Dai wrote:You're right about the wriring loom going into meltdown - you'll have to use relays. Yes, it can be done. I've just done something similar on my Bandit, so give me a day or two to dig out the wiring daigram and post it here.

Crazy Frog wrote:Here is an upgrade with relays. You can plug the dual headlight instaed of the single one when the relays are installed.
One of the other critical upgrade is to install ceramic headlight connectors.

The schematic is here





Thanks. I have ceramic connectors already!

Dai wrote:Does CF's diagram solve your problem?

Dai wrote:Okay - we'll wait till you get home

Two Wheels Better wrote:To be clear, the voltage regulator is under the petrol tank on the right hand side towards the front and is either a tin box (original) or a smaller plastic rectangular unit. But first, does the warning bulb in the instruments illuminate? If this bulb is not working then the charging system will not get 'excited'. To test this bulb, disconnect the neg strap for the battery and remove the front engine cover (timing chest). Remove the wire from the DF terminal on the alternator. Turn on the ignition (after reconnecting the neg strap). Touch the wire you've removed from the DF connection to a suitable ground surface. The charge light should illuminate.

If you have a small multimetre with you (essential with Airheads) you can check resistance across the slip rings of the charging rotor after raising the brushes off the slip rings with something like a business card. An R90S, assuming original equipment components, would measure 3.4 ohms if good. If you don't have a multimetre then press a screwdriver, blade or other metal object across the two surfaces of the rotor's slip rings (the shiny place where the brushes ride). If the bulb burns brightly then the rotor has an open circuit. The rotor is the majority of failures with Airheads, followed by the diode board.

Look for burn marks in the diode board at the top of the timing chest. Also check pos and neg battery connections for tightness. 

Dai, did you make that /8 bit up? This is not a model in any of BMW's nomenclature that I'm aware of. Type 247 /5, /6 & /7, plus the '80s models, or Type 248 - R45 & R65?

Dai wrote:Typo I was on my way to a vintage vehicle show this afternoon when a little devil popped up and went 'oi dickhead! did you really write /8?'. Should have been /6 and /7 

Thanks for the additional input TWB. It's been almost thirty years since I did the last 800/7 and yes, I did manage to snap the nose off the camshaft, which is why I remember it so clearly. I had a huge dose of luck when I fed the replacement camshaft in and was able to pick up the oil pump without having to strip the engine.

Same problems as a good ol' Moto Guzzi, btw. Same charging system, but marginally different dimensions on the stator and rotor diameters which makes them absolutely not interchangeable. Thanks, BMW.

Dai wrote:Typo I was on my way to a vintage vehicle show this afternoon when a little devil popped up and went 'oi dickhead! did you really write /8?'. Should have been /6 and /7 

Thanks for the additional input TWB. It's been almost thirty years since I did the last 800/7 and yes, I did manage to snap the nose off the camshaft, which is why I remember it so clearly. I had a huge dose of luck when I fed the replacement camshaft in and was able to pick up the oil pump without having to strip the engine.

Same problems as a good ol' Moto Guzzi, btw. Same charging system, but marginally different dimensions on the stator and rotor diameters which makes them absolutely not interchangeable. Thanks, BMW.

MarcS wrote:Good for you. We are waiting for a forcast -2c in the morning. My brass monkey has packed his swag and moved north

RicK G wrote:We had a -6°C here a couple of days ago.