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Author Topic: K3 Crank  (Read 1273 times)

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Offline Ridgeback

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K3 Crank
« on: September 07, 2012, 07:01:35 PM »
I've taken the engine (CB750 K3) apart and notice some wear on the crankshaft.  I have never been this far into the motor before and have no idea what is acceptable.  Does anyone know of an expert I could show it to in the Brisbane (Australia) area please?  I don't want to put it back together again unless it's viable.
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Offline Ridgeback

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Re: K3 Crank
« Reply #1 on: September 11, 2012, 08:25:12 PM »
No one replied to this, so I guess no one knows an expert in the Brisbane area.  Is there anyone out there who could give me some advice as to what constitutes excessive wear vs acceptable wear please.
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Offline Duke McDukiedook

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Re: K3 Crank
« Reply #2 on: September 11, 2012, 08:27:06 PM »
Pics please and have you read the Honda manual concerning wear on the shafts?
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Offline ekpent

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Re: K3 Crank
« Reply #3 on: September 11, 2012, 08:33:12 PM »
Without pics for people to see its impossible to judge. Calipers are good for the experts and if your fingernail can snag anything it may be bad.
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Offline nancy

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Re: K3 Crank
« Reply #4 on: September 11, 2012, 11:41:08 PM »
I am NOT expert in affairs of the crank - but can concur with EKPENT on the fingernail trick....as a very basic guide.
I took my crank along with the cases and my Clymer manual to a local motor machinist - he mic measured etc...and told me the journals were within maximum allowable wear - JUST. One journal had wear that was only just "feelable" with my fingernail... I had to rub the edge of my thumb back and forward several times before I could feel anything....others if more "feelable" indicate a crank that should be considered "toast".
 Any more he said and you should chuck it. There were scores around the central area of each journal - where the oil hole is and this wear is - according to him - caused by dirty oil circulating too long.
If you have to have a rebuild done - decide who the machine shop will be, talk prices for a bore etc and suggest he could "quickly" check over the crank first..i.e. for free.
Taking tolerance/wear meaurements yourself is an absolutely pointless hopeless task. Needs the right tools and experience. Like measuring pubic hairs.
Regards
Mark
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