from flying away is one thing. If you have worked on a 2 stroke, the only thing added is the valve train. Once you get the intake and exhaust pipes off, you can look at the valves to see if they are carboned up bad. If not, you may not have to do anything with them, unless you have a compression problem. They can be cleaned up and reseated if they are leaking.

Most of the ones I have worked on just needed cleaned up, oiled, and put back together with new bearings. Saito's are reasonably easy to work on, and I have yet to see one that needed a new ring, and most times you can even reuse the gaskets. I did have one that had a bad pushrod from the factory. I had to make one from music wire as Horizon was out of them at the time. That was on my own 56, and it has been running for a long time now with the homemade pushrod.

So, between Mike and I, we can help you do this. If you run into to much trouble, you can send it to me, and I will do it for you.

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Jim Kraft
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« Reply #5 on: February 10, 2012, 04:10:33 PM »

Jim,
How does one go about seating valves?
I was thinking of lapping my new valves to the old cylinder with some fine rouge(?) spinning the valve by the head.

Thanks

Mike
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« Reply #6 on: February 10, 2012, 04:37:17 PM »

Mike; I use very fine rubbing compound, (Dupont #7) or finer. Dab a little on the valve, put it in the head, add a short piece of small fuel tubing to the valve stem, and chuck the other end in an electric drill. By pulling slight pressure on the fuel tubing with the drill you can lap the valves in. If you pull to hard the tubing will just slide off the the valve, so just a slight pressure will do. After lapping, clean everything up good.
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Bill Barber
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« Reply #7 on: February 11, 2012, 09:55:55 AM »

  Jim , yes I would like to have your's & Mike's help . I would enjoy doing this project
using your input  . Busy with work for the next two weeks but after that I can dive into this project .
    Bill
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Bob Reeves
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« Reply #8 on: February 11, 2012, 10:33:32 AM »

Sure hope you guys post pictures and keep up up on how eveything works out. All I've done is take them apart enough to install a cam but as time goes by am sure myself and others will need to do more than replace a cam.
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Mike Callas
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« Reply #9 on: February 11, 2012, 09:46:05 PM »

This abused 56 is the one Bob tried to turn into an Otais.
It took about 20 minutes to strip down.

The crank was tapped out after heating in a small toaster oven. The bearings were tapped out with a drift. Hand tools only so far.

The bearings feel gritty and the exhaust valve has some serious deposits.

Waiting for a few more parts and then it goes together.
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« Reply #10 on: February 12, 2012, 11:11:35 AM »

The RC boys work on Saito's all the time. In fact, they have even figured out how to "hot rod" these motors something fierce. One guy has an actual roots blower on his!! A lot of experimentation with valve timing, and cam hop ups.

One guy blew up his Saito by going a little too far with the machining modifications. Be brought another one, and went right back to work. His pistons looked like swiss cheese.

Another guy was experimenting with reducing "pumping losses" like they do in current Suzuki GSXR 1000's.

Someone needs to take the "Hot Rod" magazines away from these guys. Layingdown
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Milton "Proparc" Graham
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« Reply #11 on: February 12, 2012, 03:58:43 PM »

The RC boys work on Saito's all the time. In fact, they have even figured out how to "hot rod" these motors something fierce. One guy has an actual roots blower on his!! A lot of experimentation with valve timing, and cam hop ups.

One guy blew up his Saito by going a little too far with the machining modifications. Be brought another one, and went right back to work. His pistons looked like swiss cheese.

Another guy was experimenting with reducing "pumping losses" like they do in current Suzuki GSXR 1000's.

Someone needs to take the "Hot Rod" magazines away from these guys. Layingdown

Or, they could get a YS.
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Bill Barber
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« Reply #12 on: April 13, 2012, 11:00:35 AM »

   Here is an update on the donated to our club Saito 72 .
 Lou [ Greg] Bahrman took the motor apart and found it pretty worn .
It had been run at high RPM's for long periods to the point the valves had been floating
on a regular basis. Long story short the motor is not worth fixing and we are looking for
a new or used motor .
  Bill
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Bill Barber
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« Reply #13 on: April 15, 2012, 03:00:41 PM »

  Horizon Hobbys has the Saito 72 0n sale for $210 , looks like the way we will go.
   Bill
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Bill Barber
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« Reply #14 on: May 05, 2012, 11:07:46 PM »

  Well we bought the Saito 72 and Greg Bahrman has done the intial break-in . So know it's going in
the P-38 , will post pictures soon .
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« Reply #15 on: May 28, 2012, 06:00:03 PM »

   Well today we flew the P-38 with the brand new Saito 72 using a Zinger 12-8 prop . This P-38  built & designed
by Bob Brooks is a semi scale stunter and is a very large plane . Model flew way too fast on the first flight
turning lap times around 4.30 sec. using 64' lines , lots'a  line tension!  Nearly pulled Chris Forbes arm off
and the motor still needs more break in. Next flight we switched to a Zinger 13-6 and set it a little richer .
I was the pilot this time and lap times were 4.5 seconds , model is very nose heavy and with fast lap times
no stunt flying was attempted [ still pulling like a bear ] .
   So we have more trimming & break in  to do , but the P-38 looks stunning in the air . A great model
for club demo's that was donated to the Valley Circle Burners by Bob Brooks . Pictures to come .
   Bill Barber
« Last Edit: May 28, 2012, 09:53:42 PM by Bill Barber » Logged

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« Reply #16 on: May 29, 2012, 12:14:49 PM »

  Well today we flew the P-38 with the brand new Saito 72 using a Zinger 12-8 prop .    Bill Barber

Welcome to the big block club. y1
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Milton "Proparc" Graham
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« Reply #17 on: May 31, 2012, 11:03:12 PM »

Valley Circle Burners finally got the donated P38 plane in the air with the new Saito 72. Pictures posted for Bill Barber club President. Fun project and it looks really neat in the air. Team players shown: Bill Barber, Lou Bahrman, Chris Forbes, Perrry Ohal. Saito 72 puts out more than enough pony's to haul the P38 around and stretch your flying arm a couple inches longer.
« Last Edit: June 01, 2012, 11:49:21 PM by Greg L Bahrman » Logged

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« Reply #18 on: June 01, 2012, 08:36:00 AM »

One trick to the "big block" is to get it on 70 footers. That's when it really comes in to it's own.

Glad to see you guys are having fun with the 72. Bill how's the movie business?
« Last Edit: June 01, 2012, 09:11:18 AM by proparc » Logged

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« Reply #19 on: June 01, 2012, 11:40:17 PM »

Proparc,
Yeah, we've got more lines ordered. It still has less than a gallon of fuel through it. It's at a point where it will hold a needle setting, but I'm thinking after another gallon it will be making more power still and probably get better mileage. It likes to backfire a lot now when starting, usually that goes away eventually. Still have to play with props also. All the guys shown are having fun. yeah, you have to be really careful when starting because it acts like you are the enemy and it wants to eat you for lunch........The plane is really big and heavy so we were worried did the 72 have enough pony's......Not to worry dude it flat hauls the freight and we don't even have it peaked out yet. I set the needle at peak and then back it off 5 or 6 clicks, so new motor running rich and it still pulls like godzilla on crack.
« Last Edit: June 12, 2012, 09:55:34 AM by Greg L Bahrman » Logged

Greg Bahrman, AMA 312522
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« Reply #20 on: June 02, 2012, 12:23:57 AM »

Greg, I heard the Borders Book store closed in Simi. Must have caused a riot. Layingdown

Anyhoo the 72 is kicking back because the compression is too high. Sounds like you got a "hot one". Some of those are still out there. Yes the Saito's will make more power as it breaks in. Head over to Autozone on Tapo Canyon Road,or Pep Boys on First st. (this is obviously strictly for Greg and I) and pick up a high quality automotive feeler gauge. The little blue gauge that comes with Saito's is not worth crap. Makes a big difference.

I have to warn you about Saito's. If you learn to master them, you will become completely addicted to them.  The guy at Marty's hobbies in Thousand Oaks where I brought mine, warned be about this.  He said "once you start with them you can't stop". Some of the guys over at the RC Universe have over a dozen!!  

P.S. As I am writing this I am playing with my 72. I have it on the desk next to me.

Attached is a picture of a Saito 115 in a very nice setup. This guys knows what he is doing!
« Last Edit: June 06, 2012, 09:04:50 PM by proparc » Logged

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« Reply #21 on: June 23, 2012, 08:00:10 AM »

Our next step on this project is to try the new longer lines and work on the balance issues. Hopefully we will be able to get a better corner which is pretty much non-existent at this time. Also on the list of things to do is try different props. In the meantime our two pilots on this project, Bill and Chris are concentrating doing curls with 50 pound weights to get their flying arms in shape for this arm stretcher motor/plane combo. Soon Bill will be able to hug his wife with one arm. After a few flights with the new longer lines we might have to shorten them a foot or two to compensate for arm stretch. y1
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Bill Barber
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« Reply #22 on: July 26, 2012, 09:00:27 PM »

    Chris Forbes and I braved more flights today on our club P-38 . Chris had added 1 1/4 ounce of tail weight ,
switched to a 13-5 prop and went to 70' lines . The model was more responsive with the tail weight and with the 70' lines it didn't want to pull your arm off. Lap times were just under 6 sec. with still plenty of line tension .
          We are planning to fly this model at the upcoming EAA Fly In at Compton Airport .  Because of space restrictions we will have to go to 60' lines for our demo flights . So with our  Saito 72 powered P-38 on shorter lines , is a 13-4
a reasonable choice to control speed ?
     Bill
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« Reply #23 on: July 26, 2012, 09:10:55 PM »

13x4 on a big block where you have a line length restriction, sounds like an excellent idea.  Hoff

May even want to drop nitro if you have to,(skinny like me).

Just want to say that I miss you, Larry, and all the guys at Sepulveda. I didn't compete much in LA, because I was doing my "Skunkworks" thing. I am now getting ready to make my assault on the L pad.

I'll try my best not to shame you guys.
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Milton "Proparc" Graham
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« Reply #24 on: July 26, 2012, 09:51:49 PM »

  Thanks Milt , wish you were to help us play with this big block .  My concern that even with a 13-4 prop on 60' lines that
this Saito 72 will stretch your flying arm .
  Bill
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« Reply #25 on: July 26, 2012, 10:04:52 PM »

  Thanks Milt , wish you were to help us play with this big block .  My concern that even with a 13-4 prop on 60' lines that
this Saito 72 will stretch your flying arm .
  Bill

Remember, you are putting a 72 on lines for a Fox 35. One way or the other, you are going to pay. Layingdown

But hey, what are you going to do? You have a line length restriction. If you have the RC version with carb, you can always throttle down. If you know what you are doing, then it's no problem.

Gene Molnar has flown my big block, and he was shocked by how mellow it was. But remember, you are flying a motor that was designed to pull a 7lb. RC ship straight up from dead horizontal.
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« Reply #26 on: January 08, 2013, 03:35:32 PM »

  Well , 3 members of the Valley Circle Burners put  up several flights today with our club P-38 . We seemed to have tamed the
Saito 72 a bit with flight times around 5 1/2 seconds on 70' lines . Only getting 4 1/2 minutes of flying time so need to replace the tank with something larger. Plane has a good corner and pulls like a freight train . We  planed to use it for club demos but might consider selling it because of lack of storage space . Still it looks great in the air !
    Bill
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« Reply #27 on: January 08, 2013, 04:12:11 PM »

And why I always say I wouldn't want to be on the handle of anything that needed the power of a 72.. I'll stick with my 56/62's  Grin
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Bill Barber
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« Reply #28 on: January 08, 2013, 04:26:39 PM »

 Bob I read your advice about tuning 4 strokes on another thread ;

  " If you notice any slow down in the overheads at all.. Your prop doesn't have enough pitch and isn't loading the engine enough. Move to the next higher pitch and adjust the intake to get your lap times back down. Never try to adjust lap times with the needle, it should always be set just to the rich side of peak."
 
  So we will try your advice , but yes the 72 is a handful to fly !
   Bill
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