Make an engine work from a completely different bike

[magifesq]

Here's What I did -

History - bought a 1997 Derby GPR 75 as a neat little 2 stroker just for a fun little bike.

On the way to work the engine locks up - rod is one with bearing and crank pin. With pretty colors.

First step - decide on a replacement engine - 250cc 2 stroke engine, water cooled. I bought a 93 YZ 250 Engine kit from ebay complete with pipe, carb, wiring harness, coil, pipe, cdi.

Now here's the real work -

First- I had to cut out the Derby engine cradle

I purchased some 1" box tube steel, and some flat plate steel to create a custom engine cradle to build onto. I had to carefully put the engine in the cradle while I welded tabs and drilled holes to make the motor mounts. I then sprayed painted the cradle with rust resistant, heat resistant paint.

I had to move the radiator, now understand this, the radiator has no fan and has significantly more cooling capacity than the YZ250 pair of rads. Given this is the case, I moved the radiator from the front / behind the front wheel to under the seat - there's ample airflow with the way its setup to help cool while moving, the size alone should be enough to take coare of the cooling while stuck in traffic - if traffic gets crazy slow, I can always kill the engine and kick it over when traffic picks up.

The expansion pipe wouldn't fit with the bends the manufacturer put in it so I had to cut it in several places and weld it back together. I did my best to use gentle angles - hard angles reduce the ability for the sound waves to make it back to the ports properly at the right time and with the right force.

The YZ 250 airbox wouldn't fit in the bike so I put a clamp on filter on the back.

I won't be able to put lower cowls on the bike, but who cares when you stuff 5 X the engine in the thing.

I'll post pix tomorrow of this mutant project as it sits today.

Edited August 17, 2009 by magifesq
Added pix

[Cheech]

This sounds awesome. Can't wait to see it's progress.

[magifesq]

It sounds like a whole angry community of Africanized killer bees trying to escape out the exhaust. You can feel vibrations through the handlebars and footpegs. Runs like a scalded dog!

[Strictly Street]

It sounds like a whole angry community of Africanized killer bees trying to escape out the exhaust. You can feel vibrations through the handlebars and footpegs. Runs like a scalded dog!

[oldschoolsdime92]

I know this threads old, but do you have a sound clip? Ive developed a soft spot for two strokes after the 250 project ive been working on..