Fuel Pump

[Mike G]

I have just refitted the vacuum operated fuel pump to my Skorpion Sport (1996). I have run without it for about 6 months but have never got the carburation quite right. It was fine in town but when I made (infrequent) trips out of town there was often a misfire or stutter in the fueling. I experimented with needle settings and cleaned and checked the carburetors and air filter many times. Refitting the fuel pump has cured 95% of the problem so I thought I would let everyone know my experience. It is a shame that the pump seems important as it complicates the engine and limits access but I think it is needed because the one needle valve and float bowl feeds 2 carburetors which is something that I doubt it was designed to do.

On the subject of fuel consumption; around town I get 5.5 to 6.5 l/ 100km (52 to 44 mpg) and out of town 4.3 to 4.6 l/100km (65 to 62 mpg). How does this compare to your bikes?

Mike

[Nils D]

My Skorpion Traveller '96 have been without the pump for the last two seasons. And it works quiet well.
However, the mixture-screw is opend about five - six turns.

Nils

[Bill Jurgenson]

whatever the causes of your problems, the fuel pump is not the cure.
Countless Skorpions run and have been running without the pump. Really good dealers here removed the pumps right at the start before even selling the bike. The prototypes had no pump to start with.

austrian press report 1993

See if you can find one in these pics. And while you're looking, cast a glance at the Brembo wheels (3.5" rear), fully adjustable RSU fork (from TZ250R), aluminum swingarm or those pretty rearsets... You may also think you see a steeper steering head: they had 24º instead of the 26º the series then had. Better quicker handling without sticking the fork thru or jacking up the tail...
These prototypes were the ones tested by chosen dealers and racers in Spain 1993. They have the frame with the bonded CNC maschined aluminum swingarm mounts. Based on these and personal experience during the testng, many such dealers ordered as many as 100 machines.
They got what they got. In the States, that would have been cause for legal action and MZ would have disappeared right then.

None of my 3 Skorpions (1994 bought jan.1994 new, 1995, 1998 built without a pump from the start) had a pump.
To my knowledge pratically no one in the German Skorpion Forum has one mounted.

Many Yamaha SZR riders remove the pump although that bike actually needs the pump to scavenge the last 1/3 of the tank. They just gas up more often.

Even most racers, inasmuch as they are using a tank in the original position, don't use a pump and they are consuming 2-3 times as much fuel per second as you possibly could. Viz; 75-80hp running with two 38mm flatslides being fed by 8mm ID hose directly from the tank without a petcock. Lots of problems at such a stage of tuning, but starvation was certianly not one of them.

The MZ tank is higher than the float chamber. No pump is necessary; that's called gravity feed and has worked for motorcycles from the word go and for lots of cars as well: Model T, Model A...

Your starvation trouble has a cause(s) certianly: petcock, tank vent, needle valve, the connecting tube from the left needle chamber to the right valve-less chamber...