Basket Cases

[David Lahey]

Somebody has had one hell of a loop out to dent the tank like that David.

I've been working on a Cota 247 project.
The bike came with a Mikuni VM26 in place of the AMAL mk1 minus the slide, spring and needle.
Down to the local wreckers and I found a loose spring and slide and he had a selection of needles.
The Queen provided the retainer plate for the cable and needle.

After retarding the timing from my first guess I had a very smokey but running Montesa.

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God save the Queen.
I love the look of 247s. I hope you've got a standard fuel tank for it. They have amazing styling. Pretty nice to ride too.
Your 5c part in the carby reminded me of a trail riding buddy in NQ who used stacks of 20c pieces to increase the fork spring preload on his KLR600. At least you would never run out of money to put in a Telstra payphone if you were stuck somewhere.
Same bloke had a 23 litre Acerbis tank on it (no wonder he needed lots of 20c coins) and for tank stickers he used SULO stickers, removed from his green wheelie bins at home and named his KLR600 "my big green garbage machine"

[David Lahey]

I got past procrastinating and started opening the seam on the TL125 tank yesterday

[Kurt]

Yes I have a tank that is in a very sorry state where the fuel tap fits.
Somebody has knocked a massive hole in it so will need to do a significant repair of the fibreglass and the fitment of another fuel tap spigot.

How do you join the seam on a tank steel petrol tank? Silver Solder?

The Montesa 247 came with a set of Japanese looking motocross forks on it but thanks to Captain Sherco in Tassie it now has a set of Cota 172 front forks.
I have also manufactured a longer front axle from K1045 steel and spacers as the 172 must have the forks closer together than the 247.

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[David Lahey]

Hmmm... you've got me thinking about those forks Kurt. Cota 172 forks have an in-line axle. Maybe Cota 200 forks?? They look good whatever they are.
had a thing going in 1981 where they slimmed the trials bikes down by reducing the fork tube spacing but it made it easier to knock the front end out of alignment compared to the wider-spacing tubes front ends on the 247 and 348.
As for the TL125 tank joint, I was planning to oxy weld the edges. I think that TIG would probably be better but the bike was made in the oxy welding era after all.
Cota 200

[David Lahey]

tat ty currently has his hand in a fibreglass cast after an operation so I'm going to try and relay a fuel tank repair story of his here.

There's a bloke who tat ty knows called Dave who had a decent old crash on his TL250 and damaged the aluminium fuel tank fairly well including a "whopper of a crease" above the filler neck.
The tank was sent off to a panel beater who did a fabulous job fixing the tank. The panel beater also used the cut-the-tank-top-off-the-bottom technique as I (definitely not a panel beater) am going to attempt with the steel TL125 tank shown previously.
In the case of Dave's TL250 tank though, the cut was made inside of the seam, rather that at the seam and so the finished product not only looked amazing as far as dent removal went, but the seam still looked totally original. Being inside the original seam, the panel beater's welding is hidden from view with the tank mounted on the bike.
Now Dave didn't come off unscathed from the big crash that damaged the tank. He suffered a badly broken leg in the crash which took quite a while to recover from. It was nine months before Dave rode his TL250 again and tat ty was there to take a photo to celebrate the happy occasion of Dave back riding his TL250

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[Rod]

Hmmm... you've got me thinking about those forks Kurt. Cota 172 forks have an in-line axle. Maybe Cota 200 forks?? They look good whatever they are.
had a thing going in 1981 where they slimmed the trials bikes down by reducing the fork tube spacing but it made it easier to knock the front end out of alignment compared to the wider-spacing tubes front ends on the 247 and 348.
As for the :Honda: TL125 tank joint, I was planning to oxy weld the edges. I think that TIG would probably be better but the bike was made in the oxy welding era after all.
Cota 200

Here's a pic of the grubby original forks on my '74 Cota 247 black frame (LW, Light Weight apparently). As you can see, slight axle offset, so maybe somewhere in between the offsets of 172 and 200. Cheers.

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Here's a brochure shot of the '74 Cota 247. Back in the day I thought they all looked magnificent, Sherpa/Cota/MAR and I think they still do.

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Kurt, I see your Cota has been modded for laid down shocks, tricky!

[Kurt]

Rod
The laid down forks were not of my doing, somebody was using it as a development bike at some stage.
Their Ideas are quite good though with the Mikuni carb, laid down shocks and the handle bar clamps off a Japanese dirt bike that raise the bars and shift them forward.

I was thinking they were 172 forks due to the square shape of the Leg but you are onto something with the leading axle being from a 200.
Couldn't be many Cota 200's without a front end around.

David - TIG would be much easier to control the heat with steel as thin as a petrol tank.

[brent j]

I'm working up the courage to do my first-ever tank repair using the technique of cutting the tank top off the tank bottom, panel beating it and welding it back together.
The side and top rear dents could probably be removed without cutting it apart but there is some damage ahead of the filler cap that is too tricky to access.
I tried to pull out the damage ahead of the filler cap using a jig and some heat this morning and did make progress there but the filler neck is bronze welded in place so there are limits to how much heat can be used there.
There is not enough space between the top of the tank and the top of the tunnel at the neck to get tools inside via the neck.
The shape of the tunnel blocks access to the damage site from underneath.
I think that posting about this is helping my procrastination
This is what it initially looked like with some paint and bog removed

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This is the jig I made to pull up on the filler neck while heating the creases

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This is after I gave up with the jig and removed the bog in readiness to cut it apart

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I've been looking at my dented tanks and working out what I'm going to do with them. I have enough of them to make a project of their own. In the past I've tried compressed air which reduced the dents in a TL250 tank and even a garden hose on a TS100 tank which had enough pressure to collapse the tunnel. The TL tank was done on the bike with ratchet straps wrapped around it. I've read the tales about using ice but don't think it's likely to be successful as you have no control over where the ice will expand.
The next plan is to use a plumbers test pump and water.
Have the tank on the bike and even pack rags under the tank. Wrap ratchet straps around the tank to prevent expansion. I figure I can start with low pressure (maybe 5psi) and tap around the dent with a nylon hammer. Even tapping into the dent may "bounce" the dent out.
With this method I figure I'll have good control over the pressure and can add or subtract as I feel fit. I also have the safety feature that if the tank splits the water pressure drops immediately where as with air the tank can burst open violently.
We'll have to see what happens

[David Lahey]

David - TIG would be much easier to control the heat with steel as thin as a petrol tank.

Yes Kurt I've been thinking a bit about the welding on this tank and because it is someone else's tank I want to give them back a nice looking job. I've started looking at TIG welders and am getting a bit excited about the idea of learning a new welding technique at 62 years old

[David Lahey]

This is what a TY250A model flywheel looks like. The TY250A has the same cup as the other TY250 twinshocks but has a thinner steel band around the outside

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