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Post by freestone71 on Dec 5, 2020 20:51:08 GMT
hi all
about to build a pro cup 3 based engine to go in a 50 special
i have et3 cases , going to go with 27/69 polini gears , vmc tree with short 4th , and vmc exhaust and ignition
would reed valve make much difference or would the 25mm dellorto on rotary inlet be ok ??
also was going to get an ets crank but do i get a standard one or a race one ?
cheers in advance
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Post by jbcollier on Dec 7, 2020 15:58:43 GMT
Sorry, not familiar with the pro-cup regs so I can't give you specific advice as to what is legal.
Generally speaking:
- if you go reed, then you make the inlet opening as big as possible. Most reed set-ups use a special cylinder with a colossal opening to compensate for the inherent restriction of the reed valve itself. You would also go to a full circle crank for better balance. You can use an intake manifold with a reed valve built in but that is usually only if the rotary pad is toast.
- The "race" crank has a larger "cut-out" for a longer intake duration. You can also machine out larger the rotary pad area. Bigger hole = more flow but it also affects idle and low rpm. It's a compromise. If you do a lot of in-town group rides, a really high performance engine can be horrible.
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Post by henri on Dec 8, 2020 7:30:35 GMT
JB the pro-cup is a cylinder kit , basically a quattrini 125cc clone , available quite cheaply from places like aliexpress or banggood and ebay . freestone , i'd stick with a opened rotary pad , an stock ets crank possibly cut .as jb says how far you go depends on what you want from the engine n riding the scooter .H
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Post by jbcollier on Dec 8, 2020 14:20:28 GMT
Ah, thanks for the illumination.
Here's what I built with an M1:
- cases welded and port matched
- polini race rotary crank (beautiful crank)
- rotary pad opened up as low as possible, sideways to within 1mm of crank coverage
- rotary intake opened to match manifold and passage blended
- reverse mounted inlet to have carb exit out the side
- Hammerzombie pipe
- 30mm Dell flatslide
- DRT runner xmas gear
- DRT primaries and clutch
- SIP geared clutch cover
Pluses:
- %$#& it flies
- gearing is perfectly spaced
- falls off the pipe at 116 kph
- carb easy to get at for jetting
- did I mention it %$#& flies?
Minuses:
- it HATES putting around town
- always wants 5 to 10 more kph than what traffic is doing
- it's like riding a chainsaw without a muffler
- everybody loves it until you start it
- rain plugs air filter, and to fab a cover to keep it dry
- you absolutely have to upgrade your suspension and brakes
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Post by freestone71 on Dec 8, 2020 17:48:28 GMT
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Post by freestone71 on Dec 8, 2020 21:10:05 GMT
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Post by gugne on Dec 9, 2020 10:22:00 GMT
hi all about to build a pro cup 3 based engine to go in a 50 special i have et3 cases , going to go with 27/69 polini gears , vmc tree with short 4th , and vmc exhaust and ignition would reed valve make much difference or would the 25mm dellorto on rotary inlet be ok ?? also was going to get an ets crank but do i get a standard one or a race one ? cheers in advance I built one recently vespasmallframeforum.proboards.com/thread/23211/vmc-pro-cup-3 with much the same spec as you have there apart from I used a Pinasco race anticipated crank 20mm: www.officinatonazzo.it/crankshafts-crankshaft-anticipated-pinasco-race-51-cone-20-vespa-125-pk-primavera-et3.2.15.42.gp.2834.uwYou are going for 24mm cones so I don't know what the difference will be. I went with a Polini 24 carb and it all seems to work well. I didn't bother with a reed valve as the rotary pad was perfect. I have my doubts about the VMC short 4th tree as it threaded itself when I was torquing up the nut. I bought a DRT instead and it was much better quality. |
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Post by jbcollier on Dec 9, 2020 13:57:25 GMT
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Post by jbcollier on Dec 9, 2020 13:58:06 GMT
Don't go for a standard crank.
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Post by henri on Dec 10, 2020 7:20:24 GMT
if you want a standard ets crank ,you wont go wrong with one from stoffi ,https://www.stoffis.com/shop/artikel/490.010 , ive had a few an they have all been good .H
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Post by tzsteve on Dec 11, 2020 18:09:23 GMT
my cylinder is the quatrinni M1-GTR 56mm
i`m running an ETS crank with the big taper, from stoffis`
30mm dellauto
franz pipe
and a vmc ignition
inlet taken to about 198 degrees including the opening of the inlet on the case.
im getting 16 bhp 70 mph on the dyno
the only problem i have is that the clutch plates ware too quickly
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Post by jonnysnatchsniffer on Apr 1, 2021 21:16:49 GMT
steve ive taken the inlet to 215 degrees and find it much better
the shape of the inlet in no way should resemble a bellmouth, but be cut so that from the manifold hole the transition should be straight to edge of pad of which ive taken out to around .5-.7 mm all around, it needs a load of jb weld on the back of the inlet as if you have done the porting right you will break thru to the outside, 5 or so hp to be had here if done well
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hrvespa
ETS
1981 50 special, 1977 primavera, 1964 GL 150, 1975 125 TS (early P200 engine)
Posts: 161
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pro cup 3
Nov 27, 2021 18:17:48 GMT
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Post by hrvespa on Nov 27, 2021 18:17:48 GMT
if you want a standard ets crank ,you wont go wrong with one from stoffi ,https://www.stoffis.com/shop/artikel/490.010 , ive had a few an they have all been good .H Just ordered one of these from Stoffis, been emailed the invoice, gotta transfer payment but cant understand how to add their details into my online banking. Anyone who done this got any ideas how? Or just go into bank and get them to do it? |
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