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bad fuel mileage

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arfdlt2456
L Plate Warrior



Joined: 13 Jul 2015
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PostPosted: 09:25 - 13 Jul 2015    Post subject: bad fuel mileage Reply with quote
I am riding 01 yamaha vstar 650. I'm only getting around 100 120 miles per tank. Last year's ridding season I was getting 250 275 miles per tank. My bike seems to be running fine. It's not acting like it's getting to much fuel. I'm wondering where I should start looking.
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TheGazWaz
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Joined: 12 Feb 2014
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PostPosted: 10:10 - 13 Jul 2015    Post subject: Reply with quote
I’m no expert but I’d probably start by pulling the spark plugs. This can indicate over fuelling if they’re wet. Google up sparkplug colour for definitions of what they should look like.

I’ve just been through a similar experience with low MPG. Changed my air filter and hey presto and extra 20 miles to a tank.
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talkToTheHat
World Chat Champion



Joined: 21 Feb 2012
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PostPosted: 10:43 - 13 Jul 2015    Post subject: Reply with quote
Dragstar 650 engine is similar to the old 535 with a pair of mikuni BDS downdrafts, float covers on left hand side? If so you should be able to get to the important bits of carbs without removing them from the bike.

Check rear brake for play, there should be 30mm pedal movement before the brake comes on. Check front brake spins freely, dirty pistons could mean rubbing brakes. If there is air in the system it could only be rubbing when the brakes are warm, so check your lever feel.

Check plugs as above.

Check oil does is smell strongly of petrol? is there *more* than there should be? is it super thin? If so open float bowls, clean float valve seats and replace float valves. Change oil and filter. Check oil for metal particles

Check fuel level in the float bowls. could just be a bit high and you're running rich. Open float bowl, bend the tang on the float, reassemble, recheck, repeat as required.

When did you last have valve clearances done? I know the 535 needs a check every 4000 miles, suspect the 650 is similarly annoying.
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chris-red
Have you considered a TDM?



Joined: 21 Sep 2005
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PostPosted: 10:57 - 13 Jul 2015    Post subject: Reply with quote
talkToTheHat wrote:


Check rear brake for play, there should be 30mm pedal movement before the brake comes on. .


Really? that seems excessive, I don't think any of my bikes have 30mm of movement across the entire range of lever travel, I.e. from rest to all my weight on it.
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talkToTheHat
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Joined: 21 Feb 2012
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PostPosted: 11:33 - 13 Jul 2015    Post subject: Reply with quote
That's what the owners manual recommends for 535. Is a big old drum at the rear. Is positively agricultural and getting on anything with a disk on the rear requires a few minutes of of rider adjustment somewhere quiet.

I find claims of 275 miles on 16 litres a little optimistic, touching 80mpg on a dragstar? Pull the other one, it has tassels on. I'd consider 50mpg exceptional. That would be 175 miles on a tank.

I get high 50s on the 535 if I can cruise at 55mph, about 42mpg on a backroad thrash, mid 40s 2-up at motorway speed and maybe as bad as 35mpg on short trips around town, but I am heavy handed with the bike.

Blowing exhaust killed my fuel economy.

Check plugs, filters, service servicables. Double-check your figures, and double check your riding, comparing like trips for like. Are you having more fun this year.
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 11:45 - 13 Jul 2015    Post subject: Reply with quote
MPG is never a static figure but
80mpg sounds fantastic and
40s realistic according to fuelly

https://www.fuelly.com/motorcycle/yamaha/vstar_650_classic

BTW check its set to UK in the upper LH tick box
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Teflon-Mike
tl;dr



Joined: 01 Jun 2010
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PostPosted: 13:32 - 13 Jul 2015    Post subject: Re: bad fuel mileage Reply with quote
arfdlt2456 wrote:
Last year's ridding season

Power is Rate of change of Energy.. so as a rate at which petrol get's turned into motion, MPG is an expression of 'Power'.. and where the power 'rating' given in the specs is more a 'potential' rating of how much power the motor might make at certain revs and load, MPG is actually a better guide of how much power you are 'using'.
As such, actual real MPG figures vary far more from what they say in the specs than top-speeds... My VF1000, was reportedly 'rather thirsty' with a book figure of 30mpg... was rather perturbed then to discover I could get that down as low as the 'teens' caning the thing along by-passes between roundabouts and city commuting... but conversely, quite relieving to discover that bimbling about the Cotswold on a Sunday, I could get it up near 70!.. a more extreme example, but it effects all bikes, and the 750, is supposed to return 45mph according to the book, but I can get that down in the 20's caning it every where, or doing short runs, or up nudging 70, if I'm on a longer run just bimbling.
One thing about the 750, is it's air-cooled, and needs a bit of choke to start, unless its a nice warm day, and we ent had so many of them this summer, so not had many choke-free start ups this year....

So, given the vagaries of mpg, this years weather could easily account for a bit of a drop, using more choke on start up, and more start-ups would make bigger difference; next, others suggestions imply that 'last year' you got particularly 'good' consumption for the bike.. has the way you use it changed since last year? And are you riding it shall we say 'more confidently'.. using more power, more often, bringing mpg down?

Might be little wrong with the bike... and if there is, as has been suggested, first call is basic service items; plugs, filters. tappets, carb-balence etc.. even a weak battery.. silly one that, but if the battery is a bit tired and takes a bit longer to spin the motor into life... it's more unused fuel sucked in, possibly more, on choke, not being 'used' to do anything.
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RhynoCZ
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Joined: 09 Mar 2012
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PostPosted: 13:37 - 13 Jul 2015    Post subject: Reply with quote
chris-red wrote:
talkToTheHat wrote:


Check rear brake for play, there should be 30mm pedal movement before the brake comes on. .


Really? that seems excessive, I don't think any of my bikes have 30mm of movement across the entire range of lever travel, I.e. from rest to all my weight on it.


I was about to advice you the same thing + check the wheel bearings and tyre pressure on both wheels. Dragging brakes, worn bearings, low tyre pressure can do alot to your MPG. Thumbs Up
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monkeybiker
World Chat Champion



Joined: 23 Sep 2014
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PostPosted: 17:37 - 13 Jul 2015    Post subject: Reply with quote
I'd be checking for fuel leaks Shocked
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Casper
World Chat Champion



Joined: 12 Jul 2010
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PostPosted: 18:41 - 13 Jul 2015    Post subject: Reply with quote
How many miles to the tank? Are you sure?

https://www.eaglerider.com/rentals/yamaha-vstar-650
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talkToTheHat
World Chat Champion



Joined: 21 Feb 2012
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PostPosted: 12:57 - 14 Jul 2015    Post subject: Re: bad fuel mileage Reply with quote
Teflon-Mike wrote:
MPG is an expression of 'Power'


Yes, but power consumed, not power effectively transferred into useful work. The efficiency of a petrol engine varies by gear, temperature, mixture, compression and throttle position. A thereabouts closed throttle is a significant loss known as pumping loss, thus in a high gear and thereabouts idling may generate more internal losses than a lower gear and more throttle opening. This is amplified by rich idle circuits.

But by Tef logic my 535 makes more power than an R1. Nope it's shorter geared and the engine is significantly more primative and less efficient. The R1 is also more aerodynamic. Thus the R1 gets better fuel economy whilst being significantly quicker than my tired old cruiser.
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