Float height ...

I recently purchased an old 1990 Kawasaki gpx 250. The bike has been totally restored but laid up the last 3 years.

With a small amount of fettling the bike is running again.
It starts instantly off the button and revs smooth through to the red line.

Having a bit of trouble with idle. If you Rev the bike from idle the revs hold around 4000rpm act erratic and I can only lower it by adjusting the idle screw. Same thing over & over.

I've checked the air/mix screw and it's factory 2 turns out.
All cables have freeplay.
I found 1 vac leak on the carb > head rubber. Was revving better but suddenly same fault again.

I've pulled the carbs off hoping they would be gunked up but they are spotless.
The only thing which looked wrong was the float height. Manual states 17mm from base of carb body to float.
I measured it with the float just resting on the fuel needle valve and it was a lot less around 10mm height?

Would this cause the revs to act irratic and hold on?
It's a twin carb and only mod is aftermarket cans. Factory carb setting & jets.

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Luckily for you I'm an expert in such matters
Had exactly the same problem with mine and no amount of carb cleaning or adjusting helped!  
But adjusting the valves did!   she's perfect now!
Just make sure when you crack the adjustment nut that you support the rocker on the side with a screwdriver or something as there are little ears that locate over the valve stem and they are prone to shear off! My mates got a gpx and that's what happened to his!  

That looks like the gpx I bought...

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Hopefully, I'll check the carb float height and check the valves.

Thanks for your help.

Do you still have your bike?

Identical! Is that the one that was advertised on Facebook from South Wales?
I got mine from Kent a few months ago as a few of us next year are doing a pre 90's 250 trip to round Europe! The fact mine was registered in march 1990 breaks the rules but it is a G Reg so it's fine in my eyes
I love the thing though! I do need to sort out a slight handling problem and a leaking fuel tank but then she's away to go!
Bloody quick for a 250 and sounds lovely at 14k!
It looks like yours has got a Predator exhaust too?
You keeping or selling it?

Yes it was advertised on Facebook in Ammanford. It's also G reg with predator exhaust pipes. It's been fully rebuilt at 31,000 miles stripped down to bare frame and rebuilt/powdercoated.

I will eventually sell it but I quite fancy having a few outings on it.

Aaaahhh GPX lovers .... relationship goals

crm250dude wrote:Aaaahhh GPX lovers .... relationship goals

It's a beautiful thing!

curl666 wrote:Yes it was advertised on Facebook in Ammanford. It's also G reg with predator exhaust pipes. It's been fully rebuilt at 31,000 miles stripped down to bare frame and rebuilt/powdercoated.

I will eventually sell it but I quite fancy having a few outings on it.

Bloody hell that's freaky! I thought mine was unique
Can't be many of them left!
How's your tank? Mine is knackered but need to weld it as I can't find one anywhere
They are really fun to ride but your bollocks do get hot

Did you also take out the emulsion tubes and drop the carbs in a ultrasonic cleaner? I would buy rebuild kits

fozzy wrote:Did you also take out the emulsion tubes and drop the carbs in a ultrasonic cleaner? I would buy rebuild kits

I didn't with mine, they were mint inside despite it being sat for years, just a really good blast with carb cleaner and air line!