Hitchcocks Forum

Hi all. Still loving the Bullet. 2500 miles since the end of May and the only problem has been a puncture! However, I am only getting just over 50 miles to the gallon. Is this normal, I expected more to be honest.
The bike is a 2003 500 electric start Classic. It has got an Amal 930 carb fitted with an S&B filter with a straight through exhaust. Would fitting a baffle help? I do have a slight leak from the head gasket which will be changed soon.

Maybe up the gearing by a tooth or two..?

You should be getting 65 to 70mpg or slightly more if on a run with that set-up. Are you just doing town driving? Leaving choke lever half on?

I do short runs to work on it but also long runs when I can. Recently did 200 miles in one go and averaged about 160 miles on a tank full. This is the 14.5 litre tank so I worked out about 3 gallons in old money. The choke is not half on so I`m looking for another explanation.
Have got a bit of an oil leak around head to barrel joint so going to change gasket soon but need to get more MPG. Any ideas anyone?

Do you know for sure how accurate the mileometer is? -C

I'm no expert, but it seems to me that if you run with a more free flowing exhaust, coupled with a carb which gets more fuel into the head a bit quicker, performance may be enhanced, but economy will suffer. Or can you have your cake and eat it?

If it's that bad, it strongly suggests a problem with the carburettor. I'm convinced it is set up incorrectly. Have you done a "plug chop" at cruising speeds to see if it is black?



You would need a massive error on the mileometer to cause such a discrepancy - I don't believe it could possibly happen. Also, the S&B air filter and straight through exhaust wouldn't cause such a loss of fuel economy on their own.



Having said that, I would definitely check that the air intake is clear and unrestricted right through. I realise this won't apply to you, but once my Electra X wet-sumped, pumped oil all over the air filter, and knocked the mpg right back to 50mpg or so.

I had a similar bike - 2004 ES 500 but in light trials trim - open high rise exhaust, 30mm carb with short bellmouth, jetting by Hitchcocks (needle needed raised and a bigger main jet as it was far too lean due to open pipework). Things that affected mpg downwards:

1. round town chugging and stop starting big drain on mpg
2. hammering the bike with throttle held at 3/4 for long stretches of sweeping highland roads (what fun!) - another hard hit
3. loading bike with luggage (heavy riders also hit mpg....?)


It returned 71mpg maximum on long uninterrupted runs averaging 40 - 50. Hammering or town stuff brought it down to mid or even low 60s.

As Thack says, do a plug chop, or better still take it to a local shop with a dyno. Probably running far too rich but you can also tick off some of the above and a mid 60s mpg should be within your grasp if there is indeed a tuning issue.

Thanks for the comments. I think maybe my riding style is partly to blame. Most of my riding is chugging up hills around where I live (South downs) and on the recent 400 mile round trip I did I was riding at an average speed of 60MPH so perhaps I need to slow down a bit.
I haven't had a chance to do a plug chop yet but did clean the plug today and it was well black so probably is running too rich.
When I got the bike I got the original carb in a box of spares so I`m wondering what difference it would make to power if I refitted it? I might sacrifice a bit of power if I can get more MPG.

You will get more power with the correct mixture and better fuel consumption.