any one have any pointers as what would be the likely cause of poor tickover,
bike is a 250 2 stroke with a klien carburettor
symptons are
starts fine with choke
runs fine with choke
tickover fine with choke

take choke off will run fine-ish on anything above tickover
on tickover poor pick up and cuts out(unless run on choke)
piston/ rings/head/powervalve pilot jets/ all clean and NEW
floats seem ok when dismantled

power valve motor is currently disconected
premix 40:1 being used

any thoughts?
cheers

Perhaps ,a twiddle with the pilot mixture screw might help ,it sounds i.m.o. that it may be running slightly weak , wind in mixture screw 1/4 of a turn at ago, be prepared to raise the idle speed as well though to rebalance.
Regards Mike

[quote="fallenmikethebike"]Perhaps ,a twiddle with the pilot mixture screw might help ,it sounds i.m.o. that it may be running slightly weak , wind in mixture screw 1/4 of a turn at ago, be prepared to raise the idle speed as well though to rebalance.
Regards Mike[/quote]

unfortunately a lot of twiddling has gone on with no success,both to mixture and idle screws

Ah , unfortunately one of the draw backs of a 2T is the fact that a problem can easily masquerade itself in a variety of different ways.So having pointed the finger of suspicion at the more obvious of targets ,we now have ,through a process of elimination , to go through the less obvious ,but eqaully as likely to be faulty items.
Your post mentions a " Klien " carb , is that a Kehien ? probably so but just checking , have you tried popping a new br8es plug in ? you may have a poor connection in low ,or high charge circuits , worth checking ,especially the HTlead to plug top connection, these are notorious for furring up, but the clue to me is the fact that it will run on choke, so perhaps somehow the idle mixture is being significantly weakened off, so check the inlet track from carb manifold through, yours would not be the first bike ( especially a 20 year old MK1) to have some perished rubber /gaskets ect .
Has the exhaust system had a decoke ,and repack recently , this can make a huge difference , though most usually at higher RPMs .
Have you checked the end of the idle adjusting screw? these are known to wear to the point where they are no longer in contact with the cut away on the slide body, you should be able to feel the the slide making contact with this if you open the throttle then release it from say ,half open position.
Regards Mike

YES KEHIEN,
ill check that idle screw bit out thanks(twiddling it makes little difference increasing or decreasing revs)
as you say its an old bike--so am trying to borrow a known working carb to try-will either confirm or eliminate a carb problem

ECU MAYBE?

dnfdaly2 wrote:YES KEHIEN,
ill check that idle screw bit out thanks(twiddling it makes little difference increasing or decreasing revs)
as you say its an old bike--so am trying to borrow a known working carb to try-will either confirm or eliminate a carb problem

ECU MAYBE?

Unlikely, they appear to be more robust the older the MKs.
Have reread your post, whilst fitting a new pilot in theory should have cleared up the symptoms you outlined , a partial blockage in the pilot circuit within the carb would carry on giving the same fault.
I know it's a pain, but [ ONE HELL OF A LOT EASIER ON MK1s] get some carb spray flowing through that circuit within the carb , using a wd40 straw you should be able to pressure spray in both directions, this can normally be done with the carb still in situ on your bike , just take slide body out ,as you were going to do anyway ,just don't get that sheite in your eyes ,cus it really ,really, stings , sorry if you have already meticulously undertaken above tasks.
Regards Mike

[quote="fallenmikethebike"][quote="dnfdaly2"]YES KEHIEN,
ill check that idle screw bit out thanks(twiddling it makes little difference increasing or decreasing revs)
as you say its an old bike--so am trying to borrow a known working carb to try-will either confirm or eliminate a carb problem

ECU MAYBE?[/quote]
Unlikely, they appear to be more robust the older the MKs.
Have reread your post, whilst fitting a new pilot in theory should have cleared up the symptoms you outlined , a partial blockage in the pilot circuit within the carb would carry on giving the same fault.
I know it's a pain, but [ ONE HELL OF A LOT EASIER ON MK1s] get some carb spray flowing through that circuit within the carb , using a wd40 straw you should be able to pressure spray in both directions, this can normally be done with the carb still in situ on your bike , just take slide body out ,as you were going to do anyway ,just don't get that sheite in your eyes ,cus it really ,really, stings :cry: , sorry if you have already meticulously undertaken above tasks.
Regards Mike[/quote]


had it totally stripped,cleaned ect ect the other day made no differance(sad smillee)

a quick question though?

with fuel tap on and choke on with bike not running will the carb overflow( if left long enough) should petrol come out of one of the overflow pipes by the swingarm?

No ,your main inlet valve is letting by if you have this problem, which could also fill the crank with fuel, and worse case scenario hydraulically lock the engine [ excess fuel gets sucked up transfer ports to above piston and will not compress ,ergo engine locks ] draining of this excess, and removing plug should quickly have the engine back into working order though, and more importantly,shouldn't lead to the symptoms you described earlier.
regards Mike

[quote="fallenmikethebike"]:cry: No ,your main inlet valve is letting by if you have this problem, which could also fill the crank with fuel, and worse case scenario hydraulically lock the engine [ excess fuel gets sucked up transfer ports to above piston and will not compress ,ergo engine locks ] draining of this excess, and removing plug should quickly have the engine back into working order though, and more importantly,shouldn't lead to the symptoms you described earlier.
regards Mike[/quote]

whoops sorry misled you---- its not doing it,i just thought it should do

Had a similar issue myself, cleaned carb, replaced pilot jet but still had idle and starting issues. Cured it by setting the float height correctly. In my experience setting the float height with the carb held upside down gave a false setting as the weight of the float compreses the pin in the valve. Better to tilt the carb slightly to avoid compressing the pin. Hope this makes sense.

[quote="keithl8187"]Had a similar issue myself, cleaned carb, replaced pilot jet but still had idle and starting issues. Cured it by setting the float height correctly. In my experience setting the float height with the carb held upside down gave a false setting as the weight of the float compreses the pin in the valve. Better to tilt the carb slightly to avoid compressing the pin. Hope this makes sense.[/quote]

yes
and worth a try thankyou