81 kz 750 E2 starter clutch

So I recently purchased my first motorcycle that is a KZ 750E2. Pretty much every gasket on the top end of the engine was leaking, so me being an automotive technician I took it all apart and re-sealed the engine. I just put it all back together, filled it up with Mobil 1 20w-50 V-twin oil and went to fire her up for the first time. She started to try to crank over and then I started hearing a whirring noise. My heart dropped and I thought the timing chain fell off or broke. I tried it again and it tried to crank over again and then started whirring after a couple of seconds. I have a feeling that it is the starter clutch but I have only been able to find a new one for sale in the Netherlands for a decent amount of money. You guys have any idea if it could have to do with the cold, the oil, or if it is the clutch, is there any way to find one in the states? Thank you.

vimeo.com/115544089 here's a video of it

Take a look at the engine in your motorcycle. You may notice it has 4 cylinders. That makes it a 4 cylinder motorcycle. Unlike 4 cylinder motorcycles V-twin motorcycles have 2 cylinders. When putting oil in a 4 cylinder motorcycle it does not make good sense to use oil engineered for use in 2 cylinder motorcycles. So for starters, if someone had put V-twin oil in MY 4 cylinder motorcycle I would dump it out and put in oil intended for use in a 4 cylinder motorcycle. Mobil makes oil specifically intended for use in 4 cylinder motorcycles. It is labeled "Mobil 1 Racing 4T " Aside form the fact that the oil you used is intended for v-twin engines, it also is 20w-50 weight which is quite heavy for use in Winter unless you live in a very hot climate. Ed

Although the V Twin oil is marketed for wet clutch engines, it does not have JASO certification, and as 650ed points out, 20-50 is a bit much for these engines.
However, the VTwin oil has higher levels of zinc and phosphorus.
Check out the product guide-in
mobiloil.com/en/motor-oils/mobil-1/mobil...-twin-motorcycle-oil

Thanks guys. Looks like I'll have to try the 4T stuff and see if that fixes my problem.

It's not the oil, your starter clutch is toast. Any starter clutch from any year KZ650 and 750 four cylinders will work. Z1 sells the starter repair clutch kits.