Author Topic: Sidepipe rear subframe  (Read 1465 times)

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Offline tony27

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Sidepipe rear subframe
« on: October 31, 2018, 09:18:00 AM »
Getting ready to have the rear subframe put back to standard - LTR conversion removed & tubes straightened, is the subframe basically the same as the twinport or black frame bikes as the frame builder asked me do I have a reference for him to go off.
Last time I was there he had 1 of his friends 250 twinport in the shed so if they are the same that would work well



Online 80-85 husky

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Re: Sidepipe rear subframe
« Reply #1 on: October 31, 2018, 10:15:16 PM »
wouldnt it just bolt back to the std mount ...after you straighten it out...

Offline tony27

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Re: Sidepipe rear subframe
« Reply #2 on: November 01, 2018, 05:00:14 PM »
Standard mounts are still there but as you can see in the photos both the seat tubes & uprights have bends. I think once Steve Roberts sees the frame he'll understand what needs to happen.
Getting the swingarm out looks to be as big a issue as the pin appears to be stuck in the frame as well as the engine mount. I actually don't care if I have to destroy the mount as they're available new for about $35us from Slovakia but I may need to drill the pin out of the frame on both sides
I may end up running a 74 or Falta swingarm so that I have 1 spare wheel for the 2 bikes otherwise I could make a short spacer for the swingarm & adjuster to let me use the original arm out of my 73 

Offline bazza

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Re: Sidepipe rear subframe
« Reply #3 on: November 01, 2018, 08:49:45 PM »
soak in coke and ATF whack/ repeat 100 times  for swing arm bolts. Wurth have a anti rust/lube that finally got my bsa bolt out with, soak/whack routine
Once you go black  you will never go back - allblacks
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Offline tony27

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Re: Sidepipe rear subframe
« Reply #4 on: November 02, 2018, 06:38:29 PM »
Planning on making a start on removing the LTR conversion when my weekend starts on Tuesday, will use small cutting discs to cut the welds on the plates & try snap them off. Once I've done that I'll start work on freeing up the swingarm
Cases are with 1 of the guys who works in the same building as me for vapour blasting, have to get a rod kit out of Europe before I can start building the engine

Offline GMC

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Re: Sidepipe rear subframe
« Reply #5 on: November 02, 2018, 09:08:42 PM »
I have a rod kit here for a 380/400, not sure if they are the same for the 360

When cutting the old plates off remember to cut into the extra plates if you have to but not the frame tubes.
Also don't hit the frame tubes with a grinding disc to clean them up, grinding discs are too savage, only use them to take the bulk of the material off without touching the frame tubes.
Leave cleaning up the frame tubes to sanding discs, personally I prefer sanding discs with a rubber backing, not a fan of flap discs for this sort of work.
 
Frame tubes should be straight on top rails and pivot/shock mount tubes.
Try to salvage the frame tubes if you can, CZ's use a 18mm OD tube, most tubes are 19mm OD (3/4")
If you need to replace them you will need to replace the whole tube from top to bottom, nobody is going to notice the 1mm difference unless you want it to be absolutely authentic
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Offline tony27

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Re: Sidepipe rear subframe
« Reply #6 on: November 03, 2018, 06:44:36 PM »
Hoping to be able to get the original tubes straight, the original shock mounts are perfect so it would be a pity to have to disturb them
360s had slotted rods standard but the 380/400 rods are dimensionally the same & are what get used when replacement is needed

Offline tony27

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Re: Sidepipe rear subframe
« Reply #7 on: November 06, 2018, 02:01:45 PM »
Got the plates off pretty painlessly, right/pipe side took maybe 5 minutes with a cutting disc & deadblow hammer, other side took longer as I think the welds were longer & 1 was closer to the joint of the 2 tubes so I had to be a bit more careful.
Turns out all the welds are bronze so I'll file them smooth, haven't attempted the shock mounts yet but am wondering if the small propane bottle gas torches from bunnings would be hot enough to melt the bronze again, 1 of the sets says it produces up to 1900C which should be way hotter than needed & it will also be handy to try & get the swingarm pin to move in the frame. Thoughts on that?

https://www.bunnings.co.nz/tradeflame-propane-handyman-full-flame-blow-torch-kit_p05910245

Offline Hoony

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Re: Sidepipe rear subframe
« Reply #8 on: November 06, 2018, 07:39:25 PM »
you can get those small torches with Map Gas, i think this may even have a hotter flame than propane.

https://www.totaltools.com.au/brands/bernzomatic/91751-bernzomatic-map-pro-soldering-torch-kit-ts4000tk
« Last Edit: November 06, 2018, 07:41:12 PM by Hoony »
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Offline tony27

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Re: Sidepipe rear subframe
« Reply #9 on: November 06, 2018, 09:41:06 PM »
Looking at bunnings site it appears mapp gas burns about 85c hotter, replacement bottles are cheaper so I may see if the local place has them in stock tomorrow morning

Offline GMC

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Re: Sidepipe rear subframe
« Reply #10 on: November 06, 2018, 11:04:22 PM »
A trick with removing bronze is to heat it up to melting point and then run a wire brush over it.
Use a cheap wire brush as the bronze will often stick to the brush.
Also don't ignore OH & S, make sure you brush away from you and that your boots don't act as funnels to attract hot bits into your boots.
Don't ask me why I know
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Offline tony27

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Re: Sidepipe rear subframe
« Reply #11 on: November 07, 2018, 07:09:03 PM »
The mapp gas heated the weld enough to soften it enough for it to let go of the mount but not fully melt it.
For some reason the left mount & plate both had bad arc welds under the bronze welds. Unfortunately when I got the left mount off there was a small patch of the tube attached to the mount & on the back of the tube was a crack. I'm thinking the best way to repair this would be to remove the damaged section of tube & turn up a replacement section that fits inside the original tube at each end

Hopefully I can unseize the swingarm pin from the frame in the next couple of days & take it over to Steve Roberts for him to have a look at sorting the bends & the damage to the tubes