Ru-p Roadster 2 engine replacement

GustoGuy

Active Member
#21

I like it! Great video![/QUOTE]


A wee bit faster than a Stock Rupp. Clocked on GPS 53 mph. ARC Billet rod and Billet flywheel and 22lb valve springs. May get an aftermarket cam too. Nice and smooth idle with stock cam feels like a motorcycle. Suzuki K10 Motorcycle fork plus aftermarket hydraulic shocks in rear too
 

GustoGuy

Active Member
#22
This is what I started with. I like to ride and messing around with a tired old engine is not my definition of fun. Plus 4hp stock Rupp roadster 2 is not exactly exhilarating to ride.. I did nothing to it that can't be undone either. 20170514_024948.jpg
 
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GustoGuy

Active Member
#23
There are a few guys that rebuild/restore them properly (NOT small engine shops, don't waste your time). A Tecumseh flathead from a snowblower donor with your tins installed is a cheap(ish) way to run it, look right and preserve the original engine. A 5hp HS50 looks identical to your 4hp HS40 externally, you'll just have to research the swap because of the longer Rupp specific PTO length your engine has now.

Bike looks nice, It'd be a shame to put a Chinese engine in it IMHO.

Black Friday is coming, for less than a proper, original Rupp HS40 sells for outright you can buy a Coleman minibike and go ride instantly if you don't want to fix your vintage minibike.

I like to ride and my Resto-mod Rupp Roadster 2 starts every time in 1 to 2 pulls of the recoil. Lots of people today are putting in 4 wheel disc brake kits into their classic cars as well as great running emissions legal crate engines in their classic rides rather than rebuilding an old engine while hoping to make them reliable. I don't understand the point of owning a non running vintage bike taking up valuable garage space since it either doesn't run or it is just too unreliable to ride. It is better to put an inexpensive great running engine on a bike then to let it sit in the garage or worse outside in a scrapheap. I see no problem in getting it running with a Predator and actually riding it. I can't understand spending $800+ on Ebay to buy a questionable old period correct HS40 which may not even run at all.
 

mustangfrank

Well-Known Member
#24
I like to ride and my Resto-mod Rupp Roadster 2 starts every time in 1 to 2 pulls of the recoil. Lots of people today are putting in 4 wheel disc brake kits into their classic cars as well as great running emissions legal crate engines in their classic rides rather than rebuilding an old engine while hoping to make them reliable. I don't understand the point of owning a non running vintage bike taking up valuable garage space since it either doesn't run or it is just too unreliable to ride. It is better to put an inexpensive great running engine on a bike then to let it sit in the garage or worse outside in a scrapheap. I see no problem in getting it running with a Predator and actually riding it. I can't understand spending $800+ on Ebay to buy a questionable old period correct HS40 which may not even run at all.
You've quoted me twice now, what don't you understand about my OPINION that I clearly stated in a reply to a thread in Strictly US Vintage on a minibike forum called Old Mini Bikes a week ago?

I've never spent more than 300-400 bucks total including the engine cost to restore/refresh an original or replacement Tecumseh flathead, usually less than 200 if they don't need a piston/overbore. That's adding a lighting coil and flywheel too on most. If I don't have one start on the first pull it's because I forgot to set the choke.

Bad analogy too...restomodding classic cars is cool, crate engine swaps are cool. Until China starts selling backwards leaning cheap replacement car engines and guys start stuffing them in their 1969 Mustangs and Camaros we really can't compare that.

Do whatever you want with your minibike, you're not selling me on your opinion...which you are entitled to.
 

GustoGuy

Active Member
#26
My HS50 starts the same way. It's not that tough to get an old flathead to run good. If i can do it, anyone can.
I like good running vintage bikes. And a good running vintage engine on a vintage bike is even better. I enjoy my bikes and I have a snowblower H50 Tecumseh powered Arctic Cat and a Baja DB30 with a stage 1 Predator 212. I will only swap out a vintage engine if I can't get it to run well. My Rupp Roadster 2 was a roller missing lots of parts and now it is a powerful fast resto-mod bike which I enjoy riding.
 
#27
I like good running vintage bikes. And a good running vintage engine on a vintage bike is even better. I enjoy my bikes and I have a snowblower H50 Tecumseh powered Arctic Cat and a Baja DB30 with a stage 1 Predator 212. I will only swap out a vintage engine if I can't get it to run well. My Rupp Roadster 2 was a roller missing lots of parts and now it is a powerful fast resto-mod bike which I enjoy riding.
Like i said, it's not for me. Other owners can power their bikes with whatever they wish. I'm sure your bike runs great and and is tons of fun. Good for you, a nice running minibike is such a great thing.

The key to a great running vintage flathead in my opinion- is to lose the lawn mower carburetor, and install a slide carb instead. Billet rod, good valve springs and a cam help as well.
 

GustoGuy

Active Member
#28
I was all in on vintage but these new coleman bikes are awesome. You never feel guilty doing anything to them.

I have a 12x20 shed full of vintage bikes but only ride my coleman bikes. They are all amazing! BT200X and CT200U are the best in my opinion.
I have 1970 Arctic Cat Prowler which was coverted to Tecumseh H50 flathead from the original Sachs engine way before I bought it. I also have a stage one Predator 212cc powered DB30 which is fun to ride too. My favorite is my 1971 Resto-mod Rupp Roadster 2 with the Suzuki K10 front fork. None of my bikes are factory original yet they are still are fun to ride. I looked at those Coleman minibikes and they look pretty nice and I see they have 6.5hp Clone style engines on them.
 

toomanytoys

Well-Known Member
#30
I have 1970 Arctic Cat Prowler which was coverted to Tecumseh H50 flathead from the original Sachs engine way before I bought it. I also have a stage one Predator 212cc powered DB30 which is fun to ride too. My favorite is my 1971 Resto-mod Rupp Roadster 2 with the Suzuki K10 front fork. None of my bikes are factory original yet they are still are fun to ride. I looked at those Coleman minibikes and they look pretty nice and I see they have 6.5hp Clone style engines on them.
Im not saying they aren't fun to ride but It depends on the bike. A bike that needs a ton of parts to restore back and they are impossible or super expensive. Do whatever. But a complete bike that can easily be restored...restore I've wanted to do a resto mod rupp but even crap rupps are going for too much near me.

My black widow is completely restored. I had a predator on it when I was waiting to find a correct motor for it. I enjoy it more with the correct motor on it, feels like I went back in time!
 

GustoGuy

Active Member
#31
Im not saying they aren't fun to ride but It depends on the bike. A bike that needs a ton of parts to restore back and they are impossible or super expensive. Do whatever. But a complete bike that can easily be restored...restore I've wanted to do a resto mod rupp but even crap rupps are going for too much near me.

My black widow is completely restored. I had a predator on it when I was waiting to find a correct motor for it. I enjoy it more with the correct motor on it, feels like I went back in time!

I only paid $100 dollars for my Rupp roller back in 2017. It came with a non running cyclone recoil cover Tecumseh. 20210919_184032_resized.jpg

Despite having a Predator and a Suzuki K10 front fork it's a nice looking fun to ride fast bike that goes over 50mph. Plus it has a smooth idle but I may swap out the stock camshaft for more power and rpms
 

Harquebus

Well-Known Member
#32
I want to fix this bike. vintage for me. I waited my entire life to get one of these Rupp Roadster 2 mini bikes. Couldn’t afford one when I was a kid...
The parts in bold are key to the whole thread. Now that you have a Rupp, I think you can wait a little longer to finally have that pure experience of your first ride with the original engine, as it was intended.

With the aid of the internet and this forum, you could just tear down the Tecumseh yourself, get familiar with it and document its condition.
And even, quite possibly, get the forum to inspect your parts by eyeballing the photos you take and share here.

I bet there's more than one Tecumseh disassembly video on U-Tub.
 

DaddyJohn

Well-Known Member
#33
It’s an interesting debate for sure, and I tend to side with the original engine style crew. However, I don’t see much reason for anyone not to do what they want, especially if it can be changed back at a later date.

That said, I’ve done the reverse of the resto-mod strategy and put a Tecumseh HS40 on a Baja Doodlebug before, lol…:D
 

GustoGuy

Active Member
#34
It’s an interesting debate for sure, and I tend to side with the original engine style crew. However, I don’t see much reason for anyone not to do what they want, especially if it can be changed back at a later date.

That said, I’ve done the reverse of the resto-mod strategy and put a Tecumseh HS40 on a Baja Doodlebug before, lol…:D

Better to resto-mod an old bike than scrap and recycle ♻️ it. My wife won't let me have any non running vintage bikes collecting dust. Plus if another person wants after I done using it.. They can buy it from me and find a period correct HS40 and put on the pogo stick sprung fork which I kept. I really do like the full hydraulic suspension front and rear. Very stable and smooth riding experience. it is a 50+ mph bike now and a suspension upgrade certainly is a good thing.
 
#35
The plan is to rebuild the existing engine. As far as changing the carburetor, what modern one would be good? Is there other tweaks to be made to the original engine to make it more reliable/enjoyable? I will keep the original parts…

I appreciate everyone’s input!
 
#36
A lot depends on what your goals are for the bike. Drag racing? Flat track racing? Top speed? Off road?
Or just a nice cruiser that starts and runs good?
Ever since using slide carbs on minibikes, i won't run any more lawn mower carbs.
As far as modifications, there is a ton of information on here if you search.
 

GustoGuy

Active Member
#37
The plan is to rebuild the existing engine. As far as changing the carburetor, what modern one would be good? Is there other tweaks to be made to the original engine to make it more reliable/enjoyable? I will keep the original parts…

I appreciate everyone’s input!
Keep it stock or find a Dellorto vintage carburetor if you want it to look somewhat stock. Blackwidowmotorsport.net has all the decals you need to make your Rupp into a Black Widow look alike if you wish. Just remember If you put a Mikuni or other slide type carburetor including the optional Dellorto which was used for 1 year on the Black Widow bikes on a stock Tecumseh HS40 it will bypass the govenor and could lead to engine failure. Billet connecting rods can help to reduce the risk of engine failure but are a bit hard to find for a vintage engine. A good running Tecumseh HS40 or HS50 will make for a good 30 to 35 mph Rupp which is family friendly. My bike is only adult riden and I have ARC Billet rod and flywheel with 22 mm Mikuni carburetor and my bike is way faster than any stock Rupp ever was. In fact it demands your undivided attention while riding it and it is only adult riden since it is way to powerful for little kids to ride.
 
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#38
I may be wrong but from the pic the OP posted, he seems to have an Hs40 already?
Billet rod is easy to find and not to bad $$$.
Valve springs and retainers aren't too bad either.
Free-flowing exhaust and a Chikuni carb and should be pretty reliable in my experience
 

GustoGuy

Active Member
#39
A lot depends on what your goals are for the bike. Drag racing? Flat track racing? Top speed? Off road?
Or just a nice cruiser that starts and runs good?
Ever since using slide carbs on minibikes, i won't run any more lawn mower carbs.
As far as modifications, there is a ton of information on here if you search.

Mukuni way better than $2 Predator carburetor
 
#40
Mukuni way better than $2 Predator carburetor
I don't run predator anything so don't really know.
but imho the slide carbs perform better on the flatheads for me than the stock tecumseh carb. Stock tecumseh carb is fine too if it's adjusted correctly. I had a lot of success with the stock carb as well.
Slide carbs adjust differently but the part throttle and overall drivability is infinitely better in my opinion
 
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