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Purchased a 07 crf450r recently, it's got stage 1 hotcams, full dep s7 exhaust. When the throttle is fully open it pulls really hard. When in neutral the engine picks up revs quickly and doesn't hesitate at all. However, the issue I'm having is when travelling in 4th and 5th holding it at steady revs and constant speed, at about quarter throttle, the bike splutters really bad, almost feels like it's running out of fuel, like really harsh juddering. If you open the throttle, it pulls through it really hard. I've tried a new spark plug but that hasn't helped
Any help is very welcomed,
Cheers

Used bikes are notorious for having carb issues. It could be wrong needle/jets or clogged jets. It could also be a bad floating valve seal. If it were my carb, rather than chasing my tail, I'd install the JD Jetting kit, replace the floating valve seal, check the float valve and the float height, and install the AP update kit.

JD Kit
http://www.crfsonly.com/catalog/product ... ts_id/2150

Floating Valve Kit
http://www.crfsonly.com/catalog/product ... ts_id/3687

AP Update Kit
http://www.crfsonly.com/catalog/product ... ts_id/3932

Valve Set
http://www.crfsonly.com/catalog/product ... ts_id/4474

Here's some how-to articles that will help

http://crfsonly.com/howto/keihin-fcr-ca ... rf450r.php

http://crfsonly.com/howto/keihin-fcr-ca ... rf450r.php

http://crfsonly.com/howto/450x/jetting/ ... needle.php

Ken