Slow degradation in fuel economy (5th gen)

Sad to say I saw no change from using Sea Foam in my bike. Fuel economy stayed at around 33mpg over a number of tanks. I've now fitted a new fuel pressure regulator and will report if that makes a difference.


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You might want to try replacing the fuel filter; whenever I do a seafoam on my cars the first time, I will always replace the filter and it seems to improve the mileage. It is pretty nifty to blow the contents of the filter into a glass and see what the seafoam cleaned out of your system.

 

I might have to look into that; but intuitively I can't see why a blocked filter would affect economy as this is would only reduce fuel flow to the injectors?

So far I have:

• Changed the air filter
• Changed the plugs
• Replaced the thermostat
• Tried SeaFoam
• Replaced the fuel pressure regulator
• Checked the vacuum hoses

None of these has made any appreciable difference to fuel consumption. Next up (if I can be bothered) is to get the injectors cleaned, but to be honest the old girl runs beautifully, so aside from her thirst I am inclined to just accept the less than stellar use of our precious fossil fuel resources.

 

Cadbury64 are your brakes binding?

 

No the brakes are great; I've been through these and cleaned the seals and lubed the sliding pins, and with EBC HH pads they are just brilliant, especially when they have some heat in them. They're my first linked brakes and they make me wonder why anyone would criticise them; the stability under brakes hard into a bend is fabulous. But they don't drag.

 

Dagnabbit I thought I was onto something there.

Is the temperature in a reasonable range? I see 180°F - 220°F depending on the weather. Do not assume that the new thermostat is good. You may be the 1/1000 with a bad part. Alternatively maybe there is air in the system, which I suspect would be indicated in the temperature readings.

Smell the oil. Is there fuel in the oil? I do not know bikes like cars but I presume a loss of compression would result in blowby and significant fuel in the oil.

Could any of the valves be stuck open due to being too tight?

 

The thermostat holds the temps nicely at 77-82C when I'm moving so it works great.

I think there might be a drippy injector as the oil level does seem to creep up a little but as I said I'm inclined to leave that alone. One thing I have learned is that fuel will gravity feed into the rail so if one of the injectors is not sealing it could drip.

Thanks for your suggestions Knight.


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