The Free "B", a 1971 resto redux

[DogBunny]

The first time I removed the left spark plug, it came out hard. The threads in the head were damaged. I dug out several broken thread pieces.
I bought a cheap back tap thread repair tool on Amazon, which clearly was defective, so I never used it.
I then bought the most expensive branded back tap tool on Amazon, sold under the Powerbuilt name. The cheap tool was $10.90, and the Powerbuilt tool was $24.87, to my door.
In my pics you can see that the cheap tool arrived already expanded, even with the expander plug fully disengaged.
The Powerbuilt tool worked great.


The Youtube videos I watched were fairly useless. All the instructions that you need are on the back of the Powerbuilt tool package (above). (The cheap useless tool came without any instructions.)
Couple notes: the instructions say to make 2 - 3 passes, incrementally expanding each time. I probably made 10 passes, and I'm glad I did. I hit a couple of very hard spots on each pass.
The instructions say to "insert" the tool all the way in, completely clearing the hole threads. You will find that you don't simply "insert" the tool -- you have to thread the tool in. It will thread in with very minimal resistance, even past the damaged areas. Then, you expand the tool, catch a thread in the hole and back it out. After my first two passes, I learned that when threading the tool in, you could feel just before you are about to completely clear the hole threads, and that is when I stopped inserting. This sped things up, because you didn't have to carefully catch a thread -- the tool was already started on its back-out chasing pass.
Most importantly, I wish I had stopped making my incremental passes before I had fully expanded the tool. In other words, I wish I could take back my last two passes. The reason is that the finished chased threads are very loose -- sloppy even. I think that if I had stopped sooner that I'd have a better fit and that I'd be happier.


Now you have to remove the residual swarf-laden grease from the hole. Cotton swabs were fairly ineffective. What worked well was a very thin wire-bristle bottle-brush with a piece of mineral spirit soaked cloth wrapped around it.


After. I should have taken a "before" picture. Looks pretty good considering that it started out all screwed up.
Spark plug holes have a small, very slightly raised lip at the top. My lip has a missing area (red arrow). Not sure what's up with this, but I'm going to keep an eye on it. I can envision fuel/motor oil working its way up through my loose threads, and leaking out this gap.

 

[WideAWAKE]

In my next post I'll explain how much "free" actually costs.

Yeah, this one I'm going to actually finish. I've gone through it, and all it really needs is carbs to be a running, riding project.

In my experience, the cheaper it is, the more it costs me haha.

Killer score!

 

[Mikey]

Thanks for the write up
I never knew such a tool existed

 

[DogBunny]

I have this 2" long crack in an otherwise very nice rear fender.

I asked Google the following exact question:
Is brazing the best way to repair a crack in a vintage metal chrome motorcycle fender

The "AI Overview" answer I got boiled down to "TIG weld it."

I asked Google the EXACT same question several hours later. This time, the "AI Overview" answer I got was:

Yes, brazing is an excellent and often preferred method for repairing a crack in a vintage, chrome-plated metal (usually steel) motorcycle fender. Because vintage fenders are made of thin sheet metal that has experienced vibration and age-related fatigue, brazing offers a much lower risk of heat distortion and burn-through than traditional welding.
However, there are a few important considerations and steps you should follow to ensure the repair is successful.

Why Brazing Works Well

• Lower Heat: Brazing melts a filler metal (like brass or bronze) into the crack without actually melting the base steel. This drastically reduces the risk of warping your fender or making the metal brittle.
• Fills Gaps: It is easier to bridge small gaps or pitted areas with bronze/brass than to fuse thin, rusty sheet steel with a welder.

Critical Steps for a Successful Repair

1. Drill the Ends: Before applying heat, drill a tiny hole at the very end of the crack. This stops the stress fracture from continuing to spread.
2. Remove the Chrome: Brazing will not bond to chrome. You must grind, sand, or wire-brush the chrome plating entirely off the metal in and around the crack.
3. ...............

There were a couple additional, less important "critical steps," and then there was a paragraph stating that you could also TIG weld it, but it would take a lot of skill due to the thinness of the vintage sheet metal, etc., etc.

I'll add that I have read this thread:
https://www.xs650.com/threads/crack-in-fender.63819/
But my case is totally different.
Seeking opinions...

Bonus Question: Is the underside of the fender chrome? How can you tell? Since "brazing will not bond to chrome," I'm wondering if I can braze from the rear, without removing the chrome on the front.

 

[Jan_P]

I would look into using " Glue " many things are using chemicals in Automotive
I believe glass used Polyurethane .And it was sitting hard.
A patch on the inside.
Using a weld can have the risk Discolor as in blueing or so .And other colors.
Brazing .. maybe .. but I would do the read up on chemicals first.
I would not be able to TIG weld
Brazing I could Do

 

[Its been a long time]

I think brazing from underneath is a great option. Definitely drill the end of the crack. I know it's a later model but inside my 650D rear mudguard (fender) was definitely plated, maybe nickel, possibly chrome. I expect the steel to oxidise with the oxy acetylene torch when brazing. It's probably going to be blue by the time the brazing is done. I think after repair, you're into a rechrome job.

I had my 650D rear mudguard rechromed last year, along with the tail light parts. It looks great.

 

[DogBunny]

Thanks for the answers. You both mention bluing. This is totally not an issue for me. The crack is in a place where it will be very well obscured by the seat hoop and fender stay. My intention is to just spot paint the repair with chrome-color spray paint.
ALSO:

At the 6:15 mark of this video is a demonstration of "brush-on" nickel plating, wherein just a small area of a chrome fender that has been repaired is nickel-plated with a "brush-on" technique.

 

[Its been a long time]

I'm sure you will anyway. But I can't help myself adding that the rubber mounts need to be good and installed properly so that it doesn't crack again.

Looking forward to seeing the repair.

 

[DogBunny]

As per Jan's suggestion, I've been looking into a woven glass mat and epoxy resin (not polyurethane) repair. I think that this is a viable option, with the advantage that I can do it myself.
This would leave a visible crack on the outside, which could be filled in with a bead of JB-Weld, leveled while wet, and then brush-painted with chrome-color hobby paint.

 

[Jan_P]

As per Jan's suggestion, I've been looking into a woven glass mat and epoxy resin (not polyurethane) repair. I think that this is a viable option, with the advantage that I can do it myself.
This would leave a visible crack on the outside, which could be filled in with a bead of JB-Weld, leveled while wet, and then brush-painted with chrome-color hobby paint.

Depending on how it looks it is often possible to apply force closing the gap .Is it screw clamps in English . Or putting heavy weights at the right spots
Rope or load strapping equipment chains
For fatigue cracks in thicker material they " fit " into each other so putting them together it is visible smaller than thickness of a human hair
Not drilling the end holes it can look as a scratch only visible at close distance .If i get it right hidden

it will be very well obscured by the seat hoop and fender stay

 

[gggGary]

I'd be thinking braze with a steel doubler plate inside the fender. Bonus you can apply the heat to the doubler reducing bluing of the chrome.

 

[Jim]

You need to bring steel up to a dull red for brazing. That's gonna discolor the chrome.

 

[DogBunny]

I'd be thinking braze with a steel doubler plate inside the fender. Bonus you can apply the heat to the doubler reducing bluing of the chrome.

You need to bring steel up to a dull red for brazing. That's gonna discolor the chrome.

Thanks. I don't think either of you are going to like it, but I have pretty much committed myself to epoxy resin and woven glass mat. Biggest reason is that I can do it myself.

 

[GLJ]

I think I would be tempted to just drill a hole at the end of it and keep an eye on it. Odds are there will not be any more cracks forming.
As you said it doesn't show. It is a survivor.

 

[Jim]

I don't think either of you are going to like it, but I have pretty much committed myself to epoxy resin and woven glass mat.

I don't have a problem with that. Just make sure to use epoxy and not polyester. Poly is more prone to cracking.

 

[Jim]

Biggest reason is that I can do it myself.

Sounds like you know what to do, but here's a few tips anyway...

https://www.xs650.com/threads/van-go.64395/post-808613

 

[DogBunny]

I think I would be tempted to just drill a hole at the end of it and keep an eye on it. Odds are there will not be any more cracks forming.
As you said it doesn't show. It is a survivor.

That's a reassuring thought. If so, the epoxy probably isn't going to hurt anything.

I don't have a problem with that. Just make sure to use epoxy and not polyester. Poly is more prone to cracking.

You posted that just in time. I just canceled the Bondo brand resin that I ordered because it is polyester.
I ordered real epoxy resin by phone from US Composites:
https://www.uscomposites.com/epoxy.html
They offer a really small and affordable pint kit which is great, because you know that if you order any more than that, that it will just expire before you use it. They also have really inexpensive woven glass mat.

 

[DogBunny]

Sounds like you know what to do, but here's a few tips anyway...

https://www.xs650.com/threads/van-go.64395/post-808613

Yeah, interesting stuff. A long time ago I needed a lot of epoxy and bought a gallon of epoxy and a quart of hardener from the West Marine system (which US Composites apparently makes and sells. Great stuff.
I also bought a couple of different different West Marine Fairing fillers and filleting blends -- what you call flox. I use those fillers occasionally to thicken J-B Weld, Elmer's glue, paint, etc.

 

[Jim]

Both the West and US Composites are excellent epoxy's. West is my go to, but US Comp. is also good.
Depending on cloth weight obviously, but I'd shoot for about 5-6 layer of 4-6 oz cloth. Maybe extend the first layer about 2-3" on either side of the crack and add an inch to each successive layer.

Rough up the surface with something really coarse... like a grinding disc in a die grinder.
I think it'll hold just fine.

 

[DogBunny]

In post #21 I back-tapped a bad spark plug hole to repair damaged threads. I was afraid that some of the damaged broken-off threads might have fallen into the cylinder before I back tapped. I used a bore scope to check.
In the pic you can see a big and a little piece of thread sitting on top of the piston. I was able to successfully remove a similar large piece of thread that was more favorably located.
But these two pieces I absolutely cannot remove. I have been at this for over three hours, and I have tried everything. Including using a shop vac attached to successively smaller hoses until it's necked down to the diameter of a small straw.
I am ready to give up, and run the engine as is. The hope is that these two pieces are effectively stuck in the sludge they are sitting on. And even if they are mobile, they are too big to get inbetween the piston and the cylinder.
Comments?