Hi all,
I bought an nc30 back in October, a 1990 jap import which had 110 size jets in all the carbs. I changed these to 118 front and 120 in the back carbs and turned the screws out 2 & quarter turns to suit an after market exhaust. I know i have made it richer but i am now having to switch to reserve at 150km/93 miles, and when filling the tank back up from this it takes 11.3 liters. Working out at about 37 mpg. I was going quite hard but was wondering if that sounds right as i remember getting alot more miles before having to switch to reserve with the old jets.

Tom.

if you are flogging it then will use more fuel and sounds about right

are you still on stock sprockets as well ?

Havent checked the sprockets, how many teeth on the standard? Any size you would recommend?

dont know standard but i am sure if you search then you will find the answer

the reason i ask is because if you have different sprockets then the odometer reading ma not be true indication of distance travelled

15t front, 40t rear

To be honest, the economy doesn't sound too bad. What does seem a little off if when you are running to reserve. I'm pretty sure that like the 35, the 30 has 13 litres main and 2 reserve, so you seem to be running onto reserve very early. I was rather disappointed yesterday after doing lots of motorway miles that my 35 ran onto reserve at a paltry 175kms. However, assuming the tank was full, that's actually barely 38mpg. When it wasn't the wrong side of 118000kms, I'd routinely get to 190, which is a whisker over 41. It has a Scorpion pipe, however I don't know if the last owner rejetted to suit. It certainly goes OK, and when I eventually get around to fitting my 'new' carbs maybe I'll find that I can make it go a little better.

Anyway, I'd be investigating how your fuel tank is mounted, and if the fuel pipe might be trapped or creased. Somewhere on the board is my thread about running onto reserve silly early, and in my case I took the tank off to find the fuel tap to carbs hose had a big kink in it. If you've been ragging the bike around 37 seems fairly reasonable, bit only 11.3 litres on main doesn't sound quite right. Having said that, it might depend on how you fill it. I always sit on the bike as I have the silly theory it helps more air escape from the tank. It also never ceases to amaze me how long you can keep putting fuel in after it's reached the filler neck as air pockets keep coming out. I guess it's always going to be the case when the tank has such a big, flat top. I've only once managed to get it come out the overflow afterwards, so I figure I'm not going too mad. However, it's probably not a good idea to fill the bike jam pack full if you're about to park it when it's hot...