Tagels

You need to use the correct plug.. And as far as i know the only one that you can use is the NGK IFR8H11. But as far as why its choking and popping in the top RPM range it could be the main jet is a little rich, you could try going down a size or 2 on the main jet and see if it helps..

Raptor 660s suck IMO, tall and tippy and people have a lot of problems with them. Keep the R

Get a yamaha YFZR or a suzuki LTR if you want to be able to race it stock, get a honda if you dont mind spending 4000 on it to get it race ready..

Just go up in the pilot jet 1 size. That should fix the popping

Well then its not the fastest in its class... When it came out it was, because there was nothing else in its class but now the LTZ400 is around and it is a lot faster. Plus the new one is EFI with MUCH better suspension then the 400ex.

If its not backfiring and its just popping its not really a big deal, and pretty normal. Most 450r's do that, if you really don't like it you can put a richer pilot jet in though. (that's what i did, stopped the popping that i hated so much..)

Morning everyone, heading off to watch the AMA pro national motocross at Thunder valley!

There is a quad section on reddit, i doubt most of you guys use reddit or know what it is but if you do... Here ya go ATV Vehicles around the world

^ Yeah you can usually find parts for anything on Ebay

Widened 4" with Fox suspension front and rear

Synthetic wont break down as fast so it will stay "lubier" as rappy says for longer

Yours looks way better then this one..