Author Topic: Harsh Cer Forks.  (Read 23886 times)

Offline Vince

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Harsh Cer Forks.
« on: May 18, 2016, 10:23 »
I have been chasing a harsh fork action for a long time, changing fork oil and emulator spring preloads with not the desired effect. I did a long search on the web about emulator tuning and have found some interesting stuff I am about to try. I found a few have tried this, I suspect that my really old emulators came with 1 only slow speed compression  bleed hole. Tomorrow I am going in for another look.Here is another take on this from another forum member.

i'm using .85kg r-t springs. preload is a little more than 30mm as i recall.
blue springs @ 3 turns on the emulator. two slow speed bleed holes in emulator

Its the small hits I am trying to tune out, the bike gets a bit vague
in long sweepers with a choppy surface.
« Last Edit: May 18, 2016, 10:26 by Vince »

Offline Cosi

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Re: Harsh Cer Forks.
« Reply #1 on: May 18, 2016, 11:08 »
Surely, and I mean no offence 85 springs are a little light on for you
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #2 on: May 18, 2016, 11:15 »
I have 0.95 springs,I recently heard thats the strongest available from Ibock,sp, and there staying. Its the 2 slow speed bleed holes in the emulator,in the plate under the spring in the emulator. Seems they can have 1 to 4 holes, I am hoping mine being a very early one came with 1 hole. 4 holes = softest slow speed damping and 1 = the firmest. Going to add another and see what its like.

Offline Cosi

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Re: Harsh Cer Forks.
« Reply #3 on: May 18, 2016, 11:29 »
Sorry mate i read you had .85  springs, I guess the next thing to ask is what's the arse riding on, how much oil and weight in the front , who set it up?
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #4 on: May 18, 2016, 11:42 »
I set it up, 15wt at 130mm fully compressed springs out, 3 turns on the emulators . Big hits are fine, its the braking bumps into bends,small square edged bumps. Its easy to return to 1 hole if it doesn't work.Bit of solder. These extra holes are popular with dirt bikes running emulators looking for plush suspension. Thats usually 3 and 4 holes.

Offline Grant

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Re: Harsh Cer Forks.
« Reply #5 on: May 18, 2016, 12:00 »
Have you tried lighter weight oil?
Might help the forks react better to small bumps.
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #6 on: May 18, 2016, 12:24 »
Yep,tried 7.5 and 10. There holes are mentioned in the emulator info sheet when you buy them,seems they don't get much attention though. Lighter wt oil does flow through these holes easier and does speed  the fork reaction but it works against having the rebound I like. So I am hoping with 15wt and 2 holes it will do both.
« Last Edit: May 18, 2016, 12:27 by Vince »

Offline breganzane

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Re: Harsh Cer Forks.
« Reply #7 on: May 18, 2016, 12:54 »
If you're talking about bumps, then theoretically that is mainly high speed damping and thus handled by the emulator plate lifting off the seat to allow a decent amount of oil to flow.  This is controlled by the emulator spring weight (colour coded) and the preload on them.   I've used blue springs with 2 turns and found it to work ok as a starting point. 
Spring weights according to Racetech:
FPEV VS026   EMU VALVE SPRING 26 lb CHROME
FPEV VS040   EMU VALVE SPRING 40 lb BLUE
FPEV VS064   EMU VALVE SPRING 64 lb YELLOW
FPEV VS101   EMU VALVE SPRING 101 lb RED
The emulators often come with the yellow springs installed, which seem too stiff to me.  What springs in your emulators and how much preload?

Logically, if you want the high speed damping to kick in earlier, you want to back off the preload/weight on the emulator spring.  Be aware it's some stupid american bolt size and requires a 67/156ths allen key or some such.

The extra holes in the plate may also help, but those mainly control low speed damping such as that of brake dive, or gentle 'whoop-de-doos' in the road.

EDIT: You have 3 turns on the emulators but do not specify what springs.  Reduce to 1 or 1.5 turns for a noticeable effect and see how it goes, bearing in mind you might need to tighten them up a bit again if you lose composure in the more gnarly sections.  If you're running yellow spring then get a set of blue ones.
« Last Edit: May 18, 2016, 12:59 by breganzane »
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #8 on: May 18, 2016, 13:26 »
I think there blue springs, but the color is gone now.They have been there for at least 10 years. I have tried a few different preloads. Going to look at the holes tomorrow.

Offline breganzane

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Re: Harsh Cer Forks.
« Reply #9 on: May 18, 2016, 13:58 »
Will be interesting to hear how it changes things.
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #10 on: May 19, 2016, 03:20 »
I did something dumb, I changed 2 things at once. I like a nice soft compliant suspension so while in there I backed off the emulator 1/2 a turn,wish I hadn't. I liked it better at 3 turns. As I had hoped the emulator did have 1 slow speed compression damping hole, 7/16 of an inch. O shit I forgot I only do Imperial drill bits,here comes Brett's I told you so, we have an Imperial Metric argument going. So I drilled another 7/16 hole 180 degrees away and took the bike for a spin around the block. Its definitely more compliant to small road irregularities, feels a lot more comfortable
on the small stuff, but a far bit worst with the spring preload backed off.Back in I go.

Offline Vince

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Re: Harsh Cer Forks.
« Reply #11 on: May 20, 2016, 06:40 »
I am leaving the Cer forks on my 3C alone till after Sundays ride, be a fairer test. Today I did a lap of the Old Rd on my Pantah with 38mm Maz forks set up as I expect the same as the Cer in my 3C. Its been a good while since I rode it, a horrible 40c 600k runs last year that had the suspension beat me to a plup. Since then I fitted Emulators but haven't tested it at all. I only did half the trip it was just horrible. Even on the great surface recently redone the fork was pattering so bad I was getting dizzy from the bouncing, way way worse than the Cer in the 3c. So thats tomorrows job, the same adjustments I did to the Cer forks. I expect there is the same 1 hole and 3 turns on the emulator.

Offline Vince

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Re: Harsh Cer Forks.
« Reply #12 on: May 21, 2016, 02:11 »
Well that was an easy fix, the 38mm Maz forks,yes not 35, I think have the same emulators as the 38mm Maz forks on Laverdas. These were fitted about 8 months ago and were considerably different to the 10 year old ones in my Cer forks. The latter ones have 4 slow speed compression holes marked already,2 were drilled and 2 were just dimpals. So I checked the spring,definitely blue, to see what they were set at. Bearly 1 turn of preload. That explained the bouncing,
they had hardly any high speed compression damping and with the 2 holes of slow speed. So I went to 2 1/2 turns and did a test ride. Way better, no bouncing. Firm but not uncomfortable. There staying at that for now. So thats another with 2 holes, seems the later emulators have 2 holes and the early ones have 1 hole.

Offline Brett

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Re: Harsh Cer Forks.
« Reply #13 on: May 21, 2016, 06:25 »
I did something dumb, I changed 2 things at once. I like a nice soft compliant suspension so while in there I backed off the emulator 1/2 a turn,wish I hadn't. I liked it better at 3 turns. As I had hoped the emulator did have 1 slow speed compression damping hole, 7/16 of an inch. O shit I forgot I only do Imperial drill bits,here comes Brett's I told you so, we have an Imperial Metric argument going. So I drilled another 7/16 hole 180 degrees away and took the bike for a spin around the block. Its definitely more compliant to small road irregularities, feels a lot more comfortable
on the small stuff, but a far bit worst with the spring preload backed off.Back in I go.
So guess you didnt need the holes to be accurate is that correct ? Just remembering back to the last time I gave you an measurement of 4 1/4 inch you told me it wasnt accurate...
But wait where are racetech valves made oh yes the last bastion of real measuring...
Sitting on the fence 120 or 180 that is the question ?

Offline Vince

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Re: Harsh Cer Forks.
« Reply #14 on: May 21, 2016, 07:39 »
Walked right into that, just like tyre pressures I just seem to stick with Imperial for drill bit sizes. 7/16 is a tight hole for the usual self tapers,1/8 is snug and 9/16 is a clearance hole.To many years doing it to change.