Date: 23-10-19  Time: 14:48 PM

Author Topic: Can't get front end quite right after installing the emulator  (Read 374 times)

Freza

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Can't get front end quite right after installing the emulator
« on: 12 October 2019, 12:52:05 PM »
A few months ago, my mechanic installed the original Racetech emulator and Ohlins linear springs, following kebab19's guide.


Can't remember the details right now, but I think it set compression conservatively at 2-3 turns.


I've been riding the bike since, and the front end feels pretty harsh over bumps, but more importantly, when going faster over longer depressions in tarmac, it doesn't feel as planted. As if it floats too much, especially when forks are fully extended (under acceleration).
On my route home, there's a nice fast 3-lane curvy road going uphill, but it's plagued with depressions in tarmac (if that's the right expression, pardon my english).
So when going fast on that road + leaning, the front end plays too much and makes me uneasy. Yet, when coming off that road and slowing down, then going over harsh bumps, it puts a lot of stress on my arms.


Now, I must admit I don't quite get what which settings exactly do, and how to tweak them to remedy this problem.

I need to: a) lower the harshness and b) get rid of the fork play when under acceleration.

Do I increase or decrease rebound? Or compression? Or preload? It is now preloaded a bit (I gave them a few turns).

Can someone enlighten me please... thanks
« Last Edit: 12 October 2019, 12:53:35 PM by Freza »

unfazed

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Re: Can't get front end quite right after installing the emulator
« Reply #1 on: 12 October 2019, 02:23:01 PM »
unfortunately this will be a trial and error exercise.   I had a similar issue with the FZS1000 and  decreasing the compression solved it, but the compression adjusters on the FZS100 are easier to get at than yours.
Backing off the compression in your case is probably a fork strip job unless there is some tool to adjust it with the springs out.

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #2 on: 12 October 2019, 07:41:56 PM »
unfortunately this will be a trial and error exercise.   I had a similar issue with the FZS1000 and  decreasing the compression solved it, but the compression adjusters on the FZS100 are easier to get at than yours.
Backing off the compression in your case is probably a fork strip job unless there is some tool to adjust it with the springs out.


Decreasing compression should eliminate fork play? Are you sure? I always thought that increasing compression would stiffen it and limit its motion, reducing the possibility to play, especially when under acceleration (but I don't actually understand what compression really does).
It is a strip job but not so difficult.

kebab19

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Re: Can't get front end quite right after installing the emulator
« Reply #3 on: 12 October 2019, 07:47:38 PM »
It should not feel harsh at all, something's wrong here.
What thickess of fork oil was added to the forks after the emulators were fitted?When you had the linear springs fitted, were they the longer than the original forks springs and were the internal fork metal spacers cut down to make up for the difference in length?
Your fork caps have preload adjusters? If so, back them off to minimum and see if the ride is less harsh as a result. This could indicate the fork springs are compressed too tight inside the forks. 
Also the preload on the emulator can easily be set too high, it's usually 2 - 2.5 turns out from just barely contacting. 2.75 or 3 turns of preload feel too harsh.


kebab19

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Re: Can't get front end quite right after installing the emulator
« Reply #4 on: 12 October 2019, 07:52:46 PM »
Once you drill out the standard damper rod holes, the emulators control the compression aspect of the fork action (when you ride over a bump), the thickness of the fork oil determines how quickly the forks rebound back to their original length. The fork preload caps are used to adjust the preload on the springs, but too much preload on the fork springs will give a harsh feeling ride from the front-end of the bike, particularly over large bumps.

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #5 on: 12 October 2019, 09:40:34 PM »
Hi,

The oil added was 10W I think, and honestly don't know if he cut down the spacers. Since he was following your guide, and he's a pretty smart guy (did emulator mods before mine), I'd bet he did.
Yes, my forks have preload adjustment which I'll need to loosen up and see if the harshness is gone (could probably be the solution), but still my main problem is not so much the harshness as floaty feel when going fast over longer hollows. Feels as if they're too soft in the upper end (when fully extended)...can't describe better than that, sorry.
« Last Edit: 12 October 2019, 09:41:58 PM by Freza »

unfazed

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Re: Can't get front end quite right after installing the emulator
« Reply #6 on: 13 October 2019, 12:57:37 AM »
Check the fork movement, they have a max stroke of 120mm and work best when using as much as the stroke as possible. To much compression will prevent the forks from compressing a bit like hydraulic lock. To much rebound will prevent the forks extending fully and wind the forks down over a serious of bumps. If the forks do not move sufficiently they will not ride the bumps and cause an vague unstable front end on anything other than a billard table smooth surface..
If you are happy that the mechanic did a good job then it is probably to much damping not allowing the forks to move sufficiently.
The few test below will give some idea as to what is happening.

Tie a cable tie around the stanchion, with just its own weight and you not pushing the forks down. Put the bike on the centre stand and check the distance between the cable tie and the top of the dust seal. Write it downNow take the bike off the stand and push the forks down once. Put the bike on the centre stand and check the distance between the cable tie and the top of the dust seal. Write it down
Push the cable tie back down to the dust seal and ride the bike, brake hard a few times. When you return Put the bike on the centre stand and check the distance between the cable tie and the top of the dust seal. Write it down.
Now back off the preload completely and do the same checks again.
Post the results from both sets of checks.

kebab19

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Re: Can't get front end quite right after installing the emulator
« Reply #7 on: 13 October 2019, 06:56:29 AM »
Unfazed is bang on here with his advice. :)
Also... just wondering the size of the internal air gap for the last part of the fork's action. Any idea what level the fork oil was filled to by your mechanic? Was it the standard oil level or did he put more in?  If you have a syringe & tubing, you could extract a little bit of fork oil at, say, 10mls each time to see if the fork action improves.


Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #8 on: 13 October 2019, 10:01:45 AM »
Eh, I don't really know :/
I'll try your advices.

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #9 on: 13 October 2019, 06:47:12 PM »
Ok, did the test and here's the results: https://imgur.com/a/1VK3iM5

The ride now, after loosening the preload, is night and day difference, much plusher and comfier.
Haven't had a chance to ride it harder to see if it still floats under acceleration...

kebab19

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Re: Can't get front end quite right after installing the emulator
« Reply #10 on: 13 October 2019, 07:11:03 PM »
Ok, did the test and here's the results: https://imgur.com/a/1VK3iM5
The ride now, after loosening the preload, is night and day difference, much plusher and comfier.
Haven't had a chance to ride it harder to see if it still floats under acceleration...
Well, sounds like a move in the right direction already! Sounds like there was too much preload on the fork springs before.

So your image shows 13.8cm or 138mm of fork, but the forks have a maximum travel of 120mm. So if you use all the travel the cable tie will move up to about 18mm underneath the bottom yoke.  As Unfazed states, you should be aiming to use up most, but not quite all of the fork's travel - I would estimate you should be looking to use 110-115mm of fork travel with your usual road riding, keeping an extra 5mm spare to cope with severe potholes in the road. If your fork preload caps are unwound to the minimum and you're not getting anywhere near 115mm of travel, then either the fork spring rate is too firm for your weight, or the internal metal fork spacers haven't been cut down enough. 

Wondering if the floating feeling might be the rebound part of the fork action which is determined by fork oil thickness, but you'll need to do some more road testing & get back to us.

I also meant to ask - what's on the back - standard or an aftermarket rear shock? Standard length dogbones or is the rear raised / lowered?
« Last Edit: 13 October 2019, 07:12:49 PM by kebab19 »

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #11 on: 13 October 2019, 08:12:03 PM »
At the back is newly mounted Nitron R1 shock with standard dogbones: http://foc-u.co.uk/index.php/topic,23519.msg301335.html#msg301335

unfazed

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Re: Can't get front end quite right after installing the emulator
« Reply #12 on: 13 October 2019, 09:45:42 PM »
Normally as I said in my post, you measure the distance from the top of the dust seal to the bottom of the cable tie as this would be the true measurement for checking.In any case your issue appears to be be to much compression and this can be from too much preload or too much compression damping. Even though winding up the preload does not change the spring rate it reduces the amount of travel and have the springs reaching their limit and locking up.An easy check for to see if the springs rate is too much for your weight is to check the laden sag.
Wind the preload on both legs back to the stops (all rings showing).
With the bike on the centre stand push the cable tie down to the dust seal.Take it off the centre stand and let it rest and then put it back on the stand.
Check the distance between the top of the Dust seal and bottom of the cable tie.Now Take the bike off the centre stand and just sit on it with your full weight taking you feet off the floor for a few seconds without falling  over  :D now get off (put your feet back on the floor first  :lol )and put the bike back on the centre stand. Check the distance between the top of the dust seal and the bottom of the cable tie.Post the results.

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #13 on: 17 October 2019, 02:35:52 PM »

unfazed

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Re: Can't get front end quite right after installing the emulator
« Reply #14 on: 17 October 2019, 06:38:43 PM »
Nothing wrong with the springs, set them to 25mm static sag to get as close to 35mm laden as possible. Now check the oil level in the forks, ideally 140mm for stiffer springs. Check with springs out and forks fully compressed.Do you know what weight oil the mechanic used? Removing the springs will result in a slight drop in oil. Try to allow as much as possible to drain off the springs back into the forks as possible.

Freza

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Re: Can't get front end quite right after installing the emulator
« Reply #15 on: 17 October 2019, 11:08:45 PM »
Nothing wrong with the springs, set them to 25mm static sag to get as close to 35mm laden as possible. Now check the oil level in the forks, ideally 140mm for stiffer springs. Check with springs out and forks fully compressed.Do you know what weight oil the mechanic used? Removing the springs will result in a slight drop in oil. Try to allow as much as possible to drain off the springs back into the forks as possible.


I think he used 10W. Or 15W. Don't know, I'd need to ask him about that.
Regarding the oil level, he followed kebab's guide:


Quote
13. Once in place, pour about 250-300ml of your fork oil in. What weight to go for? Racetech mention ether 15W or 20W for the TRX forks. I'm about 73kgs so went with the lighter 15W oil. Now pump fork up & down (slowly, about 15 times) and enjoy the gurgling noises.14. Now add remaining oil. How much in total? Well, I have again gone with data similar to the TRX. Their forks use 483ml per leg (early Fazer 475ml). The emulators displace volume, but exactly how much is unknown. Most TRX owners use about 440ml per leg, so just over 40ml less than standard. For the Fazer, I have started with 430ml - 45 less than standard. I realise that Fazer fork oil height is usually a critical setup factor, but the introduction of the emulators changes all this. Besides with no one else having tried this I had to start somewhere……


How do I set static or laden sag ?
Just with preload ?
« Last Edit: 17 October 2019, 11:10:02 PM by Freza »

unfazed

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Re: Can't get front end quite right after installing the emulator
« Reply #16 on: 18 October 2019, 12:24:37 AM »
Just wind in the preload until you get 25mm.
The space taken up by the emulator is negated by the fact you cut the spacer tubes.

The important bit is the size of the air gap, he smaller the air gap the harsher the forks will be, the larger the air gap will make the forks softer, but there is a limit.An air gap that is to large could cause bottoming out. Air gap is really about fine tuning and more accurate to work from than the oil amount.
Set it to 140mm and try it, this is a relatively standard setting for stiffer springs on the 600