Carburettor help for 400

The 1990's Japanese market GSX250SSN (GJ76A) and GSX400SSN (GK77A)
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CaptainFothers
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Carburettor help for 400

Post by CaptainFothers » Sat Feb 09, 2019 3:34 pm

Hi Everyone, I am in need of some help regarding the carbs for the 400 Katana. My Katana hasn't been starting, and I've checked everything you might want to, spark, compression, valve clearances etc. but it still didn't start. Then when I checked the spark plugs, I noticed that only two were wet. To me, this meant that there must be a problem with the carbs / rust from the tank getting in, so I took them apart and ultrasonically cleaned them. Afterwards, there was still crap inside the carbs, and they still looked bad, so it looks like they might need a full restoration.

As I don't really want to pay out to get them fully redone right now, does anyone have any recommendations of carbs from other bikes that might fit? Just so I can see if it was the carbs causing the starting problems, or what the code is for the original set, so that I can maybe get a cheap set of original carbs to fit it.

Also for the record I am also in the process of cleaning the tank fully, to get rid of as much rust as possible as well.

One last thing as well, does anyone have recommendations for air filters to put on the carbs as well?

Thanks in advance,

- Fothers

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Re: Carburettor help for 400

Post by johnr » Sat Feb 09, 2019 5:52 pm

why clean out the carbs and then connect theem to th rusty tank that caused the problems innitially? clean and seal the tank first, theen ultrasonic clean the carbs and whilst apart, reebuild them with all new seals and gaskets, fossie will tell you where to get them from cos he just got some.
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Re: Carburettor help for 400

Post by johnr » Sat Feb 09, 2019 5:57 pm

if you want it to still run ok, keep the stock airbox. pod filters on these just open up a whole load of new problems.
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Re: Carburettor help for 400

Post by pookie » Sat Feb 09, 2019 6:20 pm

You've changed John, you normally tell 400 owners to drop a lighted match in the tank and walk away slowly :D

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Re: Carburettor help for 400

Post by pookie » Sat Feb 09, 2019 6:24 pm

Being serious, sort the rusty tank out, then get a litetek viton o ring kit for the carbs and fit it after ultrasonically cleaning them, did wonders for my 250 and it's still running sweet over three years later (might have jinxed it now)

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Re: Carburettor help for 400

Post by CaptainFothers » Sat Feb 09, 2019 6:43 pm

Cheers for the help, I realise now it was a bad topic idea, and I must admit, I didn't realise it was rusty the first time I put it back on I just included it to say what I'd already done. I'm already in the process of cleaning out the tank, an I do already have the viton o-ring kit so that'll be fitted once I've cleaned out the carbs again. Really I only wanted to see if anyone knew of another set of carbs that might fit, and if there was another option for the air filters.

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Re: Carburettor help for 400

Post by johnr » Sat Feb 09, 2019 6:59 pm

mk2 400 impulse has the same carbs, but theyre even less common than the 400
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Re: Carburettor help for 400

Post by fossie » Sat Feb 09, 2019 7:31 pm

Welcome to the world of leaving a 400 idle for more than a few weeks! :?
They really don't like it.
As said MK 2 impulse carbs are the only other ones (92-94 not 88-89) :roll:

Rebuild your carbs making sure they are well ultrasoniced espically the brass tube , which get blocked easy or broken , when taking carbs of, this is the choke system. The pilot jets are really small and get block or gummed so easily .......don't use unleaded petrol , use the super stuff less ethanol , less evaporation, less varnish.
Once the carbs are rebuilt try them using remote tank to test .
If you battery was flat , it won't start ...trust us experience ...sealed for life low aph bad combination.!

Pod filters ...world of pain with the 400 . Which run lean anyway, only sure way is a dyno which means carbs off/ on off/on off/on off/on....only to run like a bag of t**ts in the wet. :roll:
Stock is best , if the filter is a problem we did an attachment to use a GS 500 one but yahoo Japan will get you everything you need.
Last edited by fossie on Sun Feb 10, 2019 7:32 pm, edited 1 time in total.
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Re: Carburettor help for 400

Post by pookie » Sun Feb 10, 2019 3:05 pm

As Fossie says, use super unleaded fuel and an additive like fuel fit by Briggs and Stratton, it keeps water out of the fuel tank, and once its sorted run it as often as you can, even if its just a start up every other week, the carbs don't like sitting still for long periods of time, these smaller Kats are great fun when they are running properly 8-)

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