Marcos Nieto

Hi guys.......yesterday took to the field my new Aerowork 75cc Yak 54/ZDZ Super 80 combo. It is the first time I started this engine and I was surpised by the amount of fuel tank shake. It looks like a blender cup when the engine is at full throtlle. At this condition it is predictable that some bubbles will get through to the engine making tuning much more difficult.
As indicated in the instruction manual, I used the stock foam rubber pad under the fuel tank but it did't stop it from shaking. The prop, a carbon-fiber one, was very carefully balanced.
Is this normal???? My olny other gasser is a GP Pitts/ZDZ 50NG and there is now way to see the fuel tank while the engine is running.

Thanks

Marcos

bubbagates

My Feedback: (32)

Marcos,

A big single cyl. engine will shake. Maybe you need a bit more foam under the tank and to tie the tank a bit tighter. If you used the foam Aero-works gave you did you dbl it up or jsut use one layer. The foam they give you is kinda crappy.

Also, if you used a spinner is it way out of balance. That's easy to check, just remove it and the backplate and see if it goes away. Aluminum and CF spinners are usually balanced well but I have seen both, mainly the aluminum ones be way out of balance, especially the stamped ones

Another thing I have seen is the prop bolts. Some people will strip the heads of the bolts and replace them with a different type. What I mean is most engines come with aluminum bolts like 3W and I believe ZDZ, but they will replace on or two with steel bolts which are heavier.

Tired Old Man

My Feedback: (1)

Prop balanced? All engines cause vibration, The amount that gets through to mounted components is controlled by the user in the manner they installed the component. A few bubbles getting into the gas is no big deal and will not effect tuning. If you use a fiber filter in the gas tank most, if not all, of the bubbles will never make it to the line.

Firebird25

As I recall it, when mounting couplings on a power transmission drive shaft for industrial apps, all the bolts, nuts, washers etc. are weighed and selected to be within a very, very close range to prevent imbalance in a set up that may reach high rpms [20-40K]. I can imagine that you need all the help you can get with a one cylinder engine, so if I were in your shoes, I would make sure that all the elements that make up the drive train are well balanced. This assumes that the prop is attached with multiple bolts.

Marcos Nieto

Thanks guys for your inputs...........Where can I get those filters??? Are there any specs??

Thanks again

Marcos

Tired Old Man

My Feedback: (1)

Any decent saw and mower shop in the U.S. Walbro is the manufacturer. Part number 125-527

bubbagates

My Feedback: (32)

Aircraft International sells them as well if you cannot find them any other place

Digger44

My Feedback: (4)

Another thing to consider is that the vibration from the engine is more apparent with the wheels on the ground. In other words when flying there is not as much vibration absorbed by the fuel tank as when the plane is sitting on the ground.

Truckracer

My Feedback: (19)

Nobody has asked whether you had the wings on that Yak when it was running. Wings absorb a lot of vibration! I've watched guys running gassers at the field with the wings off and they shake like the devil ..... everything shakes! Wings on and they smooth right out. Just a thought.

I use 1/4" to 3/8" foam between the tank and tank floor and strap the tank down with two bands of 3/4" wide Velcro. Hardly moves at all and no foaming. I dislike tywraps for this purpose.