MB Speed and Economy

[DearthVader]

I have a Schwinn Jaguar with a 66cc engine and a 41 tooth sprocket. So far I'm very pleased with the setup but there seems to be some discrepancy in my speed and fuel economy figures in comparison to others.

It cruises comfortably at about 19-20mph and if I hold it wide open I can hit 23-24 but that's with the motor vibrating at an uncomfortable level. I see several post from people claiming to cruise at 25 with a top speed over 30mph on a 44 tooth sprocket. How in the world does that happen?

I'm not complaining about fuel economy but there's no way I'm getting over 100mpg like so many people claim. I ride conservatively by coasting downhills and often times peddling uphills. Raw figures indicate I'm getting around 70-80mpg.

Has anyone had these same experiences?

[Dave31]

My mpg ranges from 60-120, what cause's it too change so drastically? I have no ideal. I do understand that sometimes I run it harder then other times and sometimes I stay on relatively flat roads to climbing mountains.

But I get good and bad mileage wot, flat, and mountains so I cannot explain it. I never said it because I thought no one would believe me, but my best mileage was going up Mount Lemmon wot for over 20 miles. I took extra fuel because I thought I would be low once I reached the top of the mountain, I was shocked to see I barley used any fuel at all. It was just a hair lower from where I started at the bottom of the mountain.

If your motor is relatively new, it may get better mileage after time.

[BarelyAWake]

From what you've said it sounds like yer motor may not be broken in yet - it's a night and day difference. Everything you described sounds exactly like mine before it finally stopped acting silly and began to run properly.

If not, if you have well over 200 miles on it and it's still vibrating like **** - perhaps it's not mounted as securely as it could be? Excessive vibration can cause fuel frothing in the carb making it run worse, an annoying cycle if there ever was one (mine took over 300mi to break in, I blame good oil).

Stuff to look at;

plug coloration and fuel/air mix
air leaks
properly sized gaskets*
centered rear sprocket

It does really sound like yer motor is just still "too new" though, that's an easy fix


*The center hole in these gaskets is usually far smaller than their respective manifolds, make sure the hole is as big around as the inside diameter of the pipe it goes to.

[bairdco]

my car gets 11 miles to the gallon. i'm not complainin...

[stv1jzgte]

Originally Posted by bairdco

my car gets 11 miles to the gallon. i'm not complainin...

bairdco are you drivin a tank?

[Bikeguy Joe]

Sounds to me like you are running a little too rich, Dearth.

[DearthVader]

Originally Posted by BarelyAWake

From what you've said it sounds like yer motor may not be broken in yet - it's a night and day difference. Everything you described sounds exactly like mine before it finally stopped acting silly and began to run properly.

If not, if you have well over 200 miles on it and it's still vibrating like **** - perhaps it's not mounted as securely as it could be? Excessive vibration can cause fuel frothing in the carb making it run worse, an annoying cycle if there ever was one (mine took over 300mi to break in, I blame good oil).

Stuff to look at;

plug coloration and fuel/air mix
air leaks
properly sized gaskets*
centered rear sprocket

It does really sound like yer motor is just still "too new" though, that's an easy fix


*The center hole in these gaskets is usually far smaller than their respective manifolds, make sure the hole is as big around as the inside diameter of the pipe it goes to.

Perhaps it's not broken in enough, yet. I thought it was broken in because I saw a significant change in torque over the first thee-four tanks and haven't noticed much change since.

I do feel I was running a little too rich because when I would turn the fuel valve off and let the engine die on it's own it would rev up right at the last second before it died. According to many these forums that indicates a rich condition. I moved the needle down one notch last week and now it doesn't rev right before dying when I close the fuel valve. I had been checking the plug color every so often and it looked good (at least I thought it did) so I thought my mixture was good. Perhaps it should have been a lighter color brown. I'm going to keep checking the plug now that the needle is in the second position and see how that goes.

I checked the exhaust gasket (haven't got around to checking the intake gasket yet) and its really close to the same size as the exhaust manifold. The exhaust pipe connection on the other hand is smaller than the manifold but there's not much left to widen the hole. I did, however; drill (5) 3/16 holes in the end of the pipe and it helps my acceleration significantly. Perhaps I'll start to see fuel economy go up now?

Either way, I really enjoy riding this bike and look forward to many more miles in the future.

[stv1jzgte]

That rev up is normal and means its leaning out from lack of fuel as you've turned the feed off

[DonnnN]

Maybe you got an air leak?

Try this...

1) Start your engine like you normally would..
2) Pull the clutch in and get off your bike
3) Turn the choke thingy to on..

Your engine should die immediately if there are no air leaks..
If there is one the engine will not die..

[Kevlarr]

Moving the clip on the needle down makes it richer not leaner. I moved my clip to the top notch and not only did my engine run better I gained about another 8-10 miles to the tank.