Thread: How many miles can I expect from gas tank?

Are you sure the factory tank is in the bike? Maybe somebody put a differen't tank in there before you got it.

Originally Posted by zeriods

Are you sure the factory tank is in the bike? Maybe somebody put a differen't tank in there before you got it.

That's what I was thinking. There's no way it could be running so rich that you'd only get 10 miles out of a tank- It wouldn't even run if it were that rich. I'm betting it's leaking, your tires are low on air, both brakes are dragging, the chain is extremely worn, your gas tank was replaced with a mason jar, and you're towing a boat uphill.

Ok here goes!

It is the original plastic tank holds about a gallon of gas!

The fuel lines were leaking a bit at the petcock got that fixed!(just a few drops nothing major)

But ever since i started playing with the mixture screw and the throtllestop I can't seem to go faster than 30mph! We'll see how far I get with this tank I filled her this time with premium instead of regular gas!

I just remembered an article that had I read about a Monkey Bike (Replica) that was getting very poor gas mileage...The problem was that the front brake was sticking! So, I would check your front and back brakes...That might be the problem. Good Luck!

Overoiled/dirty airfilter,Id make sure theres not a critter nest in the frame/back of the airbox. Critter den dosnt flow like k&n. Black smoke means your rich grey is rings valves leaking most of time.

As Karen mentioned, dragging brakes will slow your top speed. Additionally, a unlubricated/poorly maintained drive chain will slow your Trail 70 down too. Heck even low tire pressures or large riders will slow the bike down considerably.

Important keys to a great running engine: Correct valve lash gaps & timing, good cylinder compression, and a clean & properly jetted carbuertor. Upper 30's to low 40's can easily be had on good running CT70.

When I was 11 years old, I tucked in as tight as I could, on a level stretch of old country road and got my HKO up to 50 mph. I was so excited, you would have thought I broke the land speed record.

Originally Posted by kmcrab

I just remembered an article that had I read about a Monkey Bike (Replica) that was getting very poor gas mileage...The problem was that the front brake was sticking! So, I would check your front and back brakes...That might be the problem. Good Luck!

It's a good suggestion, but on the other hand, I would think when a person is riding they would feel that. When you let up on the gas and just coast, I would think you would feel the drag, and if you don't, then it wouldn't be dragging enough to cause such a drop in gas mileage. But, I could be wrong.

Originally Posted by Haas

It's a good suggestion, but on the other hand, I would think when a person is riding they would feel that. When you let up on the gas and just coast, I would think you would feel the drag, and if you don't, then it wouldn't be dragging enough to cause such a drop in gas mileage. But, I could be wrong.

I thought those exact thoughts also, but then I remembered that this is Stevo's fist CT and the guy in the article...It was his mini first too...And it was new, So I thought that maybe if you don't really know how something is suppose to feel or handle, it could happen. Heck, I don't know..

CT70 tanks hold about .6 gallon, "reserve" is reached at the .5 gallon mark. 10 miles from a full tank would be less than 20mpg; it'd be reasonable to expect more than that if powered by a 700-cubic inch V8!!! On the other hand, "...85-90 miles out of a tank...cruising at 50mph+..." works out to 140mpg+. Clearly, something is seriously amiss in both examples. A reasonably healthy stocker should be able to crack the century mark, though actual riding conditions can have a huge cumulative effect. For a bike capable of 50mph+ cruising, 75-95mpg is about as good as it gets, until someone manages to completely science-out EFI for one of these bikes. A number of riders running large-displacement motors see less than 40 miles from a full tank; wild cams & oversized carburetors will do that. That's still an order of magnitude better than what you're reporting. It only takes so much power to reach 35mph and I really doubt that a stock motor can make enough power, at it's absolute peak, to burn through gas at a rate corresponding to <20mpg. If that much fuel is actually passing through the motor, then it's absolutely amazing the plug doesn't foul-out in seconds.

If you're still seeing 35mph, then the mpg numbers are highly suspect. To reach that kind of top speed (which isn't too far away from normal) the whole system has to be reasonably healthy, unless you're measuring top speed down a steep hill. First thing that I'd check is the actual quantity of fuel being used. Start with a one-gallon can, carefully filled with exactly one gallon of gas. That's one critical control in this experiment. Next variable to eliminate is odometer accuracy. With those two out of the way, you'll have a reliable baseline. A not-too-wild-assed guess is that you'll come up with a less bizarre number. It may be still be subpar. Just cannot see how a true 20mpg is possible with a stocker that runs this strongly.

Only two basic elements will remain, engine operating efficiency & parasitic (frictional) losses. The exhaust, carb, & air filter assembly must be in tip-top condition, free of blockages & dirt. The engine must have decent compression; low compression = low efficiency & power. Spark timing has to be dead-on. Insufficient point gap can have a big impact on running. As for parasitic drag, the brakes can more than absorb engine power; they're easy enough to check. Less obvious areas are the chain & sprockets and rolling resistance of the tires. These little motors don't make much torque, thus worn sprockets & an arthritic chain can can act like a dragging anchor.

I don't think anything is dragging if I let go of the throttle it still runs freely not like anything would be dragging!

What I did do today is take the gastank out and got new fuel lines as the ones that were on the bike we 1/4 and I saw on dratv's site thay should be 3/16 or 10mm! So I bought a few ft of the right rubber lines! I also cleaned out the crap that was in the frame behind the air filter so that this couldn't restrict the air flow!The air filter itself is a NOS OEM one! So it's time for a test drive now as it's almost 80 outside!I'll keep you posted later