Britbike forum

Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supplyJob Cycle

Upgrade to Premium membership HERE! Premium Membership

New Sponsor post
15% Off Black Friday Sale
by The Bonneville Shop - 11/24/22 5:51 pm
New FAQ post
Member Spotlight
Central Virginia
Posts: 14,691
Joined: July 2001
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
kevin 55
Top Likes Received (30 Days)
Bry 24
Newest Members
Hedgehog65, NDarwin, Bas classic bikes, lojo, Doug McLaren
12,333 Registered Users
Who's Online Now
6 members (Magnetoman, htown70, Shane in Oz, Richrd, Linden, Tridentman), 10 guests, and 29 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Most Online204
Jul 10th, 2022
Thread Like Summary
Allan G, fullchoke, gavin eisler
Total Likes: 3
Original Post (Thread Starter)
#878511 04/24/2022 9:40 PM
by fullchoke
I bought this bike as a non-runner, and it still is. I found a key that worked for the ignition so I added a battery, and fried the wire without a fuse that ran from the regulator to the neg side of the battery. The bike has a boyer system on it and I can tell that the bike has been re-wired, and messed with after that. It didn't have a ground wire from the frame so I added one believing the bike to be pos+ ground. The 1st mistake I made was grounding the battery to the battery box mounting bolt. When I realized the battery box was isolated from the frame, I started removing it. That created a direct ground short. I unwrapped the harness, and it looks to me the bike is wired correctly. Would this signal a bad rectifier/regulator? or is the bike negative ground? I do know regulators don't like to be mounted wrong, but I'm not sure how to tell. The red wire that comes off the boyer was ground, and the coils were grounded to it also. Are these BSA regulators a weak point, or did I just make it one? Do people commonly change from pos+ ground to negative, on these bikes? I've got some studying to do, but I thought I'd ask this quick question.

Liked Replies
#878541 Apr 25th a 05:49 AM
by quinten
looks like you are making some progress .
The 2 wires came together at the battery, 1 wire terminal with both wires i
the rectifiers negitive output ( brown/white ) needs to join the harness before the fuse at the battery
( otherwise it is not fused from the battery )
... if more than one wire is connected to a battery termial ... or battery terminals
you gotta check that they are all fused

[Linked Image from]

Diagram shows rectifier output joins harness at ammeter .
if you dont have an ammeter , it does not matter , ( still joins harness before fuse )
just view the the ammeter as if it is a full current wired through-connection ( which it is )
1 member likes this
#878779 Apr 27th a 02:28 PM
by Roadwarrior
I’ve wired a lot of british bikes. You have to make sure all of the wiring is correct before any battery is connected. Trace every single wire using a continuity tester. Use a single point ground and don’t forget to ground the motor. Pods work best, but there is nothing wrong with the old Zener/rectifier set up. Just make sure it’s wired correctly. Correct color coded wire is available, so you don’t have to buy a harness. Verify all connections, then add the battery. Positive or negative ground doesn’t really matter as long as your consistent.
1 member likes this
#878595 Apr 25th a 05:23 PM
by quinten
an old lucas rectifier is harder to read , but the wiring position layout was standard .
center stud mount and male terminal are positive ( as maked )
( but there are negative stud mount types also made for when the industry went negative ground in 79
and these could show up anywhere , on purpose or by mistake )
[Linked Image from]

lower outside terminals are equal AC inputs from the stator
middle lower terminal is negitive output .

The fin paint on the outside is insulation , if chipped or worn
some of it will be negative , some of it positive . So it needs to be treated with a Little Tenderness
from contact with other objects and tenderness when stud mounting .
( if the piece looks chipped up or otherwise manhandled during mounting , bin it ,
It's not worth the aggravation )

newer reproduction rectifiers have color coding , like this
[Linked Image from]
these repo bits are overpriced , but look correct ... if that's the way you want to go

the good news is
this funky old finned technology
can replaced with a 5 dollar "Cube" rectifier that is a little more efficient
And a lot more robust ... ( tens of millions of cube rectifiers are still made and used every year )
Anything from 35 to 50 amps will work , whatever is on sale . ( most Carry up to 1000 volts )
they are serious overkill for the application , but ridiculously cheap . ( when not bought from a retailer
with excessive markup )
they look like this ,
[Linked Image from]

the center hole can be used to mount to the same spot as the old rectifier .
( these are not polarized components , so no polarity is conveyed through mounting )
... or you can just nylon-tie this piece in place , but stud mounting will help dissipate Heat .
( dont hide it inside of insulation , it need to dissipate a little Heat )
1 member likes this
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor

© 1996-2022
Powered by UBB.threads™ PHP Forum Software 7.7.5