Poor Idling

[Chriswilly]

Good Day everyone!
Can anyone please help?
I have a 2000 M900ie (wreck) - bought Feb 2011 - Fitted a 900ss rebuilt motor and the correct ECU.
Tuned it up to 'Brad the Bike Boy's' specs in 2015 and has run well until about a month ago when it became hot on one trip and the idle speed dropped to about 950 rpm.
Have cleaned fuel injectors, New fuel filter, new plugs, plug leads, plug caps, and re checked the TPS.
Fouls up front plug (rich) but will still pull 100 in 4th without a problem.
Will tick over but only on the rear cylinder and 'fluffs' and 'complains' at low revs.
Have checked the sparks - not very impressive but the same on both cylinders.

So - fine with the throttle open and crap idling and low revs.

Any ideas please?
Thanks

[Darren69]

Have you tried switching the coils over and see if the problem goes to the other pot?

[Chriswilly]

In a word - No!
Checked sparks on both cylinders with the plugs out - not a very impressive spark but both the same.
Also checked the coil resistance 4.6 ohms.

Will swap tomorrow.
Thanks

[Mr Gazza]

Darren made a good call with the coils.
The next thing to check would be the pick-ups.

Assuming that you ultra sound cleaned the injectors? Even if they are spotless it doesn't mean they are not worn out... Might be worth swapping those too, to see if the problem goes with them.
It's also worth checking that the electrical connectors to the injectors are making proper contact... I bought my bike as a non-runner and it was just those connectors not making. (I still have a couple of new Marelli plugs if you find you have the need)

My money would be on slightly un-synchronised butterflies, but ending at the beginning, as it were. No carburation issue should begin without a valve clearance check.

Plenty to be going on with... :D

[slob]

a spark in the air and a spark under compression are quite different animals, the front ht leads in the line of fire of a lot of weather, it's quite common for them to start breaking down under load as they get old

[Darren69]

Coils are funny things, they can check out ok static, but then break down when they get to a certain temperature. I know this from first hand experience. And BTW Gary's our resident Sie expert but I thought there was only one pickup (crank sensor) on those but I may be wrong. anyway I believe he had a similar issue which turned out to be a faulty injector connector.

[Mr Gazza]

And BTW Gary's our resident Sie expert but I thought there was only one pickup (crank sensor) on those

Thanks Darren, but I'm no expert.
Luckily I've not had to interfere with the crankshaft sensor(s), but thinking about it, the set up will differ from carb models which fire the coils with a pick-up each.

If ie models have one sensor to tell the ECU when to fire the coils, then the problem would not favour a particular cylinder as in this case. So pick-up(s) become a lesser suspect for now.

[Chriswilly]

Many thanks Gents - some items to check.
I admit I have played with the throttle settings so will look at those.
Will also check the injector wiring.
The temp sensor on the front cylinder would not affect the situation would it - only weakens the mixture when engine reaches a certain temp!
What about a check on fuel pressure?

[slob]

oil temp on the dash is provided by a sensor on the filter screen (900ie may precede this) the ecu reads oil temp from the front intake rocker cover. this might give false readings if it's coated in 'mayonaise'. what does the oil level sightglass look like?

[Birdy]

Have you got the sensor thingy on the horizontal cylinder? My 900ie was running pants and wouldn't idle, turned out to be a gammy sensor plug. All cleaned up now she runs fine.