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Makotosun

Gas millage question

  • Quinton144
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Gas millage question was created by Quinton144

last summer when I took my 78 dt250 up north I could go more than 75 miles before running empty. Giving me a gas millage of roughly 30 mpg. I just got back from a trip to the same area and I couldn't go more than 40 miles before running out completely. The only modification Ive done to the bike recently is I changed out the stock spark arrestor tail pipe for a 1 inch stinger style exhaust. What could cause such a dramatic loss in mpg? The bike runs fantastic just like it always has making me think 14 mpg should not even be possible. Any thoughts or advice would be greatly appreciated thank you!
Last edit: 26 May 2020 16:17 by Quinton144.
26 May 2020 16:15 #1

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Replied by mdscott on topic Gas millage question

Make sure the air filter is clean for starters.
Thanks Mark
Roseville, Ca.

'03 ST1300
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26 May 2020 18:52 #2

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Replied by MarkT on topic Gas millage question

Exhaust restriction is very important to a two stroke with an expansion chamber.

If pipe was properly tuned... and Yamaha factory pipes are decent... reducing restriction over stock will almost always loose power.

Seems like a large drop though... unless maybe you had to apply more throttle, terrain was steeper, or you were just riding harder/faster.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
26 May 2020 19:48 #3

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Replied by Quinton144 on topic Gas millage question

Thanks for the suggestion mdscott. Air and fuel filter both look good I also made sure there was nothing in the air box openings like a mouse nest.

Thanks for responding MarkT. I changed only the end of the pipe where the silencer/spark arrestor was. Before this my bike wouldn't go above 55 mph and when I removed the silencer/spark arrestor at the clamp I got my top speed and low end power back so I figured my problem must be that the spark arrestor was clogged. So I fabricated a straight pipe where spark arrestor used to be and my bike ran harder than it ever has with some minor carb adjustments. As far as ridding differences I may have been riding slightly harder/faster but I was on the same trails and terrain I once got twice the miles per gallon on
27 May 2020 10:59 #4

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