Another Motorbike Build

nate25tenn · Oct 7, 2013

Well I've been collecting a ton of parts for my next build. This one is far more ambitious than my first build but that's the way I like it. Here is the candidate for the build.

It's an old Rollfast I believe. Not sure on the year or model but it was cheap. Hopefully no one gets mad it's going to get chopped. Now for the interesting part of the build...the engine. I debated using a 5hp briggs for quite a while then stumbled across something I've never seen before.

It's a 300cc opposed twin 2 stroke engine from a 2 man chainsaw. A Titan Blue Streak. Picked it up off a buddy for $30. The internals are spotless and I cannot wait to fire it up.

So far I've disassembled the bicycle and have slowly been stripping the unnecessary weight off of the engine and have made it far more manageable to attach to the bike.

nate25tenn · Oct 7, 2013

That's my progress so far. Not really sure exactly the look i'm going for but I keep looking at the 1919 Harley Davidson Model W Sport Twin for inspiration. I'll leave this with a video of one of those engines operating. I love the sound.

http://youtu.be/MPC6znBYuTE

atombikes · Oct 7, 2013

Wow, this is really good. Will keep an eye on this build for sure!

Moisstink · Oct 7, 2013

This looks about as cool as it gets. Post a lot on the progress. I would love to do something like this!

maniac57 · Oct 7, 2013

Very cool engine! I bet it sounds awesome too! Two stroke multi's have some of the most hair raising exhaust notes of any engine type.
Remember the H-2 Kaw's?
RD-400's?

pedalslow · Oct 8, 2013

I will have to keep up with this for sure that's bad to the bone.

CranbrookKid · Oct 8, 2013

^+1, coolest small motor I've seen so far.

curtisfox · Oct 8, 2013

KOOOOOOOOL. Kind of reminds me of the old Monark twinn i use to have.

Douglas motor cycle has a twin like that...............Curt

nate25tenn · Oct 9, 2013

The Harley Model W was based off of the Douglas Twin. The Harley made about 6hp. This one made 10hp at least back in 1947 when it was built. I'm not concerned about top speed. Hoping I can make around 50mph while reliably climbing hills. I live in a very mountainous region. I plan on fully registering it once complete. Friday I'm removing the cylinders and cleaning the carbon build up and if all goes well ill be uploading video of it running. If anything breaks though I'm screwed. Haven't found any spare parts yet.

2door · Oct 9, 2013

I can just imagine what that engine would sound like with twin pipes, baffled of course, running out back on either side. Oh yeah. That would be cool.
Keep us updated on your progress in this thread. We'll be watching.

Tom

Ron344 · Oct 9, 2013

I don't want to disappoint you but that motor will ripe the wheels off the bike. I had one just like that on a mini bike in the 60s it was a mercury 2 man chine saw it had HP they are so powerful they will tear up anything you put on the bike. Mine was only 250cc at 12 hp it would do wheel stands at the crack of the throttle. You could not build a bike frame to hold the power.

msrfan · Oct 9, 2013

Don't be discouraged, enough triangulation and gusseting along with heavy duty wheels and other components, you'll have a winner.

nate25tenn · Oct 9, 2013

Ron344 said:
I don't want to disappoint you but that motor will ripe the wheels off the bike. I had one just like that on a mini bike in the 60s it was a mercury 2 man chine saw it had HP they are so powerful they will tear up anything you put on the bike. Mine was only 250cc at 12 hp it would do wheel stands at the crack of the throttle. You could not build a bike frame to hold the power.

Your fine I've thought about that quite a bit actually. If it breaks no big deal ill build a stronger frame. I have a general idea as to what I'm doing but am totally up for suggestions. we will be strengthening the frame along with stretching it to make it more stable. I'll also have better wheels, brakes, some front suspension at least. We will see what happens lol. What's life without risks?

Ron344 · Oct 9, 2013

You could ask Tom about his exsperience with the Mercury engine in a go kart. They would go 90 to 100 mph. Their is some vido on you tube of these motors if you want to check it out.

msrfan · Oct 9, 2013

Does it have a clutch? I always wanted to mount an opposed twin sideways and couple it to a peerless five speed trans. Turn the tranny up on end and power to the front (which was the bottom) and a disc brake on one side and a sprocket on the other to the rear wheel. Maybe a centrifugal clutch in between.

nate25tenn · Oct 9, 2013

It had a transmission so to speak. At first I thought it was going to have to sit sideways thinking the gearbox was part of the crankcase. I removed it to find it wasn't and that shortened the engine quite a bit. I haven't thought about a clutch yet. It may end up with a torque convertor. I've only gotten as far as a basic idea and some parts. That's why I love this forum. Learn awesome ideas every time I visit.

nate25tenn · Oct 10, 2013

Need some opinions everyone. I think Friday ill be ordering my wheels and have 2 different routes I can go. The first choice is a worksman set with the front drum and rear coaster. The 2nd choice is Felt wide wheels and buying a front drum hub to put on them. There is only about a $40 difference I'm just not sure which way to go. Both use 12g spokes I think. Wider rims are good but worksman have a bigger brake compared to say a SA drum. I don't want discs...doesn't look right. Is the extra width worth the smaller brake? Opinions/suggestions please. When I get home ill link the parts I'm looking at for a better comparison.

silverbear · Oct 10, 2013

My initial reaction was 300CCs!!!... deathwish, but it sounds like you are prepared to gusset and do whatever else to beef up the frame.

As for the wheels I'll go along with others regarding the Worksman rims and 11 gauge spokes. Awesome... however the front drum brake is a disappointment in stopping power. I'm familiar with three of them and they were all inadequate. Might be ok for a pedal bike, but not a motorbike. The sturmey archer stops better and I understand that the bigger Sturmey Archer (90mm) are better yet. You can also get that one with a built in dynamo.

Husky sells heavy duty rims and also 11 gauge spokes so that with a larger hub from a light motorcycle (or maybe the 90mm S.A.) you could make your own wheel with a drum brake and real stopping power. I wish the Worksman had a better brake, but they don't.

You might consider light motorcycle wheels which are stout, have tires made for durability and speed and were designed to stop something going faster than a bicycle. 300X18 or a 19" rim (measured differently than bicycle wheels... an 18" moped or motorcycle wheel is close to a 24" bicycle wheel). I know you said you aren't planning to go fast, but when you have that kind of power at your fingertips the temptation is to goose it a little more... at least it is for me.

The engine is very cool and this Rollfast will be capable of rolling really fast! Keep her safe.
SB

buba · Oct 10, 2013

i like the idea of it sideways as well ---kind of early funky bmw like

anyone think that the auger idea or some other stronger gear unit might work for that????
with a shaft coupling??? like from grange???

curtisfox · Oct 10, 2013

Yep that be Kooooool and here is a right angle gear box for it.

http://www.searspartsdirect.com/par...247/1503730?pathTaken=&prst=0&shdMod=13181364

They have 3/4" shafts and good bevel gears............Curt

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