Commando Fork top nuts

No knowledge of your particular query, but I can vouch for CPC too and found them most obliging. Run by motor cycle enthusiasts and will copy pattern parts or make them to your specification.

Long roadholders don't have damper rods so don't need a threaded hole in the top cap. Short roadholders and commandos do, so need the threaded hole. But some are cycle thread and some BSF I think.

It's hard to see how you could make a filler cap without losing the threaded hole underneath. It's also pretty easy to take the whole cap off if you want to add oil, and I'd recommend removing the whole fork and swilling it out with a solvent when changing the oil.

My twopenneth anyway!

Dan

they would be good, they would enable you to top up your forks when sitting on the bike off the stand giving the ride height helping to equalize positive and negative air pressure within the forks at that level.

i have seen the ones for sale. i suppose a hole could be added as shown in the photo then you could use a big syringe type filler with measurements to add the correct amount of oil , Baz

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Hmmm ...... snake oil methinks! Take the front wheel off, undo the cap, push the slider up and measure the level properly! Bit harder with external springs I acknowledge. These bikes are worth a bit of time in my book. You can also experiment with oil levels, it will be guesswork if you are just slopping it in!

I'm with Dan on this. How do you know how much oil is in there? What's the point of sitting on the bike while you top it up. The ride height will not be affected. Start from scratch, empty the old oil out. Jack up the front of the bike till the springs/damper rods are below the top edge of the stanchions, fill with the required amount of oil, have beer while you wait for it to go to the bottom of the forks.

Will there be a problem with "airlock"? With the big nut off, the air has somewhere to go as you pour the oil in.

Mike

Dan , that snake oil is expensive stuff.

I must admit that the roadholder forks with the damper rod going all the way to the top make it difficult to get the level left and right equal, which is MUCH more important than the same volume in each leg.

On my dommie I always undo the nut which holds the spring in and remove the springs from the forks before adding the oil.

Having drained the old oil and refitted the blanking plugs, I add the required (suits my bike for me) 160cc of oil and having 'pumped' the forks by lowering and lifting the damper rod a few times, dip the oil with a welding rod to find the level.

I then mark this length on the suction tube of an oil change 'sucker' (my car doesn't have a sump plug, before the Luddites start), add a little oil to the already measured leg and 'overfill the other leg too then simply drop the suction tube down each leg in turn to the marked depth and suck out the excess.

I then reassemble the springs and caps and it is job done.

I appreciate that it takes longer than the pour in a measured amount method, but I am happy knowing that the air pressure on each side (air volume above the oil) will be the same, and therefore the spring rate too.

George.

The spring rate is controlled by the spring, the oil takes care of the damping. Irrespective of the volume of air above the oil, these are not pressurised forks.

They may not be pressurised but I'll bet you the the air above the oil acts as a spring, surely it would only not do so if the fork tops were vented? But what I don't know is how much the air springing would contribute! Anyway the important thing as George says is to get the levels the same!