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 Post subject: GT380 forks.
PostPosted: Tue Aug 08, 2017 3:34 am 
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Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
Hi all,
I decided to give the forks on my 1977 GT380M an overhaul as I did not do it at the original rebuild stage. I know how the forks should dismantle and go together but how the devil do I get the metal inserts out of the top. I removed the the circlips and managed to tap the inserts down about 1/16 of an inch to free them up, but that's it they're stuck. No amount of compressing the forks or tapping the forks on a piece of wood will shift them. At the moment I've just filled the top of each fork with WD40 and left to soak to try and free them up. The internal diameters in the fork tops were quite rusty but I've cleaned them out with a rotary wire brush.
Any help much appreciated,
Regards,
Glyn.


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 Post subject: Re: GT380 forks.
PostPosted: Tue Aug 08, 2017 5:49 pm 
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Joined: Wed Jul 10, 2013 12:04 pm
Posts: 432
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Remove the oil drain bolt from the bottom of fork leg, attach pipe to hole and use high pressure from an airline to force it out? Just take measures to avoid ricochet when if finally comes out. e.g. Submerge end of fork in a bucket of water to avoid ricochet.


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 Post subject: Re: GT380 forks.
PostPosted: Wed Aug 09, 2017 2:11 am 
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On the main road

Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
Hi Sportston,
Unfortunately I do not have access to a high pressure air line so I may have to try a different method. I was wondering if it is possible to disassemble the forks without removing the top plugs, ie by removing the bottom allen bolt in the fork lower leg and removing the oil seal circlip to separate the stanchion from the lower leg. Could it then be possible to tap the top plug out using a long thin rod. I'm just throwing out ideas at the moment as surely Suzuki didn't design the forks this way knowing there is only one way to get them apart.

Regards,
Glyn.


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 Post subject: Re: GT380 forks.
PostPosted: Thu Aug 10, 2017 11:46 am 
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Joined: Wed Jul 10, 2013 12:04 pm
Posts: 432
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
That may be worth trying. Not sure if it is possible. Have you removed the stanchions from the lower legs?
It sounds like you have the MAB model forks. I didn't like the inherent weakness in that style of fork top so I threw my standard stanchions away. I got a set of forks from a late 1978 GS400. They fit GT380 yokes perfectly and have screw caps at the top of the stanchions. However the bottom of the right fork is different (it has an eye for the axle to go through instead of a clamp). So I took the GS400 stanchions and innards and put them in my GT380 legs so it would look a bit more symmetrical. I have a set of preload adjusters I bought from japan on ebay that fit replace the standard screw in caps. So it might compensate a little for my lardy ass.
Some of the other GT380 models have screw cap tops as standard. Why Suzuki chose to change it I don't know. But It sure is annoying when the tops get rusted and have funneled water into the fork.


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 Post subject: Re: GT380 forks.
PostPosted: Fri Aug 11, 2017 1:16 am 
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On the main road

Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
Hi Sportston,
Yes they are the MAB forks. I haven't removed the stanchions yet as I am going to carry on using the bike until the winter, then I have plenty of time. I've purchased all the parts I need to refurbish them but if I can't resolve the issue I may go down the same route with the GS400 forks. I have seen some after market stanchions on e-bay which could also be a solution.
Many thanks for the help.
Regards,
Glyn.


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 Post subject: Re: GT380 forks.
PostPosted: Fri Aug 11, 2017 11:23 am 
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Joined: Wed Jul 10, 2013 12:04 pm
Posts: 432
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
i seem to recall that the GT380 screw cap forks (33mm) have the same springs as the honda cx500. Other than the CX500 Custom (USA model), CX500E Sports and the CX500 Turbo models, the CX500 had 33mm forks.
I wonder if they would fit? Probably not worth the trouble, maybe best to get a set of proper gt380 ones


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 Post subject: Re: GT380 forks.
PostPosted: Sat Aug 12, 2017 6:22 am 
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On the main road

Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
I have found a set of new stanchions on e-bay from Paolo Tarozzi & Franco ( made in Italy ) for £226 a pair. I was wondering if anyone has used these and are they any good. The stanchions on my bike are actually in great condition on the outside but I'm not sure of the internals, hence the rebuild. There is also a seller on e-bay supplying new stainless steel fork top plugs with O-rings for £16 so I'm not really worried about damaging the rusty old ones.


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 Post subject: Re: GT380 forks.
PostPosted: Sat Aug 12, 2017 12:03 pm 
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Joined: Wed Jul 10, 2013 12:04 pm
Posts: 432
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Sounds like a good deal on both items. If the forks aren't pitted and you are not having a problem with water getting past the seal at the top, there is not much else to worry about other than oil and dust seals and the oil itself. When you drain the fork oil does it show signs of contamination with water? Brown or emulsified oil? So long as there are no signs of problems at the bottom end and no signs of contamination, I'd stick with your existing stanchions if they are not pitted. Not a bad idea to replace the tops with stainless ones I guess especially at that price, if you can get the old ones out! But don't forget to put some waterproof grease around the inside of the stanchion to help prevent condensation corrosion. And again, to help prevent a repeat of the same problem with rust, you may want to get new rubber caps that will seal better than their ancient counterparts too.


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 Post subject: Re: GT380 forks.
PostPosted: Sun Aug 13, 2017 1:25 am 
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On the main road

Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
All good points, I haven't checked the oil in the forks yet because if let some out at the bottom I have no way to top them up. I may have to drill and tap the existing plugs so I can use a slide hammer to get them out. Maybe I can then use a grub screw in them as a seal so I don't need to take them out again to do oil changes in the future. Just an Idea going round in my head.


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 Post subject: Re: GT380 forks.
PostPosted: Sun Aug 13, 2017 11:55 am 
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To the on ramp

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 432
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Another possibility is to weld a bolt in the hole you have drilled and threaded then twist/pull it out.
Twisting might be the cure. If it still doesn't work you could twist and shout...even shake it up baby!
:lol:
Another, but more drastic alternative is to use heat. But I am not sure what the results of attacking hard chrome with a blow torch would be.

However.....
Have you tried using the bike as a slide hammer? By which I mean:-
1. Leaving the forks in the yokes, with the front wheel and brake attached.
2. Remove drain screws from fork legs. Drain oil out of forks, then pump bike up and down to get the remaining oil out of shock-absorber mechanism (this bit is important). Try not to get oil on the front tyre!
3. Remove the circlips
4. Push bike forward, then apply front brake hard, causing the forks to compress hard and bottom out, hopefully shooting the caps up and out of the stanchion.

This method might work but you would need to guard against flying fork caps. If they pop out they might fly up and hit you or delicate bodywork. So it would be wise to find some way of preventing damage to you or the bike. e.g. remove fuel tank and cover certain areas with rags, to help deflect or catch the caps. Possibly even wear an old full-face helmet to protect your face.


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 Post subject: Re: GT380 forks.
PostPosted: Fri Aug 18, 2017 7:39 am 
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On the main road

Joined: Fri May 30, 2014 5:41 am
Posts: 161
Location: High Peak Derbyshire.
Country: UK
Bikes owned: Suzuki GT380 B- Yamaha FZ1
Well finally got the little bugger out. Had to drill and tap the plug and use a slide hammer and out she popped, only done the one leg so far I hope the other one is as easy.
My new problem is the new seals Part No 51153-02B00 replacing old part number are 1.5mm thinner than the originals, is there a spacer ring I need or do I just put the new ones in as is. Also it is obvious on the originals which way round they go in not so on the new ones. The only difference I can see on the new ones is that one face has a deeper recess in than the other. I am presuming that the deeper recess goes face down in the fork leg and the shallower recess is face up open to the air. Any help will be much appreciated.
Kind Regards,
Glyn.


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