The good news for me is that the SO LS650 that I rebuilt (as a semi-rat\nrunabout) from a non-running parts bike has just passed its MOT. The bad\nnews is that I can't get the bastard running properly. It starts OK, ticks\nover nicely and pulls well - up to about half throttle. Any more throttle\nand it just hiccups then dies - until the throttle is reduced, when it picks\nup and runs OK again. It has a new coil, HT lead and new plug so it is\nunlikely to be an HT electrical problem.\n\nRight - so it looks like a carb or fuel supply problem. The carb is a mikuni\nBS40 CV type. So I swapped the carb for a spare one from the parts box -\ndidn't seem to make much/any diference. I have tried swapping out the main\njet for a larger one - didn't seem to make much/any diference. I have tried\nit with the normal size jet but with air filter removed - didn't seem to\nmake much/any diference. So now I am struggling a bit. I have checked the\nfuel flow - the tap has a "prime" position that bypasses the normal\nvacuum-operated route and turning to this position didn't make any\ndifference (but fuel flow is fine in this position). Basically I have\nswapped carbs, tried making it richer, tried making it leaner and the\nproblem seems to persist. Of course sods law allows for the possibility\nthat both carbs have the same problem but I have checked for blocked jets\netc and can't see an obvious culprit.\n\nThe only other thing that I can think of is that the CDI/igniter unit is\nflaky but that doesn't seem too likely. Anyone got any helpful suggestions?\nIt is getting personal now - I know its a heap of crap bit I WILL make the\nfucker run.