Front Forks too stiff

[biker_smith]

Hi all,
Just bought a '75 Z1B (very nice) - but the front end is way too stiff, making the ride very unconfortable.
I have no idea what's in the forks (neither does the seller) - so I need new springs and oil.
I see Wemoto have some in stock (Z power have none) from YSS (on the shelf) and Hagon (4 weeks wait) - what's best?
In the hand book it says 10 SAE motor oil at 170cc each leg - I would think fork oil should be used now - what's the best weight to use?
Thanks for any info - Paul.

[warren3200gt]

Take the fork caps off you might find that one of the previous owners has put a pre load spacer in the top and or over filled with oil.
Z forks are not stiff unless they've been "adjusted"

[BAFF1960]

Hi.
When buying a new bike that the seller obviously doesn't have a in depth knowledge about there's always going to be issues or fettling.
Back to basics is the way to go with any unknown quantity. Drain the legs, check the spring lengths and any preload spacers for correct assy. Use a good brand oil to the correct weight and volume and you'll have the base factory setting. Go from there to suit personal preference. Just remember its 70's suspension.

[Grog]

Hello mate;

Got a non-standard front end in mine so can't give you specifics, but I've recently rebuilt the forks using Hagon springs (they were very helpful in sorting me out with random requirements) and Motul10w oil, and I'm pleased with the results. As BAFF says, best bet is to get stuck in and see what you've got as a starting point, then work from there.

TTFN Grog

[biker_smith]

Hopefully a photo above of the contents of my forks.

A matching pair at 503 mm in length, with the spring at the top coiled tight.

No spacer at the top - just a small top hat to help centre the spring I assume.

Thanks - Paul.

[Hack]

According to the KHI shop manual the lengths are correct and in spec for a Z1B

Standard = 505.5mm
Service limit = 495.5mm
Oil volume = 170cc per leg

Start by changing the oil for SAE 10w and see how it goes.
Don't just add 170cc per leg (thats just how much you need available), add oil until the level is 475mm from the top of the fork tube with the springs in and the forks fully extended (front wheel off the ground).

[wilsonsjw11]

If you haven't already got one purchase a Clymer manual.
Check that the damper has been assembled correctly on previous strip downs.
The washer that is shown in the photo that has been under the fork cap is not an Z1 OEM part.
Regards
Steve

[warren3200gt]

It is on a 650 set up. It keeps the spring load square on the cap with the lip sitting in the spring inner dia.