Fuel consumption

[xskev]

How many miles should i be getting out of my 75 XS,from a full tank till resevre?.i'm getting 75 mpg !!! during normal riding,that's surely not right.i'm running a stock motor with 34 Mikuni round slides,K&N off set conicle filters and Mac headers with short reverse cone mufflers.Mikuni float heights are set at 23.75mm MJ 180 PJ 22.5 needle jet and jet are whats recommended too.

Anyone got any ideas?.

 

[breahn riley]

180 main jet? That is wayy to big. How quickly are you foulin plugs?

 

[yamaman]

180 is fine for VM carbs.

75mpg is pretty wild! You sure about that? I'd think anything above 40mpg would be acceptable, depends how you ride it!

 

[breahn riley]

i must have been thinking cv carbs. could he just have his mixture screws out too much?

 

[xskev]

sorry guys i meant 75 miles from a full tank to reserve.

 

[72XS2]

sorry guys i meant 75 miles from a full tank to reserve.

So this isn't 75mpg, it's 75 mpt (miles per tank) .

 

[xsjohn]

I would be concerned about washing the rings and cyllinders at that consumption level......

Should see Grisld1 at the garage ............he uses the 6F9 needles if I remember correctly............

xsjohn

 

[grizld1]

xskev, you mentioned your MJ size, but that's not all there is to a carburetor, and a carburetor isn't all there is to fuel consumption. On a stock engine in good condition and a decent state of tune, with VM34's and the exhaust and intake mods you mention, you should be getting in the neighborhood of 45-50 mpg in aggressive riding. One common cause of excessive fuel consumption is poor needle jet (AKA "atomizer," AKA "emulsion tube") selection. The standard NJ for the VM34 is the Q-2, which is far too fat except for use on the track with large-bore engines in full-race tune. P-5 or P-6 would be a better choice for your setup, with 6F9 needle.

 

[jayel]

what size tank? on a 1 gallon tank that would be good, on a 3 gallon specail tank not so good mpg = miles/gallons

 

[xskev]

P-6 needle jets installed along with 6F9 needles.it's just done a top end rebuild re-bore 2nd oversize,cylinders honed new pistons,rings new valves re-cut and lapped,new valve seals.iv'e done around 400 miles on it,could it be that the rings haven't seated to the cylinders?.

 

[Liftrat]

Any possibility of the carbs leaking or overflowing? I'd be belching black smoke at that MPG.

 

[xskev]

That's the thing there is no black smoke at all and the carbs are not leaking/overflowing the needle clip is on the 2nd from top groove,the carb dialing in feels pretty good.the BRP7EIX plugs have been sooted but if i lean my carb settings it starts to pop and back fire.i'm left scratching my head with this one.

 

[nj1639]

what size tank? on a 1 gallon tank that would be good, on a 3 gallon specail tank not so good mpg = miles/gallons

The missing equation in the formula.

 

[xsjohn]

If the floats are just a bit too high it will suck a lot more gas......xsjohn