Project: Black Widow

#1
Hi folks! After a bit of thinking, I have decided to build a clone of a Rupp Black Widow. I’m using the frame from a Hustler, parts from a ‘71 Enduro, and an HS50 for the motor. I already installed a billet rod into the Tecumseh, removed the governor, and painted the frame and engine black. I also have a Dell’Orto UA16S carb which I will use. Looking for a 12” rear wheel at the moment, the one on the Enduro is rusted out.
 

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cfh

Active Member
#2
The 16mm deloroto works great on an HS50 motor. But you will probably have to get a new float bowl. Looks like you have a 30 degree bowl. the most you can practically use is the 12 degree bowl, and really it should be 0 degrees (but you'll never find one of those at a reasonable price.) The 12 degree bowls are available on ebay (about $30).

what jetting are you using? i have documented dellorto jetting on my web page. jetting is all over the place depending on where that carb came from. Usually the ua16 comes with pilot jet 45, needle jet (type 1485) 260, 5mm main jet 80. This actually works fine on a HS50 motor.
 
#3
I have an adjustable main jet, the jet itself is the one Black Widow Motorsports sells for the Rupp UA19S. I don’t recall what idle jet came in the carb, hopefully the range of adjustment is within reason. As far as the float bowl, I ordered a 90 degree float bowl from Australia, hopefully it will fit my carb.
 

cfh

Active Member
#7
where did you find that float bowl?
i had to make one... you can cut a 12 degree bowl and spin it, re-weld. would be better to buy one...
please email or PM me if you don't want to post... cfh@provide.net
 
#9
So I installed the throttle and cable to carb, along with the exhaust. That’s it for this month, I have a video on Facebook minibike groups if you want to check it out.
 
#11
A video of my progress so far.
I just finished my 1971 Rupp Blackwidow #2 last night. Still have to change the high speed jet on the Dellorto to the adjustable variety. I have a #85 main jet, and it actually works quite well. But to be 'official', need to make it an adjustable type.



Very nice! Moto guzzi sells an adjustable main setup for $70, that’s the one I bought.
 
#12
I got the adjustable dellorto main jet from Blackwidowmotorsports.net since they have the jet receiver that is required too. They call it a #68 jet, but really it's just a brass jet looking thing with a big hole. I've found other places selling the Dellorto adjustable main jet, but they don't have the jet receiver. You need it too. I made one for one of my bikes. But it's better to just buy the thing. If you don't have it, the adjustable main jet won't work.
 
#13
I got the adjustable dellorto main jet from Blackwidowmotorsports.net since they have the jet receiver that is required too. They call it a #68 jet, but really it's just a brass jet looking thing with a big hole. I've found other places selling the Dellorto adjustable main jet, but they don't have the jet receiver. You need it too. I made one for one of my bikes. But it's better to just buy the thing. If you don't have it, the adjustable main jet won't work.
I bought the jet itself from Black Widow Motorsports, but everything else to make the main adjustable I got from Moto Guzzi. It was $20 or so cheaper than going with the individual pieces from BW. Came with the fiber washers too.
 

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