YZ125G Build

[80-85 husky]

great result considering the starter pac....well done

[GMC]

You've done well.
Its also good to listen to lots of advice, absorb it all and then go your own way.

The only thing I would add is that you should weld the gusset pieces on the inside as well so when you sand the outside down you will have material in behind it for strength.

I think the only thing you did wrong was to use the galvanized tube, it will play havoc with the welds and your old man is going to hate you, the gal will bubble up in the weld and cause a lot of porosity and keep contaminating the tungsten.
Looks like it is too late to get the tube back out, if you can then just sand the area where the patch is going to be otherwise hit inside that trap door area with a die grinder and remove as much of the gal as you can, allthough I think the gal that's inbetween the tubes will still give you grief.

[Lozza]

I don't have the former any more as I was soooo shitty after making 4 or 6 of them. Was a cheap plumbers pipe bender I machined a roller to ride in the groove. Roller was held by a yoke screwed down with a large bolt. The thing that caught me out was just how much force it took to form even thin metal, the vice groaned , the bench creeked and I groaned. End result looked great but it was a lot of effort.
My No1 tip with gussets is to leave the corner and the ends over bars open
 

[rocketfrog]

You are a man of quick and decisive action Alex, I agree with GMC on the Gal - awful to weld. You can make it up to your Dad by keeping up with his welding by grinding fresh electrodes in the background.

I re-purposed some 7/8 handlebar material yesterday as well, split lengthwise it makes a nice repair patch for rear subframe spar on the chain side where the chain tries to saw through after 30 years of chain slap. I like to keep a "Donor Frame" handy for all those little brackets and tube sections such as lower frame rails that have worn thin or worn through as they do from casing out or clouting rocks.

I get imense satisfaction using all the left over bits to some good purpose.

Good work.

[Mick D]

Really enjoying this thread Alex. Great stuff mate. I can honestly say I have learnt!

And some very clever input coming in as well. Great old dike bike forum

[alexbrown64]

Yep rocketfrog, i too have a few sets of handlebars welded into the inside of my YZ125K frames to protect them from the chain!
Thanks Loz for the pics.. i kinda went the way you showed in your diagrams.
Cheers Mick and Husky , It is a great forum with some good dudes all helping each other out. 
GMC and Rocket... yep, i think the galv may interfere with the tig a little.  The mig tacks ate it for breakfast. The galv is only on very lightly on exhaust tube.  I may use a combination of a flame to burn it off and a burr to grind it off. She'll be right.
Well, the old farts gone off on holiday, i am off to work again soon and i am waiting on some crush tube for the engine mounts.  This project is now on hold for a few weeks.

Today i put some work into my 125K.  Blown head gasket, blown fork seals... more work...and i want to ride it tomorrow...

[YZ250H]

One of the best threads I have ever read on this forum (and I have read a few  )  Has inspired me to have a crack at my 465 frame that is the same. 

Won't be doing the welding myself though 

What did you decide to do about heat treatment Alex ?  Nothing since you used all mild steel ??

Great thread thanks 

[alexbrown64]

Hey yz250h, glad to hear you will try to fix your old frame.
I will be home next week and start work on the frame after that.
Will use the tig rods that are compatible with chro mo and mild Steel. No heat treatment, just good fit up with no stress points. A bit of grinding, buffing and sanding and then off to powder coaters. Hopefully be better than new when finished. Updates soon....

[YZ250H]

Hey yz250h, glad to hear you will try to fix your old frame.
I will be home next week and start work on the frame after that.
Will use the tig rods that are compatible with chro mo and mild Steel. No heat treatment, just good fit up with no stress points. A bit of grinding, buffing and sanding and then off to powder coaters. Hopefully be better than new when finished. Updates soon....

Nice work mate.  I would be careful with powder coating as that is what hid the cracks in my gusset until it was too late (not catastrophic or anything).  The rust can spread underneath the powder coat and you are none the wiser.  Rattle cans all the way for me..

It's never nice to have a crack in your gusset 

[alexbrown64]

Definitely not nice to have a crack in yer gusset...

I did a bit of work on the frame today. Cut the new crush tubes where the engine mounts up.  I put a bevel on the tubes so that my old man can tig them up with a nice semi v prep.



I decided i didnt like the repair i did on the rear gussets, so i am cutting them out again and have some new plate to put in.
I went to Bunnings today and picked up a D size argon bottle.  I will get everything prepped and tacked up so we can get it all tig welded in one hit. Still waiting on some 10mm tube to arrive (7mm i.d) for the tube that will go in the rear gussets ( the tube where the seat bolts run through).

By the time i am finished, the frame will be stronger than new and i would not think it would be subject to cracks. My powder coater dude blasts the frame, then zinc primes it, then nice thick gloss black powder coat to preserve the frame for another 37 years..

Cheers,

[alexbrown64]

Aaaaawwwww man, this is the never ending frame repair thread.

Since doing the main gusset repair, and seeing the dirt and rust trapped in behind it, i couldn't leave the rear subframe gussets without inspecting them.  I had previously repaired the outer subframe gussets, but it was on my mind what was behind them.
So this morning i cut the subframe gussets off.  I exposed lots of dirt, rust and some holes.  I have cleaned them up, inspected the area and come up with a game plan.  The first plan was to storm around in a huff and throw the frame over the fence...



Plan two involved having a measure up and seeing what could be done.  The subframe has an i.d of about 16mm.  The o.d is about 19mm give or take half a mm.

Good old Bunnings to the rescue again.  I picked up a meter of 19mm pipe and a meter of 16mm pipe for under $7 combined. This has a wall thickness of about 1.2mm which seems to be the same as the subframe tubing. Yes, it has a light coating of galv on them, but its easily ground and burnt off.

The plan is to cut out the rust holes as i did on the main gusset previously and make a repair patch with the 19mm tube.  The 16mm tube will be inserted down the subframe from the ends and welded into position.  I will have to cut the subframe in one section so that i can insert a new 16mm tube up and into it. 

I also now have in my possession a sheet of 1.6mm plate.  This will be used to fabricate the new gussets.  Some tube is on the way that can be inserted through the new gussets and tig welded to act as the seat mount points.



There is a bit of work involved, but as stated before, i dont think Yamaha intended the G to be still going 37 years later.  The gussets are a dirt and moisture trap, which will eventually eat out the tubes.  So now i can safely say i have inspected, cleaned, repaired and strengthened the gusset areas.

Cheers,

[alexbrown64]

There were sparks flying everywhere this afternoon.
The rusted sections which were under the gusset were chopped out. New tube inserts were fitted the entire length of both horizontal subframe tubes and then plug welded.
One vertical subframe tube had to be cut and bent out slightly so that a tube insert could be inserted. It was then put back into position and tacked.



Next step is to make new fill in sections to replace the rusted sections that were removed. And also fab up some new gussets.

Cheers,

[mick25]

I drilled two wep holes in all my frames 1.5mm dia at the lowest part of the frame ( rear cradle area )
To let the water out , one of them I dirlled out about a cup of water came out .

[alexbrown64]

Cheers Mick,
I may add some weep holes to the tubes on this frame.  I will inject some rust converter into the holes and slosh it around to treat the inside of the frame.
I had to cut the subframe downtube completely off to do another repair. Cleaned the inside of the subframe tube, treated it with rust converter, fitted an internal stub tube and a piece of outer repair tube and fitted it all back together.
Also started fabrication on the gussets. Used a section of 12.7mm cut length ways and then gently bent into the correct curve for the gusset. Worked out well and much stronger than the original. Just need to plate the gussets, fit the seat and mark the mounting holes, drill them out and fit crush tubes..

Cheers,

[alexbrown64]

OK, after what seems like ages, we think we have the frame ready to go to the powder coaters.
Lots of work went into cutting out, fabricating, reinforcing and welding up the new tubes and gussets.
Frame has been prepped, and now needs a good sandblast, zinc dipping and a full, rich coat of gloss black.

Pic below of subframe gusset.  Both entirely replaced including crush tube, plate and 45* bend (with drain hole).  Peg tubes inserted the length of the subframe and all fully tig welded.


The same with the gusset below.  A strong back running internally the length of the frame, rusty sections cut out and entire new gusset fabricated and blended in, with new drain hole.


And finally the finished frame ready to get fresh paint after 37 years of neglect....


This is going up to Southside powder coaters tomorrow, together with the G's pegs, bars and other bits, and an XR75 frame and nickers nackers..
Thanks to my old Pa for helping with this and also all the guys on the forum here for ideas and advice...

More pics soon...

Cheers,