Gasoline mileage on my homebuilt bikes

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
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north carolina
I started my test just now I need to put the results down before I forget

33cc chainsaw engine bike friction drive. 20" rear wheel 3/4" drive roller covered with fine sand and Jb weld. Effective size of the roller approx 1"

3.5miles @ 6oz of gasoline. Effective mpg approx 74.6... I had hoped for more. I do have some hills on my test track so this is the average around my neighborhood city driving. Shoes was right a little over 10miles per tank. Those little weed eater tanks are pretty close to a pint. If you are going more than ten miles you better have spare gas.

The ryobi 31 cc did the same test track with with less gasoline

3.5miles @ 5 oz = 89.6mpg and change its a significant difference but so is the performance I noticed. This bike also has the 3/4 inch drive with sand and jb weld. It is running knobbie tires though which may account for the slightly worse performance.

Results for the 42cc chainsaw engine.

3.5miles @ approx 7oz = 64mpg The results are what you would expect. The tire is a smooth road tire. The drive wheel is much larger than on the other two bikes. about 1 1/2 inches as a matter of fact. It is also covered with jbweld and sand.

The smaller engine got the best gas mileage with good performance . The slight larger engine got 15mpg less but also got a noticeable increase in power. The still larger engine got 30mpg less than the smallest but is significantly more powerful.

I would sacrifice the milage for the better climbing of the hills I think. The 33 also seems to do a little better on the flat... but for economy in purchase and use you cant beat the 31cc weed whacker as a helper engine.

The 42cc is by far the better cruiser engine. On the small or moderate hills it is a dandy. On the long steep ones I remember it as being a bit of a dog. I think that is because of the size of the drive wheel.

But for my short run errands it is over kill. The big drive wheel makes it less acceptable for the big hills around here.

I think the best all around bike for this area would be the 33cc with the small drive wheel on the full suspension frame. Now that I know how to mount an engine on it, when the ryobi goes I expect I will switch to that frame.

So there you have my results. Very unscientific I admit, but more scientific than my swag system estimate. I had top alter the figures. i double checked my map and found that I hadn't take everything into consideration. Like I left part of the test track off. So anyway these are the numbers now.
 
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Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
63
up north now
I think I was getting around 170 with my Bike Bug...nowhere near what they claimed. It was, however, a 23cc engine.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I think some of it is the area I'm riding it in. The test route has a lot of small and larger hills heck it's all up and now no flats to let it wind out. Still as a comparison of engine sizes it's close. Also there are no gears involved it is all straight friction drive which has to eat the gas up as well.

I'm guess just from the data that a 25cc would get about a hundred set up to run as a friction drive on my course. Also all these bikes are rear wheel drive now. I think the ryobi did much better as a front wheel drive. It was a little heavy but it was doable. It is just easier to get in and out of my garage if it is rear mounted. Sounds screwy I know.

Also all my bikes have 20" rear wheels they might do better on a 26" but I don't know that for a fact. Though could account for why the ryobi did better on the front wheel as well. All the front wheels are 26"

If I ever went for a brand new bike. I think I would go for a 26" cruiser with a front hand brake. Rear mount a 42cc chainsaw with a 3/4 in drive wheel. That seems about ideal to me at the moment.

I
 

comfortableshoes

New Member
Jul 22, 2008
606
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Beverly, MA USA
If you think about it your getting pretty darn good gas mileage. Imagine what it would be in a car- anywhere form 15 to 35mpg... In my book the lowest of your MPG is better than that. And it's on something you built with your own 2 hands and there is nothing that can replace that feeling. (gave multiple pep talks today at work, still in pep talk mode, slap me silly later.)

I agree the rear mount is easier to move around, I think its because the front is lighter anyway and the bike is easy to pivot around on the rear wheel... Speaking of that, I had to move the OCC Chopper around in my garage, man its that thing heavy, it makes my MadWagon (Heavy Steel framed) seem like a feather in comparison.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
As I mentioned before I took the china bike out for a ride the other day after I got all the problems fixed. That thing is a monster at an uphill stop sign. I found it way harder to get started from a dead stop.