Modifying/Straightening Rear Sub Frame - Wrist Twisters
 
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post #1 of 11 Old 12-09-2014, 11:50 PM Thread Starter
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Modifying/Straightening Rear Sub Frame

Hello,

I was just looking at café racers and was wondering...

Has anybody tried to straighten the rear subframe of the 919? right above the rear shock?
Of course the rear would have to be shortened to accommodate for the new angle.


Any thoughts on this?

Thanks,
CJ

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post #2 of 11 Old 12-10-2014, 06:38 PM
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The subframe main tube can be completely removed past the two bracing tube welds. I did this on an '02 here: https://www.wristtwisters.com/forums/...ild-23737.html
As a bobber it worked pretty well, and if you want a typical café solo seat with tailpiece it should work as well.

Any specific plans? Or just exploring options?

Rob

If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
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post #3 of 11 Old 12-10-2014, 07:18 PM Thread Starter
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Originally Posted by robtharalson View Post
The subframe main tube can be completely removed past the two bracing tube welds. I did this on an '02 here: https://www.wristtwisters.com/forums/...ild-23737.html
As a bobber it worked pretty well, and if you want a typical café solo seat with tailpiece it should work as well.

Any specific plans? Or just exploring options?

Rob
I'm just thinking about how to make the bike flow. I have this rear end for inspiration, see attached.
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File Type: jpg honda-cb-cafe-racer-3.jpg (102.0 KB, 57 views)

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post #4 of 11 Old 12-11-2014, 12:39 PM
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Man, that is a BEAUTIFUL machine right there!!!!

2009 Aprilia Tuono - Ginger
2001 XR650R BRP (Big Red Pig)
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post #5 of 11 Old 12-11-2014, 12:55 PM Thread Starter
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Originally Posted by g00gl3it View Post
Man, that is a BEAUTIFUL machine right there!!!!
Yes it is. And I think if the same modifications were made to a 919, the 919 would literally look like that bike on steroids...Or a terminator version of that bike... Or a hulk version of that bike...

You get my point

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post #6 of 11 Old 12-11-2014, 01:16 PM Thread Starter
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For anybody interested here is the article about that particular motorcycle here.

It's a 1980 Honda CB750F Super Sport, so it has a pretty big engine. But I think the 919 can be made to look like that and even better :P

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post #7 of 11 Old 12-11-2014, 05:25 PM
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Frankly, the biggest hurdle to a sleeker look is the stock fuel tank. Let's face it -- it is a bit outsized, which works with the rest of the bodywork, but if you want to go slimmer that's a problem.

The stock tank could be modified by cutting off the wings (as they are called) and filling in with slightly curved sheetmetal. What it would look like after that is up for grabs.

Alternatively, if you can find a tank for an '77 to early '80s 750 super sport it would not be difficult to modify the tunnel to fit the 919 chassis. In fact the only problem is fitting a fuel injection pump, either adapting the stock pump to the inside of the tank or an external pump available at auto performance stores. Link to a tank:
Fuel Gas Tank 1981 82 Honda CB900F CB1100F and 1979 82 CB750F Supersport | eBay

As with any project like this (I can't possibly count the number of times I have done this sort of thing) you have lots of decisions to make.

Rob

If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
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post #8 of 11 Old 12-11-2014, 05:31 PM Thread Starter
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Actually I like the wings on the tank. Makes the big look butch. Which is why if you clean up the rear end will give the impression that it's even more butch in that mid to front section of the bike... I wish I had drawing skills to put all this on paper :P

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post #9 of 11 Old 12-11-2014, 09:56 PM
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Just want to say I support the direction this thread is going. Carry on.

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post #10 of 11 Old 12-12-2014, 04:04 AM
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Ther are a few more things to take into consideration as well to acheive the clean lines similar to the bike you showed above.

- relocating the ECU, harness, relays & tip over sensor.
- shorteneing the primary harness as well
- possibly deleting the airbox and switching to pod filters ..... relocating battery, making pod filter adapter manifold with sensor mounts.
- PC3 to be able to tune the bike and make it run half decent with the pod filters.
- switch to a low mount 900rr header

The biggest issue with doing this to a 919 is space. Once you delete the tail and attempt to reroute/shorten and hide all the componenets you quickly will run out of room ..... unless you build a big bubble butt cafe tail that kind of defeats the purpose in my opinion.

I have had my 919 torn down to just the engine in the frame a few times and tried to envision how to fabricate exactly what you are talking about.

I figured that cutting the tank open from the bottom and welding it back up to create a void would work the best. Then you could build a shelf to contain the ECU/PC3 and all the other stuff that you want hidden and tucked away.

Once you figure out the harness and wiring situation its just as easy as cut/bend/weld up a new subframe support and you are off to the races.

The idea of using a older CB tank is a great idea. As long as the frame channel inside is wide enought to wrap around the box beam 919 frame.

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post #11 of 11 Old 12-13-2014, 08:40 PM
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Looks like we're on the same page! Build off anyone?

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