front suspension

[weber1]

Have a problem with forks bottoming out. I am going to change fork seals. What is the purpose of the valves on the lower forks that share a hose to the caliper? Is there a bleed procedure? Thanks for the excellent advice so far. I ordered new emulsion tubes for the carbs which should be here Tuesday.   Rob.

[SlowOldGuy]

Those valves are an extremely ineffective attempt at an anti-dive system.  Never worked well even when new.

To avoid bottoming, you need better springs.  You need an appropriately rated spring for your weight and riding style.  Straight rate springs are best.  Typical spring rates used by the group vary between 0.9 kg/mm to 1.1 kg/mm. 

(I hope those units are correct)

Fresh oil and new seals will be an improvement, but it's the springs that keep the forks from bottoming out.

DavidR.

[racerman_27410]

+1 on the new springs

.95kg if you are lightweight (under 200lbs w/gear)

1.05-1.10kg if you are a heavyweight (over 200 lbs w/gear)


KOokaloo!

[racerrad8]

Speaking of front forks, the testing in done on the RPM fork valves. I ordered the producing run last week and I should have them online next week. I also put stock order of front springs together as well.

I will post up when they are ready.

Randy - RPM

[elbows]

Speaking of front forks, the testing in done on the RPM fork valves. I ordered the producing run last week and I should have them online next week. I also put stock order of front springs together as well.

I will post up when they are ready.

Randy - RPM

just might have to get a set of them when they are in randy how much do you think they will cost in £

[fudgejerkin1188]

Dave,
if you get a set let me know how you get on with them. I tried a set of emulators a few years back and never managed to set them up so I liked them.  The rear end of my 3CV with the ohlins shock is great but the front end could do with an update.

[elbows]

Dave,
if you get a set let me know how you get on with them. I tried a set of emulators a few years back and never managed to set them up so I liked them.  The rear end of my 3CV with the ohlins shock is great but the front end could do with an update.

i am with you all the way its just the front end that lets the bike down i dont wont to go down the route of changing the front end of another yam

[weber1]

Ok so I here it's gonna be a pain to change front springs. That's ok. Straight rate or progressive? I get different suggestions. I think the tighter the spring gets the harder you push would be the way to go.

[Arnie]

Changing the fork springs is really pretty easy.  You just have to support the front of the bike, remove the fork caps, and swap them out.
Of course you also have to move the bars (or master cylinders out of the way), loosen the upper clamp bolts, and be prepared for the caps to be spring driven towards you when they clear the threads due to the spring pressure.
With the new springs you also have to set preload (at least fairly close) with new spacers.

You'd think that progressive rate springs would be ideal, but the ride is actually much better with straight rate springs.  And, how much force the springs need to absorb isn't really determined by how hard or fast you're riding, but how sharp the bump or hole you hit is.

Cheers,
Arnie

Ok so I here it's gonna be a pain to change front springs. That's ok. Straight rate or progressive? I get different suggestions. I think the tighter the spring gets the harder you push would be the way to go.