Let’s talk crank balancing

[Deleted member 12676]

FRankfort, most people buying these engines are just now getting into 2 strokes and so have no point of comparison regarding engine vibration. I've heard that the 69cc engine is better than it used to be but haven't ridden one and so I don't know what their amount of vibration is. All I can say is that if it vibrates your rear view mirror enough so that what you see in it is blurry then it is too out-of-balance and can be fixed.
On my 48cc crank I just had to drill two 9mm holes in it. That eliminated most of the vibration.

 

[Frankfort MB's]

The more 66/80s I build the smoother they get.

The first one I had was about 1-1 1/2 years ago and it was butt awful.... My newest build (#7 btw) is pretty smooth till about 5-7k RPMs and it starts tingling your fingers but after 7k it seems to smooth out. The thing is most the time I'm cruising it's around 6k and the only time I go any faster is to outrun my neighbors very large pitbull :/

 

[45u]

FRankfort, most people buying these engines are just now getting into 2 strokes and so have no point of comparison regarding engine vibration. I've heard that the 69cc engine is better than it used to be but haven't ridden one and so I don't know what their amount of vibration is. All I can say is that if it vibrates your rear view mirror enough so that what you see in it is blurry then it is too out-of-balance and can be fixed.
On my 48cc crank I just had to drill two 9mm holes in it. That eliminated most of the vibration.

Jaguar do you check to see if your cranks are true? That is what it is all about eliminating vibration and does not matter how you do it. Seen more ways then one to skin a cat. My 69. something motor vibrates terrible.

 

[Deleted member 12676]

yes I checked its trueness

Frankfort, tingling fingers is unacceptable. For a couple hours work people can have a smooth running engine. Otherwise it will always vibrate and that can be hundreds of hours of discomfort. From my viewpoint it's an all win situation for me to split the cases and drill a couple holes in the crank wheels and re-assemble it. Any fool can do that so no one on this forum has an excuse.

 

[45u]

yes I checked its truesness

I thought you would but just checking. Have you found any bad off or what do they normally run? Now that I have most of my tools at the house I will be checking them. Will be happy when I have all my machines here.
Thanks
Jeff

 

[Deleted member 12676]

I've only inspected a couple cranks and they both were good

 

[45u]

I've only inspected a couple cranks and they both were good

When you say good to you mean perfect or not out bad? Where they out any and if so how much.
Thanks

 

[Deleted member 12676]

That was 4 years ago and I didn't take notes. Sorry but I don't remember the details