Basket Cases

[David Lahey]

After fixing the sticky KT250 float needle a couple of weeks ago, I rode a trial last Sunday and the ran unevenly at times.
While the carby was apart cleaning the gum off the needle valve before that trial, I did see a bit of wear on the needle but didn't have a spare needle kit handy so just rode with it and so I wasn't that surprised that it didn't run that well.
So last Sunday night I ordered a couple of needle kits from the Mikuni agent in Townsville. They posted the kits off on Monday and Australia Post amazed me by delivering them to my house near Gladstone on Thursday. That's three days in transit which is faster that having things sent from Brisbane to here.
Here's a photo showing the wear on the needle. I've had to replace so many of these needle kits in Mikuni carbys over the years that to me it seems to be a bit of a weak point in their design. My bikes do a lot of hours travelling in a trailer but I usually run the fuel level down in the carby before loading them, hoping to minimise the wear.

David, I used to run a :Honda: RS125 in a Superkart and I removed the carby but left it on its cable and layed it in the seat of the kart when it was being transported in my trailer.
Many others did the same thing for the reason you have.

Phil

So was that carby on the RS125 motor a VM Mikuni too?

[Kurt]

The countershaft sprocket just slides off with zero effort once you've cut through it with the angle grinder, what the problem was before with the puller is beyond me.

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With access to the innards unimpeded I have pulled apart and replaced all the bearings.
The kickstart shaft bronze inner bushing had shattered and was falling apart, so it is lucky I was pulling the engine apart.

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One of the most impressive looking ball bearings i've seen on the gearbox layshaft.

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On an unrelated note, I thought I would share a photo of a rod I recently welded with the rotary friction welder at work. 2205 Duplex stainless eye to a chrome plated 2205 rod.

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[Phil 850]

After fixing the sticky KT250 float needle a couple of weeks ago, I rode a trial last Sunday and the ran unevenly at times.
While the carby was apart cleaning the gum off the needle valve before that trial, I did see a bit of wear on the needle but didn't have a spare needle kit handy so just rode with it and so I wasn't that surprised that it didn't run that well.
So last Sunday night I ordered a couple of needle kits from the Mikuni agent in Townsville. They posted the kits off on Monday and Australia Post amazed me by delivering them to my house near Gladstone on Thursday. That's three days in transit which is faster that having things sent from Brisbane to here.
Here's a photo showing the wear on the needle. I've had to replace so many of these needle kits in Mikuni carbys over the years that to me it seems to be a bit of a weak point in their design. My bikes do a lot of hours travelling in a trailer but I usually run the fuel level down in the carby before loading them, hoping to minimise the wear.

David, I used to run a :Honda: RS125 in a Superkart and I removed the carby but left it on its cable and layed it in the seat of the kart when it was being transported in my trailer.
Many others did the same thing for the reason you have.

Phil

So was that carby on the :Honda: RS125 motor a VM Mikuni too?

David
I don’t remember other than it was a flat slide Mikuni.

[Hagsta]

Montesa Cota25 with a Honda MR50 motor. I swear it just followed me home

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[Greg Harding]

Hi Everyone,

Montesa Cota25 with a Honda MR50 motor. I swear it just followed me home....

Love your version of a ! Most of my bikes followed me home too in the trailer.

On an unrelated note, I thought I would share a photo of a rod I recently welded with the rotary friction welder at work. 2205 Duplex stainless eye to a chrome plated 2205 rod.

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Nice work Kurt, you have me curious so I have some questions for you:
1) What weld preparation is done to the two pieces?
2) Is any Abrasive or Flux used?
3) How fast is the chrome shaft spinning?
4) Does the shaft get shortened and by how much?
5) Do you realise it is no good for a conrod kit for the 247?

Just sharing what I have been working on as well:

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Period correct Lemcol wheels and imperial dimension secondhand steel stock, even the paint had been sitting in the Kaboom room for a long time!

[Kurt]

That vice and trolley looks solid, what is the second handle underneath the vice for Greg?

To answer your questions on Friction welding:
1) What weld preparation is done to the two pieces?
Rod is bandsaw cut, the eye has a spigot with the approximate diameter of the rod and a spherical radius with about 2mm height to allow the initial contact to be progressive.
The spigot controls the rate the heat from the friction weld is conducted away from the weld through the eye. This is very important to be able to allow enough heat to create fusion and also to control the microstructure formed as the steel cools.

2) Is any Abrasive or Flux used?
No and No but it would be interesting to test if flux would have any effect.

3) How fast is the chrome shaft spinning?
The eye is rotated while the shaft is held stationary, somewhere in the realm of 400 RPM is the rotational speed.

4) Does the shaft get shortened and by how much?
Yes combination of shaft/eye is shortened in the completion of the weld, around 10mm.
Actual welding time is less than 30 seconds once the surfaces contact.

5) Do you realise it is no good for a conrod kit for the 247?
We might be able to make a 247 litre version.

[David Lahey]

Hi Everyone,
Just sharing what I have been working on as well:

1630130481523.jpg

1630141689128.jpg

Period correct Lemcol wheels and imperial dimension secondhand steel stock, even the paint had been sitting in the Kaboom room for a long time!

Very very nice Greg.
It reminds me of the line from Crocodile Dundee "You call that a knife? This is a knife"

[David Lahey]

s never cease to amaze me.
At the AMA Queensland Titles for old bikes earlier this year at Lowmead, a bloke rode a standard TL125 in Twinshock. Nothing amazing there, but what happened on the morning of day 2 of competition was amazing.
Without turning the fuel on, he started it up, rode 150 metres to section 1, rode section 1, rode 100 metres to section 2, rode section 2, rode 30 metres to section 3 and finally ran out of fuel halfway through section 3.
Truly astounding fuel economy

[Greg Harding]

Hi Everyone,

Very very nice Greg.
It reminds me of the line from Crocodile Dundee "You call that a knife? This is a knife"

Thanks David, I am actually very proud to own such a vise and it is very handy!
Thanks for lesson Kurt, friction welding is something that I knew very little about except that I think it ends very suddenly, perhaps abruptly?

To answer your questions on Friction welding:
1) What weld preparation is done to the two pieces?
Rod is bandsaw cut, the eye has a spigot with the approximate diameter of the rod and a spherical radius with about 2mm height to allow the initial contact to be progressive.
The spigot controls the rate the heat from the friction weld is conducted away from the weld through the eye. This is very important to be able to allow enough heat to create fusion and also to control the microstructure formed as the steel cools. The spigot makes sense, I assume it is to get both parts to a similar temperature when they are forced together?

2) Is any Abrasive or Flux used?
No and No but it would be interesting to test if flux would have any effect. With the shaft cut in a bandsaw (rough surface) makes sense. Flux is used in other welding processes to exclude air/oxygen and/or to combat higher melting points of oxide on the surface but I think this is a lower temperature process?

3) How fast is the chrome shaft spinning?
The eye is rotated while the shaft is held stationary, somewhere in the realm of 400 RPM is the rotational speed. This surprises me as I thought it would be easier to spin the shaft but I have never seen a friction welder.

4) Does the shaft get shortened and by how much?
Yes combination of shaft/eye is shortened in the completion of the weld, around 10mm.
Actual welding time is less than 30 seconds once the surfaces contact. Something tells me the process is fairly dramatic with sparks flying?

5) Do you realise it is no good for a conrod kit for the 247?
We might be able to make a 247 litre version. Do you mean a 0.247 litre version as a 247 is one of models they made that states the actual capacity?
That vice and trolley looks solid, what is the second handle underneath the vice for Greg? Yeah I know, I am doing this backwards and you probably know why. A vise on wheels make sense so you can take Muhammad to the mountain but it lacks
practicality when it rolls with you. So this is my solution with a period correct square thread and tetescoping/folding vise handle to attach the assembly to my gantry column:

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[Kurt]

David - The TL125 fuel economy reminds me of the law of conservation of energy, energy in = energy out.

Friction welding is best described as a forging operation with the rotation the means to provide the energy to complete the fusion of the two parts. So you are correct in saying it is a lower temperature process than a conventional arc welding operation.
It is surprisingly undramatic when all the tooling has been designed with enough rigidity to avoid vibration, there is no sparks and very little noise beyond the mechanical noise of the machine itself.

The spigot as you say allows both parts to get to a similar temperature the rotation is then stopped abruptly and an even greater 'forging' force is then applied to complete the join.
Some early machines were actually using a large flywheel brought up to speed by a comparatively small electric motor. The parts were brought into contact with the energy dissipating through the welding process until the flywheel stopped.

You could spin the shaft but it produces more problems than the other way round ie. you need a hollow spindle and some way to hold the shaft so it doesn't slip while under load. Then removing the shaft from the spindle is much more difficult.