Crank - how straight is mine?

[Kool_Biker]

Honda's service limit for the 79 crank measured as shown below, is stated in the manual as .050 mm.

P1110219 (1).jpg

I've measured mine at .075 mm (.15 mm total run out, divided by 2).
This is clearly beyond the above Honda service limit, and wonder if this could account for my engine being quite vibey at anything over about 4K RPM, and becoming more so all the way to its 9K RPM limit.
Any thoughts?
Thanks, Aris

[NobleHops]

Whoa, isn't this the new-to-you part?

N.

[Kool_Biker]

Bot really Nils,

It is my original, supposedly rebuilt and tested crank ...
Looks like I will be needing a replacement part soon.

But would love to hear an expert's opinion as to how bad would such a run out be in the smoothness of the engine.

Aris

[EMS]

Aris: This is again one of these questions for which it is difficult to give a definite answer. Normally, I would say the runout measured as shown will not create a vibration. Then again....
My concern with the runout would be the load in the main bearings. It could very well be that you have an imbalance of some sort also and that would be a more likely culprit for a vibration. Now, a runout can cause an imbalance also, of course. As you see, one turns in circles trying to give an answer.
Do you have a possibility to have the crank checked for dynamic balance?

[FalldownPhil]

Aris,
I am going to suggest that you contact Jay at APE in Roseamond, CA.
Here is a link.
http://www.aperaceparts.com

Jay has done consideable head work and crank work for me on CBX's and is very respected in this field.
Ask him and I am sure that you will get a good answer to your question.
Very Best,
Phil

[cbx6ss]

just give it a few light taps with a hammer on the high side :^)

[Kool_Biker]

Thanks for the suggestions chaps, I will pursue and share back what I have learned.
Cheers, Aris