I have saito 82 mounted on H9 Ultra Stick 82 with 13x8 2 blade prop. I think hole diameter for prop is slightly larger than engine shaft diameter. When I started engine for the first time, there was lot of vibrations.

Do you guys think it is because of larger hole dia. in prop?

What else could cause excessive vibrations?

How much too big is it? That could be the likely cause. Do you have a prop reamer to properly ream a new prop with? Did you check the balance of the prop?

If the hole in the prop is larger than the engine's prop shaft, bush it. You do not want a badly fitting prop on any engine, much less a 4-stroke.

Spinners come with sets of bushings/washers that're supplied for that same reason. You pick out the one that fits the spinner AND the prop shaft, use it and the spinner won't shake your airplane apart. Look around for similar bushings. Or make one.

I have shimmed cranks with aluminum duct tape from home depot Clean shaft with thinner and don't overlap; wrap it once and cut it even with the end, if you need more, put on another wrap. I have experiencd no problems.

a prop should fit on the shaft with no slop,if you need to enlarge the hole always use a reamer a 4 step usually covers most of the crank sizes.always balance the prop and spinner to eliminate vibration.

My 82 vibrates like a son of a gun. I balance everything and my props are tight. I think my favorite is an APC 14x4. Someone said something about lining up the prop with the cylinder head on the compresion stroke, or something like that, and it will help to reduce the vibration. I'm not kidding, mine shook my Funtana something feirce, mostly at idle though.

OK, no one else said it so I will.
If the hole in the prop was reamed to large, save it for another engine with a larger shaft and get a new prop for your Saito. Props that size are not that expensive and certainly much less than repairs or replacement of that engine.

And nobody has said this either:

Some 4cycles vibrate like crazy no matter how well the stuff you tighten onto their prop shafts is balanced. Truth is, if you can't sort out the vibration, sell the sucker to someone willing to believe that vibration ain't a big deal. We got a couple of guys at one field who will tell you that a certain brand of engines that're known to vibrate something awful are proof that vibrating is an indication of power. Amazing..... Find a dummy like that and sell the sucker to him.

Vibration kills crystals, receivers, servo gears, loosens bolts, screws up on-off switches, messes up connectors, foams fuel, walks out screws, and weakens glue joints.

Agree'd, but I don't like to screw people and I love the power and performance I get from my 82. That's why I address ALL of the issues that you mentioned above and take care of the problems associated with vibration. As a moderator I wouldn't think you'd chose the route of screwing others but add helpful suggestions to minimize the vibration.

darock, you left out breaking hinges. radioflyer, I don't think selling a shaker engine to someone who thinks this just means power is screwing them, as long as they know what the're getting.

[quote]ORIGINAL: darock

Find a dummy like that and sell the sucker to him.

try another prop balance it and make sure it is properly reamed to size,if it still vibrates and you cant live with it then sell the sucker...........

Read the entire post again. It's a long description of sorts, but nonetheless describes in detail the suggested "purchaser". And it's probably not too clear to everyone that it's poking fun at people who claim that certain 4strokes that have a deserved reputation as SHAKERS don't really hurt anything.

When I typed, "like that", it referred to all the prior descriptions. I wanted to tie in all the qualifications together so it would be obvious I was kidding around about a very specific group, so I said, "a dummy like that"


Sorry I didn't tie in all those sentences together better.

BTW, we've been remiss in our advice.

We forgot to mention that there are vibration absorbing motor mounts available.

They are very popular with the pattern crowd. That bunch seems to have a large number of fans of engines of a type known for strong vibrations. It was noticed by some of them that they really couldn't keep their airplanes alive just by wrapping the RX in foam. And a couple of guys developed "soft mounts". And then they discovered those mounts seemed to increase the horsepower that was getting to the prop. The mounts were actually putting the power output of the engine into the prop instead of the airframe.

So if you've got an engine that vibrates, it would be to your advantage, in more than one way, to mount it with one of the soft mounts.

All my 4 strokers vibrate, but the Saitos are the worst. Especially the 82's I have. I believe they are responsible for the demise of my Somethin Extra. The crystal went kaput. I now soft mount any plane I'm sticking these 'Vibrato' 82's in. I use the stock Somethin Extra mount (reinforced with brass strips), and use the JTec iso bushings. Works like a charm, and you only push the mount out about 1/8-1/4 from the firewall. Red loctite on the motor mount to firewall screws, and viola!

Balance your prop. I would recommend the GP precision prop reamer and a good prop balancer. As your 82 gets more run in time, the vibration will get much lesser. How much run in time have you got on the 82, and what fuel are you using? Remember to adjust the valve gaps to 0.015" after about one hour run.

So far I have run through about 4 tanks of fuel. I have been using heli fuel because I heard Saito idles well with this fuel. I have not yet adjusted low end yet. It is still at factory setting.

Be prepared to turn that low end in 2 full turns at least. Here in Montana at 3500 feet, mine is one turn out from closed. Saitos run fine on 15%, you don't need to waste your money on heli fuel - especially in the break in stages. Saito recommends only 10% for break in. They also idle like a kitten purrs fine with 15%. Even inverted - no on board glow required if set up properly. A friend has the 125 inverted in a UCDD 60, and you can almost count the prop revolutions at idle.