What model year engines are interchangeable?

[cgreenland]

Does anyone know if the '04 engine will fit the '01?  My 2001 GS needs a complete engine rebuild, but I think it may be cheaper to score a complete engine on ebay. 

[pantablo]

the only differences that I know of are the addition of oil cooler on the 04 so there may be some routing that has to be capped. maybe the 04 had a different carb too but the basic engine should be the same.

[Alphamazing]

The carbs on the '01 and the '04 are the same with the exception of a bump up in the main jet size (130 compared to 127.5). All engines should be able to mount to any year's frame. If you'd like me to check I've got a '92 engine and an '04 bike. I can check the mounting bolt locations if you want to be sure.

[dgyver]

The 04+ has a different electrical system.

[pantablo]

The 04+ has a different electrical system.

so you're saying some of the engine electrical internals are different? Which ones?

[Alphamazing]

The 04+ has a different electrical system.

so you're saying some of the engine electrical internals are different? Which ones?

Most likely the ones that send pulses for the tach, as the '04s is electrical, rather than mechanical as the previous year models' are. That's my guess, at least.

Anyone know how the electric tach on the '04 works? How does the engine send the signal? I'm interested in getting a cheap aftermarket tach for track days.

[dgyver]

The 04+ has a different electrical system.

so you're saying some of the engine electrical internals are different? Which ones?

The ignition rotor button is different. It only has 1 main tab and a bunch of smaller ones. I do not recal if there is 1 or 2 pickups. So the ICU will be different. Have not seen how the rotor attaches to the crank but if it is the same as 89-02 then it is possible that the older rotor and pickups can be used on a 04+ motor using 89-02 electrics.