Bottomless fuel pit

The Sinful Optomist · Wed Mar 16, 2011 12:49 pm

Hello all.

A few days ago I bought a 1962 G3, its great, but I'm getting 30mpg. My only comparison is with my utterly wrecked, now non running 350 indian bullet that used to get 80mpg, which I was hoping for with the G3 (they seem like comparable plodders, but Im 25, so a bit clueless about britbikes) In the last few days Ive been told it should make no more than 40mpg, and by someone else that it should be 80+mpg. Does anyone have accurate figures?

The bike wheels freely in neutral, it starts first kick hot or cold, but not with the choke, when I put the choke on, hot or cold it dies instantly. The spark plug is medium brown in the middle and sooty at the edges. It has a 932 amal concenetric, with a 230 main jet (I believe this carb is wrong, and slightly too big?) with no air filter. Exhaust looks standard. Bike seems to ride ok, a bit slow, 50mph cruising, 60mph feels like flogging, but Im a big chap, and wasnt expecting land speed records, just economical fun. Its my only day to day transport, just as the enfield was, so I need to get this sorted, the fuel cost is crippling me! Oh, and the taps leak, cork plungers, so Ive sent off for brass lever ones.

Any help would be VERY much appreciated, particularly suggestions about the carb, should I replace it with correct monobloc (id prefer not too, Im not well off) and if not, what sort of jetting should I be on?

Thanks in advance.

iandusud · Post by **iandusud** » Wed Mar 16, 2011 2:06 pm

The carb is far too big, but more to the point the main jet is far too big. Should be about 180 on a Concentric, 220 on a Monobloc. I suggest you invest in a new carb. A new Concentric will set you back about £100. At your current rate of fuel consumption it will pay for itself in no time!

Ian

smsxr05 · Post by **smsxr05** » Thu Mar 17, 2011 8:09 am

my 500 single does about 50 mpg, suspect yours should do even more.

SPRIDDLER · Post by **SPRIDDLER** » Thu Mar 17, 2011 9:52 am

'54 G3LS - 50mpg shopping and 70mpg on a run at a max speed of 60 'ish.
HTH

Samuel · Post by **Samuel** » Thu Mar 17, 2011 10:24 am

Surrey Cycles or Burlin Fuel systems will quote you for precisely the correct carb for your machine.

Eric · Post by **Eric** » Thu Mar 17, 2011 10:30 am

If you do decide to purchase a new carburetor its probably best to get the correct replacement for the bike, then when you are trying to make comparisons of things to others with the same bike, you can easily confirm things are right or wrong in at least that part of it.

The other possibility is to consider using the carb from your Enfield there are people on here who will know what that is or should be and more about how suitable it maybe, but the engines are not very different as a place to start from.

RUSHTON · Post by **RUSHTON** » Fri Mar 18, 2011 8:58 am

The Early Enfields were fairly simple machines, however the later ones had the Euro emission carburettor. I would look out for the correct one on E-bay - they seem to come up quite often.
Best of Luck!

The Sinful Optomist · Post by **The Sinful Optomist** » Fri Mar 18, 2011 5:17 pm

Thanks for your help everyone, much appreciated. Think I'll keep my eye out on ebay then, for the correct carb. I like the idea of thieving the enfield carb, apeals to my bodgeit side, but unfortunately its a nasty jap thing I got in a breakers yard yonks ago and is well past it!

g80csp11 · Post by **g80csp11** » Fri Mar 18, 2011 5:44 pm

where abouts are you in the country ?
Kempton park on Saturday . I'm sure one of the Matchless guys could sort you out with a used carb

iandusud · Post by **iandusud** » Fri Mar 18, 2011 6:39 pm

I generally fit secondhand parts if I can find them in good nick but I'm very wary of used carbs as they've almost always been removed because they're worn out.

Ian