I have a YFZ 450 with a white bros e series. I was wondering the best combo you guys have found as far as what size jet and how many spacers you use with the spark arrestor in place. I ride in CA and have to have one. The jet I use new is causing it to bog down on the top end. Any ideas?

Thanks in advance.

 

Is it popping or back firing?

 

It is popping and lugging down. Thanks for your help.

 

Sounds like you need to bump up your main and maybe a notch on the needle.