Setting up Marzocchi Forks

[nzpeterb]

While the front fork action on the Fantic is fine, I want to make some changes as they bottom harshly a few times each trial.

The top caps have a spring loaded ball in them that releases any air so the forks don

[spud1968]

While the front fork action on the Fantic is fine, I want to make some changes as they bottom harshly a few times each trial.

The top caps have a spring loaded ball in them that releases any air so the forks don

[woody]

First issue is the condition of the springs, they could be ok or sagged out after 30 years. Difficult to tell but by increasing spacer length to counter the bottoming, what that can happen is the coils close up with the forks fully extended and there is the possiblity of them compressing completely before maximum travel is used if overly long spacers are used. Also you don't mention which Fantic it is. 35mm forks or 32mm. 190cc of oil is edging towards minimum for 35mm forks, usually the recommendation for them is 220cc. Best to start with 200cc (or 190cc in your case) and add 10cc at a time to obtain correct action. It's trial and error basis. 10W for oil should be fine in Marzocchis. However, you must be sure of the spring condition, otherwise attempts at set up could be pointless.

The other unknown is whether they are the original springs. They could have been replaced with something else by a previous owner. If they are 35mm forks, WES did progressive springs for these which work very well, if you can find anyone who stocks them. Or you could get original spec springs from Bill Pye maybe. A third alternative is fit the Magical front fork spring kit which is available from Yamaha-Majesty.com.

The problem won't be helped by air escaping because as you say, it lessens the spring affect. I've had the same problem on Ossas and Bultacos, getting a face full of oil when the forks compress. I just block off the hole. Never had a problem blowing seals. You can always fit a valve which will allow you to depressurise them if required.

Front fork settings are a personal thing really, there is no hard and fast rule, some like harder action, some softer. As a starting point, once you are happy that you have correct spec springs, either original type or aftermarket, start with 200cc of 10W and adjust from there, but that volume and viscosity should be as near as you'll need for most conditions - for 35mm.

[bilc0]

i put 220ml in mine,they work great with no bottom.

[nzpeterb]

Thanks spud 1968, Woody, and bilc0, for your replies.

The forks on my bike are 35 mm and I had put 190 ml of oil in each leg based on the Fantic 200 manual which I have a copy of.

But the manual dates from 1980 and the bike from 1983.

I now realise the 190 ml may be for the 32 mm forks and perhaps 220 ml, as suggested, is for the 35 mm forks.

Looks like I simply did not put the right amount of oil in each leg.

I will try adding oil during the weekend and see if this reduces the bottoming.

I would be interested if anyone knows the original fork spring free length to determine whether they need preloading or spring replacement. There is enough free length that even with a short preload spacer they won't coil bind, though the extra oil may be enough to stop the bottoming, as otherwise I am happy with the fork movement.

Thanks again for your replies.

Regards,

Peter.

[lee harris]

yep 220cc or go on a diat. I dont have the same value in my handbook. Mine says 220 but I use 200. I also us progressive springs from WES. Available form Steve Goode or BVM in the uk.