GSX1400 Owners .org

General => Bike Chat => Topic started by: Coopz on Tuesday, 20 February 2024, 04:33 PM

Title: Forks on the right spot?
Post by: Coopz on Tuesday, 20 February 2024, 04:33 PM
Dumb question.. Are my forks lowered on the yokes? I had a K6 years ago and I'm sure the forks were flush with the top plate. I bought the K2 on October and I just noticed this. The bike does feel a little more aggressive on the riding position.
Title: Re: Forks on the right spot?
Post by: Hooli on Tuesday, 20 February 2024, 07:34 PM
Yes the yokes have been dropped.

The top of the fork tube, not the cap, should be flush with the top of the yoke.
Title: Re: Forks on the right spot?
Post by: seth on Tuesday, 20 February 2024, 09:12 PM
What hooli said  :cheers:
Title: Re: Forks on the right spot?
Post by: Coopz on Tuesday, 20 February 2024, 09:38 PM
Cheers, time to get out the Allen key and a car jack.
Title: Re: Forks on the right spot?
Post by: Eric GSX1400K3 on Tuesday, 20 February 2024, 10:37 PM
Yes, mine were like that, I reset them flush with the top of the fork tube, meaning the alu bit of the cap still sits proud.
Title: Re: Forks on the right spot?
Post by: GSXKING on Wednesday, 21 February 2024, 03:14 PM
Is there a reason they're through tho ? :confused1:
Title: Re: Forks on the right spot?
Post by: Kiwifruit on Wednesday, 21 February 2024, 04:24 PM
Coopz, consider changing your fork oil while you're playing with the forks. Did mine recently made a great improvement to the front end. Mine had done 95k so a little overdue.
Title: Re: Forks on the right spot?
Post by: grog on Wednesday, 21 February 2024, 05:15 PM
I agree, clean oil a good move. I use 10 weight, reco by my suspension bloke. 125mm from top forks compressed, yours is different so might not be same, i dont know.
Title: Re: Forks on the right spot?
Post by: GSXKING on Wednesday, 21 February 2024, 08:01 PM
You need to establish if everything is standard. Dropping forks through speeds up steering but reduces fork travel. If they're stock and you weigh 90kg+ go with 10 weight oil as per Greg's suggestion.
It's a dark science the suspension 😵�💫😵�💫
Title: Re: Forks on the right spot?
Post by: Hooli on Wednesday, 21 February 2024, 09:13 PM
I think the fork oil air gap changes from early to late forks. I should know it as I've done enough but I can't remember.

If you do it, make sure you get the nut on the damper rod exactly 11mm from the top before fitting the cap. If not most of the adjustments will be out.
Title: Re: Forks on the right spot?
Post by: Eric GSX1400K3 on Wednesday, 21 February 2024, 09:57 PM
From memory, 110mm air gap for the K3, nut 11mm from the top of the rod as per Hooli. 5W oil in mine, may change to 10W soon.
Title: Re: Forks on the right spot?
Post by: Hooli on Wednesday, 21 February 2024, 10:09 PM
Barmy says 108mm here in the how to change your fork oil guide - https://gsx1400owners.org/forum/index.php?topic=188.0

Which rings a bell for early forks now I've read it.
Title: Re: Forks on the right spot?
Post by: Irish in Oz on Thursday, 22 February 2024, 05:00 PM
What happens when you buck in 644.0 ml in each leg like I did.
Title: Re: Forks on the right spot?
Post by: KiwiCol on Thursday, 22 February 2024, 05:03 PM
644ml each would be about the right amount I'm guessing, as ya need approx 1.2L for both.    :whatever:   or is it 44ml too much?
Title: Re: Forks on the right spot?
Post by: Andre on Thursday, 22 February 2024, 06:51 PM
Quote from: Irish in Oz on Thursday, 22 February  2024, 05:00 PMWhat happens when you buck in 644.0 ml in each leg like I did.

Depends on the amount of old oil remaining in the fork leg.
Title: Re: Forks on the right spot?
Post by: Hooli on Thursday, 22 February 2024, 06:57 PM
Quote from: Irish in Oz on Thursday, 22 February  2024, 05:00 PMWhat happens when you buck in 644.0 ml in each leg like I did.

Depends how well you emptied it. it's always been almost exactly that amount for me, it's just the air gap is a bit more accurate.

My limited understanding is a smaller air gap stiffens the forks a bit as the air is forced to compress more so assists the spring. I guess too little air gap & you blow the seals out over the first big bump.
Title: Re: Forks on the right spot?
Post by: Irish in Oz on Thursday, 22 February 2024, 07:20 PM
Quote from: Andre on Thursday, 22 February  2024, 06:51 PM
Quote from: Irish in Oz on Thursday, 22 February  2024, 05:00 PMWhat happens when you buck in 644.0 ml in each leg like I did.

Depends on the amount of old oil remaining in the fork leg.

None.
Title: Re: Forks on the right spot?
Post by: Hooli on Thursday, 22 February 2024, 07:24 PM
It'll be close enough then.

I partly do the air gap as I find it easier to get accurate than looking for a flat surface to balance my measuring jug on.
Title: Re: Forks on the right spot?
Post by: Eric GSX1400K3 on Thursday, 22 February 2024, 07:46 PM
I fit the fork in my vice or portable work stand, make sure its vertical in both planes, then fill 1/2 with oil, actuate the damper rod to get all the air out, then top off. I use verniers locked at the required air gap and set them across the top of the tube to get them spot on. Cant remember whether the spring goes in before measuring the 108mm or not, but the free air volume does affect shock performance.
Title: Re: Forks on the right spot?
Post by: Hooli on Thursday, 22 February 2024, 08:13 PM
Spring in afterwards & forks measured fully compressed, from memory.
Title: Re: Forks on the right spot?
Post by: Eric GSX1400K3 on Thursday, 22 February 2024, 08:30 PM
Sounds correct mate, so the airgap as measured takes into account the oil volume displaced by the springs.  Less air (more oil) would lead to increased pressure and more likely to blow seals out, heavier oil adds extra damping as it takes longer to get through the valves and ports.
Title: Re: Forks on the right spot?
Post by: Coopz on Thursday, 22 February 2024, 09:10 PM
Quote from: GSXKING on Wednesday, 21 February  2024, 08:01 PMYou need to establish if everything is standard. Dropping forks through speeds up steering but reduces fork travel. If they're stock and you weigh 90kg+ go with 10 weight oil as per Greg's suggestion.
It's a dark science the suspension 😵�💫😵�💫

I had a red/black K5 10 years ago, spent $350 having a race shop set it up for me, honestly felt exactly the same after they put thicker oil in the forks and changed all the rebound and dampener settings.
 I just think going from a sporty ZX12R to the 14 I was just expecting similar road manners.
Title: Re: Forks on the right spot?
Post by: Kiwifruit on Friday, 23 February 2024, 04:40 AM
My old fork oil was so mucky I kept rinsing it all out until the kero ran out clean. I hung them overnight to get everything out before refilling.
Title: Re: Forks on the right spot?
Post by: Hooli on Friday, 23 February 2024, 08:12 AM
I've had to slosh forks out several times with petrol to get sludge out the bottom before.
Title: Re: Forks on the right spot?
Post by: Roo on Friday, 23 February 2024, 03:51 PM
Quote from: GSXKING on Wednesday, 21 February  2024, 08:01 PMYou need to establish if everything is standard. Dropping forks through speeds up steering but reduces fork travel. If they're stock and you weigh 90kg+ go with 10 weight oil as per Greg's suggestion.
It's a dark science the suspension 😵�💫😵�💫
Correct on dropping forks through yokes speeds up steering GSX. But Travel is affected by spring and or oil  No ????  and preload ?  or is my old brain fading ??
Title: Re: Forks on the right spot?
Post by: grog on Friday, 23 February 2024, 05:14 PM
Agree Roo, exact same travel, just located diff position in yoke.Just means bike is higher or lower.
Title: Re: Forks on the right spot?
Post by: Hooli on Friday, 23 February 2024, 07:02 PM
Quote from: Roo on Friday, 23 February  2024, 03:51 PM
Quote from: GSXKING on Wednesday, 21 February  2024, 08:01 PMYou need to establish if everything is standard. Dropping forks through speeds up steering but reduces fork travel. If they're stock and you weigh 90kg+ go with 10 weight oil as per Greg's suggestion.
It's a dark science the suspension 😵�💫😵�💫
Correct on dropping forks through yokes speeds up steering GSX. But Travel is affected by spring and or oil  No ????  and preload ?  or is my old brain fading ??

Ahh yes BUT.....

Changing the trail of the fork affects the effective spring & shock rates.

Remember the old Brit bikes (Velos come to mind) where you could adjust the rear suspension but sliding the top of the rear shocks so they were more, or less, vertical? It's the same theory.

The more rake on a suspension unit the further the suspension will travel for the height of the bike to change by the same amount. Think of the vertical distance the bike travels & the ground as two sides of a right angle triangle. The suspension movement is the hypotenuse. Extend the length of the 'ground side' and the hypotenuse gets longer, meaning a change in the vertical height of the suspension requires a bigger change in the suspension travel.

So no the fork travel doesn't change, that's mechanically fixed by the design. But increasing the rake means the same amount of suspension travel covers less vertical height differences over bumps etc. Also because the suspension is moving further for a given change or ride height that should change the effective spring rate, the more rake meaning the stiffer the suspension if my logic is right. So if a vertical fork needs say 100lb to compress it 1". rake the fork by 45degrees & you'd need to compress the fork about 1.5" to drop the bike 1". So a 100lb load would now only drop the bike about 2/3"

Bored yet? It's too early for me to think like this, maybe I should spend more time just riding bikes?  :lol:
Title: Re: Forks on the right spot?
Post by: Kiwifruit on Saturday, 24 February 2024, 04:28 AM
Hypotenuse..........Hooli is your real name Bamber Gascoigne ??

But well explained  :onya:
Title: Re: Forks on the right spot?
Post by: Roo on Saturday, 24 February 2024, 05:31 AM
Quote from: Kiwifruit on Saturday, 24 February  2024, 04:28 AMHypotenuse..........Hooli is your real name Bamber Gascoigne ??

But well explained  :onya:
My head hurts  !  lol.
Title: Re: Forks on the right spot?
Post by: Hooli on Saturday, 24 February 2024, 06:54 AM
Quote from: Kiwifruit on Saturday, 24 February  2024, 04:28 AMHypotenuse..........Hooli is your real name Bamber Gascoigne ??

But well explained  :onya:

I scared myself by spelling it right too! doubt I've had to do that since school. Glad it made sense though, I was trying to remember what I'd read about it as I wrote that.

Of course the few degrees difference we make to the rake means the difference is practically nothing and not worth worrying about.
Title: Re: Forks on the right spot?
Post by: Coopz on Saturday, 24 February 2024, 06:55 AM
This discussion is making my small brain hurt.. I'm taking the old girl for a ride tonight, I'll see if the 25mm difference in raising the forks has changed anything.

It is a little easier to get on the centre stand though.
Title: Re: Forks on the right spot?
Post by: GSXKING on Saturday, 24 February 2024, 06:57 AM
Coopz I'm sure you'll notice a difference. Please advise the results. 👍
Title: Re: Forks on the right spot?
Post by: Hooli on Saturday, 24 February 2024, 07:02 AM
I noticed 7mm when I was sodding about with mine years ago, so you should deffo feel 25mm.
Title: Re: Forks on the right spot?
Post by: grog on Saturday, 24 February 2024, 05:18 PM
Yeah Hooli, agree with your advanced maths but noticeable riding? I reckon they should be in position designed for, think we all do. 👍👍
Title: Re: Forks on the right spot?
Post by: Hooli on Sunday, 25 February 2024, 06:18 AM
Quote from: grog on Saturday, 24 February  2024, 05:18 PMYeah Hooli, agree with your advanced maths but noticeable riding? I reckon they should be in position designed for, think we all do. 👍👍

I don't think we change the rake enough to ever notice the difference in spring rates mate.