[RedRocket]

Hello all! Been 5 years since I'v had a bike finally got a left over 2017 450x. All I can say is damn this thing rips compared to
my old 250x. So this week I bought the JD jet kit, smog block off, Crf's Only fuel screw, and the Twin Air filter and cage.
I am in the process of installing the goodies. Once installed I will mod the air box. Per the JD kit it says i need the 170 jet.
I do plan removing the baffle but not at the moment. Question is do any of you see an issue far as jetting goes?

[PW80Dad]

I’m no expert but I just did the same for an 05. Based on the difference I suspect you might run rich without the air box mod.

You might reconsider- pulling the carb for the fuel screw would be a good time to cut the airbox open. You’ll have it apart. FWIW I only cut the top of the airbox and left the side and under the battery. I think that’s pretty common and you’ll be a little less dusty/wet.

Also- if you bought the fuel screw alone you might look at some of the carb rebuild kits some of them come with a screw for almost the same price.

I also replaced the carb bowl screws with stainless Allen head screws - picked em up at true value. But I think they sell them as a kit on here. Anyway- the stock screws were really soft and JIS I think.

[JimDirt]

The jetting depends on the elevation and temps you will be riding at , leardriver , our resident carb guru , put this up as a recommendation to use for 450's (X and R) , so I would use it as a baseline to set your jetting , regardless whether you are just buying jets by themselves or using the "jetting kits"

Jetting Guide for Main Jet:(pilot #45 in all cases) CRF450R/X

Sea level....165
2000 ft.......162
4000 ft.......160
6000 ft.......158
8000 ft.......155


Temperature/Elevation:
One main jet size (up/down) for every 2,000 feet or 25 degrees in temp.

You can run this jetting with or without the baffle removed , as I have run my bike with a 05 450R muffler and with the stock baffled muffler (when I am riding a area where noise is a issue) , and it runs good either way , just snappier with the unrestricted muffler , but doing just the top of the airbox area where the snorkel itself is , will be plenty of added air and will help the engine breath much better along with the jetting for the elevation/temps