Poor Gas Mileage, Need Advice On Getting It Dialed In

LabRat63

New Member
Joined
Feb 3, 2008
Messages
25
The install was easy, easier than I expected. No problems at all except that dratted kill switch clamp.

I mounted a 32cc Tanaka from GEBE on a cheap POS bike from WalMart. The bike is a Roadmaster Mt Sport 5X. It has front suspension and a beefy looking frame with large diameter tubes, but it has real sloppy looking welds. I doubt it will last too long, but as long as it lasts long enough for me to afford something better, it was $60 well spent.

I have gone through 3 and a half tanks of gas so far, and the gas mileage is nowhere near what I expected. GEBE claims 25-30 miles per tank. I figured I would get maybe 20-25 because I am on the heavy side, about 275-280 Lbs. I went to work today to pick up my check. It is 6 miles there, so 12 miles round trip, and that took 4/5 of a tank of gas. A little math shows about 90 MPG where I was expecting at least 140-150 MPG. I think the idle is high so I'll adjust that today or tomorrow. Can too fast an idle cause that big a drop in mileage? Or is it that it is a new engine and it will improve? How far down should I adjust it? To where the back wheel does not turn at all when the back of the bike is lifted, or is that too low?

I already know I need to have the wheel trued, there is a tiny bit of wobble in it. I have seen the thread about how to get the drive ring centered and using drops of epoxy to keep it there. What else can I do to tweak the performance?
 


Skyliner70cc

Active Member
Joined
Nov 17, 2007
Messages
1,347
With the load on the engine, I doubt it will get much better. You should fabricate a larger tank. I'd get a Happy Time tank and then use a small 12 volt electric fuel pump (hobby stores sell fuel pumps that safely pump gasoline) to transfer it to the other tank.
 

kawasaki999

Member
Joined
Jan 18, 2008
Messages
335
Its probable your gearing, you could go up 1 tooth and try that but you will loose pick up and hill climbing power. I have a tanaka 47r and a 14 tooth gear and I am getting 160+ mpg. your mpg will increase a little when the motor breaks in. yes adjust idle to where the wheel does not spin. hope this helps.
 

kawasaki999

Member
Joined
Jan 18, 2008
Messages
335
tanaka 47r

this is my set up with 1.5 litre extra tank. I get 60+ miles on this tank.
 

Attachments

  • 01-20-08_1309.jpg
    01-20-08_1309.jpg
    138.4 KB · Views: 305
Last edited:
G

gone_fishin

Guest
there's a 1000-mile projected break-in with the tanaka...i wouldn't recommend gearing it "up" until then...my mileage isn't what i expected either, 13tooth, but it's pushing a heavy bike/rider. i'm at 600 miles, and am anxiously awaiting the day when i can put the boost-bottle on it and bump it to the 14tooth.

no need for a fuel pump with the diaphragm carby...didn't i link you to the aux-tank topic in yer other thread?
 

kawasaki999

Member
Joined
Jan 18, 2008
Messages
335
Augidog, If you r running the 35 I dont think u will like the 14 tooth, I am going to try the 13 and I live in flat Florida. The 14 gears me high with the 2.2x26 tires.
 

LabRat63

New Member
Joined
Feb 3, 2008
Messages
25
A few more questions (Rats do excel at being pesky ya know :) )

I got the idle set properly now, But I'm having trouble getting the belt to track down the center of the gear. I tried turning the motor and raising one side as in the how-to on GEBE's site, but it didn't work. The belt is hard up against the left side of the gear (as you look at it from the back of the bike). What size of washers do I need to use to shim the gear out? I want to find out before pulling the gear because I have to go buy them.

The stock brake pads are already shot. Which ones are the best to get? And since I'm sure I can't afford them right now, what are the lowest cost ones that will last for a while?
 

kawasaki999

Member
Joined
Jan 18, 2008
Messages
335
You can shim out the bracket at the axcel with washers and if that does not work shim the gear with stainless steel washers, measure the shaft, I think they r 3/8. Cheap pads r at walmart.
 
S

skyl4rk

Guest
You might want to check if you have dragging brakes or if you need grease in your wheel bearings. Dragging brakes will affect gas mileage quite a bit.
 

LabRat63

New Member
Joined
Feb 3, 2008
Messages
25
Getting better. The first time I rode to work from my old house, about 7 miles, I had 1/5 to 1/4 tank left. Yesterday, I rode to work from my new place, 9 miles, and back with a side trip of about a mile and had about an inch left in the tank. Top speed so far was 32.2 MPH on a level stretch. A headwind really slows me down though.
 
Last edited:
Top