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Clutch upgrade question

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Clutch upgrade question

Postby mickey c » Mon Jun 17, 2019 10:15 pm

Can I ask more experienced engine builders for opinion please?
I'm trying to upgrade my clutch but the first attempt caused it to feel like it was both slipping & dragging (if that means it was fully & not engaging almost at the same time?) !
I reckon it was the plates & corks not separating so I'm hoping to use thinner steels, which if my maths is correct will leave a gap of 2.8 to 3.0 mm; Sticky states at least 1mm. Will being 3 times this cause my scooter a problem?
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Re: Clutch upgrade question

Postby dickie » Tue Jun 18, 2019 5:49 am

3mm is very big but might work if you have a low torque motor, high friction plates and stiff springs.

What plates and springs are you using? What motor?

Also, did the spider have any damage from the tangs?
This can cause plates not to separate properly yet they may also slip if there is too much gap.
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Re: Clutch upgrade question

Postby mickey c » Tue Jun 18, 2019 6:45 am

Thanks Dickie
The spider appears fine.
I’m trying to squeeze a 4 plate clutch into a little Vega engine. This has a 140 star stream top end & j range sprocket - a bit niche I appreciate. The engine melted a 3 plate clutch in less than 100 miles!
So this time i’m using 4 of the 5 corks from a BGM set up - these are 2.4mm. I couldn’t get the BGM steels to seperate, these are 1.4 mm so got some cyclone ones from Rimini which are 0.9mm causing the 3mm play. I’m using MB springs.
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Re: Clutch upgrade question

Postby dickie » Tue Jun 18, 2019 7:05 am

I really don't know those motors at all but the principles are the same.

I can't really advise on what plates etc work well in that motor as I doubt I've even laid hands on one.

But, 3mm is huge and I'd bet my left knacker that it will slip even with stiffer springs.

Personally, I'd just make sure that everything slides nicely, steels, corks, spider and pressure plate have no notches. Soak the plates before installing. 1.5mm or so should avoid drag.
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Re: Clutch upgrade question

Postby mickey c » Tue Jun 18, 2019 9:26 am

Thanks again Dickie
I know these engines are a bit obscure & was checking the principles with those who know / understand more than I do.
Can I just ask 1 more question please? Everything is soaking in oil & will move freely / easily but to get 1.5 (ish) movement i’ll have to use different steels - a combination of 1.1 & 1.4 thickness. In your opinion will this cause me a problem please?
Thanks again
Mike
mickey c
 
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Re: Clutch upgrade question

Postby dickie » Tue Jun 18, 2019 10:27 am

mickey c wrote:Thanks again Dickie
I know these engines are a bit obscure & was checking the principles with those who know / understand more than I do.
Can I just ask 1 more question please? Everything is soaking in oil & will move freely / easily but to get 1.5 (ish) movement i’ll have to use different steels - a combination of 1.1 & 1.4 thickness. In your opinion will this cause me a problem please?
Thanks again
Mike

Just put the thicker steels at the bottom as they experience greater shock loading than the top ones when the clutch is engaged. No problem with mixing thicknesses.
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Re: Clutch upgrade question

Postby mickey c » Tue Jun 18, 2019 10:33 am

Thanks again pal
I didn’t know about thickest at the bottom. Got a day off today so will crack on & hopefully sort it in tine to get to old Trafford for the cricket.
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Re: Clutch upgrade question

Postby Warkton Tornado No.1 » Tue Jun 18, 2019 12:28 pm

The very thin friction plates & steel plates from the likes of CamLam, or similar to your current set up, should work.

If that doesn't, then I guess the principle of an extended clutch (like the way we had to gain room for six plates in SIII engines) could be applied, but apart from the hassle of a packer &/or gaining operating clearance, the SIII clutch parts should be relatively easy & cheap to locate.

My belief is that very few clutch set ups run 'true' until they are run in, but if the components are good, then they can be quite forgiving, even with regards to oil grade. (I have not used the regulation SAE or ST90 for many years, as I tend to keep an eye on what the biker boys are doing as well.....but not in a leather clad, fetish way :? )

Although I have very little knowledge of the small frame engine, I would imagine the change to SIII transmission components could reap rewards with using a (good!) duplex chain as well..... :)
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Re: Clutch upgrade question

Postby mickey c » Tue Jun 18, 2019 8:31 pm

Thanks WT
That's my hope \ intention, squeezing series III 4 of 5 plates into this little engine will hopefully give a clutch that lasts a thousand + miles, rather than the 80 the previous 1 did.
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