YS vibrating like a MO-FO! Any advice????

[jratliff]

Heres the lo-down! The heli has shook like crazy from the first tank of fuel. Its a very high frequency vibration. I'd love to think its due to the rich needles but it can be felt at idle sittin on the bench. The motor has been out to measure the runout of the fan hub and clutch along with balance. .0005" runout. Acceptable to me!
This is the equipment-
YS-91
Hatori muffler
OS #8 plug
30% Morgan fuel
I'm to the point where I want to buy an OS motor and off this YS. Would it be worth sending the YS in to them for a check up??
Any advice will be appreciated guys!

[LoveMyTrex]

is it visible in the skids, tail fin, or canopy? or maybe your tank foaming? check tail hub,if thats bent it can cause very high frequency vibration. also check your TT. is it a new motor? it is high frequency not anything to do with the main blades right?

[HELINHAWAII]

You sure it's vibrating any more than any other .90 size engine or heli of the same size?

[Kinger]

You mention the machine has been vibrating since the first tank, but you don't mention how many tanks you have through it now. Any chance you are still running it rich?

[simusphere]

Don't forget the actual balance of the fan!

[jratliff]

I should have been more specific...... The fuel in the tank foaming is the worst part. So much so that quarter size globs of bubbles can be seen in the corners of the tank. The heli has less than 10 flights on it. Its never had any kind of an incident to damage shafts. Besides, the vibration can be felt while its sitting idling.

[jwilkens]

90 size engine does vibrate quite a bit, typical to all single piston engines. The foaming fuel is a common problem on the Trex 700 and is due to the fuel tank fitting to tightly into the frames.

Remove the tank and the rubber inserts in the frame then use a pencel grinder to file open the holes in the frames by about 0.5 mm and the foaming will disappear.

[mlucia]

Dont get rid of the YS man! It kicks arse in the 700!

What head speed are you running? Since you have 10 flights I assume you have had it up there?

Is the YS brand new or from another machine previously?
What are the needle settings? Not super rich?

Did you make sure the main shaft can fall through the bearings when you assembled it?

Mine vibrates when at idle also but no problem once it spools up. Actually it is very smooth with no foaming of any kind.

[skigolfmike]

There's a possibility it could be too lean. I have noticed the YS will vibrate like crazy when it gets too lean.

[earetz]

Hi. I had the same problem. I bought a second hand 700 (my first mistake) with a YS SR engine. It had been sitting too long so I ended up having to rebuild the motor as the rear bearing went rusty. The rest of the engine looked perfect. The first hover and it vibrated, as you said, like a MOFO. I then balanced the fan hub, same problem. I then rebuilt the engine to double check my workings and reseat the bearings, balanced the fan hub again.. Same problem. With lots of swearing from me, I pulled it down again just to be sure, thinking i had missed something. Same problem. I messed with mixture settings for hours. I spat the dummy :arggg: and bought an OS HZ and I get the smallest amout of foaming in the tank, which may be due to the tank being too tight as a previous post has mentioned. I want to bench test this YS SR at some stage but I cant bare to look at it at the moment, its in the naughty corner for now. If I find anything I will let you know and if you happen to find the solution, please let me know also. Good luck. BTW, the OS HZ is a nice engine if you do decide to buy one. Regards Ed.

[skigolfmike]

Also, the stock 700 doesn't like a slow head speed. Below 1750 it will shake like crazy.

[jratliff]

I've got that baby spooled up to 1950! I even backed it down to 1900 thinking it was too hot but it made no difference. The fan hub and clutch have never been balanced per say. They were stuck on a prop balancer and held in my fingers but no heavy side was obvious. The needles are a couple, three clicks in from where YS suggests for break in. The fact that this vibration is so high frequencey from idle right thru the upper range is what has me pointed at the engine. If it was needles you'd think it would have an obvious range.
A friend suggested shimming the head. Seems a shame to take power away from it but its no good the way it is. I'm so bummed! :arggg:

[HeliSmith]

I don't want to send you off on a wild goose chase as this interjection is completely founded on no experience but something in the back of my head keeps calling out "air leak". Check your pluming, check your seals, etc..

[c_forthofer]

I know you mentioned high frequency vibrations and that would suggest motor or tail but have you checked your main and tail blade balance? FWIW.

Chris.

[jratliff]

Well.... I tossed caution to the wind tonight! I ran the needles right in to the minimum suggested settings. And guess what....???? It smoothed out a little. Quite a fair amount actually. The fuel is still rough in the tank but that may be due to it being tight in the frame. Maybe I'm expecting it to be as smooth as my 600 which may not be possible for a 90. Thanks for all the advice! Keep it coming!