plugs were jet black when i took them out not oily

This would indicate a mixture that is WAY too rich.


got myself another set of carbs on the bike now
still got my prob but aint as bad
checked battery getting 13v

OK, first, if the Reg/Rec is on the way out, you would almost certainly see "spikes" in the reading on the voltmeter when you tested the battery, especially as you wind the throttle on to bring the revs up. You should have a fairly constant reading as the revs rise and fall of around 13.5 - 14.5V.

As Jim says, double check the coolant, making sure you have no air-locks that would cause a false indication of coolant level. Ideally you should check the thermostat operation.

First thing I would suggest is a compression check.

You say that fitting a new set of carbs has partly cured your problem. Well, this would indicate a settings problem. You say you've already fitted new plugs, cleaned the air filter, and adjusted the oil pump, which apart from the possibility of dud plugs (not impossible, but highly unlikely!) would mean you're following good procedure and under most circumstances, would've cured your problem! Check the plug gap, to be sure, which should be 0.7 - 0.8mm.

Check the carb settings. On the side of the carbs there is a "type" number. For the MC18Rk you should see TA21A.

The main jet size should be #128 for both carbs.

The PJ should be #75 for both carbs.

No.1 carb (top cylinder) should have the needle BPG, the No.2 carb needle should be BPH.

Slow jets should be #38.

The Air screws should each be set to 2 1/8 turns out from closed.

While the carbs are off, remove the intake manifold. Check the rubber "boots" for perishing or cracks that could be causing an air leak. Check the reeds to make sure there are no broken petals. Use a gasket each side of the reed valve blocks as the sealing ability of the rubber face of the inlet manifold deteriorates over time.

How does the bike idle? If it idles cleanly (or even just runs OK for testing purposes!) then that is a bonus! Start the bike up, and while running, spray carb cleaner around the intake manifold. If you have a good tight seal between the carbs and the airbox, and the gaskets on the manifold are doing their job, this will nicely clean the crankcase! If however, the revs rise, it would indicate you are drawing air, and this MUST be sorted before you go looking any further.

Spray carb cleaner around the back of the flywheel too. Same rule applies: if the revs rise, the crankcase is drawing air - not good, and pointless chasing around for other faults.

If the carbs settings seem OK, there are no apparent leaks, and there is a good constant reading across the battery with the engine running, check the coils. Is the misfire noticeable on just one cylinder? If so, swap the coils. If swapping the coils, the misfire swaps cylinders, then a new coil is the order of the day! (Normally I'd probably try this first, but as you say fitting another set of carbs has partly cured your problem, their settings need to be done first!)

If the misfire continues, it would then indicate either a bad PGM (ignition control unit) or possibly even a compression failure due to worn or broken piston/rings.

Can you let us know how you get on, and what symptoms you are still encountering after following these steps, and we'll see what else you can do.

Andy.
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