CB250RS - how to run without alternator?

[russ447]

I have a CB250RS that I use for sand racing.  It currently is 'kick and go' - no charging system or battery, just the two 'power' wires from the alternator directly to the CDI.  Originally there were 3 yellow, one blue and one white wire coming from the alternator.  The three yellow go to the charging system and so were binned.

I would like to run the motor without the alternator/flywheel - connecting a battery directly to the CDI.  What I don't know is what is the difference between the blue and the white wire from the alternator.  Would I conect both directly from a 12v battery to the CDI?  I do have the manual but it is not clear why there are two wires from the alternator to the CDI.  Is there any difference, or is it purely two 12v power wires?

I know people have run this system with SLR650, XL500, XL250 but will it work on the RS motor?  Any ideas would be much appreciated!

Russ

[robG]

Russ ,

Try ringing this guy. He rebuilt the alternator on my 250Rs.If anyone knows, I suspect he will.

Chaps name is Robin Williams , Tel 01626 772 791 ,from Teignmouth .

Rob . 

[russ447]

Thanks - I gave Rob a call but he wasn't sure.  I know a guy who was running an RS with only the blue wire from the alternator to the CDI connected and it ran fine.  So ...

I conected a 12v battery to the blue wire into the CDI.  We got one spark before the CDI died.  I thought (previously) that the main problem with running a CDI from a battery was that the battery may not have enough power to run the CDI - I guess now I know better.  I didn't want to put power down the white wire as I didn't know what it did.

Does anyone know of a way to run this CDI from a battery, or of another standard CDI which I could swap in and run from a battery?

And does anyone have any cheap 250RS CDIs?  I don't have a spare any more!

Thanks again,

Russ

[jester_parks]

I could imagin - looking at my wires - that the blue wire is positive and the white negative (or vice versa). To connect only one cable to the CDI without grounding it could have caused the damage

[guest27]

I am not a lekky sparky guy but I seem to remember needing to have a +ve feed and -ve feed to the low tension side of the CDI as the HT side earths through the spark plug and this is not suited to the electric faeries on the LT side - who like to keep one foot on the earth at all times.

Was warned by a lekky faerie wrangler some years back about using the kill switch as a quick change button for the bike as the lekky faeries in the CDI would not like it.  Did not listen to him of course as I know best (ahem!) - but I understand that the proper quick change kits are not just a switch but have oter lekky faeries to damp out peaks and spikes in the power.

Would guess on the basis of no knowledge that making the CDI earth via the spark plug may not be good for it.  Might be that the spark you got was from faerie dust still in the CDI and a proper +ve and -ve feed would stir up the little buggers in the box for you.

Best wait until someone who has the first idea passes by 

End of useless Rog post No 10098

R

[russ447]

Thanks for the replies.

It certainly ran fine without the white wire so what that does is a complete mystery - to me at least.  Unfortunately since the blue input to the CDI was connected to 12v DC the CDI has most definately died:

I had the alternator on there, and the plug sparking with only the blue alternator output wire to the CDI (the pulse generator wires and CDI earth are all still connected & the ignition wire is wired to a kill switch):

Put the blue input to the CDI to 12v = one spark only.

Returned the blue input to alternator supply = still no sparks.

Different CDI connected to only blue alternator output = sparks again.

Hmmmm - back to the drawing board I guess.  Or something like that.