fork clang

Joined
Aug 24, 2005
Messages
198
Hi Guys and Gal,I have an annoying clang from the front fork on my '74 850,hitting a raised road seam or rolling off the centre stand causes a "clang", I have fitted new stanchions, new Progresssive springs,done the Covenant conversion,new fork seals and bushes,20w oil (5oz.) ( used ATF for a while),any suggestions what may be going on?,I have aligned the forks by loosening all of the pinch bolts i.e. lower yoke,wheel axle pinch bolt etc.. Thanks. Ride safely. James.
Just to eliminate -- it is NOT the centre stand bouncing!!
 
Joined
Apr 7, 2004
Messages
1,691
There are two clangs. One is top out wheel is fully extend with the sliders finding the end of thier travel. The sound your hearing is the dampner valve hitting the bottom of the dampner cap. Commando's limit the travel to 4 1/2 inches in this manner. The other clang is bottom out this is the inside edge of the hole in the stanchion meeting the bottom of the taper on the dampner tube. Progressive springs have plenty of travel for 4 1/2 inches in the stock system. The Covenant convertion adds a alum bushing inbetween the top hat and the bottom steel bushing. It also has you plug the old flow holes and re-drill them up on the straight part of the fork dampner body were they belong.
Are you sure that you have installed the dampner valves correctly? They are a one way fluid valve that uses mechanical slop to work. Did you check the 2mm dowels that provide the slop they are often bent from top outs. Hard to belive that the Norton Roadholders reley on a 2mm dowel as a mechanical stop, but it is a fluid stop top and bottom that was lacking from the start. I make a kit to fix all this there are about seventy of them out there. A look through the old posts (very old) will explain in more detail. The kit provides 6 inches of travel with fluid stops for top and bottom. Just finnished a proto type that only lifts the front of the bike 1/2 inch you can test it at the Michigan rally this July 17-21. come see me I will be running the tech sesions. Greg
 

MichaelB

"Sons of Arthritus"
VIP MEMBER
Joined
Jan 14, 2004
Messages
1,763
Country flag
Count me as one of the 75 who has used Norbsa's modifcation. Works well.

Greg, I will interested in your new 1/2" lift model for my 73. What's different with this?
 
Joined
Apr 7, 2004
Messages
1,691
Well in the stage one kit the dampner rods are two inches longer letting the sliders get pushed down by the springs no clang of the valve. Some of the inseam challanged riders found this too high. and many found that if they have no heft (under 150 pounds) the bike would not settle enough. So stage two requires that I or someone shorten the leg buy one inch and shorten the rods one inch than use different spings. Easy way if you need new legs is just order them one inch shorter from Forking by Frank. Need new dampner tubes order the new alloy ones from British Spares and they already have the holes moved.
There is a catch the stock fender could hit on severe bottom outs. I run a alloy front fender that sits lower than stock so no problem. Problem could be even more if you have to run a fork dampner the bolt and spacer stick down pointing at the top of the fender. Nothing's free.
Checked my 74 850 today on a total bottom out still have two inches to go so doing this mod should cause no problem.
 
Joined
Apr 15, 2004
Messages
1,616
Country flag
Did it just suddenly start clanking? If so you may need to go back in and see if something came loose (like the damper body cap for example).

When I first got my 750 the forks topped out badly like that. Turned out they were low on oil. Refilling with the correct amount of 20 wt fork oil fixed it. Then when I installed the disk brake a year ago the clanking came back. Turned out the nut at the bottom of the damper rod had unscrewed and fallen off on one side. Guess I didn't get it tight enough :oops: So when I redid the forks this winter I used red loctite and staked the nut. No more clanks!

Like you, I'm using Progressive springs and 20 wt fork oil. I bought one of those Covenant kits but decided not to use it. I thought about getting Greg's kit but didn't want to extend my forks.

Debby
 
Joined
May 19, 2006
Messages
1,612
Country flag
I have the same symptoms. Always a bit embarrassing to be a late arrival at a camping weekend, riding across a bumpy field with everyone watching and listening :oops:

The Covenant kit didn't work for me. I sectioned an old fork leg out of curiosity. The hydraulic bump-stop relies on the clearance between the damper rod and the alloy top cap and even with new components doesn't seem to want to work with any usable weight of fork oil.

I think that this is especially a light-rider problem (I'm 10 1/2 stone) I have never bottomed out, even when I hit a Peugeot hard enough to push the wheel spindle into the timing cover. Perhaps the kink in the fork tubes caused that though. :)

I am seriously thinking of going the Maxton route but some people I've spoken to are not keen for racing. Does anyone have experience of the Maxton conversion for street use?
 
Joined
Aug 24, 2005
Messages
198
Hi Guys and Gal, Thanks for the interest and info., looks like a fork strip this week-end for look-see.I can't make it to the Rally in Michigan,but will search for the info. posted by Greg. Thanks again. Ride safely. James.
 
Top