K75 looses one cilinder in acceleration, and sometimes at start.

[foliver]

Hi!
Here I’m again.
Today it was a special day:
I drove the motorcycle in the city for half an hour after 6 years

The general ride improved, cause I’ve installed progressive front forks, and Spiegler front brake lines.
All that was good.

BUT…i’am facing some sintoms that are back from the past.

The first start some days ago was smooth, lots of white smoke, then the engine runned smooth, without smoke.

Today It started in 2 cylinders, ouch.

The sparks are not new, nor the sparks cables.

The injectors were sent to be ultrasonic cleaned and the bank test have had very good results, so the injectors are innocents.

After looking at the sparks again, they was black, I supposed a rich mixture….no one has had oil, good sign.
After cleaning them it started again on 2 but went better and went to normal, but it doesn’t keep the 900 rpm at idlle.
Another strange behavior was the acceleration ramp: it was ok until it reached 3,5-3,8 K rpm, there it looses torque, acceleration, and becomes working at 2 cylinders for some moments until I returned to 2K

What can be the cause?, can have one cable develops false contact, as the engine starts rev up caused by vibrations?….

Here I’m a bit lost...

Here a picture of the bike after lot of work, the front fairing is not mounted yet

[foliver]

i need to add an info:
battery is new as the starter relay.
BUT, the third time i crancked the bike, 2 days ago, at the beggining of this "new era", the starter relay get closed, i was lucky cause a hit with a screwdriver unweld it.
After that i charged the battery to 12.9, and all went better, but today the relay stays welded again.
Can a bad battey cause the problem i'm describing?
can i help it with a large diameter ground cable?

[blackie1]

yes. bad battery will cause that. just because battery is new is no guarantee that it is good.

you may have a bad H.E.S  (hall effects sensor)

[daveson]

Yep, could be a bad spark plug lead or spark plug, then that plug should be darker than the others, and swapping them would shift the problem to the new location. Make sure the connections are clean and tight.

The battery might not be good, regardless you want to consider a battery isolator switch. And yep, get a larger diameter ground cable and clean the battery (and other) connections.

[Laitch]

Spark plug terminals come in three types; those with removable terminal nuts, those with solid terminal nuts and those with thread studs. Spark plug wires can have two types of terminals connecting to the plugs: those that snap onto terminal nuts or those that press onto thread studs. Here are examples.

If your plugs have terminal studs but your wires have snap-on connections, spark plug performance can become unreliable. Verify what you have.

Inspect and clean your coil terminals and the terminals of the wires that connect to them.

You're due for a full tuneup before having high expectations of performance.

[alabrew]

Low voltage will weld starter relays, so charge that battery.

The trouble shooting chart is always a good place to start diagnosing those electrical signals.
A multi meter is your friend here. Check that the computer is seeing the signals it expects.
Especially important on start is air temp. and water temp.
The HES signals the fuel pump to pump, so if one of the HES sensors were defective, you would hear the pump start and stop. (or that is how mine went out)
Coils are mentioned here often, but I don't recall intermittent failures.
Sounds like you have done most everything else, plugs and wires will be the finishing touch.

[foliver]

Hi!, thanks all for your answers.

Alabrew, i'll take a look even if all went ok, in the signals the computer reads. It will be the first time for me, but the multimeter is my friend.
Daveson, a battery isolator switch, and a easy connector for charge it are now on future plans, thanks.

Seems that everyone agree that the batterie is responsable in some ways, and you seemed right..

Yesterday and today, is holiday in my country, so all is closed.
Today i charged the batterie again, and i applied deoxit to both sides of the cable plugs.

Laitch, the plugs are the type of removable terminal nut, and the cable end has a little clip on the hole, once plugged it seems firm, but i don't know if it's the right conector...the cables had 5K end to end.
Anyway, when you plug them you feel a click, but is not too strong, so i'll buy a new set. May be the

So today the bike was in 13,2 V and fired flawlessly ( the alternator is working ok, by the way).
I have done 15 km 2up with 3 stops.
The iddle revs went higher ( 1.5K) , cause yesterday i was in need to increase it to avoid shut down.
So at the end of the ride i adjusted again at 900rpm.

The only strange thing today was that the iddle speed went to 1.8 to 2k in some moments, the idle switch is clicking when i close the gas.

Here a pic of the cable plug side and plug.