How to reduce fuel consumption with a Mikuni?

plumstead said:

Hi, I am in Invercargill New Zealand and have borrowed an early drum-brake 750 Commando from the bloke who is building one for spares for me. It has a single Mikuni VM carb and starts and runs well, with no pinking or misfires. Despite this, and keeping revs below 3500 (cops in NZ use radar from the opposite direction several miles away) it uses 8 litres of fuel per 100km - about 30 miles per gallon. I hope to get my own bike in a few weeks so don't want to get too involved e.g. jetting. I've looked at the tuning manual but I'm no mechanic and wonder if anyone can advise on the adjustment? Cheers Rob

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Depends on the bike ... some get good MPG, some bad. My first Norton (1971 750) got 30 MPG, with the original amals ... and the same with a replacement single Mikuni. :shock: My current Norton (my avatar bike) gets 45 to 55 MPG ... depending on how hard I ride it. My first KZ1000 ... got 45 MPG all day long; and my current 1977 KZ1000 is lucky to get 27 MPG. :shock: Bought a brand new HD Sportster XL1200R back in 2005 ... 38 MPG. Put a stage 1 kit on it, still 38 MPG. :evil: My 1999 Buell that I STILL have ... has gotten as high as 65 MPG At a steady 70 -80 MPH for 200 miles. Curently averages in the 50s with general combined riding. Had a 1975 Triumph T160 ... got 28 MPG with that one (barely)

I could go on and on, as MPG on all my bikes has been my "pet peeve" for 30 + years. (going on 60 plus motorcycles, had 12 Honda CB750s alone ...) Most of the bikes I sold or traded ... were due to poor MPG. Though I don't claim to be an expert mechanic, all these bikes ran great and were in proper tune. And, I ALWAYS check my MPG. Just my 2 cents on this thread ... cheers.

Thanks for informative posts. I will post results of adjustments. Cheers Rob

Bike is now a non starter, no doubt due to some error of mine, as it was running before I disassembled the carb.

Carb is a 34B Mikuni with a 240 main jet. The bike has good sparks, petrol is getting to the float bowl without overflowing, and the 'choke' lever seems to be operating the plunger appropriately. The cable pull from the throttle is good with no slack, and raises the slide cleanly. Needle clip now restored to the middle needle notch

Will attack the problem in a couple of days.

Time Warp said:

plumstead said:

borrowed ... I'm no mechanic and wonder if anyone can advise on the adjustment?

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Why not ask the person who owns the bike before touching it ?

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MMMMMh... That sounds like a good :idea: :idea: :idea: :idea: :idea: