the only way i can think of a sleeved engine consuming more petrol is that the sleeving has drastically increased its displacement .. like by more then 10-15cc .. even then it wont consume more petrol by itself .. U yourself have to adjust for that increased displacement by rejetting ..
what was its stock bore and whats its bore now ? and also whats its stroke ?
is its carb still stock ?
what is its crab model ?
try getting a baseline reading for its avg and then check urs against it ..
first try checking its avg by using little precisely measured petrol say 100ml .. and ride on constant speed on stragiht road .. be in the economy range .. like if ur economy range is b/w 35-50 .. try to maintian the central value ..
then repeat the same experiment from point b to a .. then find the avg of these two readings ..
then perform same experiment this time try some middle speed ... like say ur top speed is 100 .. and ur max economy speed is 50 .. try running at 75km/hr ....
then try the same at top speed ..
post the results for further discussions .. this will tell where is the issue .. if its in carb then what circuit is not ok .. these values can be an excellant tool ..
however if u feel lazy .. then just replace its pilot jet .. main jet . and the needle at minimum .. and at best change any thing that is changable and then hope it will work out ...
all in all i would suggest u to replace its jets ..