Friday, April 13, 2012

Big Twin Flathead stroker project update

So the flathead engine I've been putting together is almost done. I've been lousy at posting pics about it, but at least I have them - and I'll post a few from now on to show the process and hopefully a successful kick sometime soon.

I'm using a T&S 4,5" stroked flywheel to make an 84" Flathead (originally an 74", but has been bored to 80"- and then plus the stroke it ends up at 84"). The pistons are standard flat-top flathead pistons, which have been shaved 3,5 mm so they clear the casings/baffles when coming down. The connecting-rods just clear the houses, but only barely and I think any minor discrepancy there be between each housing mould might mean that something should be shaved off them as well - but not on this engine. A longer stroke than 4,5" would require that - and that would also require other pistons as far as I can read from clever people. 



The clearance to the head is 1,2mm - out of which 0,5-0,6 is the copper gasket. This means the pistons stops at 0,6mm before the deck. This distance was created will a quite small stroker-plate + a gasket on each side lifting the cylinders about 2mm higher that stock. 



The calculation of the compression is below here (in cc's) - ending up at 7:1.




The cams had to be smoothed out as they where like sandpaper on the lifters - another little detail.



Getting closer!

The observant viewer will notice that the spiral drive breather valve gear has the threads the wrong way...ie it wouldn't engage with the pump. Hadn't noticed till assembly was full under way - so had to find one during easter holidays really quickly, but that's where Frank comes in. Every time - great stocker and great guy. Thanks for all the parts!



Half way there!

More to come.

Old Dirty Motorcycles

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