G'day team The old girl has recently been behaving poorly =( Under half a tank of gas and riding on a highway for 30mins or 1hr she begins to bog down like she's run out of fuel. Changing to normal then to reserve and back again sometimes solves this even though it was always on reserve on the fuel tap anyway. Seems to be some sort of fuel starvation issue. My mechanical mind is almost non existent but could this not be happening when above half full tank because of the weight of the fuel aiding the carbs getting their fuel? Is there a leak somewhere? Are the filters in the tap dirty (are there any filters in the tap or tank anyway? Someone mentioned an in line filter? Any advice would be appreciated Cheers!
Check the cap breather ... if its blocked then as the fuel is used it creates a vacuum ..... when it happens next time just open the cap slightly and see if it comes good
There are a couple of filter's on the inside of the fuel tank , they sit in the top of the fuel tap If they were partly blocked up then it wouldn't want to rev out when you first ride it, so it wouldn't happen after half an hour of riding I would do as @GreyImport has suggested and when it happen's pull over and open the fuel cap, you may hear so air getting sucked into the tank See how you go, and post up your result's Does it happen again after riding another half an hour or so ?
What revs are you sitting at? I find that the 7,000rpm flat spot creeps up in the revs when I'm highway cruising. Try putting the fuel tap on prime when the issue occurs as this bypasses the diaphragm. If the issue is the fuel cap then this may not help.
It does not happen again once tinkering with the fuel tap or stopping to fill the tank up to full. After filling the tank up to full once the engine has started again it struggles momentarily and feels like its running on 2 or 3 cylinders at idle. Once you get going it and rev it up it likes that and no more problems. Im a fat ba***rd so highway cruising is 8500 or 9k rpm at 100kmhr. I don't notice any flat spots throughout my rev range. Extremely weird that my bike hasn't been having this problem the past 4 or 5 rides (I do use it on long rides 140km or so very often ) . Seems to just happen every now and then. The fuel cap is aftermarket with the twist top thingy on it.. No key required. Maybe this cheapo Chinese replacement has something to do with it ??
I would try a standard fuel cap. Would also inspect the fuel tap screen filters and replace the fuel filter, then drain the fuel bowls and re-fill on the prime setting.
