SOHC.co.uk Forums > CB350/400

CB400f with K&N Pods Filters - what carb jetting are you using ?

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Laverdaroo:
Wicked, thanks for the info that’s a great place to start. I’m restricted to a good old colour tune here those settings will accelerate the progress no end, parson the pun

Cheers for that.


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zombie365:
Ayup Dennis

Thanks for sharing your settings , I'm going to be using them for my bike. I have K&N with Delkavik exhaust. Currently my build has standard jets 75 40 and notch is in middle , bike is bogging down with full throttle. Hopefully your settings will be good for me as well!

Just wanted to clarify that I've adjusted the needles correcty? See pictures below . Top is original, bottom is new needle with one notch down. Is that correct?

Thanks again bud !

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Oddjob:
Depends on whether the bogging down is caused by weak or rich mixture. If rich then no, if weak then yes.

400 Cafe Racer:

--- Quote from: zombie365 on April 23, 2023, 06:14:32 PM ---Ayup Dennis

Thanks for sharing your settings , I'm going to be using them for my bike. I have K&N with Delkavik exhaust. Currently my build has standard jets 75 40 and notch is in middle , bike is bogging down with full throttle. Hopefully your settings will be good for me as well!

Just wanted to clarify that I've adjusted the needles correcty? See pictures below . Top is original, bottom is new needle with one notch down. Is that correct?

Thanks again bud !

(Attachment Link)

--- End quote ---

Hi zombie365,

Thats good timing I think.  It just so happens that I decided to change my "Shorty" silencer late last year because it was a bit too obtrusive at full throttle. My choice was the Delkevic. A nice tonal balance and road legal.

Your needle clips is in the same position as mine ie one below centre.

You will see from my previous tests the Air/Fuel ratios which were recorded.

What I have found since fitting the Delkevic is that it bogs down slightly when pullling out of roundabouts or sometimes when pulling away from traffic lights.  The Air/Fuel ratio at say just above idle to 1/4 throttle has now gone significantly richer at 9.8:1 far too much for clean combustion.

I haven't got around to the carbs strip and change yet, but my plan is to go for the 35 pilot jet to lean out the small throttle/intermediate opening and set the mixture screw to give around 13:1 for a clean idle. After this it will be down to road test and results. Due to shortage of time at the moment I am unlikely to be able to get back to it until late May - June. Check that your float levels are equal and true. Also that centrifugal advance system is working correctly on timing, to give correct full advance when checked with a strobe light. Retarded ignition will raise heat and reduce power.

I would say that for me, the other Jet and needle settings I made still retained the good power and torque results, pulling strongly in 6th gear, with the Delkevic fitted.

Let us know how you get on when you have set up and tested. ;)

Hope this help you,

Cheers Dennis :)

zombie365:
Thanks for the info Dennis.

I'm going to be rebuilding my carbs tomorrow, currently they're stripped down ready to be ultrasonically cleaned.

I've ordered some #35 slow jets as per your recommendation. 

I will build them back up with the following:

-Needle cir-clip 1 notch down from middle.
-35 slow
-85 main

I don't have AFR Meter, what would you recommend setting the mixture screw to?

Cheers,

Sam

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