Topic: Engine Swap

[thenewbie]

So I've been bored lately. I was looking around in my shed the other day and I saw my 98 kx250 that i bought for 115$.  The longest I've had the motor running is about 1 minute. Every time I would get it going it would seize up and I would find small chunks of metal in the exhaust port and wedged in between the crank and the crankcase. I'm not sure where its coming from because once I get the metal out it turns over fine. If anyone knows what that is I would love to know because I'm stumped.

But anyway, I figure that motor is shot. So I've been thinking, since I've got a bill of sale for this bike I might as well put a streetable motor in it and ride off into the sunset. If anyone has a cl360, cb450 or similar sized parallel twin motor from some other manufacturer, I'd like to get some measurements from ya. These dirtbike frames are small so obviously I will be having to make some modifications to the frame. The one thing I don't want to do is buy a motor and realize I would have to stretch the frame to make it fit. If i could get the overall width, overall length, overall height, the position of the drive sprocket, the position of the exhaust ports, a measurement from the front of the motor to the inlet of the carburetors, a measurement from the bottom of the motor to the top of the carburetors and the width of the rearmost section of the motor (transmission), that would be great. Please don't talk me out of this. I need something to do or I'm going to go jump off the highline bridge.

[Garage_guy_chris]

trying to get a big parallel into the frame is gonna be a big problem the overall dimensions of the engine chain location.....

Why not open up that KX250 engine and split the cases, im willing to bet before you bought it a piston probably disintegrated and put bits of the piston down into the bottom end. Two stroke dirt bikes are usually pretty easy to deal with. you could probably rebuild that engine top and bottom end for $500 - 750. with a bike that age Ebay is likely to be your friend. 

[bjbuchanan]

Rebuild the 250, definitely gonna be easier and cheaper. You could be a single piston/cylinder away from running

[thenewbie]

When I pulled the motor apart the rings were literally gone but the piston and jug looked to be in excellent condition. As a precautionary measure I installed a new piston and a set of rings (probably should've mentioned that before) so ive already got 200$ into the motor. But By running the motor with that metal inside I've destroyed the piston, the head, the rings and scored the cylinder wall quite badly. So ill have to split the cases to get the metal out, bore the jug, and buy an oversize piston kit. But like I stated before.

Please don't talk me out of this. I need something to do or I'm going to go jump off the highline bridge.

[calj737]

I don't want to do is buy a motor and realize I would have to stretch the frame to make it fit. Id be astonished if you can achieve this swap without modifying the frame for the motors you referenced.

Please don't talk me out of this. I need something to do or I'm going to go jump off the highline bridge. With or without a parachute?

[thenewbie]

Birthday suit for style points

[Oldtech]

I put a CB450 engine into a Suzuki PE250 frame. I mocked up the engine in the frame to get the chain line right then welded in engine mounts. Had to cut and reangle the front downtube but other than that it went in OK.  A bit front end heavy but loads of fun on a flat track. A co-worker bought it to use as a trail bike and he and his son rode it for years. If you have a hacksaw and a welder I say go for it.

[thenewbie]

So after looking at the bike again I realize that their may not be enough room to fit 2 carburetors. The engine would also stick out quite a bit on each side of the frame. So I'm thinking single cylinder xl500, xt500, or a gn400. Did kawasaki ever make a bike to compete with the likes of those?