400 carbs information

[fossie]

I know the title seems very formal but , I think it's something we should know about , well I do now , and so will you .

History; My 400 started to run a touch unsteady , it was always a bad but reliable , ( By which I mean I know the sequence)
No this was something else a stutter when I thottled off and the revs dropped below 5000ish. Overfueling?/Coil?
Check coils and Ht leads new plugs , found split in vacuum pipe, --Better but no cure.

Stuff it carbs off check for stuck float.

Spoke to Andy at NRP who showed me some needles from a Bandit, apparntly they wear , at the topas it enters the emulsion tube , so do GSXR ones and many others . It turns out the new needles are not coated like the old ones and modern fuel eats them.

So I went to look at mine but couldn't get the float bowls undone (They have never been off)
Gave the job to Alan in the bike shop up the road .

This is what was revealed.

This shows what was wrong, 3 needles worn like the left one 1 completely snapped with the needle in the emulsion tube , hence the working at full throtttle

This is what it should look like.

This is to show that the nick looks almost machined in but is worn away
I know my 400 is higher milage than usual but it's only 110,000 km's
but at 10,000rpm I suppose.

As a foot note Alan ultrasonicly cleaned the carbs refitted all jets and new needles I swiped fronm the 250 (for now) all for £50.

[johnr]

yup, its a peculiarity of the flatslide cv carbs that the needles wear, plenty of gsxr owners will tell you that (gixxer uses the same type of carb, though on the gixxer its just a bit bigger. cant think what coating would be best, i suppose they could be annodised if they were ally or perhaps ceramic coated, but that might alter their dimensions which are pretty critical on the smaller 250 and 400.