Musings on clutch overhaul.

[Its been a long time]

After domestic chores, I got to start disassembling the clutch to do the start motor grinding fix.

First thing I found was the clutch spring screws are a very good fit on a JIS 2 screwdriver bit. Second thing I found was pounding the screws via a solid steel JIS 2 screwdriver with a 4lb lump hammer conditioned the screws such that they very easily came undone. Maybe I was lucky but the screws did come out really easily. No need today for an impact driver. (To clarify, when I say pounding the screws with a 4lb lump hammer, I mean using the weight of the hammer. Definitely not like you're trying to destroy the clutch).

So, the springs and pressure plate came off in a couple of minutes. To reveal the centre nut and the plates. A couple of notable things here. This is the first XS650 clutch I've opened up. I was expecting to find a tab washer on the centre nut. But there isn't one. Mine has a belville washer and a plain washer under the nut. Obviously, at some point this changed from a tab washer? I don't know when.

Snag is, I can't go any further today because I don't have a 29mm socket. I have ordered one but it will be next week now before I can remove the clutch basket to get at the start motor grinding problem.

On the plus side, the friction plates and springs are within spec. Plates 3.07 v 2.7mm, springs 34.7 v 34.6mm.

Maybe I'll look for someone locally with a lathe and do the modification to take M6 x 40mm cap head screws modification on the pressure plate while I wait for the 29mm socket to arrive. Pictures-

 

[5twins]

The first time I encountered that 29mm nut (before I had the right size socket), I got it off by shimming a 30mm socket with some sheet metal on a couple of the sides. It worked well. Even though the springs measure OK, they may still be weak. I pretty much always replace them because the clutch always seems to slip with the stock springs. Aftermarket heavy duty springs are cheap, only about $10 to $15 a set.

 

[Its been a long time]

A set of EBC clutch springs ordered as suggested. Seems they're the only ones readily available in the UK. I don't trust any of the unbranded ones I see out there. The EBC ones are cheap enough.

A set of M6 x 40mm caphead screws are on their way. Just need to talk to someone about turning the heads off the original screws flat and drilling them through to suit the M6 screws. By then I'll have the 29mm socket and I can carry on.

The kick start shaft oil seal is proving very tough to remove. It needs replacing. But the one in there for the last 47 years doesn't want to play at leaving the casing behind. I wouldn't have thought such a small oil seal could be stuck so tight.

It's coming out one way or another though

 

[Its been a long time]

29mm socket arrived today, a day or two later than anticipated so no progress until today. Did the starter motor grinding fix. Tested it with the plugs in but the caps off. Cranked well four times so it's declared fixed. Then put the clutch back until tomorrow when the new clutch spring retaining screws are due. I have the EBC spring set to install. Supposed to be 15% stronger. I'm not sure that's going to be a great idea with my knackered joints. So we'll see how we go.

I found it a bit tricky measuring the tension on the starter drag spring. As found I think it was about 1.5kg tension. I fitted a brand new old stock spring and that measured around the same. So I squashed the spring in a drill vice. That's got the tension up to around 3kg as near as I can measure. The distance across the "ear" of the spring is now noticeably narrower by almost 2mm. I think I could have broken the spring if I wanted to. So if anyone is following me, don't go mad squashing the spring to get more tension.

Hopefully the right side of the motor will be buttoned up tomorrow and I can change the gasket on the left side starter motor gear train cover as planned. I might just have an oil tight motor then. We'll see.

Pictures -

 

[Grimly]

The "over squashing of the spring bit" was dealt with by using a drill bit of the right fit in the earlug to prevent cracking.

 

[Its been a long time]

The "over squashing of the spring bit" was dealt with by using a drill bit of the right fit in the earlug to prevent cracking.

Thanks, I must have missed that bit in the thread I read.

 

[Its been a long time]

Just to mention. If I have to check the tension again on one of these assemblies, I believe it would be much better to use weights to check the spring drag rather than a scale. The scale I used held the maximum detected pull but I couldn't get repeatedly reliable readings. I don't think I would have had this uncertainty if I'd used increasing weights to test the drag from the spring mounted on the gear.

 

[Its been a long time]

The final bits arrived today for me to put the clutch back together. Just a few observations on the new type after market clutch spring screw retainers. The original Yamaha ones are case hardened steel. Obviously, the Yamaha engineers went to some trouble making then hardening the screws. The ones I have now, the spacers are machined from alloy and soft as the proverbial. Also disappointed with the surface finish and the variation in dimensions on the six pieces. In my previous lifetime, they wouldn't be considered acceptable. Finally, as per the picture below, the cap head screws provided in the kit are A2 (304) stainless steel. I fitted the black cap heads shown in the picture instead. I don't want stainless steel screws under stress inside an engine. Even this engine, which will do very few miles.

On the positive side, the EBC clutch springs that are supposed to be 15% heavier than stock haven't really resulted in much of an increased clutch lever pull.

Anyway, enough of the moaning for now. The clutch is back together. All that remains on the right side of the engine is to clean the gasket surfaces and change the kick start shaft oil seal. Then it's ready to close up. Pictures -

 

[5twins]

Another thing about those aftermarket aluminum spring holders - their O.D. is usually a little bigger and they won't fit into the stock springs. Oh, and you did properly align the pressure plate, right? .....

 

[Its been a long time]

Another thing about those aftermarket aluminum spring holders - their O.D. is usually a little bigger and they won't fit into the stock springs.

Thanks, that's useful to know. When I get a few minutes I'm going to do a sketch of these and put it here. But properly toleranced. I'll try to remember to measure the springs I took out and see how it compares to what I measured from those alloy parts. In all, I can't say I'm especially impressed with the alloy pieces. I would be a lot happier with steel pieces in there, even if not hardened like the originals are.

 

[5twins]

You can mod the original screws by cutting off the threaded portion, grinding the dome off the top, and drilling a 1/4" hole through them. The trick is to get the hole drilled straight through. I had mixed success at that but now that I have a mini lathe, I'm going to have another go at it .....

 

[Its been a long time]

You can mod the original screws by cutting off the threaded portion, grinding the dome off the top, and drilling a 1/4" hole through them. The trick is to get the hole drilled straight through. I had mixed success at that but now that I have a mini lathe, I'm going to have another go at it .....

View attachment 328616

Yes, that was my plan A. But the machine shop I asked to modify my original ones cut the top off the screws in error, so they are scrap. The ones I have now are plan B.

 

[member43148]

5 twins, Now that you have a lathe there is a possibly better process to consider.
Could you just drill an original eliminating the philips just deep enough and broach the original to have a 5mm Allen head?

 

[Its been a long time]

5 twins, Now that you have a lathe there is a possibly better process to consider.
Could you just drill an original eliminating the philips just deep enough and broach the original to have a 5mm Allen head?

That would be a very good idea. I found there's 0.002" of case hardening to get through, then the screws are soft.

 

[Its been a long time]

Oh, and you did properly align the pressure plate, right? .....

I did, yes. Thanks for the interest, it's more than helpful.

 

[5twins]

Well, I wasn't familiar with broaching, but after watching some YouTube vids, I am now. Unfortunately, the 5mm hex tool required costs $50 (or more, lol) so I won't be doing that.

 

[member43148]

Well, I wasn't familiar with broaching, but after watching some YouTube vids, I am now. Unfortunately, the 5mm hex tool required costs $50 (or more, lol) so I won't be doing that.

The broach cutters cost under $50 (EBay) Of course the broach holder cost is several hundred (new) but I know guys online here are very good at finding real good deals !

Here are thoughts on this.
The seen Aftermarket Aluminum clutch spring holders look like a bad idea to me as I would be concerned with wear which could lead to loosening. As well as adding to the number of components.

Now, if a guy were tooled up (initial investment) and proved a method to broach those original clutch screws, well then that guy would be in good position to make a product which many XS owners want out of those owners own material !
So “No material” turn around. It’s a machining dream to profit. And to help many XS owners.
You Being a lathe owner now it’s easy to see that machining tooling costs could be “skies the limit”
But, when you learn to broach, tap, or whatever on known components such as this,
Boom .. in the money now
Lol
Wish I were lucky enough to have a lathe in the garage…

 

[Jim]

The seen Aftermarket Aluminum clutch spring holders look like a bad idea to me as I would be concerned with wear which could lead to loosening.

On the other end of those spring sits the aluminum pressure plate.... a steel spring under compression, with no rotation or rubbing involved isn't going to wear on the surfaces it's compressed against... aluminum in this case. It's a non-issue.

 

[member43148]

So why would MamaYama use hardened steel?
If those are made of lower grade soft & gummy aluminum it is a concern.
Hi grade , hard & strong maybe not.
What do you guess it is ?

 

[Jim]

So why would MamaYama use hardened steel?
If those are made of lower grade soft & gummy aluminum it is a concern.

If it was a concern, why didn't Yamaha use a steel washer 'tween the spring and the aluminum pressure plate?
'nother question... if aluminum is so bad, why did they use it on the pressure plate in the first place?
Last question... How many aluminum pressure plates you seen worn through because of spring rub? I can't recall a single one. Anyone??

Simple answer... aluminum is actually pretty durable. Cast aluminum is actually one of the softer alloys, yet our pressure plates endure.
In other words, nothing to be concerned with.