CLUTCH SLIP

My Mk 3 has a slipping clutch when I try to 'give it the beans', usually in 4th gear.

As I don't have a clutch puller, I gave it to the local engine shop who looked at it and said that all was to spec, plates not worn and the spring is new (less than a 1000 miles). After researching on the Owners club site, I spotted this suggestion.....

'When the clutch on my stock 850 Commando began to slip at high r.p.m. (it has the bronze metal plates) and no amount of adjustment seemed to cure the problem, I assumed a new clutch was in order. At the advice of a local Norton shop, I did the following to the bike which quickly (and cheaply) remedied the trouble:

Empty the oil from the primary chaincase (simply loosen the centre nut on pre -'75 models) and let it drain into a pan
Retighten chaincase and fill with about 1/2 pint kerosene
Start the bike and runs for about 10 minutes, disengaging the clutch and revving up several times to cleanse the plates
Empty the chaincase as in 1. above
Tighten up and refill with automatic transmission fluid


This procedure has proved quite satisfactory for my machine, and no more clutch slip. I used Ford ATF in mine, but I'm not sure if this is a factor. '

Brian Moran in RH 120 - Mar/Apr 1985

Would this simple idea work? Would the primary chain etc get damaged running it with no oil? What about the auto chain tensioner, isn't that reliant on oil to make it work? What about the residue kerosene left in the chaincase after draining it?


Do I need to just buy a puller and get my hands dirty?
I have never had the clutch work properly and it spoils the machine so i want to sort this, with perhaps a new belt drive coming late this year. Would this do it?



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If you wear gloves your hands don't get so dirty. :mrgreen:

I'm not sure if I'd take such a simplistic approach to cleaning the primary. I'd much rather disassemble everything so I know that it's all good. Or do the kerosene trick and then disassemble.

It's quite a quick job to pull the clutch plates if you have the puller, and you know that the job is done correctly.

I have put surflex plates in mine with a pushrod oil seal on the clutch pushrod, and also run a belt and never have (yet) any clutch slip.

You can make a clutch spring compressor from many different materials. A large pipe cap, a kitchen sink strainer, a round electrical work box, etc. Just drill a hole in the center and insert a bolt with two nuts, one to lock against the spring center and the other to turn to compress the spring. No actual "puller" is needed.

My clutch compressor tool is a 4" cast iron pipe cap. The through bolt is 1/2-20 thread, you may have to use threaded rod if you can't find a bolt with enough threads. It's served me well for over 30 years. Every Commando owner will eventually be inside his clutch for the ritual cleaning, so a well made tool is a necessary investment.

'' think that the most common maintenance job ( by far ) on a Commando is disassembling the clutch . Do yourself a favor and get a spring compressor .''

Ordered one this morning and it's in the post. I shall delve into the darkness of the internals when it gets here and see how it goes.

How hard can it be......

mcmarvelous said:

'' think that the most common maintenance job ( by far ) on a Commando is disassembling the clutch . Do yourself a favor and get a spring compressor .''

Ordered one this morning and it's in the post. I shall delve into the darkness of the internals when it gets here and see how it goes.

How hard can it be......

Click to expand...

Like all things mechanical, read up as much as you can before delving in, take your time, take notes (digital cameras help here) and ask questions. There is no substitution for experience but you can't get the experience without getting your hands dirty.

I put an RGM motors belt drive, with a thicker STEEL end plate, sureflex plates and a clutch rod oil seal.
I finished it off with a Venhill teflon lined cable.
My clutch works fine now, but it should...I replaced everything!

If I was going to do oONE thing, it would be the clutch pushrod seal. The clutch plates do not like that thick oil on them.
Your clutch stack height should be about enough to fill the basket. You should not have much exces room to fit the wills ring on assembly...

By the way, was it Harley D that said put kerosine in the engine and run for 30 secs to flush? Or was I dreaming...(if it was a Harley it may have been a nightmare).

Stuart

Another "tool" you'll want to have on hand... is a pair of hooks for removing the clutch plates from the basket. Something as simple as two 6 inch pieces of steel wire with a 1/4 inch hook on the ends. Use them to hook behind the plates and slide them out of the chainwheel.

By the way, was it Harley D that said put kerosine in the engine and run for 30 secs to flush? Or was I dreaming...(if it was a Harley it may have been a nightmare

It was on the Norton owners club tech bit, i was reading it the other day. The belt drive sounds like an idea, but I have only had the primary chain and replaced about a 1000 miles ago so maybe later. Rgm reckon on about £200.

The hooks will be constructed when the clutch tool arrives.

Old right angle dental picks work very well to pull out clutch plates.

When removing clutch plates, put the bike on the side stand, and let gravity help you. Give the basket a few "taps" and they often drop down the splines reasonably easily, unless they are really stuck together.

bigstu said:

By the way, was it Harley D that said put kerosine in the engine and run for 30 secs to flush? Or was I dreaming...(if it was a Harley it may have been a nightmare).

Stuart

Click to expand...

Kerosene in the sump is an old way to de-sludge an engine. My father used to to this in all his vehicles every 50K or so. I've learned that it is not necessary if a modern detergent oil is used. He used to use Quaker State, leading to waxy deposits of gunk all through the engine. Draining the oil and flushing with Kerosene dissolved the wax deposits.
When I switched to Castrol, 30+ years ago, never had an issue with sludge.

I think the Pennsylvania-grade crude that Quaker State was based on had a high paraffin wax content, and refining into motor oil did not remove all the wax, leading to sludge build-up.

BillT said:

bigstu said:

By the way, was it Harley D that said put kerosine in the engine and run for 30 secs to flush? Or was I dreaming...(if it was a Harley it may have been a nightmare).

Stuart

Click to expand...

Kerosene in the sump is an old way to de-sludge an engine. My father used to to this in all his vehicles every 50K or so. I've learned that it is not necessary if a modern detergent oil is used. He used to use Quaker State, leading to waxy deposits of gunk all through the engine. Draining the oil and flushing with Kerosene dissolved the wax deposits.
When I switched to Castrol, 30+ years ago, never had an issue with sludge.

I think the Pennsylvania-grade crude that Quaker State was based on had a high paraffin wax content, and refining into motor oil did not remove all the wax, leading to sludge build-up.

Click to expand...

THe kerosene rinse is similar to using something like Sea Foam.

Right guys, the clutch tool has arrived and I have emerged from the garage after stripping it all down and cleaning the clutch in petrol. It was covered in oil and as I had put a bowl under the primary chaincase to catch the oil (a stainless one from the kitchen, schush!) I thought i would measure how much oil there was in there- 1 1/4 pints (UK) or 25 fluid oz according to the measuring jug (also now cleaned and back int he kitchen as if it had never been away).
My Haynes manual and the service notes both agree on 7 fl oz to go in which seems a big difference!
Could it just be the bike shop that last looked at it refilled it with too much, when they replaced the primary chain or could it be getting there through some other means. It would seem that this is my problem causing the slippage in the first place?
Lastly, the bike engages gear ok and I rode it up the road, but it is blowing a gale and poring down here at the moment so haven't tested it fully yet, but it now leaks oil-bugger. Used a new gasket but will have to strip it again and apply some sealant,gasket stuff- any suggestions?
Lastly, one of the guys in the local club suggested a mono grade oil to go in there, the books both suggest Castrol GTX (or equiv), what say you?

hi mc,i beleive oil can migrate down the clutch pushrod and through the crank oil seal but yours seems excessive, sounds like it was overfilled

mcmarvelous said:

My Haynes manual and the service notes both agree on 7 fl oz to go in which seems a big difference!

Could it just be the bike shop that last looked at it refilled it with too much, when they replaced the primary chain or could it be getting there through some other means. It would seem that this is my problem causing the slippage in the first place?

Click to expand...

Possible reasons?

1. It was overfilled?
2. Engine oil has leaked past the primary seal, or leaked through the threads of the inner chaincase to crankcase bolts if the sump was left full of oil for long enough?
3. Less likely but small amounts of gear oil can find its way through the pushrod tunnel of the mainshaft (as Chris said), and gear oil will contaminate the plates causing both slip and/or drag? There is a pushrod seal conversion available to stop it happening.

mcmarvelous said:

Lastly, one of the guys in the local club suggested a mono grade oil to go in there, the books both suggest Castrol GTX (or equiv), what say you?

Click to expand...

You can use engine oil, or many owners now prefer to use ATF in the primary case (I use 10w/40 in my MkIII's primary as it seems to suit the auto chain tensioner better than ATF).

Just be aware that modern UK "GTX" isn't the same stuff that it used to be! http://www.castrol.com/castrol/sectiong ... Id=7027413

As it is now only available in 15w/40 or 10w/40 grade, and is no longer a 20w/50 oil, so I don't suggest that you use it in your engine!

Yup,

I've not only seen the migration of gearbox oil but seems like I've heard of folks firing up a wet sumped bike and filling the primary.

What happened to me, after my first long, high speed, run, was the crank seal in the primary case behind the rotor came loose.

Symptoms were the clutch would slip a little when engaged, and drag when disengaged. I managed to ride it home and checked it out the next day. I found the primary had about a pint and a half of oil in it. Investigation revealed the crank oil seal had popped loose. Due to the proximity of the rotor, it can only pop out a little bit, but enough for engine oil to weep into the primary.

Disassembly of the primary drive, clean the clutch pack, remove the rotor, replace the seal (this time with loctite), and replace the oil with 7 ounces of ATF type F.

5000 miles and counting since this with no further issues. I like the ATF because you can tell if engine oil has leaked into the primary, as it will turn the red ATF brown/black.

Yep,

That why I have ATF in there as well as it is good for seals.