Forum

[Ivor]

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.

[Gwilly]

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

[sofiaspin]

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?

[Ivor]

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?

[Chris [Stockport]]

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

[wilf]

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?

[Thack]

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.

[sofiaspin]

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.

[Ivor]

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.

[simon]

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