Katana 250 fuel starvation.

[McDuck]

if i let it sit for a few min then it will idel or rev untill the revs drop. If they drop it dies. Even if just a few rpm. Anybody know what is causing this? Any help would be good before i light the fucking thing on fire and buy somthing else.

[Paul in NZ]

Blocked fuel filter or vent in the petrol tank?

A slightly more acurate description of the problem could aid in diagnosis... ;-)

[McDuck]

Ok so if i let it sit for a few min it will revv happily, i held it between 6 and 8000 rpm for about 1min but once it got below about 2000rpm it would stop then not restart. Any idears?

[McDuck]

Blocked fuel filter or vent in the petrol tank?

A slightly more acurate description of the problem could aid in diagnosis... ;-)

i am not a mechanic, what are some things you need to know? If it was a blocked filter wouldnt it not go at all, insted of the way it is? Do you think maby rigg up a different tank sending fule directly into th carbi?

[McDuck]

any help would be good, i am real close to giving up on the fucking thing.

[betti]

try running it with the fuel cap open, to eliminate the vent in that.
If that's all good, check all the clips that hold the carbs on, make sure they are tight and no splits in the rubbers.
You might pull the fuel pipes off the tap , and check for blockages. Also move the tap to reserve and prime, and see if she behaves any better.
The carbs on these gum up real quick if they have been left with old gas in them for any length of time, so if all quick fixes fail,
pull the carbs off , and fill em with carb cleaner.

[Paul in NZ]

i am not a mechanic, what are some things you need to know? If it was a blocked filter wouldnt it not go at all, insted of the way it is? Do you think maby rigg up a different tank sending fule directly into th carbi?

No disrespect but these are relatively complex bit's of kit that will either need time or $$ sooner or later. You CAN do it yourself but patience and or talent, a few decent tools and a place to work on it are required.

You could start with the bikes history. I’m fairly certain that these were never sold new here in NZ. That means at some stage it has sat for some time. If it has sat, invariably the carbs need cleaning and setting up properly and that’s not cheap to get done assuming you could even find a bike shop to touch it. (they don’t like old bikes)

So for starters you could let us know if you have ever had it running well and when or what happened to make it not run so well.

Remember that these are really small cylinders sucking through relatively humongous carbs so everything has to be right or they get really moody. The valve clearances go out, rings loose their tension and compression falls away, they get hard to start, won’t idle etc etc. They are generally a good wee bike but I’ve seen some bandit 250’s develop some pretty odd carb / starting behaviour if neglected.

Cheers

[JimO]

it ran fine when it was here so something thats been done in between has to be the problem, did katt have a look at the carbs??

[McDuck]

all fixed thanks guys, the mother off all air locks. All wofed and regoed up to now :)

[McDuck]

the air must have gotten in when the tank was put back on after coating.

[Paul in NZ]

Well done that man! WAAAY more satisfing than pushing then out into the street and setting fire to them (just)... Try to never run them out of fuel and when they get old - try to avoid reserve unless you are sure it's got a clean fuel cell...

[McDuck]

yea all true....

[McDuck]

no thanks, that is what nz250s are for.
Just went out for about 30 min ride after youth group, in the wet with a green frount tyre... and i loved it. I think i may doa fair bit of riding tomorrow... lol

[gsx kid]

Ok so if i let it sit for a few min it will revv happily, i held it between 6 and 8000 rpm for about 1min but once it got below about 2000rpm it would stop then not restart. Any idears?hi i have the same bike. it should tickover @ 1000 rpm or just slitly over a 1000rpm. you should check the vacum pipe from to carb up to fuel valve on the tank for craks ect. oh the diafram in that valve chould be woren.
see dos it do it when you turn the valve to resrve .

[McDuck]

Lol it was was a big air lock, and connected up the vacume hose to which helped.

[gsx kid]

ah shes all sorted, good good. the are a grand bike. i am getting it hard to find a workshop manual for my katana250