front fork repair 1974 350b - MVAgusta.net
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post #1 of 15 (permalink) Old 03-06-2016, 01:29 PM Thread Starter
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post #2 of 15 (permalink) Old 03-06-2016, 01:56 PM Thread Starter
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350b front fork repair

My 1974 350b has a problem with the forward mounting lugs for the gas tank.

The lugs are threaded but bottom out at the steering column. The threads are damaged beyond repair. I want to restore the threads with helicoil inserts. This requires drilling them out and tapping for the inserts. Before I can drill them out I have to remove the inner steering shaft (in the parts manual the "fork basement").

I removed the aluminum plate which mount the instruments and it looked like the "fork head" and "fork basement" should simply just slip apart.

See first attached picture.

But they seem firmly attached. I tested by firmly tapping the head using a wooden block and hammer.

My parts and owner's manual are no help.

Bummer!

Is it possible that they are force pressed (with a press) together. I would guess not, because access to the steering bearings for service would be very difficult for the home shop. However the lower end of the "fork basement" reveals a slot to the shaft end which holds the vibration damper.

See second attached picture.

Is it possible that this slot acts as access to unscrew this shaft thereby releasing the parts.

I am soliciting opinions because I am very cautious to not apply large forces if I don't know what I'm doing.

Help

Roger Craig
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post #3 of 15 (permalink) Old 03-06-2016, 02:56 PM
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The stanchions have conical top ends in the upper top yoke. So I think you have to rebuild the handlebars and the headlight brakets and losen the screws which fix the stanchions in the lower yoke. Then fix the chrome plated screws on top of the stanchions only half the way and use a plastic hammer to pull them out of the upper yoke. It's just the same as on the 750s. Excuse my bad English, hope you can understand it.

Regards

Alexander
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post #4 of 15 (permalink) Old 03-07-2016, 10:22 AM Thread Starter
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Alexander
Many thanks for your reply. I'm stuck at this point. I will set up what you suggest and take a picture and post it to make sure I understand you, before applying force. Since you're German, or at least in Germany I will tell you some thing that might encourage you to trust that I will do work honorable to the moto. I owned a 4 cam Porsche Carrera, roller bearing version, for many years. More that once I have completely, and totally, rebuilt the engine myself. And it ran like a dream.

Again thanks for your help.

Roger
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post #5 of 15 (permalink) Old 03-07-2016, 11:53 AM
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So you really had a wonderful car and a mecanical challange too. Probably you can look for your little problem in the workshop manual from the 750s. It's just the same method to dismantle the front fork.

Take care of our nice bike.

Alexander
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post #6 of 15 (permalink) Old 03-07-2016, 12:58 PM Thread Starter
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Alexander
Do you have workshop manual for the 750S. I can't find one on the web. If you do, and could scan the relevant pages, you will make an old man happy. I'm told that gives credit for the here-in-after. At least that's what Rudyard Kipling said.

You know about the mechanical complexity of the 4 cam Porsche engine? One of my Bugatti friends said they call it a 300 lbs Swiss watch. I attached a picture of the engine open showing the roller bearing crank and the start of the shaft/bevel gear train that drives the 4 camshafts. Its fun to work on if you're not in a hurry and if no one is watching (critically).

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post #7 of 15 (permalink) Old 03-07-2016, 02:15 PM
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Thank you for the great picture of the wonderful porsche engine. It is a technical juwel. Why did you sell the car? Have a look on this picture. I just made from the manual of the 750 America.

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post #8 of 15 (permalink) Old 03-07-2016, 04:17 PM Thread Starter
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Alexander

Many thanks. Is it possible to get a higher resolution of that page? I can't read to text or examine the illustration with any confidence. Perhaps take pictures of only portions of the page? This is very close.

Here's my car at the 2009 Pebble Beach Concourse: the big one.

Roger
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post #9 of 15 (permalink) Old 03-07-2016, 06:32 PM Thread Starter
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Alexander

I was able to download the photo you kindly supplied, and enhanced it a bit to enable me to read the directions. These instructions seem to show how to remove the telescopic forks. I really need to remove the steering shaft that resides inside the steering column. I need to do this to be able to drill out and re-tap the stripped threads on the gas tank mounting studs. Recall I want to renew the threads for helicoil inserts. Its this internal shaft that's in my way, and seems to be tricky to get out. The lower end of it is shown in the second foto that I used in my initial query. Does your 750S address this operation?

Do you have a 750S? I've only sat on one. Pretty nice, I must say. Right up there with a 4 cam Porsche!

Don't text and ride.

Thanks for your patience,

Roger
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post #10 of 15 (permalink) Old 03-07-2016, 06:37 PM Thread Starter
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Here's a picture of the gas tank mounting studs with the stripped threads.

Roger
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