1981 SD900 Darmah - Restoration Project

Post pictures of your twin cylinder Bevel Drive Ducati (pre-1985) along with a description here.
machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Thu Nov 17, 2011 3:20 am

George,

For my money, you can relax on the sprag issue and carb tuning. In my humble opinion it would be almost impossible to tune a carb to stuff up a sprag that wasn't about to fail anyway. Ignition timing - yes, battery - definitely, cam timing - possibly, but carb - I can't see it.

Kev

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Sun Dec 18, 2011 11:47 pm

I'm not writing anything. This time I'll let the picture do the talking.....

http://www.flickr.com/photos/21807291@N ... otostream/
1981 SD900 Resto project

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Mon Dec 19, 2011 2:13 am

OK, I'll bite. Is that oil or brake fluid? (or something else entirely) :cry:

Kev

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Mon Dec 19, 2011 5:47 am

Water. It's just had a bath and then wheeled into the sun for a good rub down and it's tummy tickled...... :lol: ;)

G
1981 SD900 Resto project

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jaffa
Mariana
Posts: 28
Joined: Sat Jan 29, 2011 9:32 pm

Post by jaffa » Mon Dec 19, 2011 1:42 pm

Nice looking paint job Pilot.

She looks far better now than the purple she came in.
Jaffa
Volvo Aware Motorcyclist

'78 Darmah
'92 907ie
'82 900 MHR

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Mon Dec 19, 2011 2:46 pm

Water. It's just had a bath and then wheeled into the sun for a good rub down and it's tummy tickled......
Phew!!! For a moment there I thought ......

It looks really sweet. Congratulations! 8)

Kev

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Mon Dec 19, 2011 4:04 pm

Devastated.......

The sprag blew for a second time outside the testing station. It had started fine ten minutes before, was warm with a fully charged new battery. I know the pick up timing is good. It has new plugs, new fuel.

The only thing I can think of now is that the cam timing might be out. I've had enough now. I'm not touching it until the new year.

As I said before, looks fantastic but is stationary.

Has anyone any experience with the sprag upgrade kits that are available? Before I splash out $600 AUD I'd like some feedback.

Merry Christmas! :cry:
1981 SD900 Resto project

radecal
Parallel Twin
Posts: 102
Joined: Thu May 18, 2006 7:40 am
Location: Australia

Post by radecal » Sun Jan 01, 2012 5:59 am

Check out VeeTwo website. Brook Henry makes bloody good gear and he is an ex-pat NZer as well :-) http://www.veetwo.net/
The sprag upgrade kit will be going into 3 of my Darmahs (not done yet). Brook has done work for me over the years and I trust his stuff.
Availability of parts is the attraction.
Regards,
RAD

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Mon Jan 02, 2012 7:02 am

To blow one sprag is unlucky. To blow two quickly would seem to me to be stretching coincidence. I've owned two darmahs, one for 32 years, the other for about 7. I've never had a sprag problem with either of them. I have another friend that's owned his for 30 years, and ditto, no problem. They have a "bad reputation", and it is a weakness, and I've seen them fail, but it's a weakness that materialises generally because of another problem in my expereince.

When the sprag "blew", what happened exactly? Was it the same as last time? Can you post some pics of the failed parts? (either this one or the last?)

Kev

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Mon Jan 02, 2012 11:23 pm

Hello Kev,

Sprag number 1:

http://www.flickr.com/photos/21807291@N ... /lightbox/
http://www.flickr.com/photos/21807291@N ... /lightbox/

This was way back at the start, about 6 months ago. At that time I hadn't read all the posts about how to start a bevel twin and I was treating it the same way that I've always tried to start Jap fours, press the start and twist the throttle. There were a few back fires and then the bang that did the damage. I will add that the battery was sus at that time and as I found out when I checked the pick ups, one was quite a bit different to the other.

Sprag number 2:

http://www.flickr.com/photos/21807291@N00/6626158951/
http://www.flickr.com/photos/21807291@N00/6626147679/
http://www.flickr.com/photos/21807291@N00/6626142473/

I pulled it apart again today. I'm getting quite good at this now!

The history for this one is a little more detailed.

The bike was rewired last month. The pick ups were checked for resistance and setting. All good there. A new, large battery was installed and fully charged. Fresh fuel. The sprag was changed for a new SKF one purchased from Steve. When I tried to start it all I could get was back fire after backfire. I must have tried 30 or 40 times. This is where I think the problem started. I gave up in the end. I thought it was the pick ups so I pulled the clutch cover off again and took it to the auto electrician to check the resistance and to make sure that it hadn't been wired up wrong at the plug. The bike came with a really ugly block connector and the auto elect had put in a flash new one. Both the resistance and wiring checked out (220ohms on both).

As a passing comment he suggested that I try swapping the coil leads over as he wasn't THAT certain he wired them right. I did just that when I got home. First touch of the starter and the bike fired. The idle is set a touch low and so after it fired again I gave the throttle slight twist and away she went. Magic. I couldn't have been happier.

The next day I started it again. I was still sure that the bike wasn't that well tuned and the carbs definitely needed to be balanced but it was starting quite easily once you knew how and would run and rev beautifully.

I put it onto the trailer to take it to the testing station. Once the bike was off the trailer I tried to start it, got one bang and then whizz whizz. Good Bye Mr Sprag.

I checked the pick ups again today and they haven't moved. Luckily the sprag has stayed in one piece but as you can see, it's rooted. Even luckier, when I bought the last sprag, I ordered two. The flywheel is sitting on the bench waiting for the new sprag and I'm holding off refitting it until I get some feed back. There does not appear to be any other damage.

I'm sure that I can get to the end of this mini nightmare but it is a struggle. My own opinion is that the constant back firing with the cross wired coils did all the damage and that the low set idle and a tad early twist of the throttle outside the testing station was the final straw.

I'm about to order parts for a carb rebuild but need to know if I should hold off starting the bike until I've done the rebuild or carry on as before.

Many thanks for your advice.

Best regards

George
1981 SD900 Resto project

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Tue Jan 03, 2012 1:09 am

Any chance there's a problem with the ignition module? Just a thought...

Luckily I just got hold of a couple of spares, if you think thats a possibility...

Regards G
1981 SD900 Resto project

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Craig in France
Cagiva Gran Canyon
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Post by Craig in France » Tue Jan 03, 2012 1:47 am

pilotg wrote: Sprag number 2:

My own opinion is that the constant back firing with the cross wired coils did all the damage ...
+1, George. 30 or 40 backfires!? Man, that's just plain mean :twisted: ! I reckon your careless auto electrician owes you a big apology and the cost of the sprag, at least ...

(And a word to the wise: if a Ducati doesn't start after 3 or 4 attempts, don't keep trying. There's a problem. Find it, resolve it, then start it ... :) .)
pilotg wrote:I'm about to order parts for a carb rebuild but need to know if I should hold off starting the bike until I've done the rebuild or carry on as before.
If it was me, I'd do the carbs now George, while the bike is down. It shouldn't be more than a couple of hours careful work.

When you buy the parts, think to get all the little O-rings and gaskets. They only cost pennies,and it is just frustrating to have to wait for another delivery thru the post. And it's not a bad idea to change the choke pistons and the inlet valves as a matter of course, too. You only want to do this once and then not again for the next 10 years ... 8)

P.s Be very meticulous about:
1. Setting the float heights. The way to do it is described in the Dell'Orto manual, section 3.2.2. Personally, I have a little gauge cut out of a piece of hardboard that I slip over the floats to make 100% sure they're right.

2. Clearing the air passage that feeds the idle circuit; and ditto for the progression hole. A careful read of the Dell'Orto manual, especially sections 3.4 and 3.5, and all should be come clear (pun intended).

Good Luck! You WILL get there!

Ciao

Craig

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Tue Jan 03, 2012 2:39 am

Craig's said it all I think. That number of backfires under start will do it. I'd definitely do the carbs now too.

Kev

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Post by pilotg » Wed Jan 04, 2012 1:27 am

Ok, Ok, I know. I was a plonker for making the bike backfire that many times but I was so excited to be so close to having it running again that I let me heart rule my head. In my defense, I had no reason to believe that the wiring wasn't as it should be. I'd had it done by a professional, hadn't I?

The advice given has been just what I was looking for and for that I am truly grateful.

The new sprag is in. I've decided to leave the 38mm Dellortos in place. I'll go through the setup procedure detailed earlier and see how that works out. In the meantime I'll order the bits I need to rebuild a set of 32mm Dellortos I bought on ebay. As soon as they are ready I'll renew the manifold gaskets and fit them in place of the 38s. I should be able to get an idea which one works best for me.

I am, at some future date, probably during our winter, going to check out the cam timing. I really wanted to be really up to speed (forgive the pun) for this summer but that looks unlikely now. I'll focus now on the long term position. I do feel somewhat isolated being in a small town here in NZ. There are very few bevels down this way and so this place has been a beacon of hope on a dark and stormy sea.

Sincerely, thanks for the help. One thing is now certain. I have bevel disease....

V best

George
1981 SD900 Resto project

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Wed Jan 04, 2012 4:25 am

George,

For the rest of us, it's good to know who our sprag change expert is now!
I've decided to leave the 38mm Dellortos in place.
I'd do the same. I've always thought the 38's would be a good compromise between the the 32's and the PHM 40's for a darmah. I'd be interested to hear how it turns out.

From Craig...
(And a word to the wise: if a Ducati doesn't start after 3 or 4 attempts, don't keep trying. There's a problem. Find it, resolve it, then start it ... .)


I totally agree. A reasonably set up Darmah will fire and start on the first ignition stroke on either cylinder every time with choke and no thriottle. My 78 would do that even when compression was down to 105 psi before its rebuild.

If it makes you feel any better re persisting with starting whilst getting the backfires, I can recall one time relatively recently where my 78 didn't fire at all and i was 500km from home. I checked the fuses (OK), pulled the plugs to check for fuel (OK), pulled off the body work to check the earths (seemed OK). As it turned out, I'd attempted to start the bike from the LHS (I usually start from the RHS), and in doing so had brushed the the kill switch (which I never use) and inadvertently turned it off. I did that at a classic race bike meeting in front of a number of Ducatisti. Now that is embaressing... :oops:

Kev

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