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Discussion Starter #1
Hi all. Like so many, I've got an SV650 with a k5 gixxer front end. Mine's been 'streetfightered' with with tapered bars mounted into the top clamp.
My problem is the bike sacrificing instability for cornering performance. As much as I enjoy the 'flickability' of this bike, it's too unstable to really push the bike through fast sweepers on road or track. The bike literally turns too fast even with the stock heavy wheels; I'm more than happy to sacrifice some turning speed for stability. I don't know enough about geometry to go about fixing the problem the best way. I know I can remove the triple tree and mill out the centre and fit a gixxer 750 k6 up (06-09 are the same fork right?) bottom clamp and forks which will net me an extra 13mm in length. That plus the 70 profile front tyre will get me pretty close to the stock SV fork lengths. But it doesn't fix my rake issue. Judging by how much closer the forks are to the radiator, I'm guessing Iv'e lost some wheelbase, could I consider extending the swingarm an inch? I haven't pulled the trigger on a decision as I'm worried of screwing the whole bike up!
Thanks for any help! :)
 

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Lowering the rear a touch with either a slightly shorter shock or lowering links would give it a bit more rake and slow the turning a bit. Not sure if you're tall or short or if that would have other undesirable effects for your riding style. Something else to consider is a GSXR rear wheel, with a wider tire, is reported to slow turning a bit. I put one on mine, but I didn't ride it before so I can't comment on how much it changed.
 

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Look into extended fork caps. That will give you an additional 20mm or so of length on the fork tubes. You haven't mentioned what shock is on the rear, but that could be affecting things as well.

Assuming you have a stock length rear shock, the 20mm longer fork tubes and a 70 front tire should put your geometry back to stock.
 

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as stated, extended caps are a decent option but I'm not sure they're still available for 04/05 forks

06/07 are comp/rebound while 08/09 have separate high and low speed comp, plus rebound. in both cases 600 is gold and .90 fork springs/softer valving and 750 is black with 1.0/firmer valving.

I wouldn't want to extend the wheelbase any more than you get from correcting fork length.
 

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Discussion Starter #6
Yes, as stated, going longer on the forks slightly, plus the 70 profile tyre will get my forks to stock length, but it won't fix the acute rake. Extending the forks isn't easy, as fork caps weren't sold for the k4 k5 gixxer as the forks had to be lifted in the clamps on the gixxer to better the geometry. Extending the forks is not a cost effective solution considering a small 10mm increase. I am not going to lower the rear, if anything I was going to go from stock to the zx10r swap and raise it a little bit as I'm cramped on the bike, especially after I put aftermarket rearsets on it.
No-one has mentioned extending the swingarm a lil bit, does anyone know a rough distance vs effect as a guide?
Thanks for your replies everyone, cheers.
 

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Yes, as stated, going longer on the forks slightly, plus the 70 profile tyre will get my forks to stock length, but it won't fix the acute rake. Extending the forks isn't easy, as fork caps weren't sold for the k4 k5 gixxer as the forks had to be lifted in the clamps on the gixxer to better the geometry. Extending the forks is not a cost effective solution considering a small 10mm increase. I am not going to lower the rear, if anything I was going to go from stock to the zx10r swap and raise it a little bit as I'm cramped on the bike, especially after I put aftermarket rearsets on it.
No-one has mentioned extending the swingarm a lil bit, does anyone know a rough distance vs effect as a guide?
Thanks for your replies everyone, cheers.
If the front end is at stock height, why do you think the rake changed? Short of cutting and rewelding the steering head to change the rake angle, the only thing that affects rake is ride height. (Both front and rear).

Trail is what you really need to be concerned about, rake is only important in as much as it affects trail. One problem with the GSXR swaps is that GSXR triples have more offset (how much more depends on year/model) and more offset reduces trail.
 

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if you go to a better fork length and 70 profile tire, rake will be back where it should be

lengthening the rear shock won't help make it less cramped unless you're also doing other things

as far as swingarm length goes, I don't think I've ever seen a stretched SV race bike and there's a good reason for that
 

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OK, let's try a different tack:
--You don't like the steering feel and would like to make the bike more stable. What is your budget?

--You feel cramped on the bike after putting on new rearsets. Put the stock rearsets back on the bike. Raising the rear will not help, the rearset to seat distance is fixed.
 

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Discussion Starter #10
If the front end is at stock height, why do you think the rake changed? Short of cutting and rewelding the steering head to change the rake angle, the only thing that affects rake is ride height. (Both front and rear).

Trail is what you really need to be concerned about, rake is only important in as much as it affects trail. One problem with the GSXR swaps is that GSXR triples have more offset (how much more depends on year/model) and more offset reduces trail.
Like I originally said, I don't know much about geometry, but I could see straight away how much closer the forks are to the radiator. I'm pretty sure the triple tree decides the trail -or whatever- angle. The length of the forks won't change the angle between the two lines- 1. the straight line down the forks and 2. the straight line to the ground from the head stem. And it's this problem I'm trying to fix
 

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Discussion Starter #12
as stated, extended caps are a decent option but I'm not sure they're still available for 04/05 forks

06/07 are comp/rebound while 08/09 have separate high and low speed comp, plus rebound. in both cases 600 is gold and .90 fork springs/softer valving and 750 is black with 1.0/firmer valving.

I wouldn't want to extend the wheelbase any more than you get from correcting fork length.
I don't think they are, I tried everywhere..

I see, so 06/07 and 08/09 and 600/750 are all interchangeable, just different internals?

Yes, that is what I intend. The problem is, all is not all the same. For example, raising the rear 10mm, dropping the front 10mm, decreasing wheelbase by 10mm, are all the same measurement and all in favour of increasing turning speed, but the size of the effect will vary with each individual adjustment... So I have no idea how much extra wheelbase to give it..
 

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Like I originally said, I don't know much about geometry, but I could see straight away how much closer the forks are to the radiator. I'm pretty sure the triple tree decides the trail -or whatever- angle. The length of the forks won't change the angle between the two lines- 1. the straight line down the forks and 2. the straight line to the ground from the head stem. And it's this problem I'm trying to fix
They are closer to radiator because they are shorter, not because those 2 lines are closer together. In fact they are further apart.
Offset on triple decides trail but change in ride height will also change trail.
 

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Like I originally said, I don't know much about geometry,
Yes, I can see that. :)
but I could see straight away how much closer the forks are to the radiator. I'm pretty sure the triple tree decides the trail -or whatever- angle. The length of the forks won't change the angle between the two lines- 1. the straight line down the forks and 2. the straight line to the ground from the head stem. And it's this problem I'm trying to fix
Changing the length of the forks does change the rake angle, and hence the trail. Shorter = steeper rake = less trail, longer = shallower rake = more trail.
 

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Here's what I see as your options if you really want to change the front end feel.

-Buy stock complete set of forks (ebay) and reverse the GSXR swap, then sell the GSXR forks. $ (maybe only time spent depending on pricing)

-Either track down extended fork caps or have some made, Traxxion may be able to make some for you $$
-Have forks internally lengthened $$

-Buy aftermarket triple tree $$$

-Swap to a newer year GSXR, then buy some of the stuff above $$$$
 

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Which rear shock are you using? Is it adjustable for ride height?

I have an 09 SVS with a K5 GXSR fork swap and a Penske 8987 in back. Before I had the Penske, I had an 07 ZX-10R shock and the bike rode like a dream. It got 10 times better with the Penske.

The K5 GSXR fork in a Gen 2 SV works fine. There are a lot of guys riding this combination without any issues whatsoever. With a 120/70 tire up front, the K5 forks return the geometry of the bike to nearly stock specs so the shorter forks are not the issue.

When I installed my Penske, I set my rear ride height to 335mm eye-to-eye and tweaked it a few mm shorter to give me a very neutral turn in. The bike rides perfectly in a straight line with hands off the bar, turns with a thought and is responsive without being unstable under any conditions I've run into on the street.

So, again, which rear shock are you using? Did you service the forks yourself? Do you know which springs are in there? Is the oil fresh, with an air gap set to proper levels? Were the cartridges bled properly?

Something is off, and I don't think its the fork length.
 

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...instability for cornering performance.
Worn tires with lots of highway miles can get squared-off and make the bike feel terrible in turns.

Low tire pressure, especially on the front, can have the same effect.
 

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Discussion Starter #19
Yes, I can see that. :)


Changing the length of the forks does change the rake angle, and hence the trail. Shorter = steeper rake = less trail, longer = shallower rake = more trail.
Hahahaha! :(

I see what you mean, makes sense.
 

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Discussion Starter #20
So, again, which rear shock are you using? Did you service the forks yourself? Do you know which springs are in there? Is the oil fresh, with an air gap set to proper levels? Were the cartridges bled properly?

Something is off, and I don't think its the fork length.
The rear spring is stock. The forks are as they were when I bought them from the wreckers.. :oops:
 
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