TOPIC:

Is the crank well lubed while spinning?
Steve

VTEC wrote: Maybe I'm overanalyzing.

Maybe… but I can tell you that I have the same problem, it would keep me up thinking about it.
It would probably run many miles maybe vibrate a touch more but who knows . I am rebuilding a old dirt bike right know and I am trying really hard not to get to technical because like you I am compulsive , it really sucks.

Have someone else put it together then you can blame them

Did you ask Stan if he would run it???

VTEC wrote: Guess I jumped the gun. Been spinning the crank and still feel a slight tight spot. It's random, not any particular number of turns. I put a dial inch pound torque wrench on it and the tight spot is only 5 or 6 inch pounds.

I'm getting a straight edge to check the line bore.

It's either the bore is off, a bad bearing I can't detect otherwise, or maybe just the .0025" run out at the center of the crank. The runout is within specs but new is closer to 0. I'm sure most people wouldn't have noticed it. Maybe I'm overanalyzing.

I spoke with Stan at grc cranks and he suggested swapping case and/or crank and see which fixes it. Wish I Had a few laying around.

I'll stand corrected but I can't see a crank or any major item out of alignment having a random tight spot, my crank was badly out when it twisted and it still spun freely, sounds more like a bearing nipping up once in a while. The other thing to consider is a cam chain, if it is not new or the link (if it is riveted) is too tight it might bind once in a while.

"I'll stand corrected but I can't see a crank or any major item out of alignment having a random tight spot, my crank was badly out when it twisted and it still spun freely, sounds more like a bearing nipping up once in a while. The other thing to consider is a cam chain, if it is not new or the link (if it is riveted) is too tight it might bind once in a while."

Chain is off, crank only. This crank spun freely in my previous case because the twisted crank enlarged the journals so the bearings weren't held tight.

SWest wrote: Is the crank well lubed while spinning?
Steve

Yep. poured oil into the oil switch housing hole to lube and confirm oil at all bearings.

Man, It's only 5 inch/lbs. I bet most would have spun it and said it was fine. Hope I'm not chasing ghosts.

Spinning it fast you feel nothing, just slowly by hand.

If it were me I'd put it together and ride the piss out of it.
Steve

Torqued the case and checked line bore. Couldn't get a .0015" blade under anywhere. Ordered another eBay crank to test. After all this work I just can't put it together knowing something's not right.

OK. Test crank from ebay came in. Installed and no tight spot. Sending the first crank to GRC. Stan says he can rebuild it if the welds weren't extensive. This stuff never stops.

Don't worry, winter is a long way off...

Hey Im doing the same work on a 750, I can only find the max clearence spec for the crank to main bearing. You guys have any idea on a min spec for the crank to bearing?? I currently have .002 . Thanks

The big fours use roller bearing cranks. I suggest you start a thread on it. Lots of smaller four guys here and good info.
Steve