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Unmatched Dominator Crankcases?

Submitted by aston_key on Thu, 18/08/2022
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Heavy Twins

I bought a Dominator 1955 88 dynamo crankcase to replace the damaged one I was hoping to rebuild.

When the crankcase arrived I noted that the drive side is stamped K181 but the timing side is stamped F811. Does this mean I have been sold a pair of unmatched crankcases?? If I have - is this a dead duck??

It does look as though the two halves have been built together and run before the engine was broken up for spares....the red hermetite used on the halves "matches" on both sides - and the damaged barrel gasket appears to be the same on both sides. I fitted the camshaft from my old engine to this "new" crankcase, and it seems to spin freely enough, but I am loathe to fit the crank (and thus risk damaging the bearings) if the consensus is that unmatched halves will not work together.

All thoughts gratefully received...!!

Submitted by tony_wood on Thu, 18/08/2022

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Hi Aston. I believe that both crankcase halves should have matching numbers. My Dommie 99 engine’s cases have matching numbers, so I reckon you do have mis-matched cases. However, if the camshaft bushes and crank bearing bores have been parallel line-bored, then they may well be fine to use together. Hopefully someone with more knowledge than me will confirm/reject my ideas.

Good luck with it
Regards

Tony

Submitted by john_holmes on Thu, 18/08/2022

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Agree with Tony, if it lines up then use them, my B40 is non matching but runs fine. I am the guilty party on that one but as it all lined up.

Submitted by howard_robinson on Thu, 18/08/2022

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Hello again Aston - In my experience if the camshaft rotates freely then so will the crankshaft.  The joint where the cylinder barrel fits will be the tricky one. If there isn't a step you're laughing and even if there is a slight step you can sometimes get away with a thicker type of cylinder base gasket.  The later 650 Models used a 'green' base gasket that was thicker than the usual Dominator type.  The 650 gasket will be ok on your crankcases but don't try and use an Atlas or Commando type. Wellseal is better to use than Red Hermatite and was preferred by the Norton factory.  Good luck, Howard    

Submitted by john_holmes on Fri, 19/08/2022

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On that joint I had a step with the B40, my hours of filing during my early apprenticeship set me up so with a flat file I could restore flatness.

the best way would be to machine the faces square to the crank bores. this would  make sure the barrels are true to the crank might be necessary to use a thicker base gasket to maintain the compression ratio any machine shop with a milling machine should be able to do it .

Submitted by aston_key on Tue, 23/08/2022

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Thank you all for your wisdom and experience.  What a great club this is.

There is no step between the crankcases where the barrel sits - so as Howard says I "may" be laughing. Fitting the crank is probably the next sensible thing to do, and see how it all works out.

Thanks again.....

 



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