Would putting a 1999 TRX300 fourtrak engine into a 1997 work ok. I know honda did some changes to the cdi at some point in time so i was wondering if this would work.

Thanks

 

The engines are the same, provided they are both 4wd or both 2wd. Honda changed the cdi three or four times in the 300s lifespan, and the voltage regulator three or four times as well, but the engines remained the same. There may be a temp sender unit for the fan on the late engine, but if your earlier frame has no fan, just leave it disconnected.