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 Post subject: Gt250K forks
PostPosted: Fri Aug 17, 2018 5:50 am 
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Still in the Driveway

Joined: Tue Jul 24, 2018 3:56 am
Posts: 6
Location: Isle of Wight UK
Country: UK
Bikes owned: 1973 GT250
Hi all. Recently picked up a 73 Gt250 and whilst I owned one back in the seventies, I don't recall the front forks topping out as this one does when putting it on the centre stand or riding on rough roads under acceleration which results in a hefty clunk!. Forks have been overhauled by the previous owner and have fresh oil ( transmission fluid by the look of it) any thoughts or advice would be much appreciated. Thanks


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 Post subject: Re: Gt250K forks
PostPosted: Fri Aug 17, 2018 8:57 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3231
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
Check the fork spring sag. Its how much the forks compress going from no weight on the forks to you sitting on the bike & barely using your feet to balance the bike.

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 Post subject: Re: Gt250K forks
PostPosted: Sat Aug 18, 2018 4:02 pm 
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Road race school

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 799
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
I wonder if he reassembled incorrectly. Possibly he omitted a ring or assembled in the wrong order? Springs might have sagged, as already mentioned. Or there could be insufficient oil.
Since it goes bang I would consider the damping being faulty. Check the amount of oil is correct. If that doesn't fix it, strip and check the assembly against a parts diagram to see if he has put it back together incorrectly.


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 Post subject: Re: Gt250K forks
PostPosted: Mon Aug 20, 2018 4:21 am 
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Still in the Driveway

Joined: Tue Jul 24, 2018 3:56 am
Posts: 6
Location: Isle of Wight UK
Country: UK
Bikes owned: 1973 GT250
I was thinking along the same lines that it may be a damper issue as the rebound is fairly instant without much control. In terms of fork oil grade, I know may people use atf fluid but I'm unsure what SAE that is compared to conventional 10 or 5W.


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 Post subject: Re: Gt250K forks
PostPosted: Mon Aug 20, 2018 4:48 am 
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Still in the Driveway

Joined: Tue Jul 24, 2018 3:56 am
Posts: 6
Location: Isle of Wight UK
Country: UK
Bikes owned: 1973 GT250
I see that Suzuki specified SAE 30w for the forks, I presume using a much lower weight oil as has been used in my bike would result in the poor rebound damping I'm experiencing . Any advise would be welcome.


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 Post subject: Re: Gt250K forks
PostPosted: Tue Aug 21, 2018 9:41 am 
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Road race school

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 799
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
The GT250 had rebound damping? The GT380 of the same era didn't. That is why so many guys modify their shocks to give them a little.
Dollydog is the resident GT250 expert on here. He might be able to tell you if they had rebound damping or not and how to counteract your problem


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 Post subject: Re: Gt250K forks
PostPosted: Tue Aug 21, 2018 2:34 pm 
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Still in the Driveway

Joined: Tue Jul 24, 2018 3:56 am
Posts: 6
Location: Isle of Wight UK
Country: UK
Bikes owned: 1973 GT250
Well when I said 'Rebound damping', what I meant was returning from compression!......Think I've found the issue, only 100cc of oil in each leg, think its supposed to be 220!


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 Post subject: Re: Gt250K forks
PostPosted: Fri Aug 24, 2018 2:50 pm 
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Road race school

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 799
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Tapnell wrote:
Well when I said 'Rebound damping', what I meant was returning from compression!......Think I've found the issue, only 100cc of oil in each leg, think its supposed to be 220!

Yes according to Suzuki service manual 220cc is correct. Glad you found the solution!
I knew what you meant by rebound damping. According to this guide http://www.ozebook.com/compendium/suzi/ ... AtHome.pdf" onclick="window.open(this.href);return false;
"Compression damping on the mid-sized Suzukis is fine, but rebound is way too light."
From that I would assume most of the Suzuki bikes of the era were similar. However, that doesn't mean to say they can't be a lot of fun!


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