900S2 1982 Ducati Electrical Query

[Johan M]

Hi

My name is Johan and new to the forum. I have picked up a 900S2 1982 ducati and restored it. I have taken everything off and apart except the main engine block – decided to see what will happen when I start it. It eventually started and I must say not too many concerns.

My biggest concern is to start the bike. Currently it is standing in the garage as I’m never confident that I will be able to restart the bike once I went somewhere, so reliability concerns.

The electrical side. Let me first explain what I have done electricals on the bike:
1. Replaced the old electrical harness completely.
2. Redone the starter completely.
3. New alternator/generator installed.
4. New battery – 18Ah

When trying to start the bike a few questions came up:
1. The 900S2 is the first (one of the first) electrical start ducati’s. As a result of this being new, were there a lot of problems experienced initially and was that overcame? Let me explain the question, when the spark plugs are out the engine turns freely with the starter. Once the spark plugs are in the engine struggles to turn. If you don’t get it started with the first few (3) turns, the battery is flat and needs to recharge. Is this due to the excessive compression that makes it turning so slow/difficult?
2. Is/was this a concern for this model bike?
3. Is the battery too small for the duty?
4. Was/is there something additional that can be done to minimize/remove the problem? Any advancements in the past 30 odd years I can incorporate?

Thanks in advance.
Johan

[rwhc80]

Hi Johan,

I think you will get some good replies on this question, but from my perspective, I think the 18ah battery would really struggle to turn over the S2. I think from memory these bikes came with a much larger capacity battery. I had similar problems with my 1980 SD Darmah and eventually with a decent battery and having an Auto Elec fit a relay that bypasses the 31 year old electrical switches and components, solved my starting problems.

Having said that, the starting issue was always evident at cold start, and presented no problems when the bike had been running for a while.

Good luck
Regards
Rick

[mgh1955]

Hi Johan,

you need a battery with more punch ... Yuasa 53030 (30 amp hour) will easily kick it over but not sure if it will fit in an S2. Alternatively try an AGM battery around 24 amp hour

Mick

[Craig in France]

Hi Johan,

Like the others - sounds like your battery is too small (but see my follow-up posting too).

All I would add is that the Amp Hour rating is not really what you're interested in. All the amp hour rating tells you is how many hours the battery will provide a constant supply of 1 amp - 18, in your case

But starting a bike isn't like that, of course. What we need is a BIG push of energy over a very short period. This is what is called the Cold Cranking Amps rating, aka CCA. And the more you can get, the better.

In my Darmah, for example, I have a Westco SVR30. Kicks out an impressive 370 CCA, 70 more than the original specification wet-cell Yuasa. Go

http://www.tayna.co.uk/SVR-30-Sealed-AG ... P7810.html

The only thing you need to be careful of is which way round the terminals of the battery are (i.e positive to the left or right); and, if they are reversed, whether you can still fit the leads on - you can on a Darmah, don't know about a S2.

Ciao

Craig

[Craig in France]

Like the others - sounds like your battery is too small (but see my follow-up posting too).

Hi Johan (again ),

I thought I'd just check what the original specification of the S2 battery was. Only 19 Ah, I see. So really quite small compared to a Darmah, for example ...

Which makes me think, if you know your battery is good (i.e. it holds a charge of at least 12.4 volts), you should also check the condition of the starter solenoid and the earth connection. Also, feel the starter leads - do they warm up when you push the start button?

(But get a bigger battery anyway )

Ciao

Craig

[Johan M]

Hi

Thanks for the help. A few things I have observed:

1. The battery seems good, had it tested and they say it is fine.
2. No marking on battery or spec sheet regarding the CCA.
3. Earthing seems fine and no excessive heating of cables.

The one message that is constant is to get a bigger battery. As you indicated the S2 was specified with a 19Ah battery. The 18Ah battery that I got hold of dimentions are 160(h) x 180(l) x 95(w). I am constraint by the width of the battery. Without doing any mods I will probably get maximum 105mm in.

So it is either to find one that will fit or to make mods to fit the 30Ah that was mentioned.

Johan

[Craig in France]

1. The battery seems good, had it tested and they say it is fine.

Always best to take your own measurements, of course . Do you have a volt meter?

2. No marking on battery or spec sheet regarding the CCA.

What's the make and model number?

3. Earthing seems fine and no excessive heating of cables.

Good. Remember to check the solenoid too. If it's dirty or worn, it will draw a lot of current.

EDIT: Ah, I see the S2 has the same one as was used on the Darmah - part # 0820.38.460. Dreadful thing, made by Lucas. They corrode inside. Replace it. You don't need to buy an expensive one. They were also used on loads of British cars from the period, including Landrovers and Minis. Here's one, for example:
http://cgi.ebay.co.uk/Land-Rover-Series ... 230557586b

And another - genuine Lucas, this time!:
http://cgi.ebay.co.uk/Lucas-4ST-Starter ... 2c5c4bb48e

I am constraint by the width of the battery. The 18Ah battery that I got hold of dimentions are 160(h) x 180(l) x 95(w).

This is a good battery - 275 CCA. Measures 165 x 178 x 76, so maybe it will fit? I use one in my Laverda Formula - which really IS a challenge to turn over .
http://www.westcobattery.com/battery_pa ... d=6&vid=-1

http://www.tayna.co.uk/51913-BMW-Westco ... P3394.html

... or to make mods to fit the 30Ah that was mentioned

Just remember it's CCA you want, not Ah (the two are related, but they're not the same).

Also: I'll pm you the e-mail adress of a friend who has a S2. You can ask him what battery he is using, etc etc.

Ciao

Craig

[Johan M]

Hi Craig

Thanks for the info, on the battery info.

What's the make and model number?

MS (Maan Shyang) Battery, CB18L-A

Thanks for the alternatives on the solenoid makes, even though the one on the bike seems fine I'm going to replace it!!!

Regards
Johan