Gas mileage on rebuilt 1974 R75/6

[stevenrankin]

Any news?

Any news or progress?

By the way, Bing never said to replace diaphragms yearly. Inspect and replace as needed. Depending on riding style and miles frequency of change varies. St.

 

[pglaves]

Any news or progress?

By the way, Bing never said to replace diaphragms yearly. Inspect and replace as needed. Depending on riding style and miles frequency of change varies. St.

As does the quantity and frequency of alcohol contaminating the fuel.

 

[stevenrankin]

Any news?

So any news? did you change the needles, drop the needles? My answers to mpg on the Vintage forum all came back with similar bikes getting forty to fifty mpg. St.

 

[kbasa]

So any news? did you change the needles, drop the needles? My answers to mpg on the Vintage forum all came back with similar bikes getting forty to fifty mpg. St.

I usually get right about 42mpg on my airhead, no matter how I ride it. '84 R100CS. I used to get a little better on my '83 RS, but not by much.

I tend to ride them like sport bikes, so plenty of big handfuls of throttle on corner exit.

 

[80092]

Welcome to the forum! The height of the fuel in the center of the bowl should be about 24mm or one inch. If the level is too high, the fuel will be more easily sucked up into the carb. Also be sure that the choke (or enrichener) is completely off when you move the handle to the off position.

For / 5 model carbs the snowbum spec recommended fuel level is 19-20 mm. the lower mpg could be from the 25-26 mm float level.

 

[20774]

For / 5 model carbs the snowbum spec recommended fuel level is 19-20 mm. the lower mpg could be from the 25-26 mm float level.

Good info for the /5 carbs. The OP seems to be working on /6 carbs.

 

[davidcboyer]

Thanks to all for the information on my 75/6 gas mileage. I never heard back from the previous owner about the carb rebuild kit - for a 9/10 or a 13/14. I have not lowered the needle. But after 500 miles on my engine/carb rebuild I did go back and check the head bolt torque and reset the valves. I discovered that one of the intake valves was off by several thousands - too much gap. After resetting the valve clearance my next two tanks I got mileage in the low 40’s. The R75 is asleep for the winter now but I continue to ride my RT.

 

[stevenrankin]

Forties

Great to hear back from you. Low forties is better than 33. LOL, spring time, you can maybe improve even more. I love NY but barely tolerate the winters. St.

 

[80092]

Good info for the /5 carbs. The OP seems to be working on /6 carbs.

{Quote OP}
Looking a little further at the Bing carburetor book I see that my carb numbers are listed for an R75/5. The R75/6 carbs should be 64/32/13&14 according to them. The needle jet is different for those two carbs - a 2.70 for the 9&10 and a 2.66 for the 13&14. So if I replace them I should go with the carb numbers and put in a 2.70?

 

[20774]

I don't think there is a great deal of internal differences in the two sets of carbs, but the engine they were attached to were different. I'd be inclined to use the ones for the /6 but monitor the performance, spark plug color, and gas mileage. The 2.66 should allow more fuel at any given throttle setting. There are a couple of other jet changes for the 13/14 carbs. Might need to consider changing them all for the /6 engine. If you need to purchase the new jets, maybe given Bing a call and explain your situation and see what they say.