Dual-sport bobber project

[dm11590]

on that other post was it that you didnt pass emmisions? and thats some bull on how u cannot rtv seal the header, cuz the good silicone gaskett maker wont melt and that shouldnt be a problem at all

[Metal_God50]

There is no emissions testing in my city. I had a leak in the header pipe manifold, which was do to a stripped stud. It was an easy fix and I passed.

[Metal_God50]

This is roughly what my frame will look like when im done with it. although I still may use the original swingarm or perhaps a longer swingarm, if I can extend mine or get a longer one to fit. Also im going to extend and rake out the forks and set up some forward controls. I will have to get a rear brake cable and longer chain as well. The welding will need to be extremly well done becuase I intend to take this bike off-road. Alot of people are gonna think this is a crazy and flat out stupid idea. But the whole purpose of this project is just to prove that it can be done and will be done. and that (to my knowlegde) a dual-sport chopper/bobber is something nobody has ever seen or built before.

[Metal_God50]

Originally Posted by Metal_God50

This is roughly what my frame will look like when im done with it. although I still may use the original swingarm or perhaps a longer swingarm, if I can extend mine or get a longer one to fit. Also im going to extend and rake out the forks and set up some forward controls. I will have to get a rear brake cable and longer chain as well. The welding will need to be extremly well done becuase I intend to take this bike off-road. Alot of people are gonna think this is a crazy and flat out stupid idea. But the whole purpose of this project is just to prove that it can be done and will be done. and that (to my knowlegde) a dual-sport chopper/bobber is something nobody has ever seen or built before.

I forgot to attach the file LOL!

[RichLockyer]

Stick with the stock swingarm.
Without a frame jig, you'll never get the rear end straight and that thing will be a deathtrap.

Sorry... but it has to be said.

DON'T take it off road once you convert it... the springer seat may save your a$$, but the frame will take the full beating and those welds WILL break.

[Metal_God50]

Originally Posted by RichLockyer

Stick with the stock swingarm.
Without a frame jig, you'll never get the rear end straight and that thing will be a deathtrap.

Sorry... but it has to be said.

DON'T take it off road once you convert it... the springer seat may save your a$$, but the frame will take the full beating and those welds WILL break.

Even if a pro does the welds?

[RichLockyer]

I wouldn't. There's a reason my dirtbike has 12" of suspension travel, and not all of that is for rider comfort.
With no suspension, there is no force holding the tires in contact with the trail... honestly, it'll be the worst handling POS you've ever ridden off road... even on a fire road... the smallest rut is going to play heck with handling, even if the frame does survive (and for how long).

The issue with rear wheel alignment, even with a pro doing the welding, is something that is up on the level of a pro bike builder.

I really think you would be better off looking for a junked Kawi 800, Honda VLX, or other bike with the "Softtail" swingarm design and building from there.

[Metal_God50]

Originally Posted by RichLockyer

I wouldn't. There's a reason my dirtbike has 12" of suspension travel, and not all of that is for rider comfort.
With no suspension, there is no force holding the tires in contact with the trail... honestly, it'll be the worst handling POS you've ever ridden off road... even on a fire road... the smallest rut is going to play heck with handling, even if the frame does survive (and for how long).

The issue with rear wheel alignment, even with a pro doing the welding, is something that is up on the level of a pro bike builder.

I really think you would be better off looking for a junked Kawi 800, Honda VLX, or other bike with the "Softtail" swingarm design and building from there.

True, but its a matter of making a 100cc engine fit into a large frame. And I know first hand what its like off-roading with no suspension. Awhile back I removed the springs from my shocks. And I had no problem controlling it. Generally. I stand up on the pegs all the time letting my knees be my suspension. And flying off the bike off-road is rather fun. (granted I have full gear on and its muddy on the ground. I assumed that if little bolts that hold on the springless shocks wont break, than a good weld wont break. Maybe I should bolt the hardtail section of the frame to the swingarm, then weld over it for extra support. The frame tubing is rather thin as well. We're talking about a 200lb 100cc bike, not a 400cc motocross.

[RichLockyer]

YZ450F is only about 250 pounds... a bit more "wet"

I still don't think it's a good idea for a dual-sport beyond basic gravel roads and driveways. I see the attraction to a bobber... I'd love to have one too, but there are things that they aren't good at... long highway rides is one, and off-highway is the other.

The bolts on your makeshift hardtail didn't break during the time that you rode it, but that doesn't mean they would have lasted a year or two.

Again, I think the SAFEST way to go would be to simply eliminate the subframe behind the top shock mounts, but retain everything else from the original frame, then replace the shocks with solid pieces, shortened to give you the rake angle you want (which will cost you ground clearance BUT you won't have any rear suspension compression to deal with so the clearance will not change much.


But honestly, I like how you currently have it... it doesn't look like a dual-sport, and you can still pick up a honey and give her a ride to your favorite corn field. Go with a solo bobber and she's going to have to have her own ride

[Metal_God50]

Maybe I should buy this eBay Motors: New 2006 Mini Chopper Soft Tail Frame (oc) (item 260156349935 end time Sep-10-07 09:15:31 PDT)

although the frame looks rather wide, im not sure I could make my tiny engine fit. It says "mini chopper" though.

[RichLockyer]

Does look pretty wide. $170 shipped? Could be a good project, wish they provided measurements.

Hmm... maybe not....
eBay Motors: NEW MINI CHOPPER REAR RIM & TIRE W/BRAKE HUB A (item 260155250327 end time Sep-06-07 18:32:58 PDT)
Rear tire is a 130/60-10.
Front is a 90/90-12
That whole frame is probably about 2 feel long.

[Metal_God50]

It would be hard finding a chopper frame that my engine would fit in. And since welding the frame is starting to seem like a no go. I may just have to abandon the project altogether. I didn't know that welding was so weak. I was thinking of simply putting heat on the top of the frame (where the seat and gas tank meet) and bending down that whole portion and bolting it to the swingarm where the shocks would normally bolt on. And then reinforce it with a weld. I don't "have" to take the bike off-road (I rarely do) Its just that if it looses its off-road capabilities, then its no longer a dual-sport. Just a mini chopper. So I guess its a principle kinda thing.

[RichLockyer]

Welding done properly is plenty strong, but a part of the problem is that you are working with a frame of an unknown alloy, and that makes a difference in how it needs to be treated. If it's 4130, it's totally different from mild steel or aluminum.

If you will keep it on the highway, you could get away with replacing the entire rear frame section (using the stock swingarm to maintain geometery) with two tubes running to the center upright piece, perhaps with some reinforcement running down to the area in front of the swingarm mount.

Welded properly, that would last. What you don't want to do is have any unsupported bends in the middle of a frame member.
Custom ideas 1 and 2 are both asking for trouble.
Better would be to go with something like the shopped photo of the '78 frame, but retain the stock swingarm.

[Metal_God50]

Originally Posted by RichLockyer

Welding done properly is plenty strong, but a part of the problem is that you are working with a frame of an unknown alloy, and that makes a difference in how it needs to be treated. If it's 4130, it's totally different from mild steel or aluminum.

If you will keep it on the highway, you could get away with replacing the entire rear frame section (using the stock swingarm to maintain geometery) with two tubes running to the center upright piece, perhaps with some reinforcement running down to the area in front of the swingarm mount.

Welded properly, that would last. What you don't want to do is have any unsupported bends in the middle of a frame member.
Custom ideas 1 and 2 are both asking for trouble.
Better would be to go with something like the shopped photo of the '78 frame, but retain the stock swingarm.

You mean something like this?

[Metal_God50]

The specs say the frame is made outta high tensile steel.

[RichLockyer]

Originally Posted by Metal_God50

You mean something like this?

Bingo.

[Metal_God50]

I already posted this in another thread but it applies here as well. Here are some more recent pics of the bike.









They give a better idea of how the bike will look when its bobbed out.