1975 CB500K1 crank rotation resistance

[martin_uk]

Im in the process of reassembling the engine on my 75 CB500K1 basket case that came already stripped.

Crankshaft checked for wear which was minor and well within spec.

Minor marks to crank main shells on 1 and 5 but replaced with new genuine Honda Green shells in line with calculations of housing and journal.

Checked with Plastiguage and all mains came out at 2 thou.

Reassembled with top case down and inserting primary shaft after cases together.

Bearings well oiled and fitted evenly.

Cases closed up easily with light taps with rubber mallet and gradually torqued up as per recommended order but on final torque crank becomes more difficult to turn.

It turns with a spanner on the alternator bolt but feels tighter to turn than I would expect.

I have rebuilt 3 CB750 enfines without this issue.

I have just checked and force required to turn crank is 9 lb ft.

Removed primary shaft and does not change.

Would be interested to hear if any similar issues .

Thanks

Martin

[McCabe-Thiele (Ted)]

Does the crank have that free movement feel if you make a very small rocking action with the crank?

Do you have any doubts that the crankcase halves were a factory pair?

[Bryanj]

You didnt oil the back of the shell did you?

[martin_uk]

You didnt oil the back of the shell did you?

no, but good point.

[martin_uk]

Does the crank have that free movement feel if you make a very small rocking action with the crank?

Do you have any doubts that the crankcase halves were a factory pair?

I will check for end float.

Pretty sure halves original

[McCabe-Thiele (Ted)]

A bit of a head scratcher - not trying do doubt your ability - are you sure when you fitted  the main shells in the correct  main bearing positions as number 1 main is then on your right when inverted.

Even so a tight clearance shell should not make it so resistant to rotation.

[Bryanj]

Only thing i can think off is either something between case and shell or the disaster of a bent crank, i have built engines with all black shells with no rotational problems

[martin_uk]

End float on crankshaft is approx 6 thou.

I did not check crank for run out as wear on shells was minimal.

[McCabe-Thiele (Ted)]

When you assembled the crankcase halves is it possible that an excess of Hondabond could have entered somewhere to lead to this problem? Could the crank seals be somehow causing the extra binding if they have distorted?

I'm assuming you have not fitted the block yet.

I think you will have to split the cases again to investigate further.

[martin_uk]

When you assembled the crankcase halves is it possible that an excess of Hondabond could have entered somewhere to lead to this problem? Could the crank seals be somehow causing the extra binding if they have distorted?

I'm assuming you have not fitted the block yet.

I think you will have to split the cases again to investigate further.

I have considered if the seals were the problem, but fitted well and tightening only happens on final torque of mains bolts.

I will try easing them off and re torquing.

You can turn the crank but do need a spanner on the alternator bolt.

Wondering if I am being too cautious.

Can you normally turn by hand on rotor without pistons fitted?

[Bryanj]

Can normally tyrn by hand WITH pistons fitted

[McCabe-Thiele (Ted)]

On both my 400 & 500 I could rotate the crank by hand easily using the alternator rotor as a grip point.

It probably depends on your grip strength in my case it was not as easy with the pistons in place though it was easy to rock it through what I call the null pont.

[martin_uk]

Thanks for comments and suggestions.

I have come to conclusion that need to take apart and check further.

A friend has offered use of surface plate and V blocks to check crank main journal run out.

The engine was apart a long time and moved around by PO so crank may have been dropped and bent

[McCabe-Thiele (Ted)]

I hold the view (probably wrongly) that cranks are not easy to bend when out of the engine.

I have always believed that a bent crank is generally associated with some sort of catastrophic engine failure such as a con rod tries to exit the block or casing.

Best of luck with finding the problem please keep us posted.