Tips for improving MPG

[hubskadub]

I have the brand new Mikuni VM32 carbs on my 74 T500 (VM32-193, VM32-33) and they fuel great! Bike runs strong all over, pulls over 100mph, no flat spots or hesitations and idles perfectly. Granted this took a lot of tinkering, but it works now!

Here is my issue. It only gets like 27mpg... 3.5 gallon tank means no long days in the saddle without many stops.

I replaced the wheel bearings, no change. Brakes are not dragging, clutch is rock solid, I am running pod filters only because these new carbs have bigger inlets and the stock airbox rubber won't fit.

I feel like I am a little ham-handed and get in the throttle a lot when riding it, but I mostly see people posting about getting 50mpg on these bikes. Is riding it fast going to cut the MPG almost in half??

Am I just gonna have to get used to stopping for gas or are there some potential fixes??

[ro55o]

Hi, any chance you could share what configuration of jets needle etc. you ended up with on the new Mikunis?
I was thinking of giving them a try.


Hope you get an answer to the mpg, but mine drinks the juice too if I hammer it.
Thanks
Ross

[karl pa]

but I mostly see people posting about getting 50mpg on these bikes

On my 75 T500 I get around 35 mpg, On my 76 GT500 I get around 40 mpg. Both are stock setups and my riding style is easy on the throttle, If you start cranking the throttle open the mpg starts dropping fast.

[Craig380]

As said above, any big 2-stroke will make the juice magically disappear if you're working them hard, it's one of their party tricks

Also the T500 always drank more juice than the GT500: the GT500 had a number of detail changes which reduced peak power, lowered the torque peak and were intended to improve economy.

I converted your mpg figure to UK miles per gallon (I can't work with your 16oz pints, a pint should have 20oz, dammit ) and it's around 34mpg, which I think is OK for a modified bike.

If the spark plug colours look good then I would suggest leaving it alone, and simply refuelling every 80 miles or so (I usually need to empty my personal tank at about 80 miles, anyway ). Fuel is cheap, fixing holed / seized pistons from going too lean on the jetting is expensive ...

And by the way, she looks like a very nice bike indeed. Enjoy!

[tricky1962]

Craig - note the US fl oz is smaller than the UK one, not sure if you're aware - apologise if you are
I get a comfortable 150 miles per tank before I have to switch to reserve so maybe I'm a but delicate on the throttle

[sportston]

My old man had a KH250 that did 22mpg (UK) at best on pod filters and micron pipes.
It's something you'll have to put up with I think.
You may find your economy, and even performance, improves a little if you can find a way of putting a standard airbox back on it.

[Alan H]

If you buy fuel in Imperial gallons, rather than US ones, you will see an immediate 18% increase in 'gas mileage'.

Another option would be to get your weight below 150 lbs as most of us did when we were 21 years old back in the 70s.......

Failing all that, adjust the brakes, don't race anyone, keep the revs below 4000 and the fuel mileage will be much better.

Or bearing in mind that in the UK, our fuel is over (equivalent) $8 a gallon, stop complaining and enjoy the bike for what it is. Cheaper option is walking or public transport, you fancy that?

My GT550 can get 50 mpg+ if I keep below 50 mph and small throttle openings, or 20mpg if I spank it. I know what's more fun. Sod fuel cost.
How old are you FFS?

[Craig380]

Craig - note the US fl oz is smaller than the UK one, not sure if you're aware - apologise if you are

It's the other way around - a US fl oz is just over 1ml (or about 3%) more than a UK fl oz, but a US pint is 16fl oz = 473ml rather than our 568ml ... so we always get more miles per gallon

[hubskadub]

It's not really about fuel cost, more about being able to pass a few gas stations on a day ride... I will do a few rides keeping the revs down and see what the result is.

I'm no spring chicken BTW. I will be 45 in 2 weeks and I have been riding since I was 18.

[dorT500]

....I will be 45 in 2 weeks...........

aahhh, 45.......I remember when I was 45.....kinda.




I don't get any better than around 30 MPG but I don't keep '75 T500 tuned up as often as I should.

[Alan H]

It's not really about fuel cost, more about being able to pass a few gas stations on a day ride... I will do a few rides keeping the revs down and see what the result is.

I'm no spring chicken BTW. I will be 45 in 2 weeks and I have been riding since I was 18.

It's nice to stop for the occasional coffee and 'P' anyway.
As far as the spring chicken goes, I bought my first GT550J back in 1972 as a 21st birthday present to myself.
I now have four - sold one last year - one running, one in resto and 'spares', plus a GT750B and a GSX1400 for times when I need a bit more.......

[tricky1962]

Craig - note the US fl oz is smaller than the UK one, not sure if you're aware - apologise if you are

It's the other way around - a US fl oz is just over 1ml (or about 3%) more than a UK fl oz, but a US pint is 16fl oz = 473ml rather than our 568ml ... so we always get more miles per gallon

Cheers - I got that wrong then!

[ConnerVT]

....I will be 45 in 2 weeks...........

aahhh, 45.......I remember when I was 45.....kinda.

Who are you kidding? You have a hard enough time remembering the two weeks.

[dorT500]

....I will be 45 in 2 weeks...........

aahhh, 45.......I remember when I was 45.....kinda.

Who are you kidding? You have a hard enough time remembering the two weeks.

What kind of misconception are you under this time?

[hubskadub]

Hi, any chance you could share what configuration of jets needle etc. you ended up with on the new Mikunis?
I was thinking of giving them a try.


Hope you get an answer to the mpg, but mine drinks the juice too if I hammer it.
Thanks
Ross

I got the stock T500 rebuild kits for the stock carbs and put everything in as normal if I am not mistaken... They are essentially the same carb as back in the 70's, just the body is bigger and there are more vents.

The fit is tight since the bodies are bigger. The left carb sits right on the case. You have to use the early T500 short intakes for them to fit and you will have to run pod filters.

Only tweaks I think I had the hardest time with was getting the idle right and the air screws so it revs good.