Just about had enough now. Bought a mk2 in August and rode it few times then stopped starting, I've got compression and piston/rings look ok via a peek up exhaust port. I've got a spark and changed plug anyway. I took carb off and removed and cleaned jets etc... Put it on and it started first kick and ran better than it had, left for a few days and won't start again had carb back off and cleaned twice more but still won't start not even trying. Any help would be much appreciated.

Two obvious things to do -

Place a filter between the petcock and the carb.

Everytime you stop using the bike turn off the petcock.

If the problem is only down to things you have discussed then you may have flooded the engine. Turn the petcock off and take the spark plug out. Leave it to dry out for a few days before you try to start it.

I would also suggest having another careful look at the carb. Many people rebuild carbs these days with cheap Chinese kits. They are not always good quality. Maybe the float needle is sticking or not sealing? Either situation would cause poor starting. Intermittent faults can be a real pain but at least you know the bike will start well when you find the cause.

Good luck!

Keith

Hmm if the compression tester is to be believed it's only reading 50 psi. Going to try and borrow another one just to make sure it's not a dodgy gauge but looking like a rebuild is on the cards.

Ah, that would do it! My CRM was very hard to start from cold with a scored bore and worn rings and that had over 100psi. It ran pretty good once going though!

Keith

Ok so I adjusted float height to 16mm refitted carb and it starts but the tickover is high and the idle screw isn't doing anything. If I blip the throttle the revs pick up and keep going up so I have to kill it. The idle screw seems to be missing it's o ring don't know if this would cause this problem?

I can't remember how the idle screw works on these carbs. Does it just lift the throttle slide when it is screwed in? Almost defiantly you will need the o-ring.

High idle and reluctance for rpm to drop is either an air leak or a sticking throttle slide.

Keith

Check the o-ring on the mixture/air screw