gt380 front forks too soft

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Ramjam
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gt380 front forks too soft

Post by Ramjam »

Hi All
Is there anything i can do to firm them up? I recently put SAE40 regular oil in them which i intended to use to stop them leaking. In fact it worked but has this made them 'weaker;? Or is it all about the spring being knackered?
thanks for your advice
MJ
sportston
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Re: gt380 front forks too soft

Post by sportston »

I can't believe no-one has answered this one. At risk of being a tad slow to reply, I will give it a bash.
You mention the forks are leaking. So that is one problem that needs to be fixed.
Check the bushes are not worn in the fork leg, check the stanchions are not pitted on the seal area. Then replace the seals.
That will fix one problem, but...while you have it apart it might be worth sticking a set of progressive fork springs in. That should cover the other possible cause of saggy springs.
And the other option as you have already gathered is use a different thickness of fork oil. Make sure you have the correct amount in each leg.
If the front end is a little too soft for a heavy rider, it might be worth installing a set of adjustable caps with preload adjustment. I have got a set of these for my GT380 from ebay in Japan. Didn't cost a lot, but that was a year or two ago.
Oh and make sure your front tyre is pumped up to the correct pressure.

There now, I think that is most common problems covered.
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jabcb
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Re: gt380 front forks too soft

Post by jabcb »

Check the sag. Its how much the springs are compressed with you sitting on the bike.

Start with a convenient reference like the length of the fork boot, or distance between the dust seal & triple tree.
Measure the length with no load on the fork (on center stand if you have one).
Measure the length with you sitting on the bike & just balancing it with a foot.
Pump the forks a bit for both measurement to overcome fork friction & get a good reading.
The sag is the difference between the two measurements.

Total fork travel is 4.5” (I think). Ideal sag is 1/3 of the travel or 1.5”. Around 1 ~ 1.5" is good.
How much sag did you get?

Suzuki typically used fork springs that were stiffer than optimal and didn’t use much preload.
Then the springs collapsed a bit after 40 years, and you can end up with way too much sag.
If you have too much sag, you may be able to use a plastic or steel spacer to get the correct amount.

Cycle World had a good article about your forks:
http://www.ozebook.com/compendium/suzi/ ... AtHome.pdf
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
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GT550 72 project & 75
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sportston
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Re: gt380 front forks too soft

Post by sportston »

jabcb wrote: Cycle World had a good article about your forks:
http://www.ozebook.com/compendium/suzi/ ... AtHome.pdf
Thats a great article. I wonder how changing to progressive springs would alter things. Will definitely try the rebound damping mod of brazing the hole up on my own bike
rngdng
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Re: gt380 front forks too soft

Post by rngdng »

The rebound mod works. I have it in my GT750. I also did the "increase the travel" mod.



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sportston
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Re: gt380 front forks too soft

Post by sportston »

I don't think I can do the "increase the travel mod" as you have to pop the forks up in the yokes and I think that will foul the ace bars. I have pre-load adjusters which are taller than the usual fork caps
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