My 07 XB12STT fan comes on but seems to stay on making it so hot under the seat after about 40 miles that I need to stop and cool myself down. I had a rear shock changed under warranty maybe because the original one overheated causing it to leak? The shock gets really hot as does everything else under the seat.

The dealer checked the fan and the temperature switch and said they were working fine. It does switch off occasionally but is running most of the time once the bike is warmed up. Is this normal?

The bike is stock except for Micron Serpent exhaust and headers.

Standard HD mineral oil, running super plus unleaded.

No engine warning lights, or fault codes (according to dealer).

Just wondered if anyone else had a similar issue or ideas?

I did post a while ago and was told to run on super plus. Now had 5 tank fulls (some V Power, some Tesco 99) but it still gets really hot.

How many miles have you done? They seem to take up to 5000 to loosen up properly (so I'm told)

I also find running around at lowish speed makes it worse, maybe they run a bit lean down low with intake/exhaust mods?

The bikes done just over 7000 miles.

It does it on a good run, A & B roads at good speeds (over 50-80 mph) at low revs.

It gets much worse in traffic of course.

Hmm, got me there! Mine doesn't come on that much at 50-80 down A/B roads, only when I start pottering at 30-50 in traffic or when I'm thrashing it up the motorway (144-ish on the limiter in top )

Nearly forgot, mine's only done about 2500 miles too

i've fitted a rhs air scoop on my stt - courtesy of blackbear

don't have any heat problems now - only comes on when its had a good thrashing or been sitting in heavy traffic

your engine is running lean/ hot.

micron exhaust needs a more fuel than the stock map

That's what I was thinking reckon you should richen the map.

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Norrie.

The Micron was fitted by MCN when it was their test bike, to prove that it worked without any adjustment of fuelling. They said it had worked well!

Any other Micron system owners had to remap?

When does your fan come on? Most of the time (part throttle) your bike is running in closed loop, therefore your rear cylinder is running at stoichiometric no matter what. Nothing you can do to the fuelling is going to make it run any other way. Your fan is triggered (via the ECM) from the engine temperature sensor, which is in the rear cylinder....

Not much you can do about that (apart from fit a RH scoop which Buell thought they didn't need)...

I don't have a RH scoop, nor do I feel the need to buy one...

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08 Specialized Langster

did they test it on a dyno ? measuring afv
and not full trottle testing, but cuise speed testing and 3/4 trottle testing

3/4 throttle, cruising? Up a steep hill?

I am in closed loop during cruise from "start moving" to about 100mph... In closed loop, the mixture in the rear cylinder will be stoichiometric and the temperature to turn the fan on and off will be measured with a stoichimetric mixture.

I will bet that a bike with a Micron on will make less power than wth a stock exhaust due to the effect of the change in front header pipe length... The mixture will be all over the shop...

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08 Specialized Langster

The fan comes on part throttle when riding around and also when stationary as you would expect. It does occasionally go off but pretty soon is running constantly.

I doubt MCN had it on a dyno. I contacted the journo who had it as a long term test bike and he just said he was pretty impressed with it.

How much is a temp sensor? Might be worth swapping just to see if it is faulty? Local dealer said it was ok, but ??

How does a temp sensor fail? I don't think they fail with a high temp reading... Could be wrong though...

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08 Specialized Langster

Is the lambda sensor still working (or still connected)?
More likely problem than a temp sensor failure imho...

If the fan is moving such hot air, it's seemingly quite necessary to run.

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"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett