GSXR SRAD fuel consumption

[SMOKEU]

A few thousand kilometers ago (3,000-4000km) I had some pretty bad carby problems. I took the bike to a mechanic who stripped, cleaned, balanced the carbs, fixed fucked emulsion tubes, set float heights etc and after that the fuel consumption dropped by around 25% to about 6L/100km on the open road. The fuel filters were replaced at the same time. I'm pretty sure the bike has Yoshimura MJN jets in it, which came with the bike.

Over the past 2,000km or so, I've noticed a steady increase in the fuel consumption of my 600 SRAD. The bike still runs great throughout the rev range, and I don't think it's down on power. But every time I fill up, I notice that it's using more and more fuel. I'm certainly not riding it harder, as even a gentle open road commute at 100kmh now is using more fuel than a hard ride over to Akaroa 2,000km ago.

The spark plugs (the same kind as suggested in my workshop manual for this bike) are around 10,000km old, and were cleaned and gapped about 3,000km ago. The air filter is also around 10,000km old, and it looked very clean when I last saw it about 3,000km ago. What could be causing this? Is it time for another carby strip down? (it better fucking not be, they've been apart twice in the past 10,000km). I always use the same fuel; Z 95.

[Vinz0r]

First off, are your fuel consumption measurements reliable? Using liters filled per distance traveled on the odo?
How big of an increase are we talking?

[FJRider]

A few thousand kilometers ago (3,000-4000km) I had some pretty bad carby problems. I took the bike to a mechanic who stripped, cleaned, balanced the carbs, fixed fucked emulsion tubes, set float heights etc and after that the fuel consumption dropped by around 25% to about 6L/100km on the open road. The fuel filters were replaced at the same time. I'm pretty sure the bike has Yoshimura MJN jets in it, which came with the bike.

Such maintenance should not just be an annual (one off) event ... to be done when you think/know there is a problem. The longer the time you leave such things ... the more likely there will be increased (unnecessary) fuel use. And ... less HP available for use. The gradual loss of a few ponies (over a few months) is seldom easily noticed.

Fuel consumption varies ... even over the same roads. At best ... you can only get average over a period of time. Measured in months or even years. My average fuel consumption (for the FJ1200) over most years is 7.1 liters per 100 km's.


The spark plugs (the same kind as suggested in my workshop manual for this bike) are around 10,000km old, and were cleaned and gapped about 3,000km ago. The air filter is also around 10,000km old, and it looked very clean when I last saw it about 3,000km ago. What could be causing this? Is it time for another carby strip down? (it better fucking not be, they've been apart twice in the past 10,000km). I always use the same fuel; Z 95.

Many replace the plugs after 5000 km's ...as well as clean/replace the air/fuel filters. The air filters are the main cause for extra fuel consumption (aside from the twitchy right hands) ... And you cant clean them too often ... especially on the Christchurch/Canterbury roads at present. A blocked filter (even just partially) makes it run richer ...

Using the same fuel means nothing .. it all depends on what gets pumped out of the station tanks. Not all tanks are created equal ... nor is the fuel quality IN them always the same. If the tanks are getting low ... or the fuel sales volume is lower ... the more likely you get the crap/water at the bottom of the tanks.

[SMOKEU]

First off, are your fuel consumption measurements reliable? Using liters filled per distance traveled on the odo?
How big of an increase are we talking?

My measurements are reliable. I take the same route over to Akaroa every time, and I used to do it with about 9L of fuel, there and back. Now it's about 11L. So what's happening with that extra 2L of fuel?


Such maintenance should not just be an annual (one off) event ... to be done when you think/know there is a problem. The longer the time you leave such things ... the more likely there will be increased (unnecessary) fuel use. And ... less HP available for use. The gradual loss of a few ponies (over a few months) is seldom easily noticed.

Fuel consumption varies ... even over the same roads. At best ... you can only get average over a period of time. Measured in months or even years. My average fuel consumption (for the FJ1200) over most years is 7.1 liters per 100 km's.



Many replace the plugs after 5000 km's ...as well as clean/replace the air/fuel filters. The air filters are the main cause for extra fuel consumption (aside from the twitchy right hands) ... And you cant clean them too often ... especially on the Christchurch/Canterbury roads at present. A blocked filter (even just partially) makes it run richer ...

Using the same fuel means nothing .. it all depends on what gets pumped out of the station tanks. Not all tanks are created equal ... nor is the fuel quality IN them always the same. If the tanks are getting low ... or the fuel sales volume is lower ... the more likely you get the crap/water at the bottom of the tanks.

I'll start by replacing the spark plugs and washing and re-oiling the foam K&N air filter. Should I wash the air filter in hot soapy water, then wash it in turpentine, then rinse it clean with water, dry it out, and re-apply standard foam air filter oil?

[FJRider]

My measurements are reliable. I take the same route over to Akaroa every time, and I used to do it with about 9L of fuel, there and back. Now it's about 11L. So what's happening with that extra 2L of fuel?

The same route maybe ... but ... always the same weather conditions (head winds ??) ... the same traffic conditions (same number of vehicles overtaken) ... and the same mood/style/speed of riding ??? Even luggage carried can make a difference.

Such variables often not taken into account.


I'll start by replacing the spark plugs and washing and re-oiling the foam K&N air filter. Should I wash the air filter in hot soapy water, then wash it in turpentine, then rinse it clean with water, dry it out, and re-apply standard foam air filter oil?

Usual policy is just warm soapy water. Dry ... then re-oil. (Well rung out of course) Excess oil is the same as a dirty filter ...

Just remember ... if compression has dropped ... (even slightly) an extra 2 liters is not unheard of. How long since the valves were looked at .. ???

[hayd3n]

my mechanic has always said never reuse spark plugs , always replace

[SMOKEU]

The same route maybe ... but ... always the same weather conditions (head winds ??) ... the same traffic conditions (same number of vehicles overtaken) ... and the same mood/style/speed of riding ??? Even luggage carried can make a difference.

Such variables often not taken into account.

Usual policy is just warm soapy water. Dry ... then re-oil. (Well rung out of course) Excess oil is the same as a dirty filter ...

Just remember ... if compression has dropped ... (even slightly) an extra 2 liters is not unheard of. How long since the valves were looked at .. ???

Well, I can certainly say that after many trips down the same route, the fuel consumption would be pretty similar, around 6-6.5L/100km, so around 9, never more than 10L. Now, even if I ride it gentle the whole way in light traffic with no headwind, it's using more fuel than it used to when riding hard the whole way.

The valve clearances were checked about 2,000km ago, and the mechanic said they were pretty good, but he adjusted them to within spec. Cam chain tensioner has been replaced at the same time.

[FJRider]

Well, I can certainly say that after many trips down the same route, the fuel consumption would be pretty similar, around 6-6.5L/100km, so around 9, never more than 10L. Now, even if I ride it gentle the whole way in light traffic with no headwind, it's using more fuel than it used to when riding hard the whole way.

The valve clearances were checked about 2,000km ago, and the mechanic said they were pretty good, but he adjusted them to within spec. Cam chain tensioner has been replaced at the same time.

Wash your air filter and see how much crap was in it. Check how tightly it fits too ... a lot of engine issues follow on from air filter issues.

[SMOKEU]

Wash your air filter and see how much crap was in it. Check how tightly it fits too ... a lot of engine issues follow on from air filter issues.

I'll service the air filter and replace the spark plugs while I'm at it.

[FJRider]

I'll service the air filter and replace the spark plugs while I'm at it.

Even look at the high tension leads and plug caps ... even minor shorting out can lose power at the gaps ...

Run the bike in the dark and look for sparks from the leads. Most shorts will be seen (and sometimes heard at idle) ... but where leads touch engine or frame ... it may NOT show. So clear all leads from such first.
New leads may even help. The usual voltage/conductivity checks in the system is worth time spent.

Check brake pads retract properly and as they should.

Have you tried running on 91 .. ??? running on 95 isn't an automatic horsepower gain ... often just a waste of money paying the extra money ...

[SMOKEU]

Even look at the high tension leads and plug caps ... even minor shorting out can lose power at the gaps ...

Run the bike in the dark and look for sparks from the leads. Most shorts will be seen (and sometimes heard at idle) ... but where leads touch engine or frame ... it may NOT show. So clear all leads from such first.
New leads may even help. The usual voltage/conductivity checks in the system is worth time spent.

Check brake pads retract properly and as they should.

Have you tried running on 91 .. ??? running on 95 isn't an automatic horsepower gain ... often just a waste of money paying the extra money ...

In order to get to the plugs and leads, the air box has to be taken off and the fuel tank popped up with a block of wood. I'll Maori something up tonight maybe, so I can have a look. I know fuck all about ignition systems, so I've included a pic to show. It doesn't have traditional leads like cars that I've seen before.

Also, you can see that the air box has foam that connects to the ram air tubes to try and seal the connection, but that foam is fucked so there's a gap between the air box and ram air system. What do I do to replace that foam?

All brake calipers have been stripped and serviced with new fluid less than 2,000km ago (a couple of months) as the rear caliper was sticking so I thought I'd have all the brakes serviced. I haven't tried running on 91, since it's a high compression engine I thought 95 would be less prone to detonation.

Click on the pics to make them bigger.

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293659

[FJRider]

In order to get to the plugs and leads, the air box has to be taken off and the fuel tank popped up with a block of wood. I'll Maori something up tonight maybe, so I can have a look. I know fuck all about ignition systems, so I've included a pic to show. It doesn't have traditional leads like cars that I've seen before.

Dont panic about a direct look at every part of the leads ... any short should be seen (and heard if you are listening for one) in the dark. Even if only faint reflected light ...

One dirty plug can indicate spark issues on that cylinder.


What do I do to replace that foam?

Para rubber ... or most upholsterers. Such leaks will negate any "Ram Air" advantage at speed ... if it had much to start with. I gather the air filter is in the airbox and sealing well.


I haven't tried running on 91, since it's a high compression engine I thought 95 would be less prone to detonation.

[SMOKEU]

Dont panic about a direct look at every part of the leads ... any short should be seen (and heard if you are listening for one) in the dark. Even if only faint reflected light ...

One dirty plug can indicate spark issues on that cylinder.

Para rubber ... or most upholsterers. Such leaks will negate any "Ram Air" advantage at speed ... if it had much to start with. I gather the air filter is in the airbox and sealing well.

Good thinking, I'll have a look in the dark. I will also pay close attention to all the spark plugs to see if they all look the same, or if one (or more) is fouled. Those NGK spark plug charts are awesome.

I'll check out Para Rubber. What I was thinking of doing is cutting a rectangular piece of foam slightly bigger than the airbox ram air holes, then use epoxy resin to stick the whole thing on. After it's dry I can use a knife to cut the foam to size and shape.

Those K&N service kits are a bit of a ripoff aren't they? My air filter is a K&N but since it looks like an ordinary foam filter I might actually use normal air filter foam oil on it.

[FJRider]

I'll check out Para Rubber. What I was thinking of doing is cutting a rectangular piece of foam slightly bigger than the airbox ram air holes, then use epoxy resin to stick the whole thing on. After it's dry I can use a knife to cut the foam to size and shape.

Those K&N service kits are a bit of a ripoff aren't they? My air filter is a K&N but since it looks like an ordinary foam filter I might actually use normal air filter foam oil on it.

Sounds like a plan ...


I'm certainly not riding it harder, as even a gentle open road commute at 100kmh now is using more fuel than a hard ride over to Akaroa 2,000km ago.

An interesting comment ... as I get better economy at 120 km/hr than sitting at 100. Lower speeds do make it on the sluggish side ... and can use a bit more fuel to get up to higher HP making revs/speeds. Just "Going slow" is not an automatic "economical" mode ...

Max HP is about red line (usually) and on my bike .. a bit over 4000 RPM at the open road speed limit. Not even half way to the red ...

[AllanB]

I'd follow K&N's washing instructions and use their cleaner/oil only. K&N state the things don't need cleaning for friggen ages (50,000 MILES in normal conditions!!!!!).

Can gets cleaning bits here - very good quick service from a NZ site, there is a link to tell you how to clean them.

http://nzairfilter.co.nz/cleaning-kits/

Plugs - again these should last for ages on a modern bike - mine calls for replacement every 24,000 kms - darn things looked sweet when I changed them over last time.