Poor Gas Mileage 2002 Bonneville America.

[jim staudy]

I got 28 mpg and noticed that it pops whenever I let off the gas. Is it running too rich? What are the stock jets supposed to be? I bought it used with just over 3000 miles on it The pipes are really blue so it must have been lean for a while.

 

[Qship]

Discoloration could just be from a lot of in town riding. That will happen if the pipes run hot a lot.
Should be getting better fuel economy I would think. Tried any fuel system treatments in it yet? Sitting for long periods don't do a machine any favors. Seafoam is good stuff. Used in the correct amounts of course.

 

[jim staudy]

The pipes were really blue when I bought it. I realize most Triumph twins have blue pipes. I did have a 2006 that had like new pipes and it had over 10k miles and the dealer said it was running rich.

 

[243jimb]

I got 28 mpg and noticed that it pops whenever I let off the gas. Is it running too rich? What are the stock jets supposed to be? I bought it used with just over 3000 miles on it The pipes are really blue so it must have been lean for a while.

Do you know what your jet sizes are at the moment? My 2002 returns 60+mpg (imp) and it is not babied. Float levels are another cause of poor mpg if they are too high. Do you know how to check the levels without dismantling the carbs? It's the easiest check to do as no disassembly is required.
Jim.

 

[jim staudy]

I don't know the jet sizes but I do have the Haynes manual does that go through the float level with out removing the carbs?

 

[243jimb]

I don't know the jet sizes but I do have the Haynes manual does that go through the float level with out removing the carbs?

Yes, it does. It can be a little tricky to get the air out of the line and I would suggest taking several readings.

 

[frankster]

If your bike has sat for an extended period of time carbs can certainly have issues. Worse is if it sat with eythnol based gas. Try some Star Tron fuel treatment. A good product and will certainly clean out the carbs. I run it all the time. Hope this helps!

 

[sikatri]

If your bike has sat for an extended period of time carbs can certainly have issues. Worse is if it sat with eythnol based gas. Try some Star Tron fuel treatment. A good product and will certainly clean out the carbs. I run it all the time. Hope this helps!

Do motorcycle’s use different gas treatments than cars or will the same work on both?

 

[jim staudy]

Thanks I'll give it a Try and let you know.

 

[sikatri]

This the stuff?

 

[jim staudy]

That's what I was told.

 

[Greyfell]

Try this, too.

 

[frankster]

I got 28 mpg and noticed that it pops whenever I let off the gas. Is it running too rich? What are the stock jets supposed to be? I bought it used with just over 3000 miles on it The pipes are really blue so it must have been lean for a while.

The Star Tron bottle says "for all gasoline engines" so you should be safe. Give it a shot - a good product.

 

[frankster]

This the stuff?View attachment 49829

That's the stuff!

 

[frankster]

This the stuff?View attachment 49829

That's the stuff!

 

[sikatri]

That's the stuff!

I’ve been using ethanol free gas since there are periods the motorcycle sits. I’m thinking I might add an ounce of this to some of my stored gas. Put an ounce already in the motorcycle’s tank.

 

[Trevor]

I have a 2001 Bonneville and had to re-jet after fitting a K&N air filter and an after-market exhaust which made the bike run lean. I would check to see if the previous owner had made these sort of modifications. A common mod. is also to blank off the air injection to the exhaust ports, this is thought to stop 'popping' in the exhaust on overrun and stop the exhaust header getting over heated. If your bike is running lean I would expect the fuel consumption to decrease. I get the same sort of consumption as 243jimb- 60mpg, 28mpg sounds as if you may have a leak in the fuel tank or lines.

 

[jim staudy]

The original owner installed the mod to stop the air injection. I don't know if he changed the jets after installing after market exhaust. The fact that it's popping and the poor mileage tells me that I need to lean out the jetting. That's my next move. I found a dealer that retired and is doing some light mechanical work on the side.

 

[Trevor]

Sounds like a good plan Jim, I relied on the advice of the local bike shop when re-jetting. The burn state of the plugs will indicate the mixture- mine are mid-grey. Also the most obvious culprit- choke stuck on.

 

[jim staudy]

I got my bike back from the retired dealer and after a 90 mile ride I checked the plugs. They are both burning properly. I then filled up the tank again and can happily report that I now get 38 miles per gallon. All he found wrong was that the carbs weren't synchronized.