MK2 wont tick over

[Cadiddy]

Got my mk2 running this weekend and sounded sweet and smooth only problem is it'll tick over quite high for maybe 30 seconds then pick up a little bit more and then as if you open the throttle to the stop it'll rev its 2 stroke titties off, and then mechanical sympathy kicks in on my part and i hit the kill switch, i let it cool for an hour or so and tried again but with the same result, the idle adjuster changes absolutly nothing, this all happened after i'd thoroughly cleaned out the carb set float hight and checked and cleaned all jets, i've been told it's possibly a jetting problem but thats just a shot in the dark really, i'm about to order new o rings for the mixture and idle screws as the present ones are very hard.
Any suggestions?
Thanks in advance

[john7780]

youve not trapped the throttle cable by any chance? or happened to put the throttle slider in the wrong way?

[knackeredMk1]

Sounds like you are running lean at idle specifically . Check the airscrew. But I don't think that running lean at idle would have that much effect.

There is another thing that I have come across before is that the PV is not in the correct position and is 'too closed' when idling. This raises the compression ratio massively and leads to very hot running and even running on when the ignition is turned off. Check the PV position.

Whilst your at it check the oil pump setting.

[Cadiddy]

Okay will check that this weekend when i'm home or sooner if i get the chance, the air screw is set at 1 1/4 turns out, i believe this is the correct setting?
Thanks for your help again chaps will update when i know more

[fallenmikethebike]

Also check that the flow of fuel from the tank is flowing constantly.
Mike

[knackeredMk1]

There is a chance that you are just running out of petrol. Fill the tank to be sure.

[Cadiddy]

i'm pretty certain it's got plenty of fuel but saying that i could be wrong, it doesn't however sound like it's running out of fuel as its running a lot higher revs than it usally would.

[knackeredMk1]

When you are on the brink of running out. eg When you need to change from main tank to reserve your revs will rise as the engine runs leaner.

[Cadiddy]

Yeah i remember that from when it was running before but the revs never rose as much as they are doing now

[fallenmikethebike]

You have an air leak, look carefully around the rubber manifold/carb boot for a good contact, with no gaps for air to bypass the air filter.
Mike

[Cadiddy]

Cheers Mike will check that clamps done up proper:)

[Cadiddy]

I've managed the check all the suggestions given by you helpful people:) and have been told it's drawing air from somewhere, both clamps on either side of the carb are tight and the rubbers are both in good condition, however i do have 3 pipes and a 't' piece from somewhere and i'm not sure where from, i have 2 similar pipes from the vents on the carb but am not sure where they are from, any suggestions anyone?

[fallenmikethebike]

There should be 1x overflow pipe, off the bottom of the carb, 2x breather pipes, above the float chamber.
When the engine is running, spray some wd 40 around the rubber manifold area, see if this give a short term cure.
Mike

[Cadiddy]

Thanks for that Mike, thats how it is at the moment but i have an extra 't' piece left over so wanted to know where that was sposed to go, and what does the wd 40 do?

[fallenmikethebike]

It will [ temporarily] seal and small or porous areas of the manifold, if this works, voilà, you have the answer.
Mike