the answer to your question is , in the gas tank!
inside the gas tank
It is under the intake manifold.
The horn are located in the driver side front fender
In the fuel tank, it is electric high pressure
it is a small electric motor on the side of the throttle body
In the gas tank.
It has an electric fuel pump inside of the fuel tank.
It on the back of the coil packs going into the side of the block.
assume you mean Brake PDV... is located on the frame directly below the master cylinder.
No, the 1990 RM cylinder doesn't fit the 1988 cylinder. The 1988 cylinder is the only year that'll fit on a 1988 motor. This was the first year Suzuki did that. It actually sucks because I have a 1988 RM 125 I've been trying to get a cylinder for. And the 1988 cylinder is the only match. Nothing else would fit.
I just purchased one today 7-24-09 at Kragen/O'reilly for 8.86-in California Fram g-5802A
it should be on the top of the panel above your radiator but mine says .052 to .056 of an inch use a feeler gauge if you need too