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Author Topic: Love Child, an unholy union of CB400t and XR250r  (Read 3340 times)

Offline Zweihammer

  • Posts: 18
Love Child, an unholy union of CB400t and XR250r
« on: Apr 10, 2016, 00:11:04 »
  Well, I was looking for options for the rear shock or linkage for another project of mine, my unloved CM400;

http://www.dotheton.com/forum/index.php?topic=69506.msg813141#msg813141

  When I came across this fine example of '80s neglected carcass on the Craigslist for $40 and thought I had nothing to lose, so I picked it up.


  Looking at my current project, I thought I would rather not change direction on it.

  Instead, I drug out the frame from my parts bike, along with its engine (I started it before I tore it down a couple years ago).

  So began Love Child, the unholy union of CB400t and XR250r.

Here is the broke back '80 CB400t frame;


The first cut is the deepest;


This is all I need from the CB;


Will it fit?


Need to make more room here, in the middle;


You know you want to;


There, that looks better;


That'll hold it, ready to ride;


I'm feeling the love, not sure I'm feeling the seat;



So far I'm into her for about 50 bucks. Like I need another project!
Cheers, Erick
« Last Edit: May 07, 2016, 02:14:42 by Zweihammer »

Offline killerx

  • Posts: 51
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #1 on: Apr 10, 2016, 00:26:12 »
I like it! Will be following.
05 Victory Hammer(110hp 115tq @ the wheel)

73 Honda Cl350(Haven't decided what to do with it) SOLD

75 Suzuki GT380

Too much of everything is just enough.

Offline xb33bsa

  • Posts: 7726
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #2 on: Apr 10, 2016, 00:39:54 »
cool project nicely done so far ,but why did you not use the entire xr frame an recradlle it ?
how does the rake.,(the steering head angle ,the steering head location and wheelbase compare to the original as an xr ?
you would have wanted to document that before the neck swap
you dropped the height of the steering head the whole bike is now higher in front than the xr
it is going to be very tricky and dodgy trying to make that basartised cross breeded frame backbone jucture secure and strong enough ,it needs lots of help
you made lots of extra work for yourself  but carrion im with you  ;)

Offline Zweihammer

  • Posts: 18
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #3 on: Apr 10, 2016, 01:16:10 »
xb33bsa, there are two main reasons I am using the "backbone" of the CB400t frame.

First, I want the VIN from the CB, so if when this basterd moves under its own power, I can register it for the street.

Second, the CB engine was much taller and much longer than the little thumper that was first in there.

I love putting things where they don't belong. When I was 12, back in the '80s, I put a XL250 engine in a Z50 frame. Crude would have been a compliment, but I rode it and had a blast. If Z50s didn't cost so much, I would try to do it again as an adult. Despite knowing how stupid I would look trying to ride it.

Offline xb33bsa

  • Posts: 7726
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #4 on: Apr 10, 2016, 03:17:19 »
xb33bsa, there are two main reasons I am using the "backbone" of the CB400t frame.

First, I want the VIN from the CB, so if when this basterd moves under its own power, I can register it for the street.

Second, the CB engine was much taller and much longer than the little thumper that was first in there.

I love putting things where they don't belong. When I was 12, back in the '80s, I put a XL250 engine in a Z50 frame. Crude would have been a compliment, but I rode it and had a blast. If Z50s didn't cost so much, I would try to do it again as an adult. Despite knowing how stupid I would look trying to ride it.

i understand why but you could have just ground off the xr #'s and titled it as a new construction
you need a whole buch of careful stratigic strengthenthing and spreading the loads on that frame joint though
 but  you dint answer the most important bits, the geometry ,what numbers did you have ? what are you designing for?what do you have now ? what is the wheelbase ? are you using the stock suspension ? it is so easy to do it right and make sure it handles nicely or are you just playing blind man welds ?

Offline Tune-A-Fishİ

  • DTT SUPPORTER
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  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #5 on: Apr 10, 2016, 08:08:51 »
i understand why but you could have just ground off the xr #'s and titled it as a new construction
you need a whole buch of careful stratigic strengthenthing and spreading the loads on that frame joint though
 but  you dint answer the most important bits, the geometry ,what numbers did you have ? what are you designing for?what do you have now ? what is the wheelbase ? are you using the stock suspension ? it is so easy to do it right and make sure it handles nicely or are you just playing blind man welds ?

He did use the bark busters you likely made or had a hand in making XB  ;D

Hey dood... wanna sell those just above the wrist arm breaking debilitating Bark Bustersz??? $20 and a stamp??
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline Zweihammer

  • Posts: 18
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #6 on: Apr 10, 2016, 15:39:45 »
Thanks for the insight, xx33bsa, I know from following your efforts to head off other potential train wrecks on here you have the best intentions to get people to see the shortcomings of just slapping crap together.

My plan with this one was to pilfer the unmodified rear suspension, the forks, leaving the position and angle of the CM400 headstock the variable. The CM uses the engine as a stressed member, unlike the XR, though any number of lower end XLs have. I will be bracing the spliced interface between them, I am looking at what brackets I will have to finish mounting the rear structurally. If I can come up with a way to relace or replace the front to match the 17" rear, I will do that for a low rent sumo.

I'm not doing a new construction, as I have witnessed the headache to do so here in California and unless, someday, I am building something that will be worth more than the sum of its parts I'm sticking to inexpensive.

As to the resulting geometry, I don't have a baseline for comparison and I know for my purposes and intended use, something slacker than the motocross XR and quicker than the street CB would make me happy and probably keep me from being killed.

But, you never know.

The challenge is making myself something useful from these castoffs.

And to keep myself from finishing anything for myself, apparently.

Tune-a-fish, the bark busters are pretty thrashed, the throttle side is bent, cracked, and pulled out of the bar end.

Like me.

Offline Erskine

  • Posts: 2163
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #7 on: Apr 10, 2016, 17:07:31 »
I'm on board.
Big fan of the unfeasible and the improbable.
And the downright unwise.
It has to be done :)
Rock on.

Offline Zweihammer

  • Posts: 18
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #8 on: Apr 11, 2016, 02:08:01 »
Took my next step, supported both wheels and took another degree out, giving me another quarter inch clear at the rear.



The alignment on the front sprocket is surprisingly close;


Starting with random bracket, I think came off one of the 400s;


Made a frame tab for the lowest left side and tacked it on;


Cut the brake bracket of the CB frame carcass and carved a bracket for the lowest right;



Now she is supported on her own wheels;



I put my copious mass on the pegs and bounced, yup, feels like an 80's dirt bike!

I need to space the pegs out on each side as the CB engine is a fat bottom girl compared to the XR. The mounting bosses are integral to the lower frame from the XR. This is going to be a great place to anchor the rear of a cradle/skid plate up to the front engine mount bracket.

Not that any of this is rocket science, but I am happy this is going together so straight forward. Not nearly as sketchy as I expected.
« Last Edit: Apr 11, 2016, 11:15:04 by Zweihammer »

Offline xb33bsa

  • Posts: 7726
Re: Love Child, an unholy union of CB400t and XR250r
« Reply #9 on: Apr 11, 2016, 02:18:07 »
oh boy here we go you have the cs way to high