R1100s 8 valve Misfire woes.

[PBoy]

Lurker turned poster.

I'm cap in hand from Boxertrix/Gbbikers for some tips on curing the misfire, lumpy low speed running on my bike.

So Far...

'04 plate 16k OTC. 8k of smooth runnings in the last 6 months until 1 week ago.

Suddenly gets lurchy and jumpy at low revs (20 - 40mph). Was fine on hard acceleration and top end until yesterday when it started misfiring there too. Lot's of popping and burbling when the power comes off, which is new.

Sitting at the lights holding the throttle in one position it bounces from 1000 revs up as high as 1500 and back down again. Again, this is new.

It has a Y-piece and no CAT so I disconnected the Lambda Sensor below the fuel tank but it's not helped. After a look in Hall Of Wisdom I will double check the throttle cables but I hadn't done anything just prior to developing the problem. Re-seated exhaust to cut any leaks.

Common suggestion seems to be poor fuel (it's had 4 fresh tanks since the problem developed so I think unlikely).

Stick Coils?

I've removed one side, then the other and it makes no difference to the running.

Question?
On a Twin Spark, would removing the plug cap make any difference at idle since there's a second plug? Should I disconnect the secondary plug first?

Putting the plug in the removed cap and holding it close the frame I get a good spark, both sides. No discolouration on the plugs which are 2k old.

Question?
If the coil was shot would I still get that spark?

@ £60 per side how does a novice isolate if, or which coil is shot?

Any assistance greatfully received

 

[elevensies]

i would doubt its fuel,

have you checked plugs and the ht leads.

throttle body setting up?,

is it running even?


Because you have removed the cat and replaced it with the y piece, did you fit the fuel remap relay? or did you leave that as standard?

Some 11s dont mind this mod, some dont and play up, but after this length of time you would have noticed the rough running.

good luck

 

[PBoy]

Hi elevensies. That's where I'm up to...

The Y piece no cat was a dealer option from new.

Everything was fine until one week ago. I guess it's coils or ht leads but how does a novice check these things on a twin spark?

 

[DrFarkoff]

disconnect the stick coils in the centre of the rocker cover by gently unplugging them at the connector at the coil and try it if there's no change then the stick coils are probably naffed

NB be gentle with the connector you just need to lkift the tab to pull the cable out and make sure and use the tool to pull the coils out

If there's lots of corrosion then they're stuffed

Good news is if yer mates have a twin spark 1150 or a 1200 the centre stick coils are interchangeable for tests

 

[Steptoe]

Stick Coils?

I've removed one side, then the other and it makes no difference to the running.

On a Twin Spark, would removing the plug cap make any difference at idle since there's a second plug? Should I disconnect the secondary plug first?

disconnect the stick coils in the centre of the rocker cover by gently unplugging them at the connector at the coil and try it if there's no change then the stick coils are probably naffed

You've got it right - Just pulling off the main stick coil won't make any difference to the running as the engine can and will happily tick over on just the secondary plugs.

You need to pull the lower secondary plugs so it's only running ( or not as the case may be) using the main coils.

If the main coil caps have failed it'll only run on one side or miss and feel very rough.
To diagnose which side has failed or is failing connect the lower plug one side at a time and you'll feel it run normally when you've connected the side thats failing or failed.

You can't go by the amount of corrosion on a, cap it's not a sign of a failed coil cap. I have customers who's bikes run perfectly with awful looking caps, and others with failed caps that look perfect.


Try that, if no difference get back to us.

 

[PBoy]

Thanks everyone, much appreciated.

Steptoe, I'd seen you'd posted about such matters on Boxertrix. Thanks.

 

[PBoy]

OK.

So without lower plugs we've isolated LH stick coil as the culprit. Motorworks on Monday can sort that out. Whilst I'm on, anyone able to point me in the direction of what a novice needs to 'helicoil'(?) a Rocker Cover bolt which now simply pulls out and pushes back in again

 

[Steptoe]

Whilst I'm on, anyone able to point me in the direction of what a novice needs to 'helicoil'(?) a Rocker Cover bolt which now simply pulls out and pushes back in again

A 6mm helicoil kit.

 

[PBoy]

A 6mm helicoil kit.

You're a blummin star.

 

[PBoy]

LH stick coil replaced and almost all is well. Thanks Steptoe for direct input and thanks everyone else.

I think I'm gonna leave the helicoil to a professional and see if I can find a tuner to balance throttle bodies, and carbs.