front end clank

PeoriaCommando13 · Apr 13, 2023

I have a mostly stock 71 750 Commando.
Front end works great except for the common thunk on fork rebound. I accept that one.
My problem is if i attach the stock fender to the fork lowers i get a clank sound over every bump of any significance. Without the fender no clank ever.
Its not the brake cable slapping the fender. Its not insufficient clearance between fork lowers and the fender brackets that bolt to top of the fork lowers. Alljoints on fender are tight.
Anybody ever hear of this problem??

kommando · Apr 13, 2023

There should be no clearance between the fender brackets and the fork lowers, there is no spacer in between so the retaining nuts should hold the brackets tight to the fork lowers with no gap. A photo of what you think the issue is would be useful.

Tornado · Apr 13, 2023

You mentioned brake cable out of way, how about speedo and tacho cables? I've seem witness marks on some mudguards were these cables were hitting the mudguard on fork compressions.

Unlikely your issue but, When my forks were making clanks over bumps, I too put it down to the know rebound slap you noted. Later when I was changing fork oil, discouvered both damper threaded rods had come unscrewed from top caps and there was basically no fork damping at all. The clanking was from the loose rods smacking into the top nuts.

PeoriaCommando13 · Apr 14, 2023

kommando said:
There should be no clearance between the fender brackets and the fork lowers, there is no spacer in between so the retaining nuts should hold the brackets tight to the fork lowers with no gap. A photo of what you think the issue is would be useful.

Thanks for response. I do have the brackets at the bolt holes flat against the lowers. i was referring to the clearance just above that area where the brackets curve inboard a bit to create about an 1/8”of clearance. If it were less, then with fork lateral flexing maybe you might get a clank as bracket hits the lower. So i think ive exhausted that possibilty and sorry if i wasnt clear enuf.

PeoriaCommando13 · Apr 14, 2023

Tornado said:
You mentioned brake cable out of way, how about speedo and tacho cables? I've seem witness marks on some mudguards were these cables were hitting the mudguard on fork compressions.

Unlikely your issue but, When my forks were making clanks over bumps, I too put it down to the know rebound slap you noted. Later when I was changing fork oil, discouvered both damper threaded rods had come unscrewed from top caps and there was basically no fork damping at all. The clanking was from the loose rods smacking into the top nuts.

Thanks for your response
Yowsers, you had a serious situation! If that were my problem it should still do it with the fender removed….but it doesnt.
My speedo and tach cables both run aft above the lower triple clamp. So they cant contact the fender even at full suspension compression travel.
Crazy problem, eh?
I’ll temove the fender again and recheck all the bolts and rivets.

Tornado · Apr 14, 2023

You didn't mention mudguard stays?
Another source of front end noise are the headlamp brackets but again not associated with presence/absence of mudguard. Culprit there would likely be perished/missing/mis-seated rubber o-rings top or bottom of each bracket.

PeoriaCommando13 · Apr 17, 2023

PeoriaCommando13 said:
Thanks for your response
Yowsers, you had a serious situation! If that were my problem it should still do it with the fender removed….but it doesnt.
My speedo and tach cables both run aft above the lower triple clamp. So they cant contact the fender even at full suspension compression travel.
Crazy problem, eh?
I’ll temove the fender again and recheck all the bolts and rivets.

Removed fender and checked all bolts and rivets. Everything tight and as it should be. This is nuts! My own little twilight zone! Riding without fender for time being, no clank and looks fine to me.

PeoriaCommando13 · Apr 17, 2023

Tornado said:
You didn't mention mudguard stays?
Another source of front end noise are the headlamp brackets but again not associated with presence/absence of mudguard. Culprit there would likely be perished/missing/mis-seated rubber o-rings top or bottom of each bracket.

Thanks for response. Sorry, but i dont know what rubber o rings youre talking about?? My headlamp has no orings and it bolted up securely.

L.A.B. · Apr 17, 2023

PeoriaCommando13 said:
Sorry, but i dont know what rubber o rings youre talking about?? My headlamp has no orings and it bolted up securely.

There should be three O-rings, one above and two below, the headlamp bracket tubes on each side.

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

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Item 51 (x6)

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Tornado · Apr 17, 2023

L.A.B. said:
There should be three O-rings, one above and two below, the headlamp bracket tubes on each side.

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

Item 51 (x6)

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.

andover-norton.co.uk

#51 in the parts drawings...6 total.

PeoriaCommando13 · Apr 18, 2023

Tornado said:
#51 in the parts drawings...6 total.

Ah ha! Now i see what youre talking about! Just checked mine and i cant see any oring above or below. The brackets do seem to be snug on the upper rods. Ive never had the forks off this bike and guess i just assumed the brackets were a sng fit over the upper fork rods. Pushing and pulling on them ii cant detect any movement. I see a slight gap between lower edge of bracket and
the lower triple clamp. When i get some time i’ll mess around with this and see if it is contributing to my clank.
Thanks much for pointing that out!

L.A.B. · Apr 18, 2023

Tornado said:
#51 in the parts drawings...6 total.

Wasn't "Item 51 (x6)" in my post understood?

PeoriaCommando13 said:
Just checked mine and i cant see any oring above or below.

They're hidden until you lift the upper yoke then you should see the top O-rings and if you lift the brackets you should see the two on each side below the tube. Also, check the O-rings haven't been forced inside the tube because the positions of the lower O-rings on the parts diagram make it look as if the O-rings go inside the tube and not below the ends of the tubes.

front end clank

PeoriaCommando13

kommando

Tornado

PeoriaCommando13

PeoriaCommando13

Tornado

PeoriaCommando13

PeoriaCommando13

L.A.B.

Moderator

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Tornado

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

PeoriaCommando13

L.A.B.

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