Slow then sudden increase in fuel consumption

[Oakie]

600cc 2001 Bandit

Used to get about 18km/l and run onto reserve at 162 miles before running onto reserve
Slowly started to creep down ... first noticed hitting reserve at 155 miles after a safe riding session at Ruapuna about 9 months ago which I put down to different riding. Stayed about there for a bit and then I noticed it starting to splutter at 145 miles.

Last week it lurched down to 13.6km/l and then today ... 123 miles and reserve required which worked out to 12.9km/l

Thats a 30% increase. It doesn't coincide with anything done to the bike recently or a change in use. I did get a new chain and sprockets in February and new brake pads front and rear at the same time but the major dip in consumption has only just happened in the last month.

Performance hasn't changed. Still good
Not blowing visible exhaust fumes.
No smell of leaking petrol.

Anyone have any ideas?

[Ender EnZed]

Has your pie consumption changed lately?

[nzspokes]

Sniff ya oil? Smell of gas? Oil level gone up?

Also drain your airbox to see what comes out.

[Oakie]

No extra pies
Oil looks and smells normal
Airbox ... that is a bit of a mission I believe but I know what you're getting at.

Oh, choke doesn't seem to be stuck on either.

[unstuck]

Airfilter blocked?

[nzspokes]

No extra pies
Oil looks and smells normal
Airbox ... that is a bit of a mission I believe but I know what you're getting at.

Oh, choke doesn't seem to be stuck on either.

There will be a little plug in the end of a rubber hose under the bike. Pull it out and see what comes out.

May pay to put a jar there.

[Oakie]

There will be a little plug in the end of a rubber hose under the bike. Pull it out and see what comes out.

May pay to put a jar there.

Ta. Sounds like a job for tomorrow in the daylight. Tonight's job is to go and buy a bottle of Baileys for $22 and test it. Extensively. Perhaps I can use the empty bottle to catch any goo that comes out of that alleged rubber hose tomorrow?

[nzspokes]

Ta. Sounds like a job for tomorrow in the daylight. Tonight's job is to go and buy a bottle of Baileys for $22 and test it. Extensively. Perhaps I can use the empty bottle to catch any goo that comes out of that alleged rubber hose tomorrow?

Yup, thats the most important job for the night. :yes:

[EJK]

Have you checked the fuel price recently? $20 of gas of a few days ago ain't $20 of gas today.

[GSeX]

Riding with the choke left on a little bit and then a lot :innocent:

[scumdog]

Forgetting to change into top gear??:blink:

[Oakie]

Forgetting to change into top gear??:blink:

Forgetting? I hardly ever get the chance nowdays. Only left town once since about the start of winter :(

[mossy1200]

Forgetting? I hardly ever get the chance nowdays. Only left town once since about the start of winter :(

There is the answer, your comparing town riding to open road millage.

18k per litre. Are you sure that's not 18mile per litre as my 1400 runs at 19-20k per litre with 400km range per tank.

[Oakie]

There is the answer, your comparing town riding to open road millage.

18k per litre. Are you sure that's not 18mile per litre as my 1400 runs at 19-20k per litre with 400km range per tank.

Nah. I've been mostly commuting since 2010 and nothing much has changed ... apart from the fuel consumption. Did go for a bit of a hoon to a country pub three weeks ago and hoped that might have given it a bit of a clean out but it has got worse instead.

Yep ... it averaged out at about 18.5 km/l over a very long time (like 3 years) with a high of 20.5 ... then dropped noticeably over a very short time. My speedo does read in miles which is a pain but easy enough to convert.

[T.W.R]

Could be time for a new set of plugs

[kinger]

Wheels spin freely? No bearing/brake drag?

[Oakie]

Could be time for a new set of plugs

Checked during service in Feb 4000km ago although they are now 20000km old


Wheels spin freely? No bearing/brake drag?
Seem to be OK but probably worth checking again this morning.

[Drew]

Valve clearances would be high on the list of things to check. If it's an American model, I wonder if the catalytic converter isn't clogged up a bit.

[Oakie]

There will be a little plug in the end of a rubber hose under the bike. Pull it out and see what comes out.

May pay to put a jar there.

Did that and thanks for suggesting the jar! Got half a cup of water with a bit of oil in it. Came out looking about the colour of a weak cup of tea. You reckon half a cup would be enough to upset things?


Valve clearances would be high on the list of things to check. If it's an American model, I wonder if the catalytic converter isn't clogged up a bit.

Have thought about valve clearances. Done just on 20000k ago so they should still be OK? UK model so no catalytic converter.

[T.W.R]

Checked during service in Feb 4000km ago although they are now 20000km old

Can start to die unexpectedly though.

You've got a few options to look at like mentioned in other posts, but 12 simple checks are:

1) Drivers erroneous operation (Very doubtful)
2) Slipping clutch (You'd know)
3) Dragging brake
4) Insufficient tyre pressure (Doubtful)
5) Decreased compression pressure
6) Fuel leakage (you'd see it)
7) Maladjusted idling speed
8) Contaminated air cleaner
9) Maladjusted carburettor
10) Clogged muffler (Doubtful)
11) Poor spark
12) Maladjusted ignition timing

So you've got a few options to check, you said you'd had the brakes done so in reality that'd lessen over time not increase if they were dragging.
Valves you'd hear them if they were that far out of adjustment to cause that much change in consumption & it'd effect performance too.

[mossy1200]

Did that and thanks for suggesting the jar! Got half a cup of water with a bit of oil in it. Came out looking about the colour of a weak cup of tea. You reckon half a cup would be enough to upset things?



Have thought about valve clearances. Done just on 20000k ago so they should still be OK? UK model so no catalytic converter.

I think you need drop match into jar to confirm if its water or petrol.

[Oakie]

Can start to die unexpectedly though.

You've got a few options to look at like mentioned in other posts, but 12 simple checks are:

1) Drivers erroneous operation (Very doubtful)
2) Slipping clutch (You'd know)
3) Dragging brake
4) Insufficient tyre pressure (Doubtful)
5) Decreased compression pressure
6) Fuel leakage (you'd see it)
7) Maladjusted idling speed
8) Contaminated air cleaner
9) Maladjusted carburettor
10) Clogged muffler (Doubtful)
11) Poor spark
12) Maladjusted ignition timing

So you've got a few options to check, you said you'd had the brakes done so in reality that'd lessen over time not increase if they were dragging.
Valves you'd hear them if they were that far out of adjustment to cause that much change in consumption & it'd effect performance too.

Thanks for that. I can understand the maladjusted stuff but with no loss in performance it's just got me baffled.


I think you need drop match into jar to confirm if its water or petrol.

Oh believe me ... there was a large part of me that wanted to do that.

[Oakie]

Clogged up air filter is the spanner-man's assumption. Two years riding on Christchurch's dusty roasd on what is apparently quit a small filter element. Also recommended replacing the plugs as running with the clogged up filter won't have done them any good. By this time next week I guess I'll know.