Rebuilt Engine Too Tight For Starter Motor

[HRthirtyone]

i have covered basically everything, except, the reason for the rebuild was i spun a main bearing. without touching the topend i put a new crank and bearings in, so i didnt touch the head, or change the offending con-rod, maybe it was buggered?

Edited September 30, 2006 by HRthirtyone

[James_03]

The crank was measured at an engine shop, and the correct grade bearings were then installed going by the crank size.

So did you use standard rb20 bearings again on the rebuild?

What you mean by correct grade bearings I have not heard of such a thing.

Sounds like you have used the wrong bearings to me. You shouldnt need to install custom bearings or machine them at all, the crank is hardened, at least thats what I understood.

Anyway out of the 6 complete rebuilds I have done all of them used the same crank again with just new shells, then just tip oil on the crank and shells before installing.

My rebuilt rb30 in the garage turns over by hand very easy.

[HRthirtyone]

yea sorry, by that i meant when i bought the second hand crank i wanted to make sure it hadnt been ground down or anything, so yea the bearings used are all grade 0 which is the stock ones back in...

motor is out now, going to see what the problem is

[Adriano]

Undo the rods one at a time, seeing if the crank frees up. Make sure you mark the rod caps so they go back on the rod they came off, did you do that last time? If not they will need to be closed and honed. the little tongues on the big end bearings go on the same side of the rod, if they are the other way around they will make the engine tight, then possibly sieze. Hope it all works out

[HRthirtyone]

Undo the rods one at a time, seeing if the crank frees up. Make sure you mark the rod caps so they go back on the rod they came off, did you do that last time? If not they will need to be closed and honed. the little tongues on the big end bearings go on the same side of the rod, if they are the other way around they will make the engine tight, then possibly sieze. Hope it all works out

yup exactly right, big end caps were on the wrong way around. duhhhhhhh the cylinder no's are meant to line up on opposite side of oil hole in the conrod..

[Cubes]

oh...

So it would have stuffed the bearings then?

[James_03]

I would replace all the conrod bearings now for sure.

If it even began to turn over under the load of the starter then it would have marked the surface of the shells now.

[HRthirtyone]

yup back to square 1! lucky theyre only $87 (trade price)

it always helps not to do things in a complete rush (out rebuilt & back in in a day) all well, know for next time i guess.

[Rolls]

You'll never make that mistake again

Not as bad as my mate, he rebuilt a 12A motor from an RX7, expensive rebuild, cost about $2800 anyway they fired it up and some how he managed to drop a bolt down the carby. BANG, housings and rotors all had deep groves in them so needed a whole new motor.

Lucky his dad's workshop forked out for the price.

Edited October 1, 2006 by Rolls

[Adriano]

Do i win a prize? hope the crnks ok, if it has any metal on it you could rub it off with some fine emery and wd40, just make sure you get it clean before you reassemble, and check the clearances with plastigauge, you want 1-2 thou maximum