Air Box Lid

[old school R]

Can anyone tell me why the 450R wont run past an idle with the air box lid off? I have been out of atvs serious for apx 15 years, I have an old 89 250R (mint) that just sits in the garage so I decieded to buy something that I can ride without worring about scratching it . Back in the day with the old atc 350X and even with the 250R we always just removed the air box lid and they ran a little better. I see that the HRC kit comes with a modified air box lid so obviously I am missing something.

You need more fuel. You are giving it more air so it is running lean. Get some bigger jets and rejet it.

[old school R]

Have they changed things that much? I buy what you are saying but not to run at all?

[old school R]

I took the spark arrester out and i think that it helped it breath alittle better why doesnt that effect its proformance? Maybe its just in my head because it sounds better!

[250rpilot]

the new breed of four strokes is already burning super lean from the factory. that is the reason removing the lid makes it not run. it just needs more fuel. the older quads did not have to pass the stupid california green sticker requirements, so they could be run a bit rich from the factory. not to mention the only way they can get the power out of them is to make them lean.

[old school R]

If they are set that close from the factory then why doesnt removing rhe spark arrester require rejetting?

[250rpilot]

probably because the spark arrestor isnt restricting the flow of air as much as the airbox lid....just a guess

[honda350r]

Take the 117 main and replace it with a 180! Go ride it !!

[old school R]

117 to 180? thats apretty big jump is that what the HRC kit comes with? Usay with the 180 and no air box lid it will be alot better?

[dn1911]

i recently took my factory pipe and pulled the core and chopped it flush with the end cap. put it back on and it ran a little lean. i then removed lid and replaced filter with one from white bros. and installed 180 main. its close but i think a 175 main and onn clip down on the niddle would be better.

but i have a new HMF coming and i will probally have to leave the 180 and adjust the needle but will have to wait and see

[ATVX4]

The HRC kit comes with a 185 main jet. Look at the front of the airbox where the snorkle is. That 42 mm carb is breathing through an intake hole the size of a quarter! Honda REALLY choked this one down. It runs ALOT better with the HRC kit.

[4fiddyR]

I have a sparks cam, and air filter and Sparks full exhaust, I am running a 190 main and it is perfect! Jet that sucker!

[ThumPIN_450R]

i have the spark arrestor out and it quit running on me i put a 155 main in and pulled the air box lid and it seems a tad rich to me

[old school R]

This may sound really stupid but how can you tell if a 4-stroke is running rich or lean?

[TRX600R]

I'm running a 172, needle raised 2 clips with no airbox lid, and no spark arrestor, and I think I might try a bit bigger. Its a totally different machine after its jetted.

[snow4fun]

I have seen a couple of varying comments in this post about the spark arrester and jetting. If I take out my spark arrestor and leave the air box lid on will I need to rejet? It is stock until I get the HRC kit in a couple of weeks. Also I am riding between 4,200 to 5,000 feet in elevation. They told me I have a 118 main. Isn't that a little big for my elevation. Aren't some of you running 117 mains at a lower elevation? Thanks