CBR400RR Pod filter jetting

[Iain.]

Inb4 the obvious BCF answers;

Yes, it will run better with an airbox.

No, I can't use the airbox.

Yes, this is the only way it'll fit under the tank.

Yes, I've tried making a cut and shut airbox out of various bits.

No, it diddn't work.

CBR400RR engine in CB-1, CBR carbs & trumpets, CBR fancy race headers/shouty can. Need to know roughly what sort of main I need to be running as more than 1/8th throttle, and more than 6,000rpm the fuelling goes completely down the pan.

[chris-red]

First off with carb tuning is you need to get it right at WOT.

Take it for a run and see what it is like a WoT if it feels like 95% throttle is faster you need a bigger Jet. Once you have that set up there you can play about with the other jets/needles.
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[Pol Anorl Fam]

as above, unless someone here has a setup the same as yours theres no way to check it.

give it some wot see how it runs then work from there.

[RhynoCZ]

Check if you can find a Dynojet kit for your bike.

Pick a STAGE, that suits your situation. OEM exhaust + K&N filter. Or OEM Filter and open exhaust etc.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[P.]

But...he's got open filter and open exhaust.

What I would do... find dyno fwend and bags of jets.

[RhynoCZ]

[MCN.]

It's going to run like shite whatever you do so you may as well stick flat slides on and get some decent power out of it.

[Kickstart]

Hi

Flat slides might be fun and easier. But given the tiny throttle openings that it bogs down I would wonder about the needles first. I would try shimming the needles up a bit first (essentially free and easy to try out).

All the best

K
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[Iain.]

Flatslides are mega money though, and space is limited. I have around 1mm either side for them to not hit the frame

Will try and pick up a set of small washers to lift the needles with and see what happens. Google indicates that +20 on the mains is a good place to start, so will also try this.

[Fizzer Thou]

I run pod filters on my Exup1000 and the Dynojet kit that I bought for running those and a less restrictive end can comprised of a selection of DJ main jets,needles with a completely different profile and some air jet blanking plugs for running the Stage 3 setup.The flow characteristics of the DJ main jet are quite different to a standard Keihin or Mikuni item.

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/2013-11-14164610_zps384543f8.jpg
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/dynojet_zpssxvoqatx.jpg
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/Needle_zpsx50ualln.jpg

The instructions that came with the kit suggested that the pilot jets can be left as standard,but that a hole needed to be enlarged in the CV carb slide so as to change how this lifts when that circuit was enabled.looking at the diagram you can see which component comes into play at a given throttle opening.What it does not show is that on a CV carb the slides do not start to open until around 5-6,000 rpm,so up to those engine revs it is mainly the air screw,float height and pilot jets.

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/calchart_zpsqw9waci5.gif

On my Exup I could run the engine at tickover and up to 4,000 without the slides in place while I made other adjustments.

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/jettingeffects_zpsfppa7sat.jpg
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/carb_zpsitqkxjic.jpg

These people are a good source of individual components.

https://www.allensperformance.com/

Going by the OPs experience so far,it does sound as though there may be a problem with the seating of the diaphragms in the top of the carb or maybe even a split rubber
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[Iain.]

I do wonder if it is perhaps wise to make a new baseplate to adapt the CBR trumpet panel to fit the CB-1 airbox top and panel filter.

Thinking about this today, if I made a mould from florists foam or some simmilar material, smothered it in vaseline then set about layering strips of glassfiber mat down soaked in resin, that ought to work surely? I'm not too clued up on airbox design, however that'd retain the factory element, a simmilar volume and the all important rear facing snorkels/carb trumpets.

The more I read into this I find horror stories of GSXR400's loosing 20% power below 13,000rpm so wish to explore all options open to me as theres no point having an engine that's faster than stock for the final 1000rpm near the redline and an utter dog the rest of the time!