clutch slip

[to v or not to v]

replaced the friction plates and springs with genuine parts on the Thunderace but still getting clutch slip at higher revs.
its not consistent, sometimes worse than others. clutch is hydraulic not cable.
when i replaced the plates the whole clutch looked in fairly good condition to me, the metal plates were fine and unmarked, friction plates and springs well within their limits. clutch basket was a bit notched and i filed it smooth, which made getting into neutral a lot smoother on reassembly.

where should i look next?
i have heard theres a tiny fluid return hole in the clutch reservoir which can block causing mild slip?
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current bike Yamaha Thunderace.
Moto Guzzi V7.

[jeffyjeff]

[WD Forte]

I've seen these 'bleed ports'get clogged on older bikes
braking systems so its a possibility I suppose.
Same cylinder on a clutch.

Found this simple diagram and added the Deflector part which is found in lot of them
It's just a spring plate to stop fluid squirting back all over the place if the brake is operated when the cover is off
when bleeding for instance.

It's easy enough to check pressure is being released by observing it to see if fluid rushes/flows back into the reservoir when the lever is released.
It's worth mentioning the slave cylinder could be getting stiff/sticky as well of course.

https://imgur.com/dA2Uq1Y.jpg
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bikers smell of wee

[stinkwheel]

If it's hydraulic, I presume it'll have a long pushrod going through the engine between the slave cylinder and clutch centre? If it does, check it for rust binding on seals and make sure it's straight by rolling it on a sheet of glass.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[to v or not to v]

push rod is fine and no sign of corrosion around the slave cylinder.
how would i go about cleaning/unblocking the return hole in the reservoir?
do i have to remove it and use brake cleaner?
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[WD Forte]

I'd whip the master cylinder cover off work the clutch and observe first as we're not certain of the cause.

The brake fluid should be utterly clean and you should be able to see the effect of returning fluid disturb the fluid in the reservoir when you release the lever.
If it all looks fine then a blocked return hole may not be the cause
( does the piston fully retract?)
On old bikes I've seen particles n shit which I assumed were degraded seals so new seals and a fluid flush was called for.
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bikers smell of wee

[Easy-X]

Is there any adjustment procedure to go through after replacing the plates?
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Nobby the Bastard]

Not with a hydralic clutch, aside from pumping it a couple of times, which the failure to do would not cause it to slip.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Easy-X]

[Nobby the Bastard]

[to v or not to v]

[blurredman]

Is it possible the fluid line (if a soft flexy at any point) could be swolen internally not letting fluid return at a fast enough rate?
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 51k.

[Nobby the Bastard]

The pipes on my brothers brakes managed to break down internally and started to work as a one way valve so it is possible.

Yes, we both thought that the person who suggested it was talking bollocks but it fitted the symptoms and replacing the pipes fixed the problem.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[to v or not to v]

its braided line on the bike but it is 25+ years old
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[WD Forte]

25+ years old and dirty fluid
This may not be the cause of the clutch slipping but
you my want to do a bit of shopping here
The clutch Master and Slave cylinder repair kits are pretty cheap

https://www.wemoto.com/bikes/yamaha/yzf_1000_r_thunderace/98
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bikers smell of wee

[to v or not to v]

i was hoping it would be something simple
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[jeffyjeff]

Could be as simple as the oil you are using. Energy Conserving motor oils have friction modifiers that can cause clutch slip in wet clutches.
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History shows again and again how nature points out the folly of men - BOC

[to v or not to v]

using the recommended oil. currently Mobil, was Castrol before that.
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[to v or not to v]

new master/slave rebuild kits on their way, hopefully this will fix things.
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[doggone]

With my old bandit 1200 it was a little push rod by the front sprocket would get gunked up and sticky - that was what physically activated the clutch and intermittently it would not let the plates engage properly when you released the (hydraulic) clutch.

[to v or not to v]

had the push rod out when i changed the plates last year. everything was clean and in good condition.
the bike is only used in good weather.
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[WD Forte]

Like Jeff I also wondered if a bit of the old friction modifiers had crept in somewhere, you mention Mobil and Castrol but are you sure it was pukka
Motorcycle oil?
I've heard of people getting some clutch slip when trying fully synth
and this was on bikes with far less torque than yours

25 years is high time for a clutch hydraulics service and its not expensive
so hopefully does the trick
____________________
bikers smell of wee

[to v or not to v]

the Castrol was from Halfords so i would hope it was genuine. the Mobil from an ebay shop. also had Silkolene in there but binned it and changed
to Mobil just to test if it was the oil causing slippage, before i changed the plates.
all were the manufacturer recommended motorcycle oils for my bike.
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[blurredman]