Misfiring under load

[paz0274]

'Ey up, tossers

I'm trying to track down the cause of my hunting idle and poor running under load. I took Steptoe's sage advice and did a TB sync and TPS set, I also checked and set the valve clearances. The hunting and poor running were still present.

Tested the stick coils and they appear to be working as the bike will run, albeit roughly, when the lowers plug boots are removed. Did them one at a time. However, the left hand ht boot was grounding with a fat spark to the engine case. On the right hand side, nothing until I grounded the lead and this caused the engine to cut out.

Any ideas on my next course of action?

Cheers fellas

Tim

 

[paz0274]

I should stress that the spark was leaping out of the boot on the left hand side. Would this mean that the lead or boot is duff? Or would it be the right hand one that only grounded with an old plug in it then cut the engine?

I am fairly mechanically proficient but I tend to let the magic smoke out of the cables on most electrical systems.

 

[Steptoe]

Did them one at a time.

 

[paz0274]

Mr Steptoe

I pulled one at a time hoping to diagnose which side was u/s. I've now pulled both off but the bike won't run at all. Does that mean that both are screwed? Whats the score with the lower boot sparking out of the cap on the one side but not the other, is it related?

Cheers

Tim

 

[rubberscrubber]

If you have a spark jumping out of its boot, that boot has a hole in it
The insulation is probably gone, or its damp and moist inside the hood..

 

[paz0274]

Stick coil ordered. I'm now 84 quid lighter. I'm sure I'll feel the benefit (I bloody hope so anyway)

 

[paz0274]

Motorworks have just told me that the coil is out of stock. Oh, well. Try again elsewhere, I suppose. Perhaps I'm not the only one with a failed stick coil. I definitely won't be the last. Anyone heard of the Beru ones that a uk seller (RPM, Ithink) on Fleabay sells? Not much cheaper than O.E. but at least they are in stock.


Tim

 

[Ian J Hartley]

I might be wrong, but BERU are old stock. The new batch are made in China by PULSE electronics. Whether the new type are more resilient and last longer than the old type remains to be seen.

As to suppliers, after Motorworks, I would try Moto bins or James Sherlock, or heaven forbid try BMW.

 

[paz0274]

Cheers, Ian.

Yeah, I've noticed that they were the first oem supplier now. I don't think I'll be beating a path to BMW, to be honest. I did look at Motobins and James Sherlock but the postage is ridiculous for what they weigh.

I'm thinking that I may as well buy 2. With my luck the other one will go soon as well. At least I'll have a spare. I might only be saving pennies but I'd rather that they were in my account and not someone else's.

 

[Ian J Hartley]

I tried to get a couple from my nearest BMW franchise recently and they didn't have stock. When I asked why, knowing that there is a high failure rate on these. The guy in parts said he had only sold 3 in the last year, so why carry stock.

This can only mean that some of the independents are selling shed loads of these things and probably making a tidy profit as well.

Oh hum

 

[rubberscrubber]

Just a thought, the side with the jumping spark, have you replaced that plug with another just to be sure...
Maybe the plug is blocked with some sort of black magic gunk..

 

[Ian J Hartley]

I wouldn't read too much into the lead flashing when removed from the plug.

When I was diagnosing my stick coils recently, I pulled the right secondary plug lead off nothing. When I pulled the left secondary off, there was a huge flash and spark. The energy has to go somewhere, I was just lucky it flashed direct to engine casing rather than through me.

If the lead was breaking down, then you would probably see it in the dark, though not sure whether it would be that obvious to spot with the bike running. Stick coil failure is more obvious as it is the primary ignition source.