I have a new saito 72 after break in plus 1.5 hour more but never flown.
I tried anything in order to adjust it after break in but the engine idle is still rocking very hard (it never goes down 3200 rpm)
i adjusted valve,replaced plugs,got help from club members (mostly 2 stroke fliers) nothing helps.
the problems ranged from engine can start to engine starting but can't hold idle, rocking hardly to turn off when booster disconnects.
The guys at my club tried to play with both idle and main needles and the best result was when the main needle was opened just 1.5 turns (seems to me to little) and the idle needle was readjusted again and again. at this point the engine got up to 8700 rpm and was rocking hard at 3000 and below and could not hold idle for long ( 1 m top).
I spent the last 2 days ( more then 6 hours each day ) to try adjusting the engine but all the above problems appeared.
at this stage i really do know what to do (both main and idle needle positions totally changed).

what can i do ?
- should i start adjusting main needle (how much to open)
- should i start adjusting idle needle (how much to open)
- should my my idle be above 3300-3500 rpm (under that starts to rock)


sorry for this long message but i really need some big help

thanks

* by the way disconnecting the booster from the plug engine caused rpm to get low (mostly) even thought i replaced the plug ( os F) after break in

Have you checked the valve timing?

For comparison, mine has it's low-speed screw recessed in .04" from the throttle arm and the high-speed needle is out 2.5 turns plus 4 clicks. This engine has had about 5 tanks through it on the bench.

Try starting somewhere near there or a bit richer and see if you get anywhere. You may need to send it back to Horizon for a check-up.

is the engine mounted inverted ? if so, this will make your idle mixture much more sensitive especially if the tank is a little high!

engine "bucking" at lower rpm ......especially saito's is a classic symptom of a rich idle mixture !

are you using a filter from the tank to the carb ? one tiny speck of dirt can ruin your whole day !

The engine mounted on the side and as i can recall the main needle was opened 1.5 turn (that's quite sure ) and the idle neele between 2 - 3 turn from fully closed (counterside)
yes i do use brand new filter and the carb position is just or a little higher then tank middle line.

hello,
i have read (maybe rcu) that some saito 72 carbs were defective! if the problem persists bring it back to your hobby shop as the engine is covered from warranty.
Hope this help.
Wile.

Try adjusting your carb using the procedure found here:

http://saito-engines.info/throttle_setup.html

Lynn

When you said how much to open my idle mixture, it should be the other way around. When it is knocking, that is because it is loading up with fuel. Had the same problem with my magnum, but they are the same exact concept for adjusting them, it just may be a little different. I had to close mine 1 1/2 turn from factory setting, now when I move the throttle to idle cutoff, it doesn't want to quit! For what your experiencing, turn it in 1/2 turn and see if that help. Get it good at 3000 before you try going lower, because the slower your engine is running the more it will load up with fuel. If you can run the engine so you can look at the idle needle you will be great, because you can run it and just close it in until you hear/see it running better. About the carbs being defective, if you get your idle mixture all the way in and it's still running, I'd say take it somewhere and see what they say. Good luck and let us know how it turns out

When you said how much to open my idle mixture, it should be the other way around. When it is knocking, that is because it is loading up with fuel. Had the same problem with my magnum, but they are the same exact concept for adjusting them, it just may be a little different. I had to close mine 1 1/2 turn from factory setting, now when I move the throttle to idle cutoff, it doesn't want to quit! For what your experiencing, turn it in 1/2 turn and see if that help. Get it good at 3000 before you try going lower, because the slower your engine is running the more it will load up with fuel. If you can run the engine so you can look at the idle needle you will be great, because you can run it and just close it in until you hear/see it running better. About the carbs being defective, if you get your idle mixture all the way in and it's still running, I'd say take it somewhere and see what they say. Good luck and let us know how it turns out.

I had a Saito 72, and it took a long time to break in. I was not able to get a nice idle until the fourth gallon of fuel. I had to lean out the low speed screw quite a bit. It sounds like you are running too rich on the low end. Turn the low end adjustment screw clockwise to lean it out until the RPM drops only slightly when you remove the glow driver. Your idle speed will increase when you lean out the low end, so use your radio to lower your idle speed back down. You can also try to adjust your low end while the engine is running because you will be able to tell the RPM increase.

I spent many hours in the last few days playing with both needles
(with help from some fliers). but is seems that nothing won't stop the engine from rocking starting at about 3300 rpm.
can it be some structural damage (like unbalanced shaft ?)

i must admit that this is my first 4 stroke engine so it's hard for me to determine whether this problem is caused by some wrong tuning or some big structural damaged.

thanks

Do like we have said and lean out the low speed needle (the one in the center of the throttle arm). If you turn it all the way in and it wont go any further, but continues to rock send it in. I had the same problem, and thats what fixed it, and it sounds like your having the same thing happen. If you can't find the needle, or arent sure if its the right one or anything, don't be afraid to ask, all of us didn't know at one time or another. Let us know how it turns out.

Alex

Also, double check your valve clearance like bgi said above. Mine was off straight out of the box. In fact, I had to reset the valve clearances on all of my four strokes after the initial bench runs. If you can slip the supplied 0.1" gauge in between the rocker arm and the valve stem, then your valve clearance is too loose. Get either a 0.01" or a 0.04" feeler gauge and use it to set the valve clearance. Is your prop balance?

Richard,

Just want to clear a little confusion here on the valve lash adjustment. I believe you are referring to .1mm (.004") and .04mm (.0016")

I knew what you meant!

In standard terms, one should be able to pass a .002" thick leaf between rocker and stem where a .004" will not pass.

Happy Fly'n....

Whew, I'm glad the units correction was made. A .040 inch clearance would have been a disaster. All dimensions in the Saito manual are in mm.

As a point of reference, my 72 wouldn't idle until I turned the idle screw in two full turns. I fine tuned from there. Do as snownskate69 said and gradually screw the idle screw in until it bottoms out. If the engine still fails to run, you have a defective engine. If it is defective, send the entire engine back to Horizon. I wouldn't bother with removing the carb or checking the timing. That's why you bought the three year warranty!

I had to keep my idle higher for quite a while on my .72. It takes a long time to break these in. I don't remember how high I kept it, but it was a fast idle for some time.

IronZ

The valve clearance was adjusted by one of the senior members so 0.01 mm supplied filler just got in the gap with a tinny bit of a slip. at this point when i rotate the prop manually i can hear metal knocking noise (good/bad ?).
other then that i use master airscrew balanced wood prop.

what do you thinks guys a about wrong/unbalanced shaft

thanks

I believe it is supposed to be .04 mm, but double check your manual. Yes this clicking noise is very normal, and as far as I know all 4-strokes do it, mine does. Fire it up, lean out the low speed and let us know what happens.

Alex

Sounds like you have adjusted the idle jet too rich to compensate for air leaking into the intake tube.

Saitos do sometimes suffer from a leaking joint between the inlet tube and the carb or cylinder, due to the rubber 'O' rings not doing their job.

Try replacing the 'O' rings

David C.

Dear David

Could you please post some diagram to show what o-ring do you refer to and how replacement can be done.

thanks

Have you tried the low speed needle yet? That is more likely the problem than the o-rings.

my plan is to go one more time to the field to make all possible tests (longing to hold back the sticks again) as mentioned at this thread.
Otherwise i will have to send it back and wait again for the my new model to fly.

thank you all

Hello rcFp....... I almost hate to add another suggestion. By now you must be totally confused and frustrated. There have been several different twists on the measurements of the valve lash. An incorrectly placed decimal point and mm. vs. SAE. etc.!! I have 4 Saitos and I can tell you the settings in good old SAE dimensions. I have a GOOD feeler guage with many leafs, or try to buy the single leafs from a good supplier. Make sure you have a .004, .003, and a .002 feeler guage.
(that is four thousands, etc.) Make SURE the piston is at TDC on the compression stroke. (take out the glow plug when doing the setting as you can turn the engine easier, "feel" the action, and you can see the piston at TDC. (Again.. on the compression stroke). At this point both the rocker arms should not be touching the valve stems and you should be able to wiggle them slightly. I then set a "snug" .004 on each valve, tighten the lock nut slightly. Now slip in the .003, then try the .002 guage.
You may (?) feel a little tension on the .003, but you should be able to slip the .002 in with NO friction at all. (I leave the prop on, and watch it's position DURING the setting so I don't move it from TDC..... it CAN make a difference if moved a little!!!) I also...RECHECK the setting after going back to final tighten the lock nut!!!
Now........ about the carb setting.... Sorry man, I know you are worn out with these suggestions.... but here goes.......
I have broken in 4 Saitos and have found that the low speed "brass screw" in the throttle should be flush with the face of the plastic throttle arm. According to Saito...... this is Saito's RICH, "approximate" starting point for the low speed screw. (All my engines, out of the box, were set like that. So, I guess the info I received was correct) Since you have some run time on your engine, I would get it flush...... and turn it in, clockwise, about 1/4 turn. Set your High Speed needle to about 3 turns out and try starting it there. I feel that at these setting you should be able to "work things out" by fine tuning. If not..... you have done about all you can do. I would then ship that little jewel back to Horizon for service. I just received my 150 back from them and they want to make things right. Just make sure you explain all your problems and have all the paper work.
Please let me know what progress if any you make. You can email me if you like.... or post.... but I am curious as to what will solve the problem.
Good luck......lownslo

Bob

PS. Ironicaly... my 150 had carb problems. Mine was not idle related. It was a defective spray bar and needle clearance fit. They replaced the parts and it still was not right. They sent me a whole new carb. (maybe a bad production run on the parts.???)

Whoops! My bad. I meant .04 mm and .10 mm. I'm looking at page 9 of my Saito 72 instruction manual, and it says to adjust the valves to a clearance of .03 mm to .10 mm (.002" - .004"). The valves must be adjusted with the engine cold due to thermal expansion. I like to set my valve clearance at .04 mm. In my opinion, .10 mm is a little bit too loose.

My YS 63 used to have a very choppy idle and didn't sound right, so I decided to check the valve clearances. It turned out one was too tight and the other was too loose. I set them both to .04 mm, and now the engine has a very nice, stable idle.

I'm not sure if anybody has mentioned this yet, but a lot of idle problems can be magically solved on a Saito if you use OS type 'F' plugs

-DC

I found the same thing on my Saito .72 as was the case with the quote above. Run it some more and then some more. It will be ok and yes, OS plugs!