Durkopp Scooter Tuning (Non-Guzzi Content)

[dgurovich]

I'm working on a 1957 Durkopp Diana Sport (200cc), with 12v electrics and Electric start.  I've gotten it running and starting under it's own power, and it's frankly an awesome little scoot.

I've got a problem that I'm having a bit of trouble with, as the scoot has a Bing carb.  When it starts the idle will creep up and up until it is very very high.  The bike runs fine, takes off fine, etc, but coming to a stop, the idle just goes through the roof.

I know that 90% of carb problems are electrical, but I think this one is actually a carb problem.  One of the dumbest things that Bing did is make the two jet fittings the exact same size.  I see that one has a screen on it, and the other one doesn't.  I'm assuming that the one with the screen goes under the float bowl?

Any other thoughts about the climbing rpms?  It did not always do this -- it hadn't run in 20 years, and when I got it running it didn't do this.  It all of a sudden started happening, and sometimes the opposite occurred when it would not take a load off idle when in gear.

Thoughts?

[Sasquatch Jim]

  It's irrevokably broke.  Send it to me and I will dispose of it free.


  BTW do you have the sidecar for it?

[Antietam Classic Cycle]

Sounds like a leaky crank seal to me. Sucking in air past one of them and leaning out the mixture.

[dgurovich]

I thought about the leaky crank seal, but the idle is very smooth, and it isn't down on power at all when at speed (hauls ass).  It's still on my list.  I think I'm going to pop the carb off and just tighten everything up. 

[Lannis]

Sounds like a leaky crank seal to me. Sucking in air past one of them and leaning out the mixture.

Is there a good way to test for that?   

Lannis

[Lannis]

Yes .

  Dusty

That's easy for YOU to say ... 

I'm just wondering whether this motor is the kind where you can change crank seals from the outside, like an old MZ, or whether it requires splitting the cases .....

Lannis

[dgurovich]

It's a sachs motor.