weird idling - cbr f4i

[bigdom86]

hi all

have a weird idling issue with my 02 cbr f4i, it was fine all throughout summer so maybe the cold air is causing some issues.

during summer start up was like this:

-fire it up
-revs go up from around 1k to 3k and hold there for around 1min
-revs start settling down to 1-2k and temp gauge comes alive
-revs settle down to around 1-1.2k and I ride off

recently in the cold weather:

-fire it up
-revs go up from around 1k to 3k-3.5k and hold there for a min or so
-revs come down to 1-2k and temp gauges comes alive
-revs settle down to just under 1k and i ride off

for the first 20-25mins whenever i stop to idle it settles at around 500-600rpm and bike feels like it is about to stall, it only does this for the first 20-25mins and then once im about 30mins in and temp gauge is reading 80-90+ it stops doing this and then settles nicely around 1-1.2k on idle at lights etc and feels normal

any ideas or is this normal and im worrying about nothing?

[UnknownStuntm...]

What oil has it got inside it?

[DrDonnyBrago]

I had one of those for 9 years, it's definitely not normal. Mine idled the same hot/cold/whatever, only thing that changed was the time it took to settle from fast idle.

The idle speed when cold is determined by a wax idle unit. It's essentially a thermostat like device with a finger that pokes out to open the throttle. As the coolant flowing to it gets hot, the wax melts and the finger retracts, lowering the idle speed. This is what causes it to take a minute or two to settle down. I assume yours is functioning ok if it drops down as expected.

As for the funny idling for 20 mins or so, maybe it's running a bit lean and the cold, dense air isn't helping? Not sure if that would differ when the engine is warm though.

[Robby]

I'd be looking at that wax thermostat on the idle control. Wax stats can and do fail, and they need a good supply of coolant to do their thing.

So first off, make sure it has enough coolant in the engine and its fairly clean. If its filthy brown, flush and change it. Then find out how to test the wax stat.

[Hong Kong Phooey]

As above sounds like dodgy auto fast idle control system. You'll need to remove throttle bodies to get to it though. Test by heating it up, should expand, hairdryer is suggested in the Haynes, retracts smoothly once cooled down again.

Any FI warning light on?

There's an IAT for inlet air temp, at 20 deg C should have resistance of 1 to 4 K ohms. Lower temps should have higher resistance . That's mounted on the front of the air box.

There's also an ECT, which if faulty may give a flash code in the ECUs FI diagnostics mode, should measure 2.3 to 2.6 K ohms.

7 flashes is faulty ECT, this also sends signals to the temp gauge though so probably ok.
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'81 CG125, '97 FZS600 : '99 CBR600F4, '09 KTM RC8

[kramdra]

Wax unit failure will not allow idle to drop below normal warm idle. Above 45c the wax should be fully melted, it becomes irrelevant, this should take minutes, not 20.

Suggest it may be more related to a temp sensor only correct at the hotter end of its range. When did you last check plugs and air filter?

Does the FI light come on when this occurs? (This shows its in the failure mapping) In very hot weather mine had an issue which Ive been unable to solve, within 10s of starting she would switch to the failure map, which was perfectly rideable other than backfires. Restarting engine after >45c fixes, so was not worth much effort. Most do not ride off until after this anyway.

Unplug either the intake air temp or map sensor as a test, this should trick the ecu to run in the failure mapping. If problem disapears you could have a dodgy sensor/ leaky map hose. Both are under tank, map is bottom left of airbox.

[bigdom86]

thanks for all the feedback and advice, it makes me realize i know very little about motorbikes and should probably learn more! where do you get those haynes manuals from these days.

No FI lights or anything come on at all when this happens.

Weirdly it has now stopped causing this issue as has been riding fine as if i was riding when it was warm but going to get things checked over just incase.

oil and coolant was changed around 6 months ago.

the issue has now stopped but do you think it could have anything with running a can with no baffles and lower pressure in cold air or something (i think i just made that bit up)

[talkToTheHat]

Cold air is usally denser so you're getting more o2 in, can mess with your mixture a little. On a carbed bike cold air in a warm engine usually makes for a punchier feeling engine, although this is much more noticable on a 125 when you're using everything the engine has to give. Note that intercoolers water injecton both exist for charge cooling becasue cold dense air is a good thing.
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Bandit. does. everything.