Re-Jetting After taking off lid

[howshnazy]

Hi i just purchased a new yellow 400ex. I was wondering if it would be ok to take off the airbox lid and spark arrestor without rejetting. Also should i wait until i break the engine in before i do these mods?

[ZSK]

I would wait until after the break in. You'll have to go up a size or two on the main, needle should be fine, maybe fine tune your air/fuel screw.

BTW welcome to the site.:cool:

[howshnazy]

The thing is i wont be able to get a jet kit for a couple months or so. Is it ok to run it without the lid during this time?

[ZSK]

No it's not. It'll cause your 400ex to run lean which is bad. Running lean can fry rings and pistons and many other things. I'd say wait until you have the time/parts to do it right. BTW buying the individual jets is a lot cheaper than the whole kit. Around here they are $4 for a main instead of $60 for a kit in which 80% of the jets are never used.

[howshnazy]

Thanks! :macho

[cals400ex]

yes, make sure you rejet. around here with no air box lid and removed spark arrestor a keihin 152 mainjet is good. also, most everyone has great luck with the 42 pilot jets.