Suddenly Started running rough...help

arbik · 09-28-2006, 04:30 PM

Hi guys,

So my bike suddenly started running rough. It back fires on shifts and deceleration, and runs VERY rough. It also is down on power and sounds like a harley. I checked both plugs, and they both look good, and there is no fowling.
This and the popping tells me, I'm good on the fuel side, and there is combustion in the chamber, at least enough to not foul the plugs. Maybe the timing is off?
Profwacko thinks its the hall effect sensor. Thats 300 dollar part, so before I take the plunge on that, I have two questions.

1. What else should I check?
2. Is there a way to check the hall effect sensor?

Thanks,

-arbi
2004 Rockster

jclark · jclark's Garage

Check that your cables are not loose at the Throttles...make sure your balance aint suddenly waaay off...
Mine's been popping back on decel for 35k miles, and I looove the sound...
I call it burbling...

jeff

Moybin · 09-28-2006, 04:51 PM

Did you fill up the tank just before this started? If it's that sudden, and yet the plugs look clean, I'm thinking it's fuel; it sounds like it's running extra lean.

When did you last change the fuel filter?

davidb2 · 09-28-2006, 04:58 PM

vacuum leak? did you check the rubber thottle balancing plugs?

Steve Carlton · 09-28-2006, 05:01 PM

Is it still under warranty?

arbik · 09-28-2006, 05:08 PM

ok so:
the little rubber plugs are there on the TB.
I didnt just fill up with gas, it ran good for the half the tank that is in there before.
throttle cables are good.
it has 22K on it, and has been serviced according to BMW service intervals.
so if the fuel filter had to be changed, then I've changed it. I just dont remember.
Warranty ran out 4 days ago!!! Called the dealer, they said sorry, if its out, its out.

tjs · 09-28-2006, 05:20 PM

Quote:

Originally posted by arbik
ok so:
the little rubber plugs are there on the TB.
I didnt just fill up with gas, it ran good for the half the tank that is in there before.
throttle cables are good.
it has 22K on it, and has been serviced according to BMW service intervals.
so if the fuel filter had to be changed, then I've changed it. I just dont remember.
Warranty ran out 4 days ago!!! Called the dealer, they said sorry, if its out, its out.

Bad O2 sensor will also make it run bad. make sure R side TB throttle cable is properly seated in the adjuster. next I would agree that it could be the hall sensor. good luck! TJS

spikethebike · 09-28-2006, 05:52 PM

Warrenty up? time for a new bike!

Moybin · 09-28-2006, 06:04 PM

Give the rubber nipple covers a really good look. They have a tendency to fuze to the brass tubes coming down out of the throttle body. What you are looking for is cracks in the rubber. It hardens with time (and gas vapors).

Jeff Williams · 09-28-2006, 06:54 PM

Arbik,
long time no see

along with the balance of the throttle bodies I would check the TPS to see if it has moved AND check when you last changed your battery.
See if your fuel filter is ok,(you should change it at 26k).
IMO a hall sensor should be the last thing on the list that could go wrong.
Over the last 27years riding BMW's, I've only seen one halls sensor go out. I've seen more coils and cd units go bad.
jeff

Crunch · Crunch's Garage

Pardon me ... excuse me .... what is the hall sensor?? Or is it Halls Sensor effect??

If its running lean, what is the first step to take? (Don't say PCIII either!)

spikethebike · 09-29-2006, 05:41 PM

The hall effect sensor tells the motronic which hallway has the secret effect on the muffler bearing.

arbik · 09-29-2006, 06:55 PM

Hi jeff and all,

A couple of people on the R1150R board said it was the pencil coil. So I checked, and who knew...one of the pencil coils had gone bad. The pencil coil is the one on the twin sparks that is in the conventional spark plug position, and has the coil at on the plug.

Since my warranty ran out 9/24/06, I had to pay for this one. Cost me $94, but the rockster is alive again...

thanks for all the replies guys.
hell, with internet support boards like this, who needs a mechanic?!!
all we need is a diagnostic port to USB adapter, where the board reads your faults and recommends a fix

happy trails to all.

-arbi

JonyRR · 09-29-2006, 08:08 PM

'diagnostic port to USB adapter,'
when someone can cadge the pinouts from the diagnostic PC to the plug, and can steal the diagnostic software (that runs on win-doze) that could be a reality.

arbik · 09-30-2006, 01:14 AM

I failed to mention something...

When I went to pickup the part for the Rockster, I sorta test rode that new R1200S. Umm.....
I'm so in love, its starting to eat away at me. Its 2am, I cant sleep!
God DAMN that thing has power!!!
and I miss that sporty handling of the S line, as opposed to the Rocksters more twitchy handling.
But i'm trying to be good, and get a decent cage, so I can score a rich wife...so maybe I'lll just wait for a few years..eh?

-arbi

Crunch · Crunch's Garage

So, let me guess ... there is no way you/I/we can check the pencil coil?? Probably have to go to the dealer and $pend just to find out if that is the problem??

Moybin · 09-30-2006, 06:38 AM

Sure you can check the pencil coil. If you lift the lead to the twin-spark plug and the roughness doesn't change, you found the culprit.

The Hall Effect sensor is a magnetic "gate". They use them in the electronic compasses, too. It turns on and off depending on the polarity of the local magnetic field. There is a magnet embedded in the end of the crankshaft. This is the electronic equivalent to a pinion and gear arrangement from the cam shaft to the distributor. It tells the Motronic when the crankshaft is in alignment with a cylinder at the correct position for firing a spark plug. All solid state, very dependable.

And now I know a reason NOT to get something with dual-spark; just one more thing that can go wrong.

arbik · 09-30-2006, 05:57 PM

What Moybin said, except...

the part about the dual spark thing. Its actually pretty cool.
You loose about 20% power and the thing sounds weird, but you can keep on going on your journey. its a redunant system, you have a separate coil for each plug, so you can fly with one coil out on each side. Furthermore, the pencil coild are swapable, so on the road, you can stay on the road and get to your destination with just 2 coils working....

-arbi

Crunch · Crunch's Garage

OK, that's good news. However, how do I troubleshoot to determine which coil is bad? I have an R1100S engine repair manual, but I don't think it applies to the twinspark. It sounds to me as if the twinspark has four different coils that could be the culprit.

Any suggestions??

arbik · 10-03-2006, 08:11 AM

its easy. Basically, you treat it like two single spark engines.
take off a set of the plugs from each cylinder. Now you have a "single spark" engine. So trouble shoot accordingly.
on mine, I disconnected the bottom spark plugs and started the engine.
then you remove the boot to the remaining one of the two spark plugs, while the engine is running, one by one. If there is a bad one in the pair, then the engine will make no change in running, if you remove the bad one, and the engine will die, if you remove the good one.
If both are good, then unplug these two, and plug in the other two you had disconnected, and do the same test.

-arbi