620 Sport Help
 

Hi,

I’ve recently picked up a 620 Sport to join in the DD fun next year (great track selection by the way, well done Chris and mt).

I’d like to refresh my forks with new oil but the previous owner doesn’t know what weight is in there at the moment and suggested I try the forum.

So is the standard recommended 7.5 oil good enough for race/track use, or do I need to try something abit heavier ie 10, 12.5, 15 etc?

If you are going to that level of stripping, you may well want to look at the spings and damping within to go to something more suitable for the race track.
I am sure that one of the DD boys will let you know who is best for this.

You need 50w oil and one of those new Ohlins solid steel rods to firm it up a bit.

HTH :P

Oil for off roaders is good:)

worth asking Maxton's etc...........

I think you'll find it reasonably stiff as std, depending on your weight !
After all, the std suspension is a compromise for single and two-up riding, so may work out ok on track.
A revalve may make it work more smoothly, but personally I would just start with fresh good-spec non-foaming std-weight oil.
If its road legal at the moment ... off you go !

Forks on the sport are waaayyy too soft as standard (unless you're a 30kg frenzied monkey). I have yet to refurb mine (or even check they're straight..... :( ) but you should look at stiffer springs/heavier oil as a minimum.

The only springs I've found so far require the fork tops to be machined (not sure how) so I'm still looking for an easier solution. Let me know how you get on.

Cheers,

Ali

ps: Race Committee, can we please, please have adjustable forks one day? It's a right pain trying to find one setup that'll last the season....

As if that'll help :lol:

It's bad enough deciding what tyre pressure and gearing to run, now you want to fiddle with suspension??? :o

;) :D

youre right about them being soft:o

but, it doesnt take too long to get them right:D the Snot has still got the 'sawn off ends of handle bars' shoved in the top of hers as spacers, which we did at Cadwell Woodland in April:o

:o

:lol::lol:

Oi you, shurrup!!! :D:D:D

:saint:

Did it happen by accident :o
or did you do that cos handlebars are free :saint:

(ali - its a _very_ common mod to forks - even as std on some machines !)

Thanks for info so far, (except Dom he he if I do the mods you suggest will you swap bikes with me for the first race:frog:

As I've not ridden it yet (track only bike at the mo as its currently French registered) I didn't really want to send off the forks to a professioanl as they will most likely be fine as is, after a change of oil.

I was hoping to get an idea of what people currently use in their forks. Then during a practice day I was going to replace current unknown fork oil with whatever the popular weight is (7.5?) and compare.

dubelg.....I think I'm right in saying you've bought Tonio's 620ss. If so, I rode his bike for 1 session at TA5 (Brands) & I'd be very surprised if it had standard grade oil in there. It dived a bit (possibly a little bit too much?) when you hit the brakes (which were surprisingly good), but then settled quite nicely.
Speaking to Tonio on the day, I thought Geoff Spencer had given him some advice as to which grade oil/ air gap to try for next year :puzzled: . Whatever it has in there now though, that bike can definitely run at the sharp end even if you left it as it is. I'm not a racer, but even I was doing 57 secs laps without really pushing (as it was a few days before Tonio's last DD round).

If you didn't buy Tonio's bike, just ignore me :D

Did you get it off antoine's ducatannonces ?
(which one was it ?)

Phil, we did that cos despite them being reworked, they still were not stiff enough for Andy round the Woodland circuit on the then 583 Snotty. The cable tie was not then being broken off at the bottom

5 mins with hacksaw + shove bits inside the tops = better ride:)

Fil2 - shut it, you nit!

I ended up changing springs twice in my forks, going stiffer each time - but I'm a heavy guy and it seems I brake harder and later than some people.

It's not just rider weight, it's how you ride, body position, use of the throttle that determines how it should be and everyone is different.

That's been my experience anyway.

[Edited on 20-10-2005 by TP]

Thanks for suggestions.

Wylie1 - thanks for info, and yep it's Tonio's 620 Sport.

Looks like I need to to a practise day on the bike with a choice of fork oils and some spacers, to come up with a combination I like.

Cheers

I finally got round to stripping my forks last night and thought I'd update this old post as it may help future / current 620 Sport owners, knowledge is power an all that ...


I took the springs out of my bent forks last night to confirm what they were and be ready to fit them to the new forks, and now know they are not standard. These springs are single rate with a wire thickness of 5.0mm and ~285mm long. This compares with the standard springs that came in the bikes spares box of being progressively wound and only 4.7mm OD wire thickness and 290mm long.

And although the front end maybe a little soft, it feels pretty good, I just need to avoid hitting stationary bikes in future
:D

eh.........................?...................... ...........u wanna fight do you...:puzzled:

Std 620 fork springs themselves are not too soft. The problem is that they are progressive springs - more suitable to road use. Because they are progressive you lose too much fork travel initially through sag. It is better to fit single rate springs.

If you go for heavier oil beware that heavier oils are more prone to cavitation i.e filling up with bubbles which, can actually degrade damping performance. It's always better to get damping valves orifices modified to increase the damping when using a lighter oil.

I talked to a few suspension houses about doing some spare 620 forks I have and the general recommendation was just to service the forks, go for a single rate spring and std oil.