3en1 Jetting query

[TyeNoodle]

Hi!

I'm helping a friend get his fzr400 3en1 ready for racing, its got a vance and hines full exhaust system (so no exup) and a pipercross air filter. No other engine mods apart from that.

I'm wondering if anyone has a rough idea of what jet size to start at on the mains, I'd guess it'll be running a bit lean with a free-er breathing engine?

I've raced plenty of two strokes so have a good idea about jetting them but not that great with four strokes, although i did manage to sort my nc30 out last year but thats another story.

Or are there 'dynojet' style kits available for them?

Thanks!
Paul

[Evilchicken0]

There are dynojet kits for them ... but I'm not sure what model they're for because it's done by year and could be a USA kit (they're bike models are a few years behind ours).

If you've got a the Vance and Hines pipe with a filter you should be able to advance the timing too ... probably

[TyeNoodle]

Thanks for that, I have found a dynojet kit but only stage 1&3, I'd say the bike is a 'stage' 2 really as it has a performance filter and pipe. Would the 3 be overkill?

paul

[Evilchicken0]

It's only needles and jets at the end of the day. Really theres nothing wrong with the original Yam ones if they're the right size.

A kit will cost £50 maybe and a set of jets about half that. As the middle are a size up (or is it down) you can go up one extra size by buying 2 instead of 4.

[TyeNoodle]

More like £85 for the dynojet kit but that replaces needles as well. I have fitted dynojet kits in the past and have found it a 'lazy' way of jetting as they supply pretty much the correct jets for the state of tune, but if I can get away with just upjetting then that I will do.

Would you have any recommendations for main jet size?

Middle will be a size up I'd say. I'll get the carbs off and see whats in it

Thanks
Paul

[Evilchicken0]

No idea about sizes tbh - but I'd be interested to find out what you use