Which Battery for 1974 John Player 850?

Hello Access Norton members,
New registered member as of today.
Was at the Hansen dam rally today for the SoCalNorton Owners club, and decided to finally register on Access Norton.
My question is regarding which battery type is the best for the 1974 John Player Norton 850 with the dual headlamps in the fairing? I went with a MightyMax last time (it always felt a bit weak), and I want to upgrade this time. Andover Norton recommends the MotoBatt MB9U., but that part no states it's application is for a 750.
I found also the Motobatt MBTX14AU, which states its for the 74 850, which seems more correct.
Any thoughts or experience with these batteries?
Thanks, Rob

How much power does the dual headlamp use? What power does your alternator make? If you run incandescent lamps you can reduce that by using LEDs. After all, a big battery is only as good as your ability to keep it topped up. You could even wire your head lamps so you can run one daytime to save power if that is indeed the issue.

The JPN is based on the 850 mk2a and uses the same battery tray running across the frame, this would be the MBTX14U . I would check your bike has the space for the larger MK3 battery first in case of any differences in close proximity parts as the JPN has the odd shaped tank.


Took ref to 16 battery out.

kommando said:

the MK3 with the same battery tray uses the MBTX16U.

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MBTX14AU.

I don't think the MBTX16U would fit in my Mk3's battery tray as it's too long. I've always used YB14L size.

Correct, as AN stock both then I assumed only the height was different.

16

151.00mm (L) 87.00mm (W) 161.00mm (H)

14

135 mm L 90 mm W 168 mm H

They must stock it for the T160 maybe or a Rotary.

Onder said:

How much power does the dual headlamp use? What power does your alternator make? If you run incandescent lamps you can reduce that by using LEDs. After all, a big battery is only as good as your ability to keep it topped up. You could even wire your head lamps so you can run one daytime to save power if that is indeed the issue.

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Hello. Once I install the new battery, I'll get the meter on it and report back. I am assuming, like all good 12v battery's, it should have a output of about 13.8v at idle. And remain consistent at 2500rpm. Keep in mind I am not well versed in electrical application here. Hence my reaching out for advice and experience.
I have heard this from other Norton owners regarding electrical output:
If I replace all the bulbs with LED's to lower the power draw on the battery, the system still puts out the same output while running. Since the current is not being used to run incandescent bulbs, then the output excess is now all going to it's endpoint, the zenor diode. Which is not designed to handle the excess.
Is there any truth to this? Does running all LED's put a major strain on the zenor diode?
Thanks, Rob

the JPN is based on a similar charging system to the MK3 - hight output stator and two zeners.

kommando said:

The JPN is based on the 850 mk2a and uses the same battery tray running across the frame, this would be the MBTX14U . I would check your bike has the space for the larger MK3 battery first in case of any differences in close proximity parts as the JPN has the odd shaped tank.

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

Took ref to 16 battery out.

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Hello Kommando, I have written down the battery dimensions, and will pull out the MightyMax battery in the tray today. I am confident the MBTX14U will fit, but will confirm. My only possible issue is the new solid state rectifier I installed: it has all the harness connecting to it horizontally, not vertically like the original unit. But it does not interfere with the Mighty Max battery. I will order the new battery today, and report back on output after it is installed. Thanks for the advice!
Rob

gforce said:

the JPN is based on a similar charging system to the MK3 - hight output stator and two zeners.

Click to expand...

Thanks, I will confirm I have two zenors in place. Learn something every day: I am used to working on my 750 Interstate, and that only has one. Never assume when dealing with a new machine I realize now.
I knew I had a low output when I brought the bike home, it would die after 4 miles. I'd recharge the battery and again, start right up, then die after 4 miles or so.
That is what led to the chain case service last week. I also knew the more than likely original crank seal was dried out: I always had an excess of oil in the case. Last week I installed new crank seal, then a new high output 150w stator, new rotor, inspected the input shaft from gearbox - no excessive gear oil coming in from there- inspected triple chain for wear, replaced crank key, gave everything a good clean and reaassembled. At the same time I installed a new solid state rectifier and a new solid state assimulator. But I was using a 3 year old battery that had been sitting idle most of that time. Which brings me up to date.
Thanks, Rob

I used a Motobat MB9 in my JPN. Worked fine. Don't overthink it.

kommando said:

The JPN is based on the 850 mk2a and uses the same battery tray running across the frame, this would be the MBTX14U . I would check your bike has the space for the larger MK3 battery first in case of any differences in close proximity parts as the JPN has the odd shaped tank.

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

Took ref to 16 battery out.

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Hello kommando,
Yes, good call. The larger MBTX14AU Motobatt battery fills the tray, and therfore is bumping up against the wire leads from the rectifier. Good thing I checked. The MB9U recommended by Andover for the Mk2 850 as well as the 750 fits much better: it is only 76mm wide and doesn't touch the wires leading to the rectifier. I will order one for the JPN, and one for my InterState. That battery in the IS died on me last week as well. And the MB9U fits perfectly in the 72 Interstate battery area.
I am also ordering a new single charger that MotoBatt offers-matching their technology to their charge systems. The battery chargers get upgraded every decade or so with the jump in battery technology to match.

Thank you for the reminder that the JPN battery area can be a bit different. My other option is to attach spades bent to 90 degrees to get the wires coming in from the top, and not from the side horizontally. But since it appears from the feedback on this thread, the slightly smaller MB9U is fully capable of running the JPN. I will order some new LED's next order as well to get the old incandescent's replaced with lower wattage draw bulb elements.
Glad I joined Access Norton Yesterday! Having run into Gary at Hanson Dam was fortunate.
Back to the order form at Andover!
Rob

milfordite said:

I used a Motobat MB9 in my JPN. Worked fine. Don't overthink it.

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Milfordite:
Right you are. I can get caught up over thinking some details. MB9 it is! The order goes in today.

Here is a US made alternative to the Chinese Motobatt:

concours said:

Here is a US made alternative to the Chinese Motobatt:

Amazon.com

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Just finished my 4th season with this exact battery, and it is still strong. My bike is a '74 MK2