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Mojavemesa · May 8th, 2015, 02:40 AM

I'm currently on day three of doing an ex500 engine swap into a pregen 250.
Everything new rider said is correct I think but I had a few things to add. It helps a lot to have the whole ex500 bike to do this. Cut the rear four brackets off the 500 frame and the triangular brackets for the front two mounts. Four aluminum spacers need to be made to replace the rubber mounts. Additional long steel or aluminum spacers need to be made to the ears on the engine don't crack off while tightening the engine bolts, just like the rubber mounts had. You don't want to rubber mount the engine since the original 250 used the engine as part of the frame. The 250 frame is basically only enough to keep the bike in one piece when you drop the engine and the ex500 racers hard mount their engines for more chassis rigidity so I think it's safe to do.
The ex500's back wheel has its sprocket bolted to its wheel about 3/16" outboard of the 250's so washers will need to be stacked between the sprocket and rear wheel. You will need shortened intake boots, I think I'm going to try to use radiator hose.
And that's about as far as I've got so far. I'll chime in again later.

May 8th, 2015, 02:40 AM	#187
Mojavemesa ninjette.org member Name: Ryan Location: Apple Valley ca. Join Date: Mar 2015 Motorcycle(s): Ninja 250 2006 Posts: 17	I'm currently on day three of doing an ex500 engine swap into a pregen 250. Everything new rider said is correct I think but I had a few things to add. It helps a lot to have the whole ex500 bike to do this. Cut the rear four brackets off the 500 frame and the triangular brackets for the front two mounts. Four aluminum spacers need to be made to replace the rubber mounts. Additional long steel or aluminum spacers need to be made to the ears on the engine don't crack off while tightening the engine bolts, just like the rubber mounts had. You don't want to rubber mount the engine since the original 250 used the engine as part of the frame. The 250 frame is basically only enough to keep the bike in one piece when you drop the engine and the ex500 racers hard mount their engines for more chassis rigidity so I think it's safe to do. The ex500's back wheel has its sprocket bolted to its wheel about 3/16" outboard of the 250's so washers will need to be stacked between the sprocket and rear wheel. You will need shortened intake boots, I think I'm going to try to use radiator hose. And that's about as far as I've got so far. I'll chime in again later.