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

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

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

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.

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

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