Author Topic: Fork oil  (Read 816 times)

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Offline bako

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Fork oil
« on: October 07, 2018, 00:03:20 »
Since buying my new Vee last December the front forks have never seemed to perform well regardless of how I set them up, so after 15000 miles I decided to take them off and have a look.
Not having the service manual for my bike I used the manual for a GSX-s which has simular/same forks.
On inspection the right hand oil level was 185mm and the left, 165mm. The oil that came out was like treacle.
I replaced the oil with 15w grade at 125mm level.
I'd also noticed that the rebound adjuster on the left had 16 clicks hard to soft and the right hand 13. Setting the lock nut on the damping rod to 11mm from the top before re assembly means I now have 14 clicks on both sides.
Set the suspension to factory default and took it for a test ride. It was like riding a different bike. The annoying jitter had gone and it took the bumps and dips much better.
So mine was definitely a Friday afternoon special.

Offline porter

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Re: Fork oil
« Reply #1 on: October 07, 2018, 09:51:01 »
Hagon and Wilbers recommend a 135mm air gap. Hagon 5w oil and wilbers 2.5w.
I had the hagon set up, it was firmer but still harsh on small sharp bumps but with a hyperpro  rear spring fitted the bike hsndled funny, felt  high at front, low at rear, and running wide it corners.  I removed the front springs and refitted the oe ones, all OK again but that harshness is still there even with 5w oil, guess it really needs a revalve.

Offline Griff2

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Re: Fork oil
« Reply #2 on: October 07, 2018, 12:40:49 »
Thanks for this thread firstly. I have all damping (compression and Rebound) backed off in my 2016 Vee forks and they are still too harsh on sharp bumps. I was also thinking of a revalve. I think the springs are OK though. However given the OP's report I might just get the forks serviced and put in a 2.5W oil before going to too much other expense. . 

Offline porter

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Re: Fork oil
« Reply #3 on: October 07, 2018, 16:25:59 »
I might try the 2.5w over the winter but I can't see it being that different than the 5w I have in now. I've a Wilbers shock heading my way soon so I'll see how that feels then maybe refit the front springs.
On a word of caution if you're stripping the forks watch the fork tops, they are mega soft aluminium,  easy to mark.

Offline Griff2

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Re: Fork oil
« Reply #4 on: October 07, 2018, 21:05:39 »
Thanks for the heads up.

Offline bako

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Re: Fork oil
« Reply #5 on: October 07, 2018, 22:48:21 »
Bit of an update:
Took the Vee for a good blast round Wales today on a range of different roads. Feels better than it was. But pulls slightly to the right....Forgot to bounce the front end to aligne the forks, duh. See how it goes over the winter. Might invest in some progressive springs in the new year.
My rear shock seems fine, but I did notice a while back that the adjusting nob wasn't working. It turned and clicked, but it wasn't doing anything, fixed it self!
Thanks for the input blokes.

Offline Ozbass

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Re: Fork oil
« Reply #6 on: October 08, 2018, 00:44:00 »
 :ty: Finally someone with a similar problem to what I am experiencing on my `14 DL1000. I bought the bike secondhand with 40K on it. It had a harsh front end ride right from the start. Road ripples and joins in the bitumen were worst. At speed with the suspension working it seemed fine. Also on dirt roads the front end seemed to be skittish.I backed off all the adjustments on the forks. Preload was taken out to the 5th line. This made no difference at all to the ride. Took the forks to a local well known suspension bloke and explained my problem. He suggested a heavier fork spring and some new seals while the forks were apart. With some new oil also. Reinstalled the forks, ran it for 3,000k`s. The was no difference. Determined to fix the problem I made contact with another suspension bloke in another city and spoke at length about the problem. He had done Strom forks before and had good results by enlarging the hole in the valve itself. This allowed a greater oil volume flow. So I sent the forks off to the other end of the country. Reinstalled the forks with great care taken to ensure all alignments and settings were correct. All settings were again backed off for the initial ride. No improvement at all, ride was still harsh although slightly better when loaded for a trip. So here I am $750 poorer and no improvement in my ride quality. "Porter" mentions air gap of 135mm. How is that measured. I also plan use a mix of 2.5 & 5 weight oil as a base to start from. Can I drain the fork oil by removing the red aluminium adjuster at the base of the forks. As our summer is fast approaching oil grade will have a big effect on fork function. Any suggestions are welcome.

Offline porter

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Re: Fork oil
« Reply #7 on: October 08, 2018, 09:16:15 »
Hello Ozbass. Unfortunately you need to remove the forks to change the oil, you need the springs out to pump the cartridges of the old oil. Then you add the new oil, pumping the cartridges as you go to fill them, then compress the forks fully (with no springs fitted) and measure the air gap from the top. Helps a lot if you have a fork spting compression tool, which you can make from a large box spanner.
If I'm bored over winter I might try a 150 mm air gap, this worked well  on the triumph tiger800 I had last, they also have harsh damping in the forks.

Offline Ozbass

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Re: Fork oil
« Reply #8 on: October 08, 2018, 13:38:49 »
Hello Porter. So the air gap is the measurement from the top of the fork stanchion down to the oil level when the forks are fully compressed with no spring installed. Thanks I will try that next week.

Offline porter

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Re: Fork oil
« Reply #9 on: October 08, 2018, 15:11:39 »
Yeah that's it. My bike measured 120mm when I removed the oe springs and what looked like 10w oil, changed to 5w and 135mm but with the firmer (hagon) springs it was no better, worse really as the front sat to tall, changed back to oe springs and it was better but now as my tyre wears thin its harsh again.
If you have harder springs try a 150mm air gap, you can always add a bit without removing the forks. Good luck

Offline Gassoon

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Re: Fork oil
« Reply #10 on: October 08, 2018, 18:00:40 »
Using the 'search' box on the forum can be a hoot. :thumb: Just type in 'forks' and get pages from up to 10 years ago with ideas to improve fork function - from emulators, progressive springs, drilling holes, different weights of oil - you name it! Fill your boots! :grin:
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Offline Griff2

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Re: Fork oil
« Reply #11 on: October 08, 2018, 19:22:02 »
Just a thought. The forks on my former 1200 Explorer were problematic in the same way as the Strom, probably worse. They were solid especially in Winter when the cold would of course affect the viscosity of the oil adversely.  I spoke to a Wilbers Tech locally and He told me that Wilbers had a spec for those forks. He did the conversion which included a reduction in both compression and rebound damping and a progressive spring. There was also a change in Air Gap and a synthetic 5 W oil. This all resulted in a significant improvement to the point that if the 2.5W oil change doesn't work with the Suzuki I will go Wilbers again. 

Offline bako

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Re: Fork oil
« Reply #12 on: October 08, 2018, 22:05:10 »
Read somewhere that thinner oils can resolve the issue.
At the moment the best setting for mine is. Pre load on the 2nd line. Rebound and damping 2 clicks out from hard.
I think when I try a different oil I might flush the forks out with, parafin or something. The oil that came out on Saturday was very gloopy, so might have a blocked valve.
Just a thought. Fit longer reach forks off another bike?

Offline porter

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Re: Fork oil
« Reply #13 on: October 09, 2018, 09:34:20 »
The lighter oil does help but it can only get you so far. If the 2.5w oil and a better spring don't work then there is nothing for it but to revalve or put up with it.
My last three bikes have had to much high speed compression damping in their forks,  this strom, a Yam fz1 and a tiger800,  it worked enough on the other two that I never went down the revalve route.

Offline Griff2

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Re: Fork oil
« Reply #14 on: October 09, 2018, 10:20:15 »
In an effort to soften the forks on mine I backed off the compression damping completely. I then also adjusted the rebound damping to a position just two clicks off fully soft. Even with those settings there is still a lot of damping in both directions on the forks.

Offline Griff2

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Re: Fork oil
« Reply #15 on: October 09, 2018, 17:19:31 »
While we are on forks I think I have a little slack in the steering head bearings that needs taking out. If anyone has the torque settings for the stem head bolts/locknut and fork clamp bolts I would appreciate getting them. My bike is a DL1000A 2016 (L6)