1986 350 K2 fork travel query?

[themoudie]

Having read through all posts on fronts forks, I am unable to find an answer to my query.

So, how much travel do others have on their K2 forks?

With 200cc of SAE30 fork oil in they were too firm for me and rattled the fillings out of my teeth on the minor roads that I tend to ride. I have drained the forks and then re-filled them with 200cc SAE10 Motul fork oil. This gives a more compliant action and I now have 80mm of travel, compared with 60mm when using the SAE30.

There are the original fork spring preload spacers still fitted and these are 95mm long.

A more compliant fork action with 100mm of travel would be nice, I think!

Using a Avon RoadRider 100/90-18 front, tyre pressure recommended by Avon is 30psi and I have found that this causes a slight rolling in HGV grooves, whilst dropping the pressure to 28psi appears to remove this.

Thank you for your time.

Bill

[Vitesse]

I am no marque expert but in all my years I have never heard of SAE30 in forks. In general SAE5 is light oil and SAE15 is regarded as thick.

[Ming]

I have a K2 Sport, and an owners' manual. The manual does not even mention forks or fork oil. I have used ATF in all my bikes' forks over the last 40 years with no problems. I think it's around SAE10. I take this page from an old Marzocchi manual as reference for volume.

marzocchi_17.jpg (106.65 KiB) Viewed 5274 times

[3potjohn]

Hi I used 220mL 15w oil on my K1 ridden by an old fat bast*rd seems to work for the roads around here. Guess for high speed track use all things become more critical.
John

[mad muller]

never sure about atf i think its a bit thin used 20w fork oil in the sport its been in there for years not bad prob needs changing, on my old brit stuff used to use 20/50 engine oil worked fine thicker it is the less to piss out , well it was the thing to do back then.

[themoudie]

Thank you all for your replies.

Vitesse I have to say that it was a surprise to me, but that is what I was told by the previous owner and it appeared more viscous than the SAE10 that replaced it.

With a similar pair of forks on a Ducati single, I found that SAE7.5 fork oil allowed full travel of the forks, but they were a bit soft, as they would 'bottom out' on some of the rougher stuff up here!

Ming Thank you for the table of oil volumes to be used, very handy.

John Thanks for the detail. Whilst we don't have the characteristic lanes up here, they can be just as deep in some parts, without the cow pat finish! My Grandmother wur Voscombe 'n Barnstaple, afore she moved on!

Mad Muller I suspect the SAE20 would give me a pattering front end again and I can't remember what I used to use in my old '53 18S, back in the day!

Good health, Bill

[EVguru]

The 'Blue Book' calls for HLP80, which was an SAE80 hydraulic oil. Engine, gearbox & hydraulic oils are on different SAE charts and HLP80 equates to something like an SAE30 engine oil.

I've run this at Cadwell in my 77 Sport, but it's far to much damping for road use. I'm now using SAE10 and have so little damping that it can raise comments at Scrutineering.

There have been several different sets of fork internals and Marzocchis aren't exactly precision machined items, so oil weight is very much a 'suck it and see' affair. Later forks for example did away with the rebound hole, instead using 'controlled' leakage between a waisted damper rod and the rebound check valve.

Changing the fill level alters the effect of the air spring above the oil. This is a racers trick for increasing the spring rate, but the air spring is non-linear and it's easy to make it far too strong.

The late Martin Gelder and I were doing some suspension modifications and testing. The articles are still mostly available via the Wayback Machine
https://web.archive.org/web/20180304125 ... uning.html