acejinx

I recently acquired a used Saito .72. I have heard so many great things about these engines that I had high expectations. It is also my first four stroke. I love everything about it except the idle. I've read the manual, looked up tips, and bought a new glow plug. No matter how much I fiddle and adjust I can't get it to idle reliably below 3000 RPM. This pulls the airplane forward, and drives me NUTS! Landing approachs are tough with that much power also.
I am running it with a 13X7 prop, have the OS four stroke plug (The LHS only had one, maybe there are others that work better?) I'm using powermaster fuel, with 3 oz of castor mixed in with the gallon. (The fuel works great with my other two strokers) I don't have an onboard ignition but am thinking I may have to get one. I fly at 4000 ft.

Any help is certainly appriciated!

alan0899

G'day Mate,
Have a look here, all the info you will need.
http://saito-engines.info/throttle_setup.html

brooke

Ace, I do not have any Saitos engines, but like you have have heard noting but good stuff about them. It may just be that since you bought it used their is another issue with it.

I do have all O.S. engines in both 2 and 4 storke that I fly. Everytime I need a new engine I look at and think about buying another brand like Saito, Mag., TT. etc...... but I just can't do it. The reason is because I have never had any real problems with any of the O.S. engines and they just work for some reason.

Mode One

I'm unclear. Is it because the engine won't reliably idle lower then 3000 RPM, or you can't get it to slow down below 3000 RPM? If the later, there is an idle stop screw that may be preventing the throttle barrel from rotating far enough to allow a lower idle. If the former, pull the carb. off and make sure the O-Ring which seals the carb. to the intake manifold is in good condition. Also make sure all the fule passages are clean. If not cleaned well when put away, old fuel congeals and can cause fuel draw problems.

krossk

My Feedback: (27)

It may also be that the engine is not yet completely broken in. I have a Saito .72 in my SSE with less than a gallon through it and I can't get a good idle below about 2800 - but it is slowly showing signs of improvement.

Hughes500E

My Feedback: (16)

15% fuel and an OS F plug, mandatory! Also a 13x7 on a 72 is too big, at least while its breaking in. Go with a 13x6 and stay away from peak power.

Tired Old Man

My Feedback: (1)

THe buyer of a used engine automatically inherits any problems it may have that were created by the previous owner. Was it crashed? Was the carb loaded up with dirt during the crash? Was the prop hand turned a few times after the crash, forcing dirt the dirt into internal components? Were any of the carb needles bottomed out by the previous owner? Was the engine run lean for extended periods of time? Is the crank straight?

You likely don't have answers to any of those questions so you don't know the condition of the engine. Order or down load an ops manual from Horizon Hobby and go from there.

daveopam

My Feedback: (9)

You did not say what kind of prop you have. A wood prop will need a higher idle than a heavy plastic prop.

David

Nathan King

I purchased a used (but immaculate) Saito a few years ago and had a similar problem. Despite the engine being used it still hadn't been run enough to be fully broken in; a gallon later it could idle at 1900 RPM for a minute and still transition well without loading up afterwards. To this day it is the best running, most reliable engine I own. I also suggest you check valve clearances since most owners don't adjust them regularly (or ever). The Saito low end adjusts a bit differently than other four stroke brands as well; however, I find the Saito engines to have nice broad needle settings which are easy to set and will hold adjustments well.

alfredbmor

I believe that is a common problem with saito engines when new or recently repaired, mine (72) works trouble free now after 2 or 3 gallons. All saitos will reach a nice idle but it takes a while, at least that is what have happened to me. I would not be worried, but I would change the prop. for a 13 x 6 and fly. If you fly only on weekends, try to adjust the nedles valves (low and high) every six flights, in one month you will find the difference (24 flights). I use 20% nitro 18 synthetic and I commonly add two oz of fresh castor oil to this blend. The field is at 4000 ft altitude.

Nathan King

Forgot to mention. I use 30% with 18% castor/synthetic blend. I don't add more oil since I use a good brand of fuel with quality oil. If you are unsure of the oil quality I would up the oil to 20% by adding some castor. There's actually a good article in MA this month that explains how to add certain percentages of oil, if you can't figure it out.

acejinx

Thank for the input, I'll check that O-ring. I know the previous owner and he ran many gallons of fuel through the engine, and as far as I know, and can guess, he never crashed it. I will also switch that wood prop for a plastic 13x6. (Master Airscrew?) Should I up the nitro content of my fuel? I'm running 15%, would it run better with the higher 'octane'? Thanks again everyone!

Nathan King

Jumping from 15 to 30% will give you a little more power, but you should be fine with 15%. Upping the nitromethane content won't solve your problem. I typically use APC props. If I need something more scale looking I use a wooden prop. I typically stay away from Master Airscrew props.

Wayne Miller

Hi,

The Saito 72 had problems with air leaks due to a problem with the back plates. A new backplate can be ordered to fix the problem. This is discussed on this thread:

http://www.rcuniverse.com/forum/m_45...tm.htm#4517246

Hope this helps.

Fly4Fun,

Wayne Miller

Stick 40

I have several Saito's and all had to have the valves adjusted thru. break in, I got real good at it. They all idled down to 1600 to 1800 and ran great.

Rodney

What Stick40 said, adjust the valves first of all. If they are not correct, no amount of fiddling with other items will help. All 4 strokes need to have the valves checked and reset from time to time.

acejinx

1600-1800? That has got to be with and ingition module on board, right?

acejinx

And also, is there a way to tell if I have the new backplate? The one on there is plastic. I've talked with my friend who said that the engine worked perfectly 4 years or so ago when he put it into storage.

Wayne Miller

Hi,

The problem with the back plate was the way it supports the air intake manifold. When the engine is running, the vibration will allow the metal tube's "O" ring to move and allow air to into the air intake and sometimes even chafe and damage the "O".

The thread mentioned above shows pictures of the new and old back plate, you will have to scroll down through a few posts to see the pictures. The new back plate has a support block that holds the carburetor tightly to the intake manifold, thus eliminating movement so the "O" ring can not leak.

Also, make sure you check the valve clearance as stated above, they do get loose over time and will cause the engine to lose power and run poorly.

Hope this helps. Let us know how you make out.

Fly4Fun,

Wayne Miller

acejinx

OK, a new back plate, a carb rebuild kit, a smaller nylon prop, and the gapping of some seriously out of spec valves and this engine runs like a clock. It''s so beautiful it brings tears to my eyes! It stumbles a little at 2100 RPM, but I let it run for 30 min yesterday at that setting and it didn''t quit! Thanks for your help everyone!
1

Wayne Miller

Hi AceJinx,

I''m pleased to hear you got it running well - good job!

I have mine on a Great Planes Big Stick 40 and it is my "fun" plane, it is almost like it was made for the plane.

Enjoy the engine.

Fly4Fun,

Wayne Miller

R/CBOONE72

I use 4-stroke apc type props, And on my big engines i use onboard glow system, wont need a glow ignitor to start it anymore, I get mine from RAM with the battery built in, and set it to be on just a few clicks above idle, this is the more expensive easy way out of idle problems, let it break in and see if it gets better, I have my saito 1.80 running slow enough that you can almost count the prop with on board glow, same with my new .91 in my piper cub. I have about 8 siato engines and prefer them over nitro, I also run heli full to. I think its 30% nitro and more oil, keeping it coller and it can be leand out a tic more.