I have a 2000 300EX.I put a DG pipe on it,I put A K&N filter on it,I took air box
lid off and put A cover on it made by the same people that make the shock wears,i cannot recall the name right now,and thats it for engine mods.I've ridden several
times w/o rejetting carb and it seems to be fine.Should I rejet?Will I see a dramatic
difference if I do?Also what size sprocket should I get for front,I want more
top end.Any other suggestions please for cheap performance.Thanks.

 

Rejet for sure!!! You will be running lean, and will damage your engine (it will run hot, etc.)!!

 

I have the same pipe and bike. I did rejet, raised the needle 1 notch (or I guess you could say lowered the clip one notch) to make it more rich. Does one need to mess with the MAIN jet as well. I've always wondered which jet to adjust main or needle??.

Thanks.

 

Yes you need to change the main jet. Also a 14 tooth is as big as you'd wanna go on a mostly stock 300EX like yours.

 

Definitly change the main jet; it's cheap, like about $4!!
If you want more top-end speed, a 14 tooth front is good, or go down 3 teeth in the rear (1 tooth in front=3 teeth in rear). Don't go too much more or you won't be able to pull it.

 

well i pulled my spark plug out and half of it is white and half is tan.if thats the case
should i still bother jetting?i mean the bike hauls a@@ and i run the crap out of it
and see no signs of overheat or backfire.i live in arizona.the only thing i see is the dg headpipe is a little discolored about 2 inches of the block.

 

Bump the main jet up like 5. the spark plug should be golden brown with no visible white. better to run a 4 stroke rich then lean..