Hi,
The forks compress and rebound but maybe too much give. Lots of clonking over bumps. Not (quite) as bad as the 1st to 2nd gearchange…
New to these forks (rebuilt Roadholder and triumph OIF forks). Any advice welcome on what to check and how to drain and replace the fluid + best weight etc.
Hello Eddie
I have these 38mm diameter forks on my 1974 750S replica too (I call it a 950S to avoid confusion!) I have a copy of the manual for them. Send me your email address via PM and I will send you a copy.
Best wishes Chris
Many thanks Chris. I do have a copy of the manual but just wanted some feedback on a diagnosis. Ideally just hoping to top up or change the fluid rather than pull the legs and strip and rebuild!
Cheers
Eddie
Eddie
A top up will depend on how much oil is in there and only by draining the forks will you find that out. If you drain the forks I would recommend new oil and new oil seals.
Best wishes Chris
It’s tricky to diagnose with your info.
If they were Guzzi forks I’d say your dampers were shot, which is typical after just a few years.
But the Marzocchis are different. If the clonking is topping-out ( which I’m guessing from your description ) it implies either something has come undone or, much more likely, there’s not enough oil left inside to provide damping. If that’s the case it’s almost certainly because the seals have hardened with age and leak for that reason. I see the gaiters which should protect the stanchion working surface, but were they fitted because the stanchions were already shot and leaking oil ? If you pull the gaiters up is the chrome in good condition and is there oil sitting on top of the fork seals ?
I’d say Chris is right. New seals and oil.
Hi Andy,
I just pulled up the gaitors. LH stanchion good. Traces of oil but minimal scoring. RH stanchion. No traces of oil minimal scoring. My Commando stanchions are new, leave more oil traces and work great.
So maybe I’ll 1st try draining and replacing the oil. Can this be done without removing the stanchions and what grade would you recommend- softer is fine as I’ve yet to top 90mph unless over a beer.
Regards
Eddie
Hmm, it’s hard to know what you mean by “minimal scoring”. My experience has been that any scoring means oil transport, and over a short period of time the small amount of oil in forks gets depleted.
In answer to your questions. Yes, you can drain and replace the oil without dismantling the forks. It would be very worthwhile to measure the amount you get out, because I think it’ll tell you a lot.
Based on your description, I’d say you need new/rechromed stanchions and new seals. Your description of your Commando tells me you’ll be rebuilding those soon, or maybe, just maybe, they’re so new that the seals are ‘bedding in’. Honestly, I don’t believe myself…Yes, they’ll work great while there’s enough oil to submerge the dampers. As soon as there isn’t, they won’t work well.
Oh, I forgot. Oil grade is not a big deal, really. I’d use something like SAE 10 or 20. 30 wouldn’t be dreadful, but you’re trying to make up for weak springs if you use it. It’s what I did back in the '80s.
Much appreciated Andy and Chris.
I’ll swap oils and follow up with a post to let you know if it cured the issue.
Regards
Eddie
After so many years your springs may have compressed with age/wear. You can take them out of the top without dismantling the whole fork, if I remember correctly. I wouldn’t go much higher than 15W and would probably try 12.5 or 10W. Certainly new seals.
If your lottery ticket comes in take them to maxton in frodsham. Super helpful people: they could either rebuild as is - seals, rechromed stanchions, oil. Or super Megabucks approach - replacing the internals with modern cartridges might be a goer. My laverda clonks occasionally but not enough for me to be bothered.
I usually find ‘clonking’ is more related to loose/worn headstock..
Unless you’ve already checked and ruled this out, have a look there too.
Good point. Will check that too. Rears are Marzocchi so worth a look too.
