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Old Apr 21, 2014, 11:23 PM
Registered User
Canada, BC, Cranbrook
Joined May 2013
59 Posts
Question
Saito 125 vibrations

Hi there
This is my first saito and first four stroker. The engine was broken in on the bench per manual and i havent noticed that much vibrating since it was mounted on the bench. But today i went out with a plane, Seagull mxsr and noticed that it vibrates a lot. It was vibrating so much i thought i was gonna break the plane lol. Vibration causes at least i think that was the case a throttle servo to stop working. I amd using a standard futaba 3004 on throttle. I havent done any low speed or idle adjustments yet and im hoping once this is leaned out the vibrations will stop.
Do you guys have any recommendations on this engine since its my first saito.
Thanks
Dan
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Old Apr 22, 2014, 12:02 AM
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los36's Avatar
United States, TX, The Colony
Joined Nov 2012
354 Posts
When mounted to a plane, it is best to have the wings mounted to add some weight to the fuselage. This will help lessen the effects of the vibrations.
YES, tune the low end. This will greatly reduce the vibrations. Even during the first flights when you want to run it rich ... do that with the high end needle. Tune the low end for proper idle and transition as soon as you're done with the initial few break-in tanks.
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Old Apr 22, 2014, 12:52 AM
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Canada, BC, Cranbrook
Joined May 2013
59 Posts
Thats good to know i didnt have the wings mounted and i will lean the low end and hopefully itll calm down
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Old Apr 22, 2014, 09:32 AM
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I TOBOR's Avatar
Joined Feb 2007
2,763 Posts
Vipe, as Los says get the LS needle set to optimum, what you're calling vibrations are actually tortional impulses cause by strong power pulses and a light engine. A prop with some heft to it will do wonders for it also.
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Old Apr 22, 2014, 05:26 PM
TigreJohn
United States, CA, Corona
Joined Aug 2008
996 Posts
A silly question: did you balance the prop?
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Old Apr 23, 2014, 06:09 PM
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United Kingdom, Craigavon
Joined Sep 2013
34 Posts
Balance the prop. Cheap wooden props are never balanced and should be avoided.
Use a heavy prop
Dont be tempted to use more than 20% nitro. Higher the nitro, the more advanced the timing and bigger the vibration. If you can hear sizzing when you apply the glow heater you get pre detonation and serous vibration. So lower nitro is needed.
Change plug to a new OS type F
Run at least 7 tanks through. Sounds like a waste but necessary.
Contact Macgregor industries(UK) or Horizon hobby (USA) if problem persists. If the problem is really bad and shows no sign of improving your timing may need retarded by a tooth. But for now buy a good APC or K series Master airscrew and borrow/buy a prop balancer.
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Last edited by Pedmondsonni; Apr 23, 2014 at 06:26 PM. Reason: Spelling
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Old Apr 23, 2014, 11:50 PM
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Canada, BC, Cranbrook
Joined May 2013
59 Posts
Thanks everyone for your answers and suggestions.
First of all i think the engine is not even fully broken in, ive ran only maybe 5 8oz tanks through. I am only using APC props, 10% nitro and ive changed a glow plug to os f type. One thing i didnt do is balance a prop, but i will do that next.
Dan
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Old Apr 24, 2014, 05:56 AM
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United Kingdom, Craigavon
Joined Sep 2013
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Check this out. Smart way of using finger ballance and save 20 http://flitetest.com/articles/how-to...ller-balancing
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Old Apr 25, 2014, 06:58 AM
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United States, CT, Guilford
Joined Mar 2006
16 Posts
Saito vibrations

Before they are fully broken in, the Saito will vibrate some, you can feel them smooth out as run time on them increases.

Not mentioned yet, but Saito recommend metal engine mounts. they used to provide one with their engines.

A plastic mount will allow the engine to shake and transmit the vibs to the airframe. Sounds counter-intuitive, but it is the case.

I always use a metal mount with my Saito 100, 120, 130t and 180. In addition to balancing my props with a magnetic balancer.

Good luck
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Old Apr 25, 2014, 10:45 AM
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United States, CO, Evergreen
Joined Apr 2014
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I have a plane that does the same thing, no matter what engine I put on it there is a terrible resonate vibration at part throttle. I thought it was the OS 40AX being out of balance, but I've had a Magnum 52 4 stroke, and now a OS 46SF, they all vibrate so badly that I had to put a Saito anti-foam clunk in the tank! The prop is balanced verticly and horizontaly. Some day the vibration is going to cause airframe issues, so I rarely fly it.
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Old Apr 27, 2014, 12:33 PM
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United States, KS, Arkansas City
Joined Oct 2012
112 Posts
Bsystemwinner
I have had this happen before! First thing to understand is that on a single cylinder engine there is no such thing a "perfect balance" At some point in the rpm curve The motor, prop, spinner combo will be out of balance and generate a harmonic vibration. Hopefully this happens outside of the rpm range that the combo is operating in. So.....
Try this: If you are using a magnetic balancer "very accurate" don't balance the prop perfectly....... leave it a little out.......... if you experience the vibration stop and just rotate the prop on the crankshaft 180 deg. and bolt it back up. This will change the overall balance slightly and hopefully change the point of unbalance outside of where you are operating.
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Old Apr 27, 2014, 05:19 PM
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Doing that only induces another vibration because the two unbalances are not in the same plain, being separated by about 2" of space.
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Old Apr 27, 2014, 07:34 PM
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Joined Jun 2011
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Quote:
Originally Posted by Pedmondsonni View Post
Balance the prop. Cheap wooden props are never balanced and should be avoided.
Use a heavy prop
Dont be tempted to use more than 20% nitro. Higher the nitro, the more advanced the timing and bigger the vibration. If you can hear sizzing when you apply the glow heater you get pre detonation and serous vibration. So lower nitro is needed.
Change plug to a new OS type F
Run at least 7 tanks through. Sounds like a waste but necessary.
Contact Macgregor industries(UK) or Horizon hobby (USA) if problem persists. If the problem is really bad and shows no sign of improving your timing may need retarded by a tooth. But for now buy a good APC or K series Master airscrew and borrow/buy a prop balancer.

Cheap wooden props???? Those are all I use and they are anything but cheap. Nylon props tend to be out of balance and are very hard to balance. As far a glow plugs go, I use Enya #3's in all my glow engines.
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Old Apr 28, 2014, 08:37 PM
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Canada, BC, Cranbrook
Joined May 2013
59 Posts
Just ordered a dubro balancer from tower and will balance the prop as soon as i receive it
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Old Apr 29, 2014, 05:19 PM
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Canada, BC, Cranbrook
Joined May 2013
59 Posts
Ok so i went out today and set the lsn and what i noticed was it was set way to lean the screw was almost all the way in. So i unscrewed it to be flush with the throttle arm. That gave me nice idle and vibrations stopped to. But now i have other problem. It only idles when i leave a glow plug adapter cpnnected, as soon as i disconnect it it dies. I am using a remote glow adpter and a new os f plug. It idles good with it connected. Please help
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