1970 Rupp Scrambler questions...diaphragm carburetor and more.

#1
3-4 years back i bought a 70 Scrambler, like the one I had in '70, and with your help i got it running pretty decent. It was a total basket case missing tons , when I bought it.

Saturday I bought another 70 Scrambler in remarkably un modified condition.

original everything except it has a Roadster exhaust and a kill switch.

Here are my three questions..

Still has the original diaphragm Carb. How do they work? Why no float bowl? 2021scrambler.jpg

Mine , in general will only run at full throttle, Starts on choke and wide open throttle together, won't idle and really only like to go flat out and even then only revs to maybe 3000 rpm [governor issue?] and will hiccup every thirty feet or so. And Ideas?

I am going to give this bike a very limited restoration. The wheels are the low point. Who restores these wheels and how much should I expect to lay out for the pair. Are there any replacement for the 10'' laced wheels?

Third question. I was thinking of replating all the nuts, bolts, spacers , bushings , sprockets etc. What finish were they originally? Cadmium? Nickel? Galvanized? And suggestion on who to perform this service?

Thanks for your help, Jim.
 

mustangfrank

Well-Known Member
#2
3-4 years back i bought a 70 Scrambler, like the one I had in '70, and with your help i got it running pretty decent. It was a total basket case missing tons , when I bought it.

Saturday I bought another 70 Scrambler in remarkably un modified condition.

original everything except it has a Roadster exhaust and a kill switch.

Here are my three questions..

Still has the original diaphragm Carb. How do they work? Why no float bowl? View attachment 284122

Mine , in general will only run at full throttle, Starts on choke and wide open throttle together, won't idle and really only like to go flat out and even then only revs to maybe 3000 rpm [governor issue?] and will hiccup every thirty feet or so. And Ideas?

I am going to give this bike a very limited restoration. The wheels are the low point. Who restores these wheels and how much should I expect to lay out for the pair. Are there any replacement for the 10'' laced wheels?

Third question. I was thinking of replating all the nuts, bolts, spacers , bushings , sprockets etc. What finish were they originally? Cadmium? Nickel? Galvanized? And suggestion on who to perform this service?

Thanks for your help, Jim.
I'll take the carb Q...the diaphragm carb is basically a carb with an integral fuel pump instead of a float bowl. Rupp only ran them for the first year (two for some) of the slant mount engines then the slant intakes with a float carb replaced them. Sounds like your low speed/idle circuit is plugged up and a thorough clean-up of the passages and probably a diaphragm rebuild kit will get you running smooth.
 
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