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Old 01-Nov-2005, 06:38
HW HW is offline
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Big Twin
 
Posts: 1,144
Join Date: Feb 2005
No problem, hope you get it sorted.

The coils can be a problem on these models regardless of age. If you've not looked at one yet, they are a combined plug cap/coil like those used on BWM and Audi cars (and others). They cost a small fortune, about £110, EACH. Whilst no doubt reliable or cars, they do not seem to do well on bikes.

All you see of it is the low voltage 3 pin connector, on the older models. On these the connector was part of the assembly. If you look at the top of the front cylinder you will see it. I actually accidentally knocked the connector part off on that one when cleaning early in my 749S ownership. Very embarrassing, after I had the AA recover me 150 miles home. Noticed the problem just before I took it to the dealer to be fixed. They suffer badly from the wet, and the later models (of coil) had a short flying lead with the same type of connector on, except you could tuck it away behind the left hand fairing panel.

Another issue with these coils is the seal around the top. It is a kind of built in double o-ring, only it has gaps in the ring (much like piston rings in fact). Apparently, they idea is this lets trapped air out that gets heated up around the plug. Fair enough, but it also lets in water! The standard V-piece on the 2003 749 modals had a convenient rectangular cut out so you could easily change the coil without needing to remove the panel. It also lets in water and muck thrown in from the front wheel! Brilliant! The rear coil fares not much better. You will notice that the top of the rocker cover is dished. If you wash your bike on a paddock stand, you would be advised to take it off the stand straight after to let the water drain out of this area before it works it's way down the rear coil. The steel tubes of both of my coils were very rusty, the front one especially. Why they are not stainless is anyone's guess!

Needless to say, you should put some "rubber grease" around the top of the seal when refitting to help keep water out.

Rambled on long enough on this ... better get bike loaded for my track day now.
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