rhoon

My Feedback: (2)

So I bought a saito 72 6yrs ago and mounted it to a pizaaz and had the time of my life. Best running engine I ever saw. I sadly flew the plane int a concrete wall after a receiver battery disconnect in flight and destroyed the motor. After crying for about a year my wife bought me a new Saito 72 and a Twist and I have never been happy with the motor. It seems to change mixture all on its own in flight and then I lose all power. If I richen the setting it has no power. I have had the idle screw all over the place and can't fix it. It seems when I have the low end set right It dies on transition. I have changed the tank, tubing, and yesterday I put the old Saito carb barrel and high needle in it with the same result. I have changed fuels- now using 15% cool power but it does not matter. It never seemed to matter what fuel I ran in my old one it ran like a sewing machine. I am so frustrated I am ready to throw it in the trash and buy an 82. I have changed plugs. I have checked valve clearances. I have checked all the seals in the carb and intake. The only thing I have not changed is the pressed in low end spray bar because my old one is bent, but nothing looks wrong with it. Everytime I have the twist in a low hover even smoking rich she suddenly stops smoking and loses power and I give full down elevator and crash plop the twist onto the ground. I don't think I can glue the gear on one more time! Please tell me there is a solution to this and its not a lemon!

jsn

My Feedback: (8)

Check the threads here on RCU regarding the OLD style back plate on the 72's... sounds like you may have one of them and have an air leak being generated at the intake tube due to the back plate flexing.

John

JettPilot

My Feedback: (6)

His problem is definately the old style backplate allowing the intake to flex and damage the gasket on the intake tube.

Replace the backplate with the new stiffer part number, and replace the gaskets on the intake manifold. I would replace both at the carb and where it goes into the Cylender head. Almost a sure thing that will fix your problems

JettPilot

rhoon

My Feedback: (2)

Thank you guys for the fast replies. Where do I get the better backplate, and how can I tell by looking at it if it is the older style?

w8ye

My Feedback: (16)

Back plate

http://www.horizonhobby.com/Products...rodID=SAI7217A

Manifold gaskets

http://www.horizonhobby.com/Products...rodID=SAI8091B

Hobbsy

My Feedback: (102)

If it dies on transition the LS needle is not set right and the backplate issue takes a long time to show up. Try starting over by setting the LS needle even with or at most 1/16th inch inside the barrel, then set the HS needle at absolute peak, now set LS needle for the best transition. the transition is far more important than the lowest idle possible. When you're satisfied with the transition and idle, richen the peak down a couple of hundred rpm with the fuel tank half full. Do this on a test stand or you'll be chasing the settings for a hundred years.

NM2K

My Feedback: (14)

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Throw it this way. I could use a .72 to fill the gap in my collection of Saito singles.

Seriously, if the engine was that problematic, you should have sent it back to the warranty folks long ago.

My suspicion is that the model is at fault. If they vibrate in certain manners, they can foam your glow fuel so badly that no setting in the world is going to work well. That is the problem with profiles, glow foamies and sometimes even full fuselaged models.

Do the Armor All trick to your gallon of fuel. A squirt or two and a good shake will let you know if it is a fuel foaming issue. If the problem lessens or goes away, you then know that you have some work to do on your model. Don't worry, the Armor All won't hurt your engine if used in small quantities, but it can solve a pretty consternating problem. If it works, then attack the real problem by trying various techniques to isolate your fuel tank from vibration.

If nothing works, mount the engine on a bench and see if you can get it to run out a full tank of fuel normally.

You did break your engine in by the factory suggested method, right?

NM2K

My Feedback: (14)

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Throw it this way. I could use a .72 to fill the gap in my collection of Saito singles.

Seriously, if the engine was that problematic, you should have sent it back to the warranty folks long ago.

My suspicion is that the model is at fault. If they vibrate in certain manners, they can foam your glow fuel so badly that no setting in the world is going to work well. That is the problem with profiles, glow foamies and sometimes even full fuselaged models.

Do the Armor All trick to your gallon of fuel. A squirt or two and a good shake will let you know if it is a fuel foaming issue. If the problem lessens or goes away, you then know that you have some work to do on your model. Don't worry, the Armor All won't hurt your engine if used in small quantities, but it can solve a pretty consternating problem. If it works, then attack the real problem by trying various techniques to isolate your fuel tank from vibration.

If nothing works, mount the engine on a bench and see if you can get it to run out a full tank of fuel normally.

You did break your engine in by the factory suggested method, right?

reyn3545

Judging from your post, I'd also follow an earlier suggestion and look into cushioning your fuel tank. I had a Twist with an .82 on it, and had similar issues with foaming. Make sure there's good soft foam all around the tank, and increase the size of the opening at the back of the firewall where your tubes come through. That completely resolved my problems.

shred_man

I also have a twist in build with a Saito FA-72. Why is it necessary to increase the size of the opening (hole) in the firewall ? I have read the same recommendation in a other thread about the twist but I don't understand why. Can you tell me the advantage when I increase the opening ?

Regards
Frank

w8ye

My Feedback: (16)

You make the hole bigger so none of the firewall will touch a hard part of the tank - cap - or tubes.

Fill in the area from the engine side with silicone RTV sealant after the tank is in place.

rhoon

My Feedback: (2)

I am certain the problem is not foaming fuel because my tank is packed well in foam, and I can see through the tank hatch while the engine is running. I do not see any foam or bubbles in the fuel line to the carburator, or in the tank. I do appreciate all the input. I am going to follow Hobbsy's advice with the needles tomarrow and see where I get. If that does not work maybe I will order a new backplate and seals. Does anyone know how to tell if I have the older-style backplate? I am skeptical that this is the problem since the seals look good and my old motor that I destroyed had the same backplate and she ran for much longer with no problems at all. Artisan you are right, I should have sent it back long ago, but I always thought I just did not have it adjusted right. I did break the motor in as required in the manual. If I don't get anywhere I will send it back and see what they say. Could I have bent the rod during a prop-strike? Could I remove the backplate and tell by looking at it?

listening to everybodys ideas,
Robin

w8ye

My Feedback: (16)

The good back plate has braces underneath the carb mounting tab

If you still have your old 72 it had the old style back plate.

Check that the back plate mounting screws into the engine block are tight.

blw

My Feedback: (3)

Another good thing to do with the older backplates is to take it off and look if the backplate is deformed. You can see it clearly. Another good thing to do is maybe run the engine at home on the plane or on a test stand after you checked that the backplate screws are tight. After running the engine for about 10 minutes, take it off and check the screws again. Mine would back out a lot. I put epoxy in the threads of the crankcase and let it dry overnight before putting the backplate back on. That cured that part of the problem. Loosening screws means loosening backplates, and that will let air get in where the manifold goes into the cylinder head as the carb/backplate is vibrating around.

rhoon

My Feedback: (2)

ok so I figured out that I do have the old style backplate by comparing it to the link provided by w8ye (thanks). I cannot order the seal kit yet because it is backordered. I will order them both right away when they are in stock. I also checked the backplate screws and they were a little bit loose and I tightened them as much as I dared hoping not to strip the aluminum threads. I have not been able to play with the needles due to rain today, but now I am convinced it must be the backplate issue anyway. I do wonder why I never had a problem with the old motor which had the same style backplate? I will keep you guys posted as to the results of all the recommendations. Thank you all again!

Sincerely,
Robin

rhoon

My Feedback: (2)

I took the backplate off and switched it with the backplate from the old crashed motor just to see what difference it would make and man what a difference! It's like a new motor! I could not even see any difference in the two backplates, but there must be a leak in the new one. I will still order a new improved backplate and seal kit when the seal kits are in stock since this is definately a problem. It runs like a new motor and I even followed Hobbsy's advice and started over with the needles. It does run much better but still has some variability at high-end, say300 rpm. It seems it should turn my 13x6 prop faster than 9100rpm. I remember the old engine idling at 2000 no problem but this one will only hold at 2400. If I lean the LS needle any more I get a better idle but she dies on transition. I will keep you guys posted and thanks again for all the help. I definately wont be throwing it away anyhow.
Sincerely,
Robin

crashland 73

My Feedback: (24)

DEFINATLY a backplate issue. Mine done the same thing. Until I took out the screws and locktited them and tightend them up real good. I should get the better backplate sometime. Somehow it fixed mine what I done.

NM2K

My Feedback: (14)

It is always good to follow Hobbsy's advice. He has a lot of experience with engines.

Hobbsy

My Feedback: (102)

Ed, the first engine I played with when I was 10, (54 years ago, man I'm I'm almost as old as old people used to be) was a two stroke Maytag washing machine engine. I built a wood go cart and it actually worked, I had to twist the belt to rear wheel so it would go forward. My first glow engine was a McCoy .36, then a McCoy .35, then a Spitfire .049, next was an OK Cub .024 all of which I still have.

crashland 73

My Feedback: (24)

Hobbsy,
I know that Maytag. My dad has one. He will be 60 this Dec. He bought another a few years back. A single cyl. Kindof a kick start but not. With a big flywheel. I am looking for a sparkplug for it so's me and him can be intertained LOL! I started up my twin cyl saito last night and he got to laughing. I know what he was wanting to do. Start up his ol maytag. His mom had one on their washer when he was a kid.

SigMan

My Feedback: (21)

I READ A REVIEW WHERE THE GUY BROKE-IN HIS SAITO 180 WITH A 16*8 PROP THEN SWITCHED TO A 18*6 PROP AFTER IT WAS BROKEN -IN. WHY DID HE DO THIS? CANT YOU BREAK-IN THE MOTOR WITH THE PROP YOU INTEND TO FLY WITH?

crashland 73

My Feedback: (24)

I am not sure of his situation but I have broken in most if not all of my engines with the props they are now using without a hitch.

PJ2008

hi guys,
help me out too please.

the same saito 72 4-stroke engine is having problems. I mounted it at 90 degrees instead of inverted in the greatplanes cessna. before that i had tuned it to perfection on the test stand, standing upright.( i know i should mount it at 90 degrees, however, the test stand doesnt allow for that.

the moment it is mounted at 90 degrees, the engine dies, when i remove the glow plug. i changed another new glow plug, it does start slightly better, but on second try, itdies very quickly once the plug is removed. however, when i move the plane orientation such that the plane is upright, the engine runs ok. this is despite, we had reset the high throttle to slight rich below peak, and leaving the low idle needle as it was.

not too long ago, the carb bolts also ran loose and luckily i saw it and tighten it again.. i swear i never tampered with the bolts. in fact i am discarding this engine, before i saw this thread. i have already placed my order for my second OS 70 FS2... no more SAitos for me now...

i am not too sure about this strange engine, and i am losing faith in saito. i have 2 x 72 engines. the other runs reasonably well except my idles are still above 2400 to be stable.
all my senior club members have helped me, by changing the fuel type, fuel tank position etc....nothing has helped for the last 2 months.

i guess only other saito users know what problem i have.
after 2 months of struggle in tuning. i have never gotten anything stable idling under 2400 rpm.

would you be able to offer any kind advice again?


pj, singapore

Cyclic Hardover

My Feedback: (3)

Going 90 degrees should not do much if anything at all but if you ever mount inverted, make sure you lower the fuel tank.

PJ2008

hi cyclic,

thanks. my midpoint of my fuel tank is slightly lower than the carb level. so i thot it was alright? i also checked my engine backplate,it has the bracings
although now i realised why they have used black " plastic" material instead of steel as in os engines? there are some traces of fuel on the back plate, and
i think it is normal, coming from the carburetor.

tough problem.