re: 60 MPH...achieveable? Who cares?!? Let blueprint an engine!
For those who have just hopped on to this thread...
Page 15...posts 142, 145, and 149 will bring you up to date.
What about the crank bearings & the seals?
They must be bad...right?
Not so fast there skippy...let's have a look at reality for a moment.
There are very few bearing manufacturers on the the planet. In order to stay competitive in a global market certain ISO, (Interntional Standards Organization), standards must be adhered to. The fact that this is a cheap Chinese Bicycle engine does not mean that there is a cheap Chinese bicycle engine bearing manufacturer. Given the capital outlay for a bearing plant, and the fact that a high volume is critical to success...there's not even the slightest chance that the crank bearings in these engines are sub-par!
Soooo...A few junior engineers have decided that the deluxe replacement is a dimensionally correct, "sealed" SKF bearing.
Certainly no one can dispute the quality of SKF bearings...but I will argue that it is best to purchase them open ended, and use the Chinese factory seals!
The spec catalog seal is actually a dust cover...it is not, nor was it ever intended to be a "seal" against internal pressure...the kind of pressure that is normal with a 2-cycle engine.
See the attached photos...
I was able to remove the dust seal, easily, with a pick. It would have popped out, almost instantly, under the pressure of a 2-cycle engine running.
The first pic shows one bearing with the dust cover...and another with the dust cover removed.
The second pic shows a profile of the bearing dust cover...and the difference between a "seal" and a dust cover.
Last edited by Creative Engineering; 04-03-2010 at 10:51 PM.