Originally Posted by cannonball2
This is a 40mm crank with the ZL rod. Look how close the pin is to the counterweight. Its what is in my FH engine. They seem to be dwindling in supply. These are $20 shipped off ebay. Mine is a fairly smooth engine. There are some cranks with the ZL rod that don't have the two balance? holes, I believe those are older/inferior.
The "Red Bat" engine I bought from BGF back in 2009 has that same crank and it has the holes drilled in it, it is the worst balanced engine of all the engine I've had and is the one I plan to retire soon and just set aside, it also has an odd ball bolt pattern for the cylinder studs that is smaller than any of my other engines, it also has 6mm studs instead of the more common now 8mm, the piston in this engine is the low pin type but it is also different than any of the other PK80 type low pin pistons, it is a much lighter casting and it is almost a flat top piston instead of the very pronounced dome piston the 66cc engines come with now, this engine has been a long life dependable engine though, probably about 1500 miles on it without a single internal failure, the reason the vibration is so bad with it is because the crank counter weights have a lot of wobble in them when the engine is spun over, personally I'm a bit shy of these cranks with the Z-L marked rod that have loose uncaged lower rod bearings because the only two engines I have ever had so far that had catastrophic failures both had these cranks in them and what caused the failure was the lower bearing failed and sent a piece of the pi bearing up through a transfer and hung between piston and cyl wall and literally busted the cylinder all to heck.
Now I still have two of these engines running, but both have serious balance issues one being worse than the other, and one has the Z-L rod on a crankshaft that has the removable cast iron "balancers" on the crank.
It is possible that I just got two bad ones but so far two major failures out of four engines with that type connecting rod isn't a good average for me...LOL!
For the same price you can get the ZAE50 "halfbreed" crank with a better rod and a better lower bearing, yeah it's for a 38mm stroke engine but I would trust it for reliability much more than the Z-L with those loose pins between the rod and crank.
On the engines of mine that failed it looked like not enough pin bearings were used possibly when it was assembled, but I'm not sure how many should have been in there so I could be wrong about that.
Don't get me wrong, I'm not hating on those cranks, it's just that out of four engines I have or have had, two failed because of the lower bearing breaking up and the two that have stayed together have serious bad balance issues so I'm not personally willing to gamble anymore on them.
but thats just me.....