Cafe Racer looking build

[BoardTrack]

This is my first build and it has been a pain in the arse (nothing new about bikes haha). I had begun the build with the hopes of fitting the engine on a smaller frame with larger diameter wheels, I'm not fond of big bikes with small engines. Anyways this is how it turned out.
Positive and negative critique is what I came here for! I have yet to begin welding so this isn't near completion.
Enjoy!
Spencer.

 

[2door]

Spencer! If you cut that top tube off you made a very BIG mistake. That frame will fail and can hurt you. DO NOT ride that bike. If you have engine to frame clearance issues you should have asked here for help. There are other ways to deal with that.
Please listen to me and do not ride that bike the way it is.!!!

Tom

 

[BoardTrack]

I appreciate the concern Tom, and it is much understood. Running along the top of the frame is a heavy quarter inch steel that is in place to be welded. If you do not believe this will suffice for a good return in structural integrity, let me know and I will scrap the bike.

 

[2door]

In your post you said there was some welding to be done. Does that "welding" include that 1/4" piece running from the seat tube to the head tube? What I can see is clamps. Clamps won't do it. Don't rely on them no matter how tight.

You have to consider that the top tube on a bicycle is a major structurel frame member. If it is compromised in any way it can lead to failure of the attachment point of the down tube and the head tube. A failure there will cause the frame to collapse, folding in on itself at the front of the bike.

Stand off to the side and look at your bike frame. Try to imagine a downward force being applied where the fork, top tube and down tube meet. Imagine what will happen when that force (bumps, rider weight, etc) overcomes the weld at the down tube and the head with no support from a missing top tube.

This is my concern. Others will have opinions so wait for them.

Tom

 

[Intrepid Wheelwoman]

You would at least need to weld in two parallel steel tubes to replace the section you've cut out to clear the carb and air filter. Using a piece of flat 1/4 inch steel to replace the missing section of frame tube just plain isn't strong enough and it will bend with possibly serious consequences to your wellbeing.

 

[xseler]

Looks like you could've avoided cutting the top tube by just rotating the head 180* --- then the spark plug would've cleared the tube. Then added an off-set intake............... I'm also scared of going fast without a front brake. Speed doesn't kill/injure, it's the sudden uncontrolled stops that get you.

If you still have the tube, you may be able to just weld it back in place.

Very cool looking seat, though!!

Good luck with the continuation of your project!

 

[2door]

I agree. Rotating the cylinder head is easy. Just remove the four nuts, lift off the head and turn it 180 degrees putting the spark plug to the front. Be sure to turn just the head and not the cylinder. However the cylinder can be rotated too but it requires a little more work. Check here > http://motorbicycling.com/showthread.php?t=13458

The carburetor/air filter issue could be solved by an off-set intake manifold.
There is a thread here that shows in detail how your frame could be returned to original.
I'll find it for you and post it later.

Tom

EDIT: http://motorbicycling.com/showthread.php?t=52039 See my link in post #10 for how I fixed a similar situation.

 

[BoardTrack]

Thanks guys/and gals, I had mentioned somewhere that I rushed the build due to excitement and Christmas break. I really wish i had known about the head rotation and the offset intake manifold, its too late for those however that will be very useful information in the near future. (I cut the frame and should not have, I understand that and have learned a lesson, we will see how the welding goes before I work on "repair" but thank you anyways Tom)

I am in the process of fitting both rear and front tires with disk breaks, the bicycle recyclery where I live just happened to have the perfect rims. The spark plug that I have now says Z4, does anyone know where I could find a low profile equivalent? And any info on the offset intake manifold would be greatly appreciated.

Also something that I am aware of is the fact that this bike would not be safe to ride in its current state. If the welds are done with precision, which I'm sure they will be, I'm hopeful the steel will add structural support. I was suprised the amount of physics that go into the frame itself though, not something I should **** with.

Who would happen to know the best style frame for the look I am hoping to achieve? I'm not really sure if there is a specific name for the look I like.

Thanks everyone,
Spencer.

 

[runnermike]

Please take the advice that the members have given. It will possibly save your life!

On another note...where did you get that seat? I'm digging it...

 

[wheelbender6]

I dig that cafe look and your resourcefulness. I just don't want you to get hurt. Repair the top tube or swap the frame. Ton up!

 

[BoardTrack]

I understand completely, very convincing people and info, new used frame here I come. Haha I didn't mention that I sanded the entire frame down, it was blue and it took me four days. That's why I was so anxious to get it on the bike, (it doesn't fit? Don't worry I'll make it)ADD kind of attitude. I appreciate the concern people, or more so the concern for the reputation of motorized bikes haha, thanks guys.

About the seat, I'm glad you like it. Its mostly recycled parts, the seat is mainly from this
http://www.genesbmx.com/X-Games-fenders.jpg
I took the plastic piece that is wrapped in the seat material and foam.
I then took the hardware from a fat cruiser seat with springs.
I bent the main supports inwards to fit the underside of the seat.
Mounted the springs on the seat.
I also added for good measure, support along the support guides or whatever it may be called(I'll post pictures as soon as i get a chance, if anyone would like to see what I'm talking about). One more thing I have is a u shaped piece of steel on the back that is connected to both support guides and springs to keep it together and possibly support two people(not recommended)only with the steel plate as back support running the distance of the top tube.

Spencer.

 

[xseler]

If you can conjure a seat like that outa 'parts', you can certainly build a bike! Just no hurries....

Again, good luck!

 

[BoardTrack]

Much appreciated xseler!