Charging system

Is it correct that my '82 750 Maxim J does not charge til 2000 rpm?
I left it idling - off choke for about 10 minutes, and the battery was flat!
Is there a mod for this?

 

You're right about the charging system, and there's not much you can do about it, but your bike should idle a bit longer than 10 minutes off the battery.. Have you checked the electrolyte levels? How old is the battery?

 

A new battery might do the trick.

 

Its supposed to be a new one, the levels are good, but I was messing about with the lights and stuff so it was a bit drained already.
Has anyone tried fitting an alternator or other parts from another model I wonder?

 

It's true that most XJs' charging systems are lacking (save the XJ1100), but... how long do you need your bike to idle before it dies? You should be spending a lot more time above 2K than below :mrgreen:

 

I had been doing some work on the bike and as a result the battery was low so I left it idling to - hopefully - put some charge back into it.
Its not that I need it to idle for any period of time, I just noticed on that occasion that it didn't seem to be charging when idling. I just wanted to confirm what I had learned, and find out if there was a way to improve the situation.

 

Consider it confirmed. It won't charge the battery at idle like a car. At idle, the bike's charging system is just barely working, and it is highly dependent on the battery for silly things like actually flashing the turn signals, etc. It starts to make real juice at a little over 2K and by 3000 it should be at full output.

When everything is working correctly.

The system is quite primitive; there are a set of old-school brushes mounted in the cover that make "face contact" with the rotor; and the whole mess is highly sensitive to corroded or overheated connectors. Unplug the big connector to the rectifier/regulator (large finned heat-sink component) and check the contacts in both sides for signs of corrosion or being burnt.

It pays to throw a meter across the battery terminals occasionally and check its output; often a cleaning is required long before the brushes actually wear out.

The 550 Secas have a voltmeter. It's very entertaining.

 

almost no bikes ever made charge at idle.
A car alternator is overdriven to spin something like 4-1 vs crank RPMs
Many bikes alternators are directly on the end of the crank thus spinning 1-1.
Although ours are "remote" and chain driven they are not overdriven.

Which reminds me of something I thought of a couple hours ago.
Anybody ever thinking of replacing sprocket(s) on our alternator to overdrive it and make more amps for nifty toys? seems like it might be less mucking about than sending out for a rewind.
Here in Seattle it's getting to be that time of year when the stores roll out their selections of heated grips, gloves and vests and I get all lustful over them and kicking myself for not getting such things on clearance in late spring.

 

I tested the output and it all seems to be correct, its just that it all happens higher up the rev range!
The battery drain is helped by the fact that I have twin headlamps i.e. 110 watts, and the lights are on permanently (well, they were... I've now fitted a switch)
I'm fitting a voltmeter later, just to watch the fun!

 

Strange... I've never found that on any of my bikes - they all seemed to charge on tickover (the gs750 doesn't count cos that has a car alternator fitted, belt driven from the crank).

 

Hey man, at least the electrical components on the XJs aren't made by Lucas :mrgreen:

 

Are you using relays to switch the lights rather than the standard handlebar switch (Which probably won't cope!)?

 

"The British drink warm beer because they have Lucas refrigerators."

(Brit car-guy t-shirt, I can't take credit.)

What's really fun about a voltmeter is watching what happens when you're idling at a traffic light with the brakes on and the turn signals flashing...

 

You almost made me spit coffee all over my keyboard!

Does it do a little dance to the rhythm of the flasher relay?

 

I think that's a myth from when a large number of your countrymen were "Over sexed, over fed, over paid and over here!"

Can't say I have ever owned a British bike but never had a problem with my cars.

 

Thats cos Britain do't make any cars! - well they assemble some maybe.

 

I don't have a on/off switch as standard (its from over there!) just hi/lo beam, so I spliced the low beam wire and a fitted a 25 amp switch in line, the wiring comes directly from the ignition switch and is heavy enough to handle another 55 watts.
I've also fitted another two auxilliary lamps but relayed those.

 

I decided not to fit the voltmeter as its an older one and a bit slow reacting, but guess who its made by :lol:
having said that - I got it from a breakers and I've had it for over 30 years, and fitted to many bikes and cars... so Lucas hasn't always been crap, probably only since they started buying in from Italy (who's had an Italian bike then? - who's had trouble with the switchgear - Californians need not answer this as us brits get the wettest weather).

 

By the way... How do I get a pic on the left here as when I tried to upload one it said 6kb max and one that size won't even show, I don't want an avatar just a picture.
... I don't have a question mark tattooed on my face or wear a hat like that!

 

Hi, Jay~Dub

I used the free image editor Irfanview to resize my picture to less than 100 x 100 and uploaded my Avatar that way.

http://www.irfanview.com/main_download_engl.htm

Let me know if you need some help and I can resize your pic for you if need more help.

Glad you are not puzzled and wearing that hat!

 

Well they sure USED to. And the electric fuel pump fitted to my '68 MGB may have single-handedly been responsible for Lucas' reputation.

(Actually I think the cloth insulated wiring may have been an accomplice...)

We'll not talk about some of the original "CV" carbs, the SU side-draft.

I'm no stranger to Lucas bike electrics-- I own a Norton.

 

On My 1969 Triumph Bonneville I knew the engine was running because my Lucas ammeter would vibrate from hard over - to hard over + constantly and did that from brand new.
That big zener diode in the the star shaped heat sink under the headlight did a great job of shorting the alternator output to ground too!
Stolen from the web:

The Lucas motto: "Get home before dark."

The patent holder for the short circuit.

Inventor of the self-dimming headlamp.

The three position Lucas switch – Dim, Flicker and Off.

The Original Anti-Theft Device – Lucas Electrics

Lucas is an acronym for Loose Unsoldered Connections and Splices

 

eeeeeek! Lucas, Prince of Darkness! I learned to despise that name (TR-3 restoration was a BIT**!). I HATE their electronics and I will vote on the cloth covered wiring as the single biggest problem with their equipment/fitment, lousy engineering at its best (or worst as the case may be).

 

Well, My voltmeter is cool... just a bit slow after all these years.

 

AHA! Surrounded by fellow mechanical masochists. I had a '58 Bugeye, a '64/65 TR4a, a '68 MGB and a '72 MGB before I gave up and decided to stick to British bikes. (And yes, some Italian sports cars too, with equally crappy electrics.)

The real downfall of a lot of the Lucas components was the poor quality of the rubber parts as well; I swear some of that stuff was dried out and cracked the day it left the factory.

 

I just fitted an induction ammeter... Looks cool (to me)
I'll take a pic tomorrow and upload it.

 

There's me thinking that Ozzy was the Prince of Darkness! Bet polock is photochopping an even better one as I type!?