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Author Topic: My little kz440 project  (Read 621 times)

Offline Venderbroeck

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My little kz440 project
« on: Aug 08, 2019, 13:09:35 »
Hello good people of dotheton.

I am new to this forum, which I stumbled upon during my research of the little bike I plan to convert into my vision.
I'm one of those peculiar people that buys a bike to mod before actually getting the license to ride it.
In my defence though, I've been around bikes for quite some time now (both parents rode at some point, now only my dad rides his suzuki and Harley) and I worked on bikes of friends on occasion including a wicked s1000rr.
This project will probably last more than long enough for me to get the license anyway.
I cut my teeth working on modifying cars (both rebuilding anything mechanical, and reverse engineering and modifying software). My fix for the itch for power is a 1994 volvo 850 turbo, which I own for quite some time now. I built the engine, and I'm in a never ending process of upgrading the turbo to something larger.
This will be the first time modifying a bike beyond bolting on some aftermarket parts.

The bike in question is a 1980 Kawasaki KZ440LTD. Many would argue it is not an ideal base for a cafe racer, and I would agree to a certain extent, but it was very cheap and it's what I could find that was to my liking. It didn't run at all when I picked it up, but it was cheap enough not to care too much. I was prepared to fix it up if required.
However the engine ran beautifully after spending 5 minutes to fix some electrical issues (the wiring has become a bit of a mess in its 39 year lifespan). It started instantly, and there's no rattle from any of its four(!) internal chains.
At some point someone put some amount of effort (and money) into modifying the thing to some sort of gaudy chopperesque ehm... creation.
It has an apehanger of sorts, and theres chromed pointy nuts and bolts everywhere.
It's not my thing, but I have to say, it was a fun thing to putt around with on the driveway for a bit.
It has been neglected some in the last few years though, resulting in corrosion everywhere and a general state of rattyness and unsafeness.
Here's a pic of it without the saddle on:



Time to start to put it right.

I have teared it down completely, carefully labeling everything in the process. Some things are still usable, and other things I can adapt for my new build.
It has forward controls for example which look like a good quality set despite their state of decay, so I think I will modify them to be my rear sets later on.
Other plans I have is to redo the entire electrical system of the bike, and bring that to a more modern standard. I will probably design a control box to make this happen.
Once it is more or less completed, and running again I might look into converting it to efi just for the hell of it. I saw a diy efi project (speeduino) that looks promising, and I want to try it out.
Of course these things do not make a cafe racer, but they will contribute to the sleek look I'm after.

Before any of those future dreamings can come to pass there's a big crooked elephant in the room that needs to be addressed.
The rear of the ltd style frame is really not very suitable for the cafe look, so it has to be modified.
I know there are options that don't require modding it, but I'd like to avoid those if I can as they don't appeal to me as much.
Frame modifications are not to be taken lightly, so I'm trying to do this the best way possible.
The plan is as follows (shouldn't be very surprising):



I can tig weld a little, but not good enough to do this kind of work, so my plan is to make the cuts in the frame myself, to make all the parts required for it, and to make them fit perfectly with no gaps, but to let a pro do the actual welding itself.
At this point I have made a brace to keep the rear of the frame into shape while it is worked on:



 It's made from quite thick steel strips, and the boltholes have quite a tight tolerance, so there is no discernable movement however much I yank it. It has a bit less leverage than the original upper frame rails have due to its angle, but I think it should be sufficient. The only movement I can imagine it making is if the whole thing twisted, but that seems as (un)likely as it is with the original frame rails still in place. It's surprisingly rigid actually. Do you guys have any thoughts? Any pointers are most welcome of course.

I wrote some emails to a few bike shops, but as it is holiday time the replies are only trickling in.
One of the shops insisted that the new parts should be made of chromoly, and charged what I think is quite a bit of cash for the welding (it converts to about 220 dollars).
I'm not sure if chromoly is the best idea, as I don't believe the frame is made from chromoly so it would mean joining dissimilar metals.
Also adding some bracketery would be inconvenient, as it is harder to weld chromoly. Mild steel of sufficient thickness (2mm) would be just fine I feel, but feel free to correct me.
Anther replied that he didn't know what kind of material these frames are made of (does anyone know this?), so he didn't want to risk working on it.
Hopefully I can find someone proficient that can do the work for a reasonable price.

I'll try to log my progress here as much as I can. It will take time, but hopefully it will be interesting to someone.
« Last Edit: Sep 20, 2019, 16:05:56 by Venderbroeck »

Offline canyoncarver

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Re: My little kz440 project
« Reply #1 on: Aug 08, 2019, 13:35:17 »
Welcome to DTT!  Looks like a fun project. 

Offline sandmanred

  • Posts: 63
Re: My little kz440 project
« Reply #2 on: Aug 08, 2019, 18:55:04 »
Welcome and good luck!  That looks like a good base bike to me.

I would look for other options than the shop that insists it be chromolly.  I don't think mixing metals is a metalurgical concern, I use the same rod for mild as chromolly.  I just don't think it's necessary.  I think most manufacturers use mild steel.  I've built several frames from the ground up and always use mild steel.

Can I offer an opinion about fitting and tacking?  I cope my joints but then grind back a bevel all the way around the cope to force myself to get to the root of the weld.  If the fit is perfect you can't be sure you are getting to the root.  If I was making a coffee table I might prep like you described to get the prettiest weld but for MC frame I want to be sure I get to the root.  Maybe find your welding outfit first and get their guidance on what they'd like to see for joint prep?

I think close to 2mm is pretty common and would be okay.  To me that's 14g and I've seen mostly that I the bikes I've worked on.  I tend to go a bit thicker.  The weight is typically of no consequence and my bending methods sometimes leave some scarring that I can safely dress out on 11g tubing (about 2.5mm)
« Last Edit: Aug 08, 2019, 18:59:52 by sandmanred »

Offline Venderbroeck

  • Posts: 8
Re: My little kz440 project
« Reply #3 on: Aug 08, 2019, 19:08:27 »
Your opinion is much appreciated and makes a lot of sense. I will discuss it with the shop once I find one, but I'm sure they will agree.
Can I ask you for your opinion on the brace/welding jig? I think it's good, but I may be missing something.

I found a shop that offers pre bent tubing for frames I think I could use as a base. I bet that will be prettier than I could make it with limited tools for bending.
If I do decide to try bending it myself, I'll make sure to get something thicker.

Offline doc_rot

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Re: My little kz440 project
« Reply #4 on: Aug 08, 2019, 20:42:28 »
you can mix and match stainless, mild steel, and chromoly. just need to use the right filler rod. Chromoly is not really necessary in most applications. it just lets you go with thinner wall tube while retaining the same strength and rigidity. 2mm is a good thickness for mild steel. if using chromoly you could safely go 1.5mm or less. I don't think that frame brace you constructed will do much as you haven't triangulated the location of the shock mounts, add a portion to connect from the shock mount to the passenger peg mount as well. its easier and better to just weld some scrap metal straight to the frame with some beefy tacks. That being said I wouldnt worry about it too much, both KZ frames I have chopped up were not symmetrical, on my kz750 the shocks mounts were 6mm different side to side from the factory.

Offline Venderbroeck

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Re: My little kz440 project
« Reply #5 on: Aug 08, 2019, 21:49:33 »
Thanks for the pointers.
By adding a strip from the shock mount to the passenger foot peg, wouldn't I just be doubling on the rear lower frame tubes?
I wont be removing the rear lower frame tubes, so they would constitute the other leg of the triangle.
I was thinking about adding a strip at right angles to the current strip connecting it to the passenger footpeg to compensate for the steeper angle the brace makes in comparison with the upper frame tubes which task I want it to take over essentially. My thought process was that in function the brace is just a copy of the upper frame tubes, only it's connecting to a lower point at the front.

Looking more closely at other pictures I have of the area, the connection of the lower tubes to the shock mount may get weakened temporarily during the modifications.
Adding that strip would help quite a bit with that I think.

Of course, worrying about it too much may be unnecessary as you say, but it's an easy thing to make, so I thought I'd give it a shot. Keeps me busy on a rainy day.
« Last Edit: Aug 08, 2019, 21:55:27 by Venderbroeck »

Offline doc_rot

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Re: My little kz440 project
« Reply #6 on: Aug 08, 2019, 23:07:56 »
You are correct I misunderstood your post. Weldmentss have a tendency to spring apart whe you cut them, so I donít think you can go too overboard here

Offline sandmanred

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Re: My little kz440 project
« Reply #7 on: Aug 09, 2019, 13:14:38 »
I agree with the point that weldements spring somewhat when they are cut.  You'll be cutting a triangles apart so they may spring differently.  When I look a the picture of your brace I'd be inclined to try to hit point that makes a bigger triangle.  I see you used convenient bolt holes to capture the frame but if have a welder a small tack can be made anywhere on the frame that would allow the brace to be placed closer to parallel with the piece you are cutting.


Offline Venderbroeck

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Re: My little kz440 project
« Reply #8 on: Aug 09, 2019, 18:16:05 »
That's quite useful information, then I know what to expect when I cut the welderdements.
I agree that the angle it is making now does give it quite a bit less leverage, and I have contemplated tacking something to the frame, as it would also have been easier than making the holes exactly to the right size.
I didn't do it because I thought that tacking to the frame could already potentially weaken it. Maybe I'm being too paranoid.
I was also doubting that a tack would be stronger than a big bolt through the frame, especially if I keep it small to avoid weakening.
Tomorrow I have some more time to work on the frame, so I think I'll be giving it a good look to see if I can make it better in that aspect.

Offline doc_rot

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Re: My little kz440 project
« Reply #9 on: Aug 09, 2019, 19:11:21 »
A couple  tack will be more than sufficient. As long as you donít grind into the original tube when removing the tacks it is totally fine