Gk73a GSXR400 Tuning fast road set-up + Bandit 400

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moforockband
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Bike owned: GK73a SP CRM250 mk3
Gk73a GSXR400 Tuning fast road set-up + Bandit 400

Post by moforockband » Sun May 24, 2020 10:38 am

I'd thought I'd list here a few of the easy to do things I've found that really work well, and easy to do to bring your old 400 up to speed. I upgraded mine for track days, but these mods work really well on the road, and you can hassle big bikes down the twisty's, and sometimes leave them behind ;) I have a 73, but the engine mods will work just great on the bandit. This will take your bike from a wheezy 50 odd hp, to around 60, and become a much more capable bike. And no £60 air filters to change!

Engine- Std tune, Bandit 400 gutted stainless 4-1 downpipes, 2" race can with baffle, GK73a cdi (any), restrictions removed from carb rubbers (13110 32c10), 33mm cv carbs, 55mm RAMAIR oval foam filters or rc098 filters. This will increase your bike by around 5 or so hp, and give it a killer midrange. It will drive right off the throttle in top and do 130mph plus. The only downside is you will have a flat spot at 3000, but the gains are worth it. Make sure your engine is pumping at a minimum 150 psi on every pot, otherwise really needs new rings/honing etc. Also when compression testing your motor, be aware that some of these 30 year old starter motors turn really slow, and can give low readings.

The gsf400 downpipes have a baffle tube INSIDE the collector, which improved midrange, and is designed for the bandit's power output but will choke the top end. Apart from that it's an ok 4-1 system. Better to find a Yoshi or similar, but the bandit one is cheap and easy to find. The race can will need a small link pipe making up with a 8 degree bend to clear the floor and make it look right. I used a zx6r hanger.
The Ramair filters are tricky to fit, the rc098 ones are easier to fit. The inside 2 go upside down. All airboxes are a total pain, and all restrict airflow.
Best to use the 33mm carbs, the jetting is 128 mains, std needle and position, and go up one size on the main air jet, otherwise the bike will run rich at the top, and you need more fuel in the mid. std air screw 2.5 turns out.

Use 13110 32c10 carb rubbers with no spacers, just RTV them to the head. The need machining out 1mm to match the cylinder head. Easy to do with a dremel and drum sanding attachment. Be careful to get them to match perfectly. Great mod this, the engine revs out quicker, and takes on a different tone.
Bandit 400 motors must use the 59hp cams or gsxr ones, with the rubbers above, gsxr cdi box with correct ignition rotor, pods, and carb set-up.




Suspension- best to get the sp front forks if you can. GSXR600 K6/7 rear shock. KTECH 35-295-85 fork springs, and increase the fork protrusion through the yoke around 30mm, as the springs have much less sag. These 2 mods are amazing, and lift the bike around 8mm, so when fitted with sticky rubber, you can get proper corner speed, without everything grinding out, or getting your leg stuck underneath the bike. Use the later braced swingarm with 17" rear wheel.

Brakes- Any of the Tokico 4 pots are great - just make sure they are free to move, ideally new seals etc, and braided lines/decent pads etc. I fitted a GSXR750K1 master cylinder which works great. SV650 curvy front discs are on my wets, and EBC prolites for dry weather, as they rust.

Remove any massive indicators, as they cause too much drag for the little motor at high road speeds. a 520 conversion is easy, use SV rear Renthal alloy hardened sprockets for light weight, and a decent 520 chain. The front sprocket has to be this part no - JTF434-14T.

A lithium battery works great, and shaves 1-2 kilos off.

That's it, may as well share the info I've learned over the last 20 years with this hardcore little bike!

mechannibalism
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Re: Gk73a GSXR400 Tuning fast road set-up + Bandit 400

Post by mechannibalism » Sun May 24, 2020 6:20 pm

Thanks!...great info now I just have to find the CDI and rotor.

moforockband
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Bike owned: GK73a SP CRM250 mk3
Re: Gk73a GSXR400 Tuning fast road set-up + Bandit 400

Post by moforockband » Mon May 25, 2020 11:30 am

mechannibalism wrote:
Sun May 24, 2020 6:20 pm
Thanks!...great info now I just have to find the CDI and rotor.
I have a rotor you can have cheap. Are you UK?

mechannibalism
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Re: Gk73a GSXR400 Tuning fast road set-up + Bandit 400

Post by mechannibalism » Tue May 26, 2020 2:42 am

No Canada...I'll start with that, it shouldn't cost much to mail.


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