CMB 27 Alpha failure

[gil sonsino]

Yesterday we had surprisingly the first CMB Alpha failure..motor was installed in a Jae rigger.running under normal conditions...this is the previous version motor not the EVO.....just curious to hear something about this.Thanks Gill

the pic was send to me but its not really good.

 

[gil sonsino]

Yesterday we had surprisingly the first CMB Alpha failure..motor was installed in a Jae rigger.running under normal conditions...this is the previous version motor not the EVO.....just curious to hear something about this.Thanks Gill

the pic was send to me but its not really good.

here's the pic

 

[Ian Inverarity]

What RPM were you running?

My 27 has never done that but I have had a few RS101's do that. At higher RPM the crank pin flexes and eventually breaks. On my 27 I made a new rear bearing housing that took two bearings to stop the crank from flexing so much.

 

[Ron Olson]

The problem that was showing up on the first ones was that the engine didn't like the regular drive and they had to use a square drive setup as the cable would push again the bearings shifting the crank forward.

 

[gil sonsino]

This is not my motor..it is from a friend of mine that obviosly is quite disappointed....don't know too much how the boat was running ..I will have more pics and details soon .Thanks Gill

 

[lohring]

We had crankshaft flexing issues with the CMB 35. The flywheel was striking the coil. It took a double front bearing to cure the problem. In addition Mike Bontoft ditched the magneto for a Quickdraw electronic ignition, saving a lot of weight.

Lohring Miller

 

[RaceMechaniX]

Gil,

It is a little hard to tell from the picture, but I can't see any bluing indicating there was heat on the bearing. Do you see signs of fatigue where the break occurred?

There was a lot iterative development work done on the big end to get oil into the bearings. All those cranks that I heard of seized and head significant bluing from heat, not fractured like you show here.

At least from my experience with the 35RS, they are not tolerant to being pushed with a collet system. I solved 95% of my crank issues on he 35RS by switching to a square drive.

-Tyler

 

[Stuart Barr]

The generation I and generation II 27's had rod bearing problems that shatter the bearing. Possible it would also take out the crank pin.

Stu

 

[gil sonsino]

Thanks guys I have to wait the motor arrive to take better pics and get a clue of this failure.I don't think it was a heat problem as that motor was in its 6th tank running rich but according to other friends the rigger was running in very choppy conditions????

Agreed Stu but let see all the parts on my workbench to take some conclusions.

Gill

 

[gil sonsino]

According to the owner parts were sent to the plant...let's see! thanks Gill

 

[gil sonsino]

Today I was informed that CMB is sending a crankshaft of the Evo to the owner.

 

[Stuart Barr]

Today I was informed that CMB is sending a crankshaft of the Evo to the owner.

Gil,

I will be sending a replacement crank to Luiz tomorrow.

Stu

 

[gil sonsino]

That's great and thanks for the support.

Gill