blubbery KX250

[211]

Have my 74 KX250 - the 10 year project that is all but done, but.....
the bike runs well in once up in the revs but like crap off idle, not fully loading up but feels really rich down low - so I think I have a jetting issue and reduce the pilot from a 45 to a 35, no difference noted, so I take a carb of my 76 and the same problem is noted - works perfect on the 76KX.
Motor is new everything - Im thinking ignition but before I start pulling stuff off and testing anyone got any ideas - sometimes the really obvious you cant see when you looking hard......
DT

[Lozza]

What happens when you turn the air screw?

[211]

tried everything from half thru 2 full turns - everything I have is always 1 and a half out; didn't seem to help. Even went back to the all out and wind in 'till the motor settles but still no good. problem followed the carbie has to be electrical.

[Lozza]

Electrical problems are usualy higher in the rpm range where the stator doesn't have enough time to recharge the capacitor (I'll assume a CDI)

[William Doe]

What piston did you use Dave  Genuine , aftermarket or a CR one ?

What about substituting the stator off your 76 and trying it , then CDI , then top coil . I always found that diagnosis by substitution of a known good part was the most conclusive method with electrical issues .

[FourstrokeForever]

You did say you might overlook the obvious Dave.... Have you tried a new spark plug?

Does the bike stall when you wind the air screw to bottom? If not, you might have an air leak somewhere.

[211]

Piston is a one ring wiseco, never liked them much.
Yes to plug
Yes to stall when all the way in

[211]

What piston did you use Dave  Genuine , aftermarket or a CR one ?

What about substituting the stator off your 76 and trying it , then CDI , then top coil . I always found that diagnosis by substitution of a known good part was the most conclusive method with electrical issues .
[/quote
Agree re coil will be the next job

[Nathan S]

Try a leaner pilot again?

I tied myself in knots with my Husky 360 recently, by not accepting that my bike needed a significantly leaner pilot jet than everyone recommends...

[Rossvickicampbell]

35 is already getting down there though isn't it Nathan?

[Nathan S]

Yep, but that same way of thinking was stopping me from jetting my Husky properly...

Too rich is too rich - the numbers have limited value by themselves.
Alternatively, if it gets to the point where it's too lean AND blubbery, then he can be sure that jetting won't fix it.

[Rossvickicampbell]

mind you I am down to 35-40 on my 360 and changed the whole bike performance.

[John Orchard]

If it wasn't for the fact that the '76 carb does the same thing (I presume that it doesn't blubber on the '76?), I would have been confident that it is a worn needle jet.

[Slakewell]

Hey Dave, would you know were to get a rod kit/piston kit for the 74 KX 250, found one the other day in a shed at Dungog.

[211]

Hey Dave, would you know were to get a rod kit/piston kit for the 74 KX 250, found one the other day in a shed at Dungog.

Mick - time and money mate; I bought my one 10-12 years ago from the US as a wreck and it took that long to find the bits..... Kawasaki's are hard work but rods are one of the easier bits - don't lose anything no matter how F#$%ed it may be. Take a long look at the front backing plate - it will be unusable and may be the sprocket hub will be cracked - just that bit alone was a 2 year quest!
I had thought of the 32.5 pilot but it didn't change one carb to another so will R&R the electrical after the Nationals in Perth
Thanks for the input
DT