Hi guys, i have an 05 montesa cota 4rt repsol the bike will start but once started runs rough and sounds like its going to stall also whilst on tick over it sounds like a mis fire/ air being compressed out the exhaust, does anybody have any ideas of this issue as im totally clueless even after reading the manual. Cheers ben

Valve clearances?

Air leak in exhaust?

Vac pipes split?

If it gets worse when its warm it's likely to be valves, worth checking them anyway.

Like Do2 says; check the exhaust manifold/cylinder junction for a leak?

Seen it before, created havoc... for such a small fault.

Do all the above +

Check the ignition timing.

Replace the spark plug and check if the plug cap and wire are ok.

Make sure the entire ignition system is ok: no cracked coil or loose wires for instance.

Check the idle speed.

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