Go on be a deville & fit a 490 crank with more stroke. Not sure what would fit without drama. "79 yz400 went to 82 bore instead of 85 so must be longer stroke than usual 70mm. I'm sure you can do it if anyone can. I did it to my dt1so became 70 x 70 instead of 64 stroke. 6mm plate under the cylinder on yours then lower the port floor. What could be easier--ummm--well, sounds easy at least. Man I talk rubbish!!.

65 hp by factory, at the engine, for my '74
Worx bike and needed the AMA license for open class, to sell.

55 or so on my '73 stock.

120 pounds of pure moto musk ecle.

cliff

I did end up widening those A transfers in the process of correcting their entry angle. I'll have to measure that exhaust port too, I can't remember where I set it up exactly. I usually widen them to at least 68 percent of the bore diameter, that would be a little over 64mm. That cycle world article advised going to 70 percent of bore diameter which would be 66.5 for the SC. I'm sure I didn't go that far.

Maybe I'll just see how it does with a good pipe on it.

Turbodan I’ll ask Joey Lunati if he has a extra cylinder from his late father’s SC500 and would he donate it for you to play with. I really like this thread

I'll be sure to try something nutty with it. Custom sleeve with a bridged exhaust port would be inevitable...

I had an rt2mx cylinder a few years back, and it had a bridge port on the exhaust. I did run it, but it wasn't right at all. Tore it down and found that the "bridge" was cracked on one side, making a nasty spot to gouge the piston, which it did lol.

They have been known to do that, especially when the cylinder wasn't originally bridged.

I'm thinking about a CR500 sleeve punched into a 360 cylinder. If that works it would result in a displacement of about 435ccs. CR500 pistons are very common and with the large, bridged exhaust port I think it could be a 50 hp motor.

That would be another cool build, for sure!  The only other 2 stroke motor I worked on with bridge ports was a 600cc twin snowmobile engine, arctic cat suzuki.  They make good power, over 50hp per cylinder I believe.  But that's also in the cold air of winter, and the cold snow makes it easier to keep cool.  Apples to oranges comparison, but the 50hp and bridge port reminded me of those motors for some reason.  They also had a problem with flaking the nikasil off of said bridge port.  I know the later engines went away from it, but I don't think it was to do with lack of power.  Hard to keep that thin piece of metal cool I suppose.

When I used Wiseco prolite pistons in my CR500s, they contained instructions on drilling 3 small holes to lubricate/cool the section of piston that slid over the exhaust port bridge. Heck of a thing to drill holes in your new shiny piston, lol. If you go that route you should see if that's still a recommendation. I ran a number of those pistons with 3 extra holes and had no issues, but that was probably `93 or `94 through the early 2000s.

A GYT DT1 cylinder i used in later years [not back in the day] had a Wiseco or LA Sleeve--sleeve. It was a nice sleeve made out oif what looked realy good material & lasted forever.
But it had a bridge & an extra wide exhaust port. So 'me' knowing more than 'them'--or not--i decided to remove the bridge.
Then thought hell that's a wide port, hope it hangs together.
It went well & was never a problem.
I think i used DT1MX piston kit not the GYT kit piston.
GYT piston had a parallel ring & i'm pretty sure the DT1MX was keystone tapered.