Can you put a new 6 inch comet driven 20 or 30 series on a Rupp Roadster 2 Jackshaft?

delray

Well-Known Member
#21
I see you put a 30 series TAV on your souped-up HS40 engine. You also mentioned that it did not perform as well as you like. Did you originally use the 20 series Comet style driver and driven before. I heard the 10% overdrive of the 30 series can sometimes bog engines with additional load especially on large wheel bikes.
yes , I had a 30 series and was not impressed with it at all. with the engine design to turn high rpm's and having no jackshaft to help with the gearing. it felt like for ever to get the motor to pull some real rpm's. i would like to try it out someday with a 20 series and 7 inch rear driven. that might help little(no overdrive?). but really the way the engine and bike is setup and for my application a torque converter is not for me on this bike.
here is a setup on my fox thunderbolt and works great with this bike off road on trails. I still runs a cast steel flywheel so I don't get any unwanted vibration. not like some people are experiencing with using billet flywheels. just a good strong motor that pulls a easy 6000 rpm's. I like it a lot. pull the motor off that bike last year to use the cam and couple other things. building a new motor this summer with a stock steel cam with a compression release and going to install a set of 1.3 rockers ,22mm carb ,header,hot coil....etc and see how it does.

https://www.oldminibikes.com/forum/index.php?threads/thunder-bolt.115101/page-3
 
#22
I really like what you did to your BlueWidow Rupp. I like the "BlueWidow" Decals you had made for it. What is your top speed and what engine mods have you done to your Honda Clone?
It had a jet kit,air filter and an exhaust made out of gas pipe using the 90 degree angle to keep it close to the frame. I have since sold it and never clocked it but I can tell you I could do the hillclimb at Windber which is a pretty good grade with no problem. AND I wright 375 pounds so the performance was excellent out of the clone with the 20 series
 
#23
It had a jet kit,air filter and an exhaust made out of gas pipe using the 90 degree angle to keep it close to the frame. I have since sold it and never clocked it but I can tell you I could do the hillclimb at Windber which is a pretty good grade with no problem. AND I wright 375 pounds so the performance was excellent out of the clone with the 20 series
Good to hear. I have often heard that the 30 series sometimes limits rpms by shifting into overdrive and some people say it has actually hurt the performance by overloading the engine. I want a fun ride that will hopefully be controllable and not a wheelie machine. My DB30 with a mildly modified Predator 212cc turned into a wheelie machine and it took 12 lbs of thick steel cut into three 4lbs pieces (two pieces over the wheel on the front fork and 1 down low on frame on front of the engine) to make the bike not want to pick up the front wheel. Three people wiped out before I decided that it was basically unridable for inexperienced people since nobody would lean forward despite me telling them to. Now it just goes forward and keeps the front wheel on the ground and there has not been any more incidents of unintended Wheelies
It had a jet kit,air filter and an exhaust made out of gas pipe using the 90 degree angle to keep it close to the frame. I have since sold it and never clocked it but I can tell you I could do the hillclimb at Windber which is a pretty good grade with no problem. AND I wright 375 pounds so the performance was excellent out of the clone with the 20 series
Good to hear that the 20 series TAV worked well for you especially on the hill climb. I have actually heard that sometimes the 30 series TAV driven shifts into overdrive too soon and actually limits the rpms of the engine and hurts its acceleration. I am going to do a stage 2 from NR racing and install a billet flywheel and Billet Con rod and 18lb valve springs which is easy to do with the piston at top dead center. NR racing says the engine is good for about 10 to 12hp with these mods and on a Rupp Roadster 2 frame it should be pretty lively when compared to a sedate (boring) original 4hp Tecumseh HS40. Some guys have moded the heck out of HS40 so it can keep up to mildly modified clones but I don't have a period correct good running HS40 to mod and I already have a Predator 212cc which I will be slapping on it as a resto-mod. Years ago I went to a Car Show and I spoke with a guy who had a beautiful 57 Chevey hardtop which had a modern Corvette engine with it's automatic transmission and all new suspension fitted to it with 4 wheel disc brakes. He said that he likes to drive his car and while the purists may hate that it no longer has the original parts. He says a modern engine and suspension and brakes make the car much safer and more enjoyable and reliable to drive. Plus he said that his big 57 Chevy hardtop gets about 20 mpg on the highway at 55 to 60mph with all those mods and a 57 Chevy is about as aerodynamic as a brick compared to a modern car. I may mock up a period correct HS40 to slap on the bike to sell it for big bucks someday but I plan on riding it and not making a museum piece which will be sitting on display afraid to ride it for it may get dirty like some people have done.
 

delray

Well-Known Member
#24
GustoGuy, I did little up date on my rupp for a short lived one race only(for now)with a clone motor installed. I think the most challenging thing was making a header fit without getting in the way and looking cool and functional.

I too did little up grade when restoring my 58. front disc,468 big block....etc..

 

delray

Well-Known Member
#25
Good to hear. I have often heard that the 30 series sometimes limits rpms by shifting into overdrive and some people say it has actually hurt the performance by overloading the engine. I want a fun ride that will hopefully be controllable and not a wheelie machine. My DB30 with a mildly modified Predator 212cc turned into a wheelie machine and it took 12 lbs of thick steel cut into three 4lbs pieces (two pieces over the wheel on the front fork and 1 down low on frame on front of the engine) to make the bike not want to pick up the front wheel. Three people wiped out before I decided that it was basically unridable for inexperienced people since nobody would lean forward despite me telling them to. Now it just goes forward and keeps the front wheel on the ground and there has not been any more incidents of unintended Wheelies


Good to hear that the 20 series TAV worked well for you especially on the hill climb. I have actually heard that sometimes the 30 series TAV driven shifts into overdrive too soon and actually limits the rpms of the engine and hurts its acceleration. I am going to do a stage 2 from NR racing and install a billet flywheel and Billet Con rod and 18lb valve springs which is easy to do with the piston at top dead center. NR racing says the engine is good for about 10 to 12hp with these mods and on a Rupp Roadster 2 frame it should be pretty lively when compared to a sedate (boring) original 4hp Tecumseh HS40. Some guys have moded the heck out of HS40 so it can keep up to mildly modified clones but I don't have a period correct good running HS40 to mod and I already have a Predator 212cc which I will be slapping on it as a resto-mod. Years ago I went to a Car Show and I spoke with a guy who had a beautiful 57 Chevey hardtop which had a modern Corvette engine with it's automatic transmission and all new suspension fitted to it with 4 wheel disc brakes. He said that he likes to drive his car and while the purists may hate that it no longer has the original parts. He says a modern engine and suspension and brakes make the car much safer and more enjoyable and reliable to drive. Plus he said that his big 57 Chevy hardtop gets about 20 mpg on the highway at 55 to 60mph with all those mods and a 57 Chevy is about as aerodynamic as a brick compared to a modern car. I may mock up a period correct HS40 to slap on the bike to sell it for big bucks someday but I plan on riding it and not making a museum piece which will be sitting on display afraid to ride it for it may get dirty like some people have done.
i think you will be better off with a 20 series. you don't need the overdrive. if anything you will need to get more gearing out of the bike and that will be hard without a jackshaft. I personally would try to make a bigger sprocket for the bike. that should help it pull better with your motor you want to install and plus with the 20series you will have two sides of the belt gripping with the V design. be cautious about what kind of billet flywheel you get. try to get the heavier one. hopefully you won't experience any unwanted vibration like some people have found with the comet units use on billet flywheel engines.
 
#26
GustoGuy, I did little up date on my rupp for a short lived one race only(for now)with a clone motor installed. I think the most challenging thing was making a header fit without getting in the way and looking cool and functional.

I too did little up grade when restoring my 58. front disc,468 big block....etc..

Modern computer controlled engines with electronic fuel injection are way better running than original engines with obsolete polluting carburetors and breaker point ignition. Lots of people like the look of an old car and buy a brand new crate engines and transmission to put in it along with suspension and brake upgrades for safety reasons. Old crappy cable brakes with drum brakes are not as good as computer controlled antilock modern disc brakes. Back in 2011 Car and Driver tested 3 new muscle cars against their late 1960's and 70's versions and the new cars out accelerated out braked and out handled the old cars plus the modern cars all got over 20mpg on the highway. Car and Driver said the new cars made the old cars feel like they all had flat tires since they were so much better. I plan to ride my bikes and this spring the China engine Predator 212cc started on 2 pulls of the recoil while the old Tecumseh on the Arctic Cat did not. I had to fix it and tune it up by removing the main bowel jet needle and cleaning it and blasting it out with carburetor cleaner. Both bikes had seafoam in the gasoline to prevent problems but only the Tecumseh was affected.
 
#27
i think you will be better off with a 20 series. you don't need the overdrive. if anything you will need to get more gearing out of the bike and that will be hard without a jackshaft. I personally would try to make a bigger sprocket for the bike. that should help it pull better with your motor you want to install and plus with the 20series you will have two sides of the belt gripping with the V design. be cautious about what kind of billet flywheel you get. try to get the heavier one. hopefully you won't experience any unwanted vibration like some people have found with the comet units use on billet flywheel engines.
I have seen NRracing sells the ARC Billet flywheel for $85. Is that a decent flywheel for a Predator 212cc and a TAV?
 
#28
I bought the 20 series TAV with a 6 inch secondary that was recommended. I will also be getting a reproduction stock Rupp TAV cover from Blackwidowmototorsports. I will be painting my bike and since I already own red spray paint I will use that to paint the frame. I will just do a stage 1 kit since a Predator 212cc with a stage 1 is running at about 10hp and that should be more than sufficient to provide power for the bike. I also have lots of parts in que at Blackwidowmotorsports but I am trying to not spend too much money which is real easy to do. I had a brand name Comet primary and secondary on my que but it ran the price up way too high compared to the China TAV. which was less than 1/2 the price. I seen that someone here on the forum had over $2000 in on their Rupp Roadster 2 since they most likely bought a good running rebuilt Period correct HS40 which I have seen on Ebay for as much a $800. I like resto-mods since aftermarket parts and engines are much better priced andvthe Predator 212cc is a darn fine easy to start and reliable engine plus 5/8 inch belt Rupp TAV's are obsolete and 3/4th inch belt Comet and clone derivatives are now the standard.
 

Top