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Marzocchi fork rebuild.


Lucky Phil
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So I sourced a used pair of late model 43mm fork assemblies for the V10 Sport. Naturally when they arrived they were not quite what I expected condition wise probably due to the less than ideal packaging. Both legs were leaking with one side disguised by a piece of absorbent material under the dust seal and the other not. There was obvious damage to the other chrome slider as shown below. Both are dead straight and the stanchions are in good condition considering their age with minimal wear. The bushes were also fine for wear but they'll get replaced anyway. The real issue is removing the brake and axle brackets to get the sliders re chromes and ground. There is a small grub screw in the brake bracket which comes out with some heat to release the Loctite but the damage to the slider threads it causes needs to be addressed before the joyous job of trying to remove the sliders themselves. I drilled a small 5mm screw ( locking grub screw size) down the centre screwed it back into the bracket then took a 3mm drill ground flat on the end with some cutting clearance ground on the tip and used that to remove the damage caused by the pointed grub screw. Worked well. A 3mm end mill would work better if you have one. Next issue is the bracket removal itself which needless to say is held on with loctite on the very fine threads used on the chrome sliders. These are notoriously hard to remove and need quite a bit of heat application to break the locking compound. I bought a 43mm clamp and also drilled a hole in the bench for an 8mm steel rod to fit through the holes at the top of the slider to provide even more resistance to turning. You have to love the flexibility of a wooden bench for things like this.

I also machined up a pair of bushes that I could clamp into the forks that fitted a piece of steel rod I had on hand. I wanted to provide as much support to the axle lug as I could. I don't have an axle at present but I thought I'd need a bit more leverage anyway. So gas burner and temp gun in hand I heated up the bracket and they finally released from the thread locker. There's a bit of loosen and tighten work involved initially but eventually taking it steadily off they came without damage to the threads. As you can see there's a lot of thread locker on there. Most people leave this sort of thing to the fork re chroming/refurbishing guys but I like a difficult life and it saves $50/leg in costs. So next job is off to get the sliders re chromed and ground. I have a seal and bush kit on the way and I need to refinish the brackets and repair a slight graze mark from an obvious trip down the road. The objective is to replace the std cartridges with aftermarket jobs and machine up a Titanium axle.   

 

Packaging!

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Damage. To the sellers credit he refunded me the cost of repair to this leg.

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The bench setup

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Brackets and axle bobbins I made up. The graze on the lower bracket looks worse than it really is. I'll just use some Devcon F to fix it and shape it back before re painting in 2 pack.

DSC01504.JPG

Thread damage from locking screw that requires addressing before bracket removal

DSC01502.JPG

Ciao

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This is interesting I have a High milage   bike that blew the seal. When I rubbed my hand over the fork tube it felt like it was shoot peened for all the stones thrown at it. I contacted someone I thought could handle the job they tried to convince me I needed beauty chrome and not hard chrome so I never followed through So I'll keep an eye on this thread and learn.

For removing threads with loctite  I started using a very large soldering iron I mean it's about 350 watts. I do have an acetylene torch with a 000 tip, but I find the iron is much more locale heat.

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14 hours ago, Lucky Phil said:

So I sourced a used pair of late model 43mm fork assemblies for the V10 Sport.

Are you going to rebuild back to standard, or do you have something better in mind?

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6 hours ago, Kevin_T said:

This is interesting I have a High milage   bike that blew the seal. When I rubbed my hand over the fork tube it felt like it was shoot peened for all the stones thrown at it. I contacted someone I thought could handle the job they tried to convince me I needed beauty chrome and not hard chrome so I never followed through So I'll keep an eye on this thread and learn.

For removing threads with loctite  I started using a very large soldering iron I mean it's about 350 watts. I do have an acetylene torch with a 000 tip, but I find the iron is much more locale heat.

The area and amount of loctite here is too great for a soldering iron. It's a 43mm dia tube and the threads are about 15mm deep plus another 20mm of plain sleeve that the loctite also affects and a sizeable alloy fitting.

Yes it's hard chromes and needs to be sized and ground and checked for straightness. I checked and mine are perfectly straight so thats fine. 

Ciao

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1 hour ago, MartyNZ said:

Are you going to rebuild back to standard, or do you have something better in mind?

No, going to use aftermarket cartridges with rebound in one leg and comp in the other. These later forks are rebound only adjustment.

Ciao

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  • 1 month later...

While the sliders are away getting re furbished I thought I'd re finish the brake and axle fittings and also the upper clamp Scud sold me in Matt Black 2K. I went to the effort of removing the casting line on the clamp which was a wasted effort in reality. I just used JB weld to fix the slight damage on the r/h fitting as it's of no structural significance. 

Before

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After

DSC01507.JPG

 

DSC01508.JPG

Ciao

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Haha, I thought about smoothing out the cast line when I got my triple clamps powder coated. Ended up not doing it - makes me feel better hearing you say it was waste of time. But you saved a couple grams of weight... 

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16 minutes ago, Scud said:

Haha, I thought about smoothing out the cast line when I got my triple clamps powder coated. Ended up not doing it - makes me feel better hearing you say it was waste of time. But you saved a couple grams of weight... 

Yes, there was a little voice in my head saying this might be a mistake. It just really doesn't add anything aesthetically to be honest and it's originally there as a kind of consistent line break where the angles change as the faces aren't flat. Mine looks fine but adds nothing really. This bike is going to confuse the hell out of someone if it's ever owned by a Guzzi enthusiast when I'm gone. 

Ciao

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