Front forks won't rebound

Hi,

I've just picked up my first Norton, a 1971 750 Commando. The bike was sent down with a bike relocation company, but I think they may have tied it down too much. When I sit on the bike the forks fully compress and don't rebound. Can these be adjusted / reset? Or is it a big repair? Thanks in advance!

You could try slackening the axle, mudguard mounts, lower yoke pinchbolts and stem nut then pump the forks vigorously with the brake on as that might realign the forks.

Yes do that , but if nothing brings things back up where they should be , I'd suspect the springs to be finished and in need of replacement .
How many miles on the bike ?

Take it apart and look. When I was doing a customized damper project I think I took my front damper cartridges in and out about a dozen times in 2 months... It's really not all that technical... or difficult. Don't psych yourself out thinking, "OMG, I've never done this before!" It's not like assembling an engine,... it's simple stuff.

Thanks for the replies! Sounds like I have a project for the weekend.

there's numerous videos on youtube showing rebuilds of your forks.... so you have a lot of resources

It could well have 53 yr old fork oil (or whats left of it, probably smelly oily water) along with corroded springs,damper rods, tubes etc Overhaul required

TheFlyingKiwi said:

Hi,

I've just picked up my first Norton, a 1971 750 Commando. The bike was sent down with a bike relocation company, but I think they may have tied it down too much. When I sit on the bike the forks fully compress and don't rebound. Can these be adjusted / reset? Or is it a big repair? Thanks in advance!

Click to expand...

Hi; Since this is your first Norton. I'm just checking that you are aware that if you remove both top nuts at the same time that the bike will collapse toward the floor.

Not trying to complicate the task, but you probably need to consider the possibility that the front end was hit and is deformed. This could mean bent fork tubes or twisted triple trees. The damage does not need to be obvious to produce your symptoms.

The fork tubes are easy to check: roll them on a flat surface and look for daylight.
To check the triple trees (still in the bike), with the bare fork tubes installed, carefully measure the distance between the two tubes. Dial calipers work well, inside calipers, or even a pair dividers. Take multiple measurements at different heights.
In a perfect world you would lay a flat reference plane against the pair of tubes installed in the triple trees to check for twist.

Should you find the triple trees are bent, it is not that hard to move them around if you know what you are doing.
Small bends in fork tubes can also be straightened, within reason.
An old machinist told me Mondays was the day they straightened fork tubes, after the orangutans crashed them on the weekends.

Most of the damping of front forks is rebound damping. There is a shuttle valve on each of the ends of the rods in each of the forks. When you push down the valves on both rods open and pass oil. . On rebound the valves almost close off completely - so rebound is better controlled. If the valves and top seals, seal completely, the forks cannot rebound. Very thick oil can cause it. When you ride a motorcycle at very high speed, the suspension often seems to pump down, making the bike more stable. I think the tubes which the shuttle valves sit in are supposed to have caps with clearance for the rods - that clearance controls the rebound rate.

The LH alloy slider is supposed to find its correct position on the Axle when the pinch bolt is loose and forks bounced . A very light nip up after. or the leg will crack!.