My winter project #3

Mini Bike & Go-Kart Parts

mustangfrank

Well-Known Member
#23
1" shaft 3" long :). I'll check into the 20. I've seen that pic before, the comet 20 looks like a good fit.
Agree, a 20 series will fit better, can't tell alignment from your picture but the 30 series driven would be flipped and have to be shimmed out a bit on the jackshaft to align the inner sheaves.
 
#24
here is what a 30 series would look like on a 71 frame.
6inch driven
6inchrupp.PNG
7inch very tight but it works
7inchrupp.PNG

also note i just made my mounting plate with ear's for the t/c cover. if you decided to use a 7inch you would have to spit the cover open and re fiberglass it in and the bottom would have to be cut open to clear the foot pegs.....lot of extra work make it look good.
if you stay with the 6inch and a 30 you would also want to look into modifying the driver so it does not go into overdrive and allows the engine to rev higher. this is a hot rod build? correct? sounds kind of funny but the way you build your motor might dictate your drive train setup. 20 series does sound better....:scooter:
 
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#25
Agree, a 20 series will fit better, can't tell alignment from your picture but the 30 series driven would be flipped and have to be shimmed out a bit on the jackshaft to align the inner sheaves.
little lost ? the 30 series would need to be flip? the 20 series would need to be flip....correct
 
#27
Ok, just a rough fit up. What's the options for a torque converter other than the orig TC? Comet 20 or 30? Hs50 setting in there. Custom jack shaft? Its my first venture from an orig
restore so this is new territory. Appreciate the feedback, thanks.
View attachment 272584
wow, that does look like a 1inch. thats one thing that photo didn't show was the shaft size. kind of harder to find them on the older points stuff. now i did point out the side cover before you purchase it that it was front fill only. so you will need a different cover or if you can just tap the rear out. couple guys here have done it in the pass. i don't know the tap size off hand?
 

mustangfrank

Well-Known Member
#29
little lost ? the 30 series would need to be flip? the 20 series would need to be flip....correct
Yeah, I should have said opposite the 20 series Skipp posted a picture of. Inboard and outboard is a better way to write it. Those smaller Rupp engine plates and narrow frames don't allow much side to side engine adjustment.
 
#30
1" shaft 3" long :). I'll check into the 20. I've seen that pic before, the comet 20 looks like a good fit.
dalpan, here is a stock rupp torque converter that the driver was modified so the belt would not travel to the top so we could get more rpm's out of the engine. at 125 ft we could get 6000+ rpm's out of it. engine on this bike was nates(rupp72) built hs-50 with a dellorto 22mm...etc..
assuming you want to build this engine(hot rod) i would make a ring spacer for the 20 series to keep the driver from traveling all the way and run a 2500+ up to 3000 rpm stall springs. i never use the aluminum weights over the stock magnesium weights,but some guys have and say they work better?
video isn't much to see other then you can tell the engine is spinning more then 3600 rpm's at 125ft...lol
 
#31
robertson's makes the best header for this bike too . much better then the stock header was built. just make sure you tell him the port size/year of the block...etc so he can make the right header flange.
20180725_134709 (3).jpg
 
#32
here is what a 30 series would look like on a 71 frame.
6inch driven
View attachment 272593
7inch very tight but it works
View attachment 272594

also note i just made my mounting plate with ear's for the t/c cover. if you decided to use a 7inch you would have to spit the cover open and re fiberglass it in and the bottom would have to be cut open to clear the foot pegs.....lot of extra work make it look good.
if you stay with the 6inch and a 30 you would also want to look into modifying the driver so it does not go into overdrive and allows the engine to rev higher. this is a hot rod build? correct? sounds kind of funny but the way you build your motor might dictate your drive train setup. 20 series does sound better....:scooter:
Try to make a hot rodder, but sure not as many R's as you can turn!
 
#33
wow, that does look like a 1inch. thats one thing that photo didn't show was the shaft size. kind of harder to find them on the older points stuff. now i did point out the side cover before you purchase it that it was front fill only. so you will need a different cover or if you can just tap the rear out. couple guys here have done it in the pass. i don't know the tap size off hand?
1" Am I a lucky man! you mentioned the side cover before I purchased the engine, I'll drill and tap the side cover.
 

DaddyJohn

Well-Known Member
#35
wow, that does look like a 1inch. thats one thing that photo didn't show was the shaft size. kind of harder to find them on the older points stuff.
Is there an advantage to a Tec HS engine with a 1" shaft in some situations?

I've got an HS40 with a 1" shaft sitting on the shelf because I typically use centrifugal clutches, and 3/4" is usually better for those...
 
#36
Is there an advantage to a Tec HS engine with a 1" shaft in some situations?

I've got an HS40 with a 1" shaft sitting on the shelf because I typically use centrifugal clutches, and 3/4" is usually better for those...
yes, on a wood chipper...lol
they do make clutch's and torque converters for 1inch,but it will more then likely cost little more$$
 

DaddyJohn

Well-Known Member
#38
yes, on a wood chipper...lol
they do make clutch's and torque converters for 1inch,but it will more then likely cost little more$$
They do, I've looked into it. The cost is a little more, but the bigger issue is the number of teeth is greater, so you need a bigger rear sprocket if you don't want to deal with gearing it taller. I've got a Roper with 10" wheels that's missing the jackshaft assembly, and was thinking of using it on that, as I could correct the ratio with the intermediate gears when I make the new jackshaft.

So, if you use a TC, the 1" shaft is fine?
 
#39
They do, I've looked into it. The cost is a little more, but the bigger issue is the number of teeth is greater, so you need a bigger rear sprocket if you don't want to deal with gearing it taller. I've got a Roper with 10" wheels that's missing the jackshaft assembly, and was thinking of using it on that, as I could correct the ratio with the intermediate gears when I make the new jackshaft.

So, if you use a TC, the 1" shaft is fine?
yes, on a tc 1inch shaft driver unit setup, the area where the belt rides on at idle does not use a bronze bushing like the 3/4 driver does,so in a round about way that area is the same size. and if i am correct dalpan can make a ring spacer for that area to control the rpm's(higher) his plan was to use a torque converter. so he will pay little more for a driver,but it won't break is wallet either...lol unless we get into maybe stroking the crank and other mod's....we do know a guy in his town that can do this(regrind the crank).....lol
 
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DaddyJohn

Well-Known Member
#40
yes, on a tc 1inch shaft driver unit setup, the area where the belt rides on at idle does not use a bronze bushing like the 3/4 driver does,so in a round about way that area is the same size. and if i am correct dalpan can make a ring spacer for that area to control the rpm's(higher) his plan was to use a torque converter. so he will pay little more for a driver,but it won't break is wallet either...lol unless we get into maybe stroking the crank and other mod's....we do know a guy in his town that can do this(regrind the crank).....lol
Makes sense, so that's another option! :)
 

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