a few things don't seem right....

Veepster · Post by **Veepster** » Sat Jul 19, 2003 10:49 pm

I am rebuilding my motor. I have had some serious main bearing failure....3 times...so this time I am doing it myself..... before the last go around crank and case were machined....so where I am at is I have cleaned all the parts REAL good and was trial fitting everything tonight......I ran into a few things that don't seem right...

note: everything is clean and I am using no lubricants or sealers anywhere

1) I installed the cam(and bearings) only in the case and torqued the bolts....Cam did not turn very easily...very smooth but a lot of friction...as soon as I loosened the case bolts it spun easily and what I would have expected. after inspecting the bearings there is no unusal wear pattern.

2) I installed the crank(and bearings) only in the case and torqued the bolts......crank spun easily for about a quarter turn and then gets REALLY stuck. I can force it throught the tough part and then it will spin freely for another quarter turn and then get stuck again, this continues. After inspecting the bearings there is some wear in the center main bearing. there was an even pattern of wear all the way around the bearing, it appears things are too tight.

what are your thoughts on these issues, and how do I correct them? Thanks for all the insight....

motor specs:
prehistoric scat 4 piece case, dry sump cut .040
88 mm scat flanged crank...cut .030
no comments please on the oversizing, I wish it wasn't that bad also, and I want to use these parts.

Peace.........BartG

69bug4me · Post by **69bug4me** » Sun Jul 20, 2003 1:58 am

I think I would try torquing the case empty and get a bore gage and see if the center main bore was out of spec then do it again with just the bearings.
Is this the first time it has been assembled since being linebored,could be the case bore or maybe a bad bearing.

Something sounds amiss it looks like if it was just tight it would be tight all the way around.try it with out the center main and see if it still does it if it is ok with it out you know where to start inspecting right away.

Shane

Veepster · Post by **Veepster** » Sun Jul 20, 2003 1:50 pm

I pulled the center bearing and everything is OK.....Reinstalled a different set of bearings and problem still exists......

One more thing....with the crank setting in one half of the case wil the bearings installed, it rocks...like a teeter totter.....so something is definitely amiss in the center...

I will take by the shop tomorrow and measure crank and case to see if I can find the problem....

this is the second rebuild(first one lasted 10 miles) since line bore....

Thanks for your input Shane!.....Anyone else have any input? The tight cam? what is too tight for a cam?

Peace...................BartG

Marty · Post by **Marty** » Sun Jul 20, 2003 5:03 pm

At this point I would send the case to RIMCO and have them fully check it out and repair whatever is out of whack. You may have to go to a type 4 main setup or something to get it all square again.

turboblue · Post by **turboblue** » Mon Jul 21, 2003 9:29 am

I agree with sending the case out to be inspected. Don't forget to have the crank checked also. Could be a combination of the two giving you problems.

Veepster · Post by **Veepster** » Mon Jul 21, 2003 4:14 pm

update....put the crank in the lathe and checked the mains for runout.....less than a thou on all of them....all of them the same size

case....straight edged everything and it is perfect.....checked journals...all the same size within one thou....

sigh......back to the garage! any ideas what to check?......I know I need to send them in but I wanted to know what was wrong with the parts...

Peace........BartG

Veepster · Post by **Veepster** » Mon Jul 21, 2003 6:52 pm

well it works now........I had read somewhere that you could put the crank and cam in separately to check things....well all the problems I had were when they were in separately..I put the cam and crank it at the same time and everything spins as expected........HHHHmmmmm...??

Peace............BartG

73SuperL96B · Post by **73SuperL96B** » Mon Jul 21, 2003 6:54 pm

I only mention this because you say you checked everything else. Try putting the crank into the case half and turn it by hand. See if the weights on the crankshaft might possibly be rubbing on the case itself. Especially around the center journal. Try on both case halves. It might be easier to tell if you take off the rod arms. My motor did exactly as you describe and somebody a lot smarter than me figured out this was the problem. We had to clearance out a little material on the case under where the center main bearing goes. I had the same symptoms you describe.

turbo_bob · Post by **turbo_bob** » Mon Jul 21, 2003 9:40 pm

Veepster wrote:I pulled the center bearing and everything is OK.....Reinstalled a different set of bearings and problem still exists......

One more thing....with the crank setting in one half of the case wil the bearings installed, it rocks...like a teeter totter.....so something is definitely amiss in the center.

Peace...................BartG

It sounds to me that your main saddle in the case is not cut the same depth as the rest?

Veepster · Post by **Veepster** » Mon Jul 21, 2003 10:32 pm

that was my thought too Bob......but..they all measured out correct

6volt66 · Post by **6volt66** » Wed Jul 23, 2003 3:26 pm

this happened to me once. when i went to put the motor together the crank would only spin about 180 degrees before binding up. what happened was when i pulled the camshaft gear off the crank when rebuilding i slightly bent it. i installed a new gear and problem solved. also make sure you have the right size bearings. have you used a plastigauge to determine your gap? everything should rotate fairly smoothly at the proper torques.

Guest · Post by **Guest** » Thu Jul 24, 2003 1:30 pm

Sounds to me like the bearing were not seated in the dowels properly.