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Wednesday, May 12, 2010


Reluctantly removed the float chambers last night (saves taking the carbs off). Fitted some new (old) floats and brand new float needles. Bike still flooding! Walked away again, avoiding direct eye contact with the hammer hanging on the wall.


Anonymous said...

Bah this sucks Tom, I really do feel for you mate. Are you sure your CDI is working correctly? Ive lost the spark on mine now and after replacing the coils with a new one Ive still got no spark so its gotta be CDI or the generator. Working (E-bay) CDI coming and we'll see .....
A couple of mates Ive spoken to have said its an ignition problem, probably CDI related, as its exactly the same symptoms as they, me, and you, are having. Runs as lumpy as hell and eventually CDI just packs up. Good job walking away from the hammer BTW :¬)
I wanted to burn mine when it wouldn't start .... Hang on in there bud

Klaas De Craemer said...

Hey guys, I have what seems to be exactly the same problem. I even swapped for another engine block but still have a very badly running bike. This makes me believe it really is an electrical issue. My CDI was already replaced but to no avail. Still no to check the plug leads. Will check for good "grounding" as well. Maybe you could start there as well.


MadDogMcQ said...

I've tried changing the CDI and as you know, it has a brand new coil fitted. It's been a real head-scratcher. Anyway, when I'm ready, I'll make another assault - but right now, I'm too damned busy enjoying the CBR :-)

Anonymous said...

Ive got a reconditioned alternator on the way from If it still doesnt spark after that Im totally at a loss .... Im looking at Fazers ATM so Im taking the same route as you Tom, walking away and doing summat else :¬)
Enjoy the CBR while we have the weather mate

Anonymous said...

I rebuilt a CB250N and it recently died with no spark at plugs. Eventually found that the ignition coil in the alternator had popped.
Check this by measuring between the white lead (two pin connector above the reg/rec) and the chassis. It should read 330-400 ohms.
Any less, like 200 ohms and the ignition coil has overheated and the windings have shorted. The coil is made up of three parts, the large one at 4.30, and two smaller ones at 6.30 and 8.30. Westcountry Windings can repair just these coils. I'm about to perform surgery on a duff alt that has the same problem so will post back with procedure if I'm successful.

MadDogMcQ said...

Well I very much appreciate you letting me know that resistance reading - I'll check it this weekend.

And I look forward to any other light you can shine on the matter.


George said...

Clean all conectors between Earth, Alternator, CDI and Coil. Undo the bullet connector on the short black/white wire from the CDI to override immobiliser (run and key switch) faults. If you havent got a spark that you can see in sunlight, youve got an aftermarket coil or the ignition winding on your alternator needs a recon. The spark coil must be genuine Honda. Cheap aftermarket coils are wired different and give a weak spark and bad idling. The original Nippondenso CDIs never burn out. Ultrasonic cleaning fixes a load of carb problems. David Silver sells photocopies of the Honda shop manual for £16. Job done mate.

Alternator resistance checks from Honda shop manual 1980.
CB250N and CB250T
Green-White 200-500ohms(Low speed coils),
Blue-White 4-7ohms(High speed coil),
Green-Light blue 100-200ohms (Pickup),
Green-Brown Not applicable,
Green-Pink 10-30ohms (Advance coil).
Green-White 387-473ohms,
Blue-White 77-95ohms,
Green-Light blue 95-116ohms,
Green-Brown 76-92ohms,
Green-Pink 126-154ohms.
Green-White 400-500 (300-400)ohms,
Blue-White 75-130ohms,
Green-Light blue 75-130ohms,
Green-Brown 73-130ohms,
Green-Pink 120-180ohms.

MadDogMcQ said...

That information is appreciated George - by me and no doubt many others! THANK YOU!

Bike Details

Honda CB250N Superdream
Reg No : ORH746W (ORH 746 W)
Reg Date : 1980
Orig Colour : Blue
New Colour : Black
Current Owner : Tom McQuiggan
Current Location : Horwich, Bolton, UK.