Author Topic: Prinz advance springs (same as Isetta?) where can I get some?  (Read 1409 times)

adi

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Well, I am slowly getting towards a running and driving Prinz!

It now has a new fuel system. Since the Prinz originally has a mechanical pump, which failed and filled the sump with fuel, this one now has a filter under the tank, a Facet fuel pump and a fuel pressure regulator. Of course, now it will never get that vapor lock issue that the Prinz is famous for either, and will never fill its sump with fuel.

The clutch works after a lot of messing around and a new disc and diaphragm spring, and everything else works nicely too. Just waiting for the master cylinder, and it should be road legal. Yay!

Anyway, there is only one problem I have encountered. The advance springs in the ignition system are too weak, since they weakened with age/corrosion, and as a result the advance curve isn't right anymore. I did have a screen-print of the curve, but I lost the usb stick that it was saved on, so I cant post it now, but anyway, the actual advance curve of the car is too steep compared with what it should have, and by about 700 rpm it's already advancing, and by 1000rpm its up to like 10* or more, whereas the stock curve should be 0*@~1000rpm, 5*@~1200rpm, etc.

From what I can tell, the advance is controlled by two asymmetrical springs, one softer giving the initial jolt of advance from 1100rpm onwards, and then the stronger one taking over at higher rpm to level the curve.

I already tried most places (yes, including the NSU club::) ) and nobody seems to have them, although they did say they were the same as used in the Isetta engine.

Does anybody know anywhere that sells them? Or can anybody confirm that they either are or are not the same as the Isetta part?

Anybody know if the Isetta club or any Isetta-specific parts sources stock these?

[ulr=http://img.photobucket.com/albums/v405/adibrook/advance.jpg?t=1311962120]Link to high-res image of parts diagram showing the two springs[/url]

Thanks

Bob Purton

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Re: Prinz advance springs (same as Isetta?) where can I get some?
« Reply #1 on: July 29, 2011, 08:07:56 PM »
Hi ADi. I just this week replaced the two advance springs on my isetta. I have no idea if they are the same as used on a Prinz though. I have the ones I took off in front of me now. They measure 20mm overall length and 5mm wide. If these sound like the ones you want you can get them from The Bromley Bubble Company http://www.bromleybubble.com/   

Big Al

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Re: Prinz advance springs (same as Isetta?) where can I get some?
« Reply #2 on: July 30, 2011, 10:08:40 AM »
A much ignored component. Learn all you Treinkelnauts with cars that do not perform. Where do you get springs for them? Hopefully the Scooter owners will have created demand and the Germans have them. I will be needing some soon.
Messerschmitt set, Goggo Darts, Heinkel 175, Fiat Jolly, Autobianchi, Fairthorpe Electron Minor, Borgward, Isuzu Trooper
Citroen BX 17TZD & GTI 16v
Held - MG Magnette ZB & 4/44
For sale - Vellam Isetta, Bamby, AC Type 70, Velorex, Church Pod, Reliant Mk5, KR200,  Saab 96, Bellemy Trials, Citroen BXs

adi

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Re: Prinz advance springs (same as Isetta?) where can I get some?
« Reply #3 on: July 31, 2011, 07:45:33 PM »
The problem is, most ignition advance springs on German stuff (as used in almost all bosch distributors and their derivitives) are a standard pattern, which is about 20mm long and 5mm wide, as you described. It's their spring rate that's important, which is unfortunately not something you can tell just visually by looking at them.

Does anybody happen to know the advance curve of a Isetta? It should be in the book, if anybody has one handy?

Also, what does an Isetta advance mech physically look like?