Slip cluth GT 750

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Filly
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Joined: Wed Nov 02, 2016 3:16 pm

Slip cluth GT 750

Postby Filly » Sun Dec 01, 2019 3:38 pm

Hi everyone, after completing the restoration work on the GT 750 I spent the summer trying to fine-tune the bike in the engine, chassis etc. It unfortunately remains a clutch problem that I can't get rid of today. When the engine is cold it shifts a lot while the problem disappears completely when hot. The friction clutch plates are new to EBC, the metal ones have remained original because they are almost perfect and flat. The springs are new and reinforced, taken by the great Reiner; the lever in fact remains rather hard! The adjustment of the clutch has the correct game, in short I do not understand what the problem is. Finally, the oil is the Bardhal Gear Box 10W40. Help please ...

barney01
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Re: Slip cluth GT 750

Postby barney01 » Sun Dec 01, 2019 4:20 pm

I think your problem is the oil you are using is modern fully synthetic. This is designed to stick to components when cold as protection and causing the problem when cold but as the oil heats it thins out and then your slip disappears.
I would replace the oil with basic 20/50 mineral oil which is what was used when the engine was made. But first you need to remove all trace of the synthetic oil off the clutch plates using petrol or kerosene first.
NO SMOKE .......NO POKE

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oldjapanesebikes
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Re: Slip cluth GT 750

Postby oldjapanesebikes » Sun Dec 01, 2019 5:57 pm

According to what specifications I can find, that oil should work as it appears to be designed for wet clutch systems. I would first double check the free play at the clutch release end (under the side cover) and not at the handlebar. Per the manual, you need about 0.2mm of axial play there. It is possible you have it just a touch too tight. Once you have confirmed the free play at the release end, you then set the the cable adjuster to give you about 3mm of slack. If both of those adjustments are correct, then I'd second barney01 and suggest you try using a standard 20W50 non-synthetic oil just to see if it makes any difference at all. 8-)
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teazer
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Re: Slip cluth GT 750

Postby teazer » Sun Dec 01, 2019 9:44 pm

I am not a fan of old style oils. There are good two stroke transmission oils around. That said, lots of us use different oils and few have any issues with our oil of choice.

Ian has the right approach. Start at the "pull Rod" and make sure there is enough clearance there before adjusting the cable. ie back off the cable adjusters at both ends and then set the end clearance for the Pull rod.

If there is already enough slack down there, I would inspect the clutch plates for signs of high spots and check the drum and basket to see if the plates are hanging up on indentations. It would be a good idea to measure the steel plates and friction plates to see if they are thinner than stock.If they are, you may have to slip an extra steel plate into the clutch pack.

Many aftermarket clutch friction plates use the same diameter and splines but may be a different thickness to stock. I like to use more thin plates rather than fewer thick plates, but I measure all the plates and work out total clutch pack thickness just to be sure.

It's more normal for plates to stick when cold and slip when hot, so it sounds like yours may be expanding or the oil is thinning out when hot.

I could not find that oil as a transmission oil - only as an engine oil and it says it has "friction modifiers" which is NOT what you want in a transmission/clutch. Try a couple of liters of Honda http://prohondaoil.com/vital-fluids/transmission-oil/ That stuff or equivalent from other manufacturers works well.

barney01
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Re: Slip cluth GT 750

Postby barney01 » Mon Dec 02, 2019 7:22 am

NO SMOKE .......NO POKE

Filly
Posts: 35
Joined: Wed Nov 02, 2016 3:16 pm

Re: Slip cluth GT 750

Postby Filly » Mon Dec 02, 2019 2:12 pm

Meanwhile, I thank everyone for the advice you gave me. I will definitely check the tolerances on the lever and in the crankcase leverage, although they are already done. Certainly 0.2 mm of axial clearance are substantially imperceptible and impossible to measure if not to the touch feeling a slight indentation of the clutch shaft, do you agree with me oldjapanesebikes? As for the oil I will surely change it with a mineral, after cleaning and checking the fringed discs (new ones installed) and steel allowing me to eventually eliminate another possible cause. Best regards to all.

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2strokejohnny
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Re: Slip cluth GT 750

Postby 2strokejohnny » Mon Dec 02, 2019 3:22 pm

I changed to 20/50 mineral and got slight slip when cold, changed back to 10/40 mineral and no slip or creeping.John
Suzuki GT750B
Suzuki GT380M
Triumph T100 Unit Bonny

barney01
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Re: Slip cluth GT 750

Postby barney01 » Mon Dec 02, 2019 5:22 pm

Another tip to help give the metal plates a quick rub with fine emery paper just to make sure there is no cork or EBC attached to it.
NO SMOKE .......NO POKE

Filly
Posts: 35
Joined: Wed Nov 02, 2016 3:16 pm

Re: Slip cluth GT 750

Postby Filly » Tue Dec 03, 2019 6:42 pm

I will certainly have a lot to do with all these tips. Thank you very much.posting.php?mode=reply&f=11&t=12268#


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