I have 2 Saito 72's. They were the greatest engines. Easy and quick to break-in, idled very nicely with great transition and torque. However since each one has now been in a crash, they no longer idle well. One hit the asphalt hard and Saito service replaced the crank, bearings, and valve rods. The other only hit the grass and only at slight angle, but it too idles poorly now and goes dead stick at low throttle too often. Does this even with tank pretty full and no air bubbles in fuel line.

Have any of you had similar problems after a crash with yours?

I have replaced the o-ring on the intake pipe at head once and that fixed it for a while on one of them. Tried new OS F plugs but no change. Valves adjusted to .004 inch. Also back flushed high speed needle valve.

Thanks for your response.

Take a close look at the plastic backplate?

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w8ye, sorry I didn't mention it, Saito service actually did replace the backplate because it was cracked on the one that they replaced the crank on. The other engine didn't hit that hard and I did look at that. Thanks for pointing that out though.

Inorris, I didn't touch the needle valves at first. But I have finally reset the high end then reset the low end checking the performance by adjusting it 1/8 turn at a time in each direction. Also, they used to maintain their low RPM when removing the Ni-cad but now one engine drops RPM dramatically. Hard to get the low mixture quite right.

I had a severe crash with Astro-Hog w/Saito 72 due to battery fail.
I lost plane and receive.

Engine loose compression due to blocked exaust valve.
Open valve cover, regulated valve gap and engine is o.k. again.

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PROMAG, I did check the valve adjustment and it was ok at .004 inch. Both engines perform perfectly well at all levels except the poor idle.

Inorris, I agree that it does seem like a low end mixture problem. Actually I get a substantial drop in RPM on these motors if it is on the lean side as well as on the rich side. If I get it right on the money, it doesn't drop off. I verify my low end mixture also by checking its quick transition from idle to full throttle. It has a nice transition. As far as the exact RPM at idle, I haven't checked it with a tach. Both engines used to idle with the plane just sitting there. Seemed as if I could count the RPM. It would just putt putt putt for 30-60 seconds or so. Now I have to have on a good pair of Nike to keep up with it taxiing out to the runway or it will die. Well, it's noticeably worse anyway.

I'd also consider tightening the wheels more with the fuel tubing on the axles but it is disappointing to have to just compensate for whatever this engine problem is. I wouldn't mind doing so if I identified some kind of costly problem with it but I'm thinking/hoping it was something minor I could resolve.

Anyway thanks again guys for your feedback.

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Time for a pair of #3 ENYA plugs !

Inorris and Lady flyer, sorry for not responding to your thoughtful suggestions sooner. I kept thinking I was going to be able to try these ideas on the engine but my schedule hadn't permitted me to.

Inorris, I have continued to use the same 12x7 APC prop which had always been awesome with this motor. Same fuel and have even tried more new fuel of the same but no change with the problem. The idle is somewhat better with glow driver but I don't think that would resolve the idle problem completely. I'll have to double check that when I get a chance. I think the valves are ok since the clearance on them didn't change and the unlimited vertical is as good as ever. Which sort of verifies the fuel quality too, I think.
And yea, I've tried $20 worth of OS F plugs and a Thunderbolt someone swore by but again no change. Also after reading your suggestion, I checked the muffler pressure nipple, cleaned it out and even swapped muffler from the other Saito .72 but no change. Replaced fuel lines as well. I think my next idea will be to sell this plane in the garage sale.

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For some silly reason, I feel that Hobby Services will have very little to say about your Saito. They might even hang up on you?

You might try calling Horizon though?

Enjoy,

Jim

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I haven't called Hobby Services about this yet. I think I'll call our dry cleaners before I'll call Hobby Services. The little elderly lady over there isn't that much more knowledgeable about Saito carburetors than the guy is on the phone at Hobby Services but she is a lot more pleasant to speak with. Last time I called HS about a part on the Saito, he said he would check on it and call me back. It has been 6 months and I haven't heard a word back from any of them.
I went out and flew today with the idle up a little. I think I tweeked this and that enough to make it tolerable at least until a solution dawns on me.
Thanks again for all your input.

If the engine is cowled take the cowl off. with engine running as slow as you can spray/squirt water on all the intake manifold junctions. If the engine speed up you have an air leak , if you are getting an air leak at one of these points could act just like you are explaining to us.. I had a very small crack in the intake on an OS .20 four stroke and like to have never found the problem.


Just my $0.02 worth

I just biffed my 72 saito into the ground. I hear a wearing metalic noise now, think I should check the bearings. If you hit the noise smack on , but no so hard, whats the most common to break? I canonly get 9000 rpms out of mine now used to get 10000

You rang?

-DC

Check if the crankshaft has pushed back and the big end is touching the backplate. If it is, the backplate will be scored in a circle slightly.

-David C.

Yup theres a few cirulare scratches going around the inside of the backplate. I tried to remove the crank shaft but couldnt figure that one out. If there are wear markes on the inside of the backplate what should I do, thanks.

Send it to Horizon to have it checked out. It's inexpensive and you'll get peace of mind that all is well.

I have a Saito .56 I sent in after a crash, They replaced front and rear bearings, prop drive hub and collet, adjusted the valves and checked the crank for straightness. All that plus a test run on the bench for $48.00 including shipping.

Yup thats what Ill do, stinks cause I have this job to do (arial photograpy) need to do this one thing. I hate being stuck between a rock and a hard place. Thanks good advice!

I also crashed my Saito 72 twice, both time w/ speed into dirt. All I had to replce is the intake manifold gasket. Power and idling are still very good. I did notice that the muffler pressure tap came loose, and as a result idling is unstable when the pressure tap is loose. It may be a source of problem for you. Did you get the new casting style muffler from Saito?