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SP250 clutch noise

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Kbeal
Posts: 148
Joined: Mon Feb 15, 2016 9:01 pm

Re: SP250 clutch noise

Post by Kbeal »

Sounds a bit like a rusty gate spring!

Just a thought - have you greased the clutch shaft bearing recently? (the 2 grease nipples either side of the bell housing).

Kevin

Falcon
Posts: 31
Joined: Sun Feb 14, 2016 9:37 am
Location: Sherborne

Re: SP250 clutch noise

Post by Falcon »

Hi Kevin

Yes I greased them both routinely last october and again last week, still have the noise, although a little quieter now having given her another good run last weekend.

I got a garage mechanic to listen and he thought it was coming from within the bell housing and wondered if it was some corrosion on the shaft that the forked release bearing runs on.

I have never removed the gearbox (yet) so don't know if the release bearing actually runs on the shaft

Ian

Vortex O'Plinth
Extra-Wise Man
Extra-Wise Man
Posts: 1065
Joined: Fri Feb 12, 2016 8:15 pm
Location: Gloucestershire

Re: SP250 clutch noise

Post by Vortex O'Plinth »

The release bearing is mounted in the clutch operating fork and articulates on two half trunnion bearings - arrowed in yellow on this picture...
clutch.JPG
These bearings are nominally unlubricated so they are certainly a possible source of your noise.

The operating fork is pinned to the clutch cross shaft (it's this pin I mentioned in my earlier post that occasionally fractures) and the cross shaft runs in the two bushes in the bell housing - which you have already copiously lubricated, so these are not likely to be the problem.

If the clutch fork pin has fractured, the fork will be able to rotate on the shaft and could make protest noises, but in this case the release bearing will be unable to depress the clutch - which is not your problem.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

Falcon
Posts: 31
Joined: Sun Feb 14, 2016 9:37 am
Location: Sherborne

Re: SP250 clutch noise

Post by Falcon »

Hi thanks for your reply and helpful photo

There is a small designed hole in the housing I wondered if I could use this in situ with borescope and very carefully and minimally lubricate the points you highlighted.

Nervous about introducing lubricants in the area of the clutch what do you think and if I should try what do you suggest in forms of lubricant?

Obviously I am having a unique issue given so few replies, so I hope when I resolve it it will help others in the future

Ian

Vortex O'Plinth
Extra-Wise Man
Extra-Wise Man
Posts: 1065
Joined: Fri Feb 12, 2016 8:15 pm
Location: Gloucestershire

Re: SP250 clutch noise

Post by Vortex O'Plinth »

It might be possible as you suggest to introduce some lubricant onto the release bearing trunnions - a couple of drops of light machine oil ought to do the trick if this is the source of the noise. Since the clutch friction faces are only exposed while the clutch is operated, contamination with the lubricant is unlikely - any contacting the carbon thrust washer itself is unlikely to be a problem.

Although possible, I personally doubt that these bearings are the source of your noise, listening to it again it seems more probable that the sound originates within the clutch assembly itself. It's worth noting that the workshop manual makes no reference to lubricating the release bearing trunnions on assembly. Both the release bearing housing itself and the forked lever are of cast iron or steel - at least one of them is almost certainly grey cast iron. Grey cast iron contains flakes of free graphite which is an excellent lubricant in itself and one reason why cast iron is used in applications like machine tool beds and slideways, since it resists scuffing or galling even in the absence of other lubricant.

Since your noise seems to be diminishing with use it may well be that during a prolonged period of inactivity some parts of the clutch housing have corroded slightly and this is now wearing off. I think the only way you'll be certain of the cause is to expose the clutch, but gearbox removal is not a five-minute job...
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

Falcon
Posts: 31
Joined: Sun Feb 14, 2016 9:37 am
Location: Sherborne

Re: SP250 clutch noise

Post by Falcon »

I did drive her for about 1/2 hr at least every month over the winter but I agree with your diagnostic and best views as to the cause.

I am going to risk continued use this summer and then have the box out. I think the box could do with a refurb as there is some minor lay shaft noise so it will give me a chance to address both issues if they still exist

Many thanks for your input it is appreciated

I will provide an update as when I find the cause

Ian

davedpc
Posts: 2
Joined: Wed Feb 17, 2016 5:00 pm

Re: SP250 clutch noise

Post by davedpc »

Had the same problem which I think was due to dry clutch springs. I sprayed some lube through the bottom drain hole and to date no noise. Dave

Falcon
Posts: 31
Joined: Sun Feb 14, 2016 9:37 am
Location: Sherborne

Re: SP250 clutch noise

Post by Falcon »

Went out for a round trip 100 mile drive today, still have the noise but reduced a little

Hi dave

Interesting what lube did you use

Ian

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