M600 forks bottoming out

[MotoNik]

Hi all,

I changed the fork oil on Emily's M600 last week, in an effort to improve the handling a bit, and try and stop them bottoming out. They seemed decidedly soggy. Upon disassembly there didn't appear to be much oil at all in each leg, so it clearly wasn't doing a lot of damping!

At the recommendation of Pedro I used 7.5wt oil, with just under half a litre in each leg.

Sure enough, a nice plush ride, not to hard, not too firm. However, the nasty jarring bottoming out still occurs on big bumps.

Surely thinner oil would reduce damping (more bouncy ride - not ideal), and thicker oil would make the problem worse.

Anyone have any hints of top tips (short of fitting Ohlins Superbike forks!)?

cheers,

Nik

[Scotty]

diet ? bet ya didnt see that one comming
new springs is the best solution
or longer travel super moto forks

[slob]

Thicker oil will give more damping and a firmer ride, with less likleyhood of bottoming out. I just rebuilt my 620 forks, after blowing an oil seal, with SAE10(because I had a bottle of Swedish stuff in the garage) and they are indeed firmer and use less travel as a result. The handling seems better to me but I like quite a firm ride(fnarr) and the stock SAE7.5 seemed a little bouncy. Have you checked the sag? As Scotty says new springs are the correct answer if the sag is wrong.

[Scotty]

out of interest (im not very clued up ) do the forks not have a bottom out elastomer then ?

[A Yerbury]

the early 600 forks are a bit ****e really, getting a pair from a 900 would be cheaper than spring work (or about the same) plus you may get a second brake. I've done it to mine so for once I know what I'm talking about.
Alex.

[Pedro]

I think you need to lay off the donuts!!!

Does it bottom out when Em rides it? Give me a shout over the weekend if you want to do a comparison with mine. Believe the Showas on the 900 are slightly better than the marzocchis and as Alex says, you could have two brakes!!

You could add some preload spacers to firm them up a little but they're not sophisticated forks so will always be a little harsh.

Ped

[slob]

Preload spacers will take up some of the spring travel, so may not do much to prevent bottoming out.
Did you put the exact recommended quantity of oil in? (02 620 takes 440Cl per leg) since the air gap provides some preload you could always try adding a few Cl of oil to each leg to up the preload a fraction.
Or Hagon sell progressive springs for around £55.

[MotoNik]

I guess I was asking for the diet comments!!

Rode Pedro's 900 - interesting to compare it to the 600. The 900 forks are defintely better, but they still feel like they go solid when you hit a big bump. It's as if the damping valves get hydraulic lock when there's a big deflection.

My feeling with the 600 is that the springs are pretty old and tired, and it would certainly benefit from a new set, but I'm not convinced that'll cure it.

Incidentally Slob - thicker oil should have any affect on fork travel, it'll just slow down how the suspension reacts.

Maybe I need to get some Multistrada forks fitted!!! Would make an interesting chopper look....

Might try 10wt oil and see how that works. Failing that, I like the idea of 900 forks - extra brake, possibly some adjustment there too.

cheers guys, I'll keep you posted. Now where did I leave that slab of cake?

Nik

[slob]

Incidentally Slob - thicker oil should have any affect on fork travel, it'll just slow down how the suspension reacts.
It shouldn't but it seems to, maybe I'm not finding big enough bumps.

[Pedro]

Now where did I leave that slab of cake?

Nik


You, leave cake? Blimey, it's snow tomorrow..... :lol: