Very nice Jay, think one of the GSR motors should go real well. Im waiting on a book by Yoshi on the F3 400's he built so some interesting reading on jetting i hope! ive put some pics of the old B4 in the Bandit section if you want a look.

Variablevalves suck wrote:

nz_gixxer4_racer wrote:ive decided to start on 115's with pretty much open box and open pipe with the gk76 400 ( )

You will have to up the pilotjets or it will massively bog when you open the trottle.
James, you should be good on the standards and Jay, im suprised your not running bigger jets with your carbs as they flow more air than the standard CV's, you got that GSR motor yet?

Cheers, I know Im running out of "free" questions, but will give one more q a crack!
What pilot jetting would get me in the ball park?

nz_gixxer4_racer wrote: Cheers, I know Im running out of "free" questions, but will give one more q a crack!
What pilot jetting would get me in the ball park?

It's extremely difficult to throw sizes at you even for a ball park. I had my bike dyno'd... Although it made a reasonable 58bhp the fuel curve below 8k was erratic to say the least and running lean. The dyno company could have set my carbs up but at great expense. From the single dyno run it's given me an insight.

On my bike I'm thinking:-
Main jet size - 112 (if still running lean 115).
Pilot jets - 47.5 (standard jetting). From looking at old posts I could not find any evidence of others changing from this.

Don't worry about questions! Perhaps one of the Jedi's on here or even master Yoda can share the knowledge

Well, I ended up getting 117.5's in. Put them in. Couldnt get it tuned with the open airbox so increased the airboz restriction with putting some foam in front of the airbox aperture(spelling? airbox intake). This made tuning the pilot system and needle position easier. still a bit boggy down of the pilot, but needle seems alright on the 2nd clip and main feels strong. it goes like a bastard above 5k RPM. so will leave it at that for now!! after 5 different needle positions and mixture screw adjustments, Im quite happy to have it close!

When my patiance recovers, I could look at putting bigger pilots in and tune the bottom end a little nicer.

Good work! if you go up a couple on the pilots you should find it very close. :)

hey guys! final update for the sake of those who have helped me and for future questions RE jetting.

I have ended up with removing the stock air filter and fabricating a cover to go over the airbox intake. Now the airbox intake is approx.140mm in diametre, massive. The cover blanked off the intake cmpletely and I then cut a 50mm dia. hole in this and placed a bit of oiled air filter foam in front of this hole to make my own air filter and system, so to speak.

with standard 47.5 pilots and new 117.5 mains and needle at top clip, it was lean on the pilot and rich on the main (evidenced by black smoke from half throttle on).

So, I ended up buying 2 drill bits, 1 x 0.6mm bit for the original pilots and an 1.1mm for the original mains. drilled out the appropriate jets with the power drill and put them back in. dropped the needles down to the 2nd highest clip.

Results, pulls really clean from down low and revs out nice and strong. Actually Im really impressed by the way it pulls for a 400cc! Cant wait till I get it on the track to compare it to the zxr's etc!! seat of the pants stuff, says that it pulls just as well as my old sv650k7, which has really impressed me!

so final jetting: 60 pilots and 110 mains (although my digital calipers measures these at 0.57 and 1.07 respectively. I am inclined to believe the factory measurements though instead of my chinese caliper!

But just to add, it is coming into winter here in NZ. come summer, with denser air, I will try out the 117.5's in and see how I get on.

TOP WORK!!! Do some fine adjusting at the track and get the carbs balanced and its balls out. If money ever allows get some FCR's like gsxr400racer's got as they will make a massive difference and the stock pipe is super restrictive and hippo heavy so plenty to got at.
Im in the process of building a system but still getting the front downpipes done in cad so as they can be bent and supper busy so a few months yet.All the best with the racing and post up your races.
Chris.