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Author Topic: Project CB690 (KTM 690 engine in a CB550f frame)  (Read 3268 times)

Offline dakine_surf

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #30 on: Feb 07, 2018, 19:53:38 »
Ambitious!!!

I like it!

What is your plan for suspension?  Are you going to try to retrofit the  ktm bits?  Iíll be watching


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Offline goodoltup

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #31 on: Feb 08, 2018, 13:46:07 »
Cheers Dakine!
I am considering;
     Front suspension
              GSXR forks, with cognito hub and other bits
              Shortened KTM forks, with KTM hub, wheel and brakes
     Rear suspension
              Fox twin shocks, with FZR 600 swingarm (modified to use the swingarm bushing in the engine case)

The KTM swingarm is too long, even if I move the motor forward as far as I can. I will still give it a try this weekend and see how it looks. Even if it does fit and doesn't look to bad, I would have to sub out the aluminium welding to get the shock mounts on, whereas the FZR swingarm is steel. Something to consider.
The KTM forks need to be shortened by 100mm if I have any chance of using them. I have not investigated yet if this is possible, but soon I will disassemble one and see what needs modification.

Offline dakine_surf

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #32 on: Feb 08, 2018, 14:51:05 »
100mm is about 4Ē I donít know the duke suspension travel is but I feel like 100 mm is doable. 

If it were mine Iíd probably keep as much of the ktm stuff as possible, just for the cool factor...  but also keep with the twin shock theme out back so fzr swingarm sounds like the way to go.


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Well I tried but I can't run no more
Tell Katie it's her that I adore
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I'm that much further west

Offline goodoltup

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #33 on: Feb 10, 2018, 11:40:42 »
Here is the start of mock up. The tank ALMOST fits, but the tunnel will need to be modified to clear the frame spine. That will allow it to sit a little lower and line up with the seat.
I also put the KTM triple trees on there just to see how it might look. The KTM steering stem is much longer than the CB neck, but that might present an opportunity. What if I were to lathe up some bearing cups that could be fitted to the CB frame? That way the length could be matched, and the KTM bearings could be used, with no need to make a new steering stem at all. Provided I can shorten the forks by 100mm, all KTM components could be used for the front end. This will be seriously considered. A GSXR front end would really look nice, but the KTM front end would be much cheaper and need almost no modification.


Offline goodoltup

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #35 on: Feb 11, 2018, 04:53:43 »
^^ Hi Irk,
That is very helpful, thank you very much! I will first measure the KTM clamp offset and determine if I can shorten the forks, and all being well I can make the cups on the milling machine at work.

Offline SONIC.

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #36 on: Feb 11, 2018, 17:27:36 »
I like it!

Just for curiosity sake though, why use the flexy old cb frame? Why not swap the swinger and modify the ktm frame for the look you're after?

Granted I'm not familiar with the frame layout, but if it were me I'd probably keep the ktm frame and lop off the subframe and rebuild as a twin shock if that's the look you're after

Offline goodoltup

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #37 on: Feb 11, 2018, 17:44:57 »
^^ Hi Sonic,
I can't say that the frame isn't a concern, but I won't be riding it at 100% anyway. Using the KTM frame would be too much 'making a modern bike look classic' and not enough 'stuffing a hooligan motor into a classic bike.'

Offline Popeye SXM

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #38 on: Feb 11, 2018, 20:15:30 »
I like your project and I get the ''classic bike with modern motor''. The closer the swing arm  pivot is to the sprocket the better, from the mock up it looks like you will have to mod the frame a lot. Also is there enough space for the throttle body & air filter? Good luck I will be following with interest. I like the tank

Offline Kanticoy

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Re: Project CB690 (KTM 690 engine in a CB550f frame)
« Reply #39 on: Feb 11, 2018, 21:08:51 »
Very interesting! Iíll follow along!


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