Broken AF frame - Do you know of any?

[mxaniac]

Based on the "my poor bike" thread it sounds like some broken frames have been experienced.  Given the variation in weld material, motor mounts, head stays etc. all we can really do is look for any trends that exist.  I thought it might make sense to start a "registry" if you will of any known breaks.

My 2006 450F based frame has broken.
DSPMOTO has had a 2006 based frame break.

Anyone else?

[mxaniac]

Here was another one, looks like it was a 2008.

http://www.kxriders.com/forums/index.php/topic,10642.0.html

[motopunk]

Here was another one, looks like it was a 2008.

http://www.kxriders.com/forums/index.php/topic,10642.0.html

in the most cases they broke, because of wrong heat treating by the aluminium-welding ..thats a very important fact.. aluminium-frames are much more stiffer than steel-frames, that makes the modifying and welding a bit more tricky as the same work on steel-frames...
there were also some years of no modified honda oem-4stroke-al-frames that broke like glass...

[jBernard]

forgot about JHolt's breakage.
looks like in same place as yours. his headstay looks a bit weird. almost like the engine could rotate in the cradle, looks like a 2pt mount system rather than a 3pt that cant rotate.
can you shoot us a picture of your headstay?

[mxaniac]

I still haven't had a chance, bit it is a cross tube between the original mount points with tabs to the head.  Not as rigid perhaps as some have suggested it ought to be.  I'm getting concerned about how much load might actually be on these engines, I doubt they were designed to be that much of a stressed member.

[jBernard]

have you seen Jfabs 'head bolt pattern to front tube' bracket? i wonder if something like that would help. care would be needed to be given in the design for easy engine removal, but to have another mounting point on something solid like the main down tube seems like it would help. so then you would have 2 anchors on extremely rigid structural material, then your 2 engine mounts on the bent tubing.

[Dutch-K5 Fan]

What about this SR head?




Kawasaki used front and back headmounts. It's even in the place where many 450f and never 250f have the Original mount.


dutchie

[Jos197AF]

have you seen Jfabs 'head bolt pattern to front tube' bracket? i wonder if something like that would help. care would be needed to be given in the design for easy engine removal, but to have another mounting point on something solid like the main down tube seems like it would help. so then you would have 2 anchors on extremely rigid structural material, then your 2 engine mounts on the bent tubing.

I am gonna find a solution for that issue, an extra head mount on the front for my AF. I think I make it fully removeable, no welding.

[sandblaster]

Already done it





Even if you weld the mount on, you can still remove the engine.

[jBernard]

i may have to do one of these for some added insurance.
wonder if it will negatively affect vibration.

[sandblaster]

I guess we'll find out.. 

[motopunk]

What about this SR head?




Kawasaki used front and back headmounts. It's even in the place where many 450f and never 250f have the Original mount.


dutchie

very rare factory gp-parts... i still dream to have one of the 3 1990/91 worksbikes or one of this engines ...

but watch out this cylinderhead is designed for the 1990-93 parallel cooling system that the production 125 and 250īs had...  the 1990/91 kx500sr is similar in some points to the 1990/91 kx250 . and i still dont know, why its never gone into production...


for sandblasters front mount, i would say : its better to lift up the mount on the frame, as high as possible to get more space to the head and using also brackets like on the rear mount... 

[ylwgtr]

It is my view that a bad head stay mostly causes this...we need to think about lateral force aswell as longitudinal ....a cross braced staggered firmly anchored headstay seems to be the answer,the plate method is just too springy for my liking and FORGET using side mounts period...I'd also be using radius tube for the under cradles...I use this on Hondas and kawasakis and not had a problem...I run a telescope join on the upper part of the y with a staggered/castellated join and a round plug weld in a hole on the upper to y join.....I also like to leave a 5mm gap in my telescope joins and sink a weld right down into the root then a dresser weld over the top ....I'm not an engineer or fabricator but this system has worked time and time over for me

[hulkteam476]

I can say yes! here is a good design to fit preparation for welding.

Mister, Ylwgtr...

[sandblaster]

Looks top notch.
Are you going to use a front head stay as well?