Ive got a stock double barrel strongburg on my 253. Its dual fuel, and I usually run on gas, but recently ive been putting fuel into it - because of the rediculas price of LPG in NT. It had a leak, and was doing some funny things, so i put a carby kit through it. It now runs like a drean but.. it leaks like a siv from the butterfly pivot shaft. Does any one know if there is a specific O ring that goes in there? there was definately nothing spare in the kit, so should it have been in the kit? or seperate purchase?