Saxon 301

[Warner20]

Hi,

Would a knackered battery cause my Saxon 301 to run terribly? Misfiring, bogging down, tempromental to get started, bogs down and dies when lights are switched on.......etc etc

I've been over just about everything else but the penny finally dropped with it cutting out when lights were turned on but just curious on other people's opinions.

Cheers

[Blurredman]

Possibly..

Can you confirm that it is actually charging? Voltmeter to the battery terminals should read about 13.5 volts with lights on, sometimes up to 15v with lights off.

Beware the charging system does not excite the battery at idle rpm. So, if the batter is bad it cannot hold enough juice to support the vehicle when it is running, even less so when idling..

Also.. What voltage does your battery read at with the bike not running? Should be anywhere between 12.4-12.6 indicating a Good battery, but slightly less than that can be passable and still usable.

[Warner20]

Thanks for the reply.

The battery was reading 10.4v even after a charge so I know it is goosed but was just curious/hopeful that this would be the issue as to why my saxon was running so terribly.

I connected the bike up to my car battery with jump leads and this instantly solved the issue, however the battery light stayed on the whole time so would you think this indicates an issue other than a degraded battery?

Cheers

[Blurredman]

I would start with a new 9ah 12v battery and go from there. Batteries between 11-12v are only sometimes savable, so any battery at 10v is kaput

Did you leave the car running? That could have been putting too much amperage into the MZ's charging circuit..


Once you have a new battery, check voltages with lights on and lights off, it won't charge when idling so you will have to give it a small rev to around 1500-2000 rpm before charge kicks in, with or without lights.

[Puffs]

10.4 V after charge --> battery = dead.

However, if the charging system is OK, it should run fine once you get it going (assuming you have an old fashioned battery--> coil--> contact breaker ignition). And if it cuts out when you switch the lights on, that could indicate a charging problem. Or maybe a poor contact somewhere (fuse box, terminal, ...?).

[Blurredman]

The MZ system can just about support itself at around just over 10v..

Typically with lights on, brake lamp on, and indicators running my on-bike voltage display reads 10.5-11v roughly..


As Puffs said, you could try getting the bike started again with the help of another battery, and leave it for a little while. But I doubt that the bike will continue to run when the second battery is removed.. ?

But if it does.. You really need to measure the charging voltage..

[Warner20]

Thanks for the replies guys, I've got a few days off coming up so I will investigate the issue a bit more stringently whilst bearing In mind your advice hopefully I can get it resolved and report back to you as a happy road going MZ owner!

[DAVID THOMPSON]

led tail lamp and brake lamp helps cut power need at an important time idling at night with brake and tail lamp on is a big hit
even on my 4 stroke bikes i run 12v battery with the biggest ah rating that fits the battery box
dave

i never met a bike that came stock with enough AH rating
bmw made a great bike in the r26 r27 then forgot to put an electrical system on it

[Puffs]

On the tail side there's not so much to be gained. The standard tail light is just 5W, and while the brake light is 21W you only brake sporadically. So the gain is small, just 4.5W. And also, I've always liked the charging system on my ETZ, which gave me plenty of (55/60W H4) light to commute through the darkest winter period on unlit Scottish country roads, without any hassle.

Of course even the biggest & best battery will drain in due time, if the charging system provides less power than what is used by the lights & ignition. If you want to reduce power consumption, more can be gained by replacing the headlight with a LED one. H4 replacement LED bulbs exist, and entire units do too (at a price, of course). That way you can gain some 50W.

Before reducing load by replacing normal light by LED's, best make sure the charging control is still effective at that lower load (so still charging at, say, 13.5V, even with the lights switched off). Some older systems rely on the load of the lights, and give maybe 16-20V without it.

[Blurredman]

I've never really had a problem with demand overtaking supply with the MZ generator.

The times I do are a response to my own wiring. That being a relay in connection with the feed from the high beam also activating low beam. This does discharge, but rarely used other than country lanes. It also identifies that the charging system 'appears' to work appropriately as after a while the discharge light will start to glow.

There is also something to be said about the 55/60w Halogen and the 40/45w tungsten. You get much more for your money with the small increase of 15w.

That being said. The electrical system of the 12v MZ's can handle fine the requirements of low beam, dash lights, indicators (and idiot light), rear lamp and brake lamp all being illuminated at the same time.

[Puffs]

I believe the ETZ system is rated at 15A 14V peak, so that's about 150W RMS. If you put the 2 filaments in a H4 in parallel, it is 115W, +5W for the tail light, +4W for the city light (the little bulb below the main one), +2W for the dash light = 126W. Not sure how much the ignition takes, but those old-fashioned coils can take quite a bit, so yes, that way you'll drain your battery.

Interestingly, a while back I had some troubles with the charging system of an SP400, and I solved it by doing exactly what you did in your MZ: put the 2 filaments in the headlight bulb in parallel. Now that was because I could not find the proper bulb for it (it's 6V in an odd fitting), and what I made was 18+18= all of 36W. Although it doesn't need a battery for the ignition, the charge system is quite inferior to the ETZ's...

[Blurredman]

According to the 1981 service manual,

The alternator is a 210w.

And although 9ah battery is what it is built for, 5ah also seem to work okay. I had a 5ah in my first one when I got it and there didn't seem to be much of an issue.


It's all good fun isn't it.. Well.. It would be on a bike that self excited It wouldn't be fun to be stuck in the country in the night time because of a drained battery.
I very rarely get a problem with the charging system of a 12V MZ (not messed around with the 6v ones), and that problems that do occur are due to my user error or just loose wires. I have however stuck voltage displays on my Mz's, the discharge light can be tempermental. For example, if the return wire (blue and green I believe it is) that leads to the alternator is broken, disconnected etc. You won't get any indication of battery discharge. For a while I was getting problems some time back on my 7 mile commute, that the bike would work great to work, even with lights on, and then be jumpy and had lack of power on the afternoon ride home.. Little did I know that the battery was hovering at a pricarious 10v. Interestingly enough, the battery went so low one time that the main fuse kept blowing. Before I realised it was not charging, that lead me to all sorts of places looking for a solution that would have otherwise been evident.

[Warner20]

Ok, so the battery is actually fine it just needed a descent long charge and is now holding at about 12.4 v consistently and the bike is running perfectly, however the charging system is not working! There is no voltage increase on the battery no matter what the RPM and the battery light is staying on. I had the generator cover off and there doesn’t seem to be anything untoward and all connections are good, what should be my next port of call? Can any of you knowledgeable chaps give me a nudge in the right direction?

Tia

[Puffs]

In 30k miles my ETZ generator has never given me any hassle, but I'd first check the carbon brushes & verify they're making good contact. If the wiring & coils are OK, next the rectifier & regulator.

Btw, the primary of those 12V ignition coils is typically 4 to 6 Ohm, hence draws about 3 to 2 A, so some 25 to 40 Watt. If I remember, I'll measure the ETZ one when I get round to it. With the breaker open for 200°, it draws current for 160°/360°= 44% of the time.

[Warner20]

I checked the brushes and they are all good with plenty of tension in the springs, so I guess the next thing I’ll need to locate and test is the Reg/rec as you say. It’s really baffling me this one!