Double adjust forks and rear coil over damper

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wurlyvalve
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Double adjust forks and rear coil over damper

Post by wurlyvalve » Thu May 18, 2017 10:44 am

Hello all,

Do we know what forks and rear coil over damper may be fitted to me GK73a? They are both double adjust. The rear has a remote canister and is a Showa - VJ22 maybe? The forks look very Suzuki. Would they be SP or RGV VJ21 maybe? The seals are going and will need replacing - I've bought a GK73a kit but I might have to reappraise that. The rear would be nice to have rebuilt or replaced but I'd like to know that it is a worthy unit first.

I know that is a very vague question. Maybe there was an easy bike to rob bits off that others know (and I don't).

Cheers,
Glen.

moforockband
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Re: Double adjust forks and rear coil over damper

Post by moforockband » Thu May 18, 2017 3:07 pm

Need pictures really. They won't be vj21 forks as they are 40mm too short for the 400... Good luck fitting them :( haha!
If they have rebound and comp adjust they are 99% sp forks, which work really well even with std spring.
Rear shock I wouldn't get excited about. It's a basic steel shock which I'd replace with a modern k6/7 600 unit.
You will need to check bushes as well, and clean the forks out properly after 30 years, otherwise your nice new racing fork oil will look like grey sludgey pee

wurlyvalve
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Re: Double adjust forks and rear coil over damper

Post by wurlyvalve » Thu May 18, 2017 3:33 pm

The forks came with the bike so I don't have the headache of fitting owt that is too short. Must be gk73aSP then. Cool. They work amazingly, better then any of my other bikes. I'm going to slip stiffer springs in when I get the chance though. Going to try my Thundercat springs for length once I get them out of my TRX. May be too long but I'll try as it's a free change to 0.83 spring rate.

Yes, come to the conclusion that K6 600 rear was the way to go. I think mine has got VJ22 at the mo - will take a pic to confirm but it's so corroded that I think a pic isn't going to be that illuminating.

Cheers,
Glen.

moforockband
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Re: Double adjust forks and rear coil over damper

Post by moforockband » Thu May 18, 2017 10:40 pm

You might not need stronger springs - the ones that are in my sp set are pretty hard. If I adjust the preload nearly to max and hit a bump/small pothole in the road at speed, the forks lock out.
Out on the road I run them at minimal preload. On track I run them 2 rings out from max. I weigh 80kgs.

wurlyvalve
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Re: Double adjust forks and rear coil over damper

Post by wurlyvalve » Mon May 22, 2017 8:59 am

Yeah, ok. For the life of me I can't spot what the SP fork rates are. I may have to whip them out and measure. They feel soft to me, I've set the static sag, unloaded and loaded, and they are only just within acceptable limits. I can't remember the figures - sorry, just too many vehicles in my life. Not sure about weights, I'm 14stone and a bit and the wife is lighter than me (couldn't say what and survive).

GSXR6K6 rear coil over in the post. :)

Cheers,
Glen.

moforockband
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Re: Double adjust forks and rear coil over damper

Post by moforockband » Mon May 22, 2017 11:58 am

Hi Glen, You will have to grind off the underneath bracket on the battery cage to fit shock, and touch up paint. Then stick some foam on the shock reservoir as it will touch the tray.
Put a cable tie on your fork leg, and go for a spirited ride using lots of front brake. You want to be using about 80% of the stroke. If you put too hard front springs in it, and hit a bump on a big lean angle you may/will lose the front. I've got the std sp forks and a 600 K7 shock in mine, and the handling is pretty good. Can keep up with newer stuff through the turns on track days.
I found it beneficial to raise the forks (mine are 8mm), as the shock is longer and will make the bike too nose heavy. An added bonus is higher corner speeds as exhaust and pegs didn't hit the floor any more.

wurlyvalve
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Re: Double adjust forks and rear coil over damper

Post by wurlyvalve » Mon May 22, 2017 12:27 pm

You Sir are a star! Thank you.

I've currently dropped the forks 10mm as the RGV rear shock is somewhat overwhelmed with my lardy arse. I think I was about 22.5degs with that (static). I'll jack the forks back to stock plus 8mm then when I slip the K6 unit in - I assume the std clip-ons live with it. :)

My battery box looks decently rusted on to the frame. Nothing that my trusty angle grinder won't cure or kill!!!!!


I think my forks are bottoming as it's sooooo easy to lock the front up well before the back is lifting. Can't use more than about an inch of front lever without front leaving black lines. I'll try with the cable tie. But I can't be certain that it has the SP springs, it's not an SP bike. With the static sag set at the min recommended the rider sag is beyond the max with me on it and at the max with the misses on it. Which is a general indicator that the spring is near it's limit.
I will try the cable tie on the way home though! :)

Thanks a million.
Glen.

moforockband
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Re: Double adjust forks and rear coil over damper

Post by moforockband » Mon May 22, 2017 2:47 pm

No prob. I'm assuming the bike needs to be a road bike capable of doing 2 up road stuff? The sp springs will be too soft for that. They're designed for solo use.
You can try CBR600 steelie springs 2nd hand from ebay for more preload, or sv650 springs which have a little less preload, or Ohlins springs from KAIS/K-TECH. I think it is 0.85kg for the Ohlins, but you will need to check.
100mm air gap, 10 wt oil as per the book.

wurlyvalve
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Re: Double adjust forks and rear coil over damper

Post by wurlyvalve » Mon May 22, 2017 3:57 pm

97mm with my fat lump on it. It's the wife's bike so she's about 10kg less than me. No two up, misses and I ride seperate bikes. I think this spring may be tolerable after all. You were right and I, once again, know sod all. Thanks chief, I owe you a beer!

wurlyvalve
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Re: Double adjust forks and rear coil over damper

Post by wurlyvalve » Sat Jul 01, 2017 8:07 pm

Hello,

Not wishing to sound more stupid than I normally do..... the K6 rear shock spring od is about 5-10mm larger than the aperture in the swingarm and a good 1/2" bigger than what came out.

Do I fish it down through there and ignore the fact the spring will grind against the swingarm? Or do we open the swingarm hole out?

Oh, mine isn't your run of the mill 73a swingarm?
http://www.rgv250.co.uk/forums/topic/59 ... -try-this/

Like the swingarm on the right.

Cheers,
Glen.


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