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R1 4XV Clutch
Sanzomat - 8/6/21 at 01:56 PM

Hi all. I'm still battling with the fuelling on my Locost R1. I took it for a rolling road session this morning but didn't get far as it turns out that the clutch is slipping! At least I know is makes 67bhp as that is the power when the clutch starts slipping!

Clutch kits for the 4XV list two different part numbers, one for 4XV1/2 and a different part for 4XV7/8. I'm guessing this can be deciphered from the VIN of the bike but I don't have that - just the engine number. Does anyone know if I can tell from the engine number which clutch kit I need?

Alternatively is there a recommendation for an upgraded clutch that is not version specific?

computid - 8/6/21 at 03:49 PM

If I were you, given that its in a car, I'd go for a Barnett carbon fibre clutch pack with a Barnet spring top conversion plate. I've got one on my 5PW thats actually in a bike and its the bees knees. Much more performant than the stock clutch.

Be wary of anything that isn't Yamaha or Barnett though, I had a Viper clutch in one engine which destroyed itself and ended up spread around the engine (disk material and all) and blew the engine up when it blocked the oil pickup.

Does your clutch pack have the damper spring at the back? You'll need to take the clutch pack out to look.

computid - 8/6/21 at 03:49 PM

If I were you, given that its in a car, I'd go for a Barnett carbon fibre clutch pack with a Barnet spring top conversion plate. I've got one on my 5PW thats actually in a bike and its the bees knees. Much more performant than the stock clutch.

Be wary of anything that isn't Yamaha or Barnett though, I had a Viper clutch in one engine which destroyed itself and ended up spread around the engine (disk material and all) and blew the engine up when it blocked the oil pickup.

Does your clutch pack have the damper spring at the back? You'll need to take the clutch pack out to look.

Sanzomat - 8/6/21 at 04:21 PM

quote:
Originally posted by computid
If I were you, given that its in a car, I'd go for a Barnett carbon fibre clutch pack with a Barnet spring top conversion plate. I've got one on my 5PW thats actually in a bike and its the bees knees. Much more performant than the stock clutch.

Be wary of anything that isn't Yamaha or Barnett though, I had a Viper clutch in one engine which destroyed itself and ended up spread around the engine (disk material and all) and blew the engine up when it blocked the oil pickup.

Does your clutch pack have the damper spring at the back? You'll need to take the clutch pack out to look.


Thanks for the recommendation. Looking these up they list the same part for 1998-2003 so should fit all 4XV as well as 5JJ and 5PW so at least takes out the confusion. Some suppliers say to omit the anti judder plate and add an additional standard plate for BECs - any thoughts on this? An ebay supplier includes an 8th standard plate and a choice of springs (softer for bikes and harder for BECs) so that seems like they've thought it through but only semes to be the one supplier and they are listed as away until July...

Don't know about the damper spring. I suppose I may as well take it apart and look as its not going anywhere till its fixed!

I used to have a 5PW bike - still miss it!

[Edited on 8/6/21 by Sanzomat]

smart51 - 8/6/21 at 09:28 PM

Are the clutch plates worn? If not, you might just need a bit more spring force. I've heard of people putting two stock springs together to do that. Quick and simple.

I had a Barnett clutch on mine. To increase the preload, I put a thick washer behind each top hat. It squeezed each coil spring by another 2mm adding to the force holding the plates together.

As you're using your foot to press it, a bit more spring force will help the feel too.

Sanzomat - 8/6/21 at 09:38 PM

quote:
Originally posted by smart51
Are the clutch plates worn? If not, you might just need a bit more spring force. I've heard of people putting two stock springs together to do that. Quick and simple.

I had a Barnett clutch on mine. To increase the preload, I put a thick washer behind each top hat. It squeezed each coil spring by another 2mm adding to the force holding the plates together.

As you're using your foot to press it, a bit more spring force will help the feel too.

Haven't taken the old one apart yet to see but thanks for the tip - worth checking. I thought the standard clutch has a diaphragm spring. Can these be doubled up or are you just talking about the coil sprung versions?

gaz_gaz - 9/6/21 at 05:10 AM

I ran a 4xv and 5jj MNR for years doing lots and lots of trackday. I would fit standard Yamaha plates and 2 diaphram springs. You won't go wrong. I tried many combinations in the early days and nothing lasted as well as stock plates and 2 springs.

smart51 - 9/6/21 at 07:09 AM

quote:
Originally posted by SanzomatHaven't taken the old one apart yet to see but thanks for the tip - worth checking. I thought the standard clutch has a diaphragm spring. Can these be doubled up?
Yup, that's right

Sanzomat - 9/6/21 at 01:35 PM

I took the clutch off this morning to check it out. The friction plates look okay. They all measure 2.98mm thick. The manual says they come new as between 3.1 and 2.9mm and should be replaced at 2.8mm so 2.98 seems to be in the middle of the "new" range. The metal plates also look fine. There was only one diaphragm spring so doubling up seems like a no brainer. I've ordered one and will fit when it comes and fingers crossed it'll be sorted.

Thanks for the information.

scotlad - 10/6/21 at 09:15 AM

quote:
Originally posted by smart51
Are the clutch plates worn? If not, you might just need a bit more spring force. I've heard of people putting two stock springs together to do that. Quick and simple.

I had a Barnett clutch on mine. To increase the preload, I put a thick washer behind each top hat. It squeezed each coil spring by another 2mm adding to the force holding the plates together.

As you're using your foot to press it, a bit more spring force will help the feel too.


My 4xv engined Locost that was used for sprints and hillclimbs before i got it has 2 stock springs fitted (much to my surprise when stripping it to check wear level). i've never had any slip at all despite the plates being half worn.