GT380M Fork Oil

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willowden
Posts: 167
Joined: Thu Nov 16, 2017 3:10 pm

GT380M Fork Oil

Post by willowden »

Hi Fellas, can anyone recommend which fork oil to use on my 1975 GT380M.
If I use a heavy grade will it stiffen the forks slightly ?
Thanks, Andy
barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT380M Fork Oil

Post by barney01 »

Oil is a personal choice with everyone having their own preference. The manual says 10w/30w. I use modern fork oil but others will say different. The more oil in the fork the firmer the ride or use less oil to soften it.
NO SMOKE .......NO POKE
willowden
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Joined: Thu Nov 16, 2017 3:10 pm

Re: GT380M Fork Oil

Post by willowden »

Thanks Barney. Do you know any threads or sites that show the method of changing the oil. I am unsure of the process.
Cheers, Andy
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BATTS
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Joined: Sun Jul 15, 2012 6:47 pm
Location: Lancashire

Re: GT380M Fork Oil

Post by BATTS »

I think the quantity of oil remains constant as per specs, the viscosity of the oil determines ride characteristics. Too much oil and it will be forced past the fork seals and out too little and it gets extremely bouncy and can bottom out.
Chris
76 GT750, 78 GT550, BMW K1600gtl
barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT380M Fork Oil

Post by barney01 »

It's really not too difficult. First raise front of bike I use trolley jack under the engine.
Undo the drain plug on the outside of the fork leg on one side. Allow oil to drain into a bowl. Lower the bike down Apply front brake and push bike so it bounces up and down. The oil will squirt out. When it stops replace drain plug. Make sure washer is on first. Lift the bike again. Then remove cap near to handlebar the spring is inside. Refill fork with correct amount of oil and replace cap. Then repeat the other side.
If you don't raise front wheel when the cap is taken off the spring will come flying out and disappear over the hedge. Don't ask how I know this! :oops:
NO SMOKE .......NO POKE
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BATTS
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Location: Lancashire

Re: GT380M Fork Oil

Post by BATTS »

Don’t forget there are two types of fork leg, J,K and L the top cap is threaded and retains the fork spring. M A B (and C for 380) the spring is retained by a circllip covered with a rubber bung in the top of the leg
Chris
76 GT750, 78 GT550, BMW K1600gtl
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT380M Fork Oil

Post by barney01 »

Okay good advice i just know about the early one! Thanks for your input
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canaletto5
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Joined: Tue Jul 23, 2013 8:43 pm
Location: Derbyshire

Re: GT380M Fork Oil

Post by canaletto5 »

Whichever version it is, please be aware of the "boing" factor when they release. I have a broken lamp fitting as evidence that they can travel a surprising vertical distance :o :lol:
willowden
Posts: 167
Joined: Thu Nov 16, 2017 3:10 pm

Re: GT380M Fork Oil

Post by willowden »

Thanks for all the advice, I am really looking forward to this job !! Not
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es2GT550

Re: GT380M Fork Oil

Post by es2GT550 »

Take your time - pay attention to the advise previously given and you will be fine. Enjoy the satisfaction of knowing you did a good job yourself :D
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