Exup 12.0:1 compression???

[e30isking]

Dear Sirs,

I have disassembled a Genesis 87 engine that has 11.2:1 compression.

The later exup engine (89>) has 12.0:1. I would like to know how did they get this compression increase.
Was it pistons, combustion chamber volume, rod lenght, or, or??

Anyone has pictures of stock exup pistons?

Thanks!
Paulo

[kolederacer]

Okay,
So this is something I have done. It is the piston and the rod. First the piston/rod from an exup has a bigger wrist pin so they can never be just swapped.
Second you can put a exup piston and rod set it a genisis. However two important things. Compression will end up around 13.5 to 1. Also the piston will have to be cut to give enough room for the center valve since they are at a different angle.

[e30isking]

Thanks a lot!

Why is it that compression gets that high when using the Exup internals?

I've read about the wrist pin and the slightly less dished pistons. Do you know if they changed the rod lenght? That would account for big CR increase...

If you buy a 1040 kit, you would get the same compression, assuming same rod lenght?

I really need a Exup rod and piston. Anyone can spare one?

I believe that the Exup and thunderace are pretty much identical but the thunderace lowers the CR again to 11.5....again more questions

[e30isking]

Hey another question kolederacer...or anyone really

Why is that the FZR1000 and YZF750 are both the same lenght but the thunderace engine is 10mm taller? This is what I read, not experienced

Thx a lot
Paulo

[kolederacer]

Yzf750 has a shorter stroke. I think the cylinder is shorter.