Mk III Clutch Drag

I was hesitant to Bogart the thread on the Mk III jumping out of first, but there was a lot of good discussion going on there that led me to ask some questions. Last Sunday I wrapped up the "wake-up" from a 13 year slumber for my Mk III and was able to take it out for a 6-8 mile test ride. Generally, all systems performed well with the exception of neutral selection due to clutch drag.

A little background is in order. One area I looked at while getting the bike roadworthy was the clutch. I ordered & installed a pushrod seal, and while it was apart I removed the clutch pack for inspection/cleaning. The odometer shows only 12k miles, but the OEM sintered bronze plates had been replaced with an unidentified aftermarket set of (5) friction plates. The pack came out as one piece; all the friction plates & plain steel plates were stuck together, requiring me to seperate them from each other with a screwdriver. This seemed strange to me because I recalled during my initial inspection of the machine last November that I had pulled in the clutch lever and broke the plates free with the kick starter. I cleaned each plate with a simple green type of cleaner & hot water, and cleaned up the clutch basket/hub spic & span with carb cleaner. The hub looked nice & smooth so all went back together as it was, and the chaincase was serviced with 20-50 motor oil as per the riders manual. This work was done about 3 weeks ago; my test ride Sunday was the first time it had been put into service. When I tried putting the bike into first gear to pull out of the driveway, the plates were stuck & the engine stalled, but they easily broke free by pulling in the clutch lever and kicking it through. During the ride I adjusted the clutch cable a few times trying to improve the neutral selection. At first it seemed like the adjustment would help, but at the next stop light the drag was back. Eventually all the slack was taken up & the clutch drag had come back.

In a discussion with a pal of mine (who works almost exclusively on Nortons) he asked me what type of clutch plates were fitted, to which I replied I was not sure. I have Sureflex plates in my Fastback, but the ones in the Mk III didn't look the same. They are made with an aluminum plate & have 4 segments of a soft cork-like material per side, each covering one quarter of the surface area around the circumfrence. The glue used to hold the segments onto the plate looked like it was applied by dribbling a thin stream on the plate by hand from a cup, not in a circular motion but rater just back and forth across the surface. Envision how chefs dress up desert plates with chocolate sauce & you'll get the idea. This last detail caused my pal to positively identify them as NOT being Barnet plates, but rather from a third supplier who's name he couldn't remember; he regarded these plates as being "real good". I'm beginning to think I don't agree with him on this point.

Since the the initial run on Sunday I have not been able to squeeze in another ride. But I have checked and found the plates stuck together using the "clutch in with kickstart" method.

Now the questions:

1) Could anyone here identify these plates by the description above?

2) Should I try ATF (F-type) prior to replacing the mystery friction plates?

3) Where can I source a set of Sureflex plates?

Thanks for your patience,

1) Sorry haven't a clue, perhaps very early 750?

2) Some have found the auto chain tensioner on the Mk3 won't work with ATF so you might be better off sticking (no pun intended) with SAE30.

3) RGM have plenty of Surflex plates.

I'm not sure if this is relavent but here goes I have a belt drive clutch with the sintered bronze and steel plates,last summer I fitted a clutch push rod seal to prevent a small amount of oil seeping from the gearbox, after fitting the seal the clutch would drag all the time I tried to adjust the clutch and couldn't get the correct adjustment..... my solution I threw the seal in the bin and refitted the clutch adjusted it correctly and no more clutch drag.....I have also been advise to pull in the clutch and kick the bike over to free the clutch before starting.I also had the clutch hanging on and not disengaging when stopping.....not funny in traffic

not-ron said:

....I have also been advise to pull in the clutch and kick the bike over to free the clutch before starting.

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That shouldn't really be necessary with the bronze plates as they don't seem to stick like the fibre clutch plates do. My bronze plate clutch has never stuck, no matter how long it has been left.

Several thoughts...

Never had bronze plates...but starting without a kick-through is a lazy habit easy to change...do it all the time and it becomes second nature....

Strange clutch plates...5...aluminum with messy gluing. After market clutch, guaranteed in 1977 to not slip...never have had a problem with them...got a good 70 thousand on them...clean with brake cleaner spray and blow off with compressor...use 5-15w oil. I wouldn't change them out. The dealer who sold them to me though...warned me back then to not do wheelies, pop clutch etc as he had two customers who had blown trannys because the clutch held too well without slippage. Never had problems though, but I have never been into poping clutches. All I know...it has always held, and saved me a few times....unlike the old fibre things which started to slip every six months.

Clutch seal..if it was causing the clutch to drag...then I think some other problem was already there...like cleaning the clutch plates maybe or adjusting the center nut correctly....sticky cable?? It's only an "O" ring for Gods sake. But without the seal in...soon she will drag again....LOL. That tranny oil does really get up the inside of the shaft and muck up the clutch...Get the seal back out of the dustbin for later...when you figure out you screwed up by tossing it in there. I installed mine last year...bit of fine tuning on fit...but well worth it...first time in thiry years, I can kick through at start up, with out breaking my foot, clutch does NOT stick and it shifts like butter. I'm happy with mine...Thanks Dyno Dave!!!

I had a problem with my clutch dragging when I piled on the power, only to find that someone before me had put triumph friction plates in my clutch.

Change to bronze - no problem since

I use bronze also, never sticks.

In addition to thoroughly cleaning the cork or fiber clutch plates, I sandblast both sides of each of the steel plates prior to reinstallation. This helps prevent sticking for some time until they get glazed over again.

Glazing is good for donuts, not for clutch plate.

Blasting must make the plates work like sandpaper...bet they don't slip much but not sure the other plates like it....or last very long....???

Sticking wouldn't be a problem if the tranny oil wasn't there to cause it...or?

What does "piling on the power" have to do with clutch drag? Typo maybe?

You might think that sandblasting would make the plates too rough, but the plates a made of quite hard material, such that blasting only cleans them up nicely removing that shiny glazed finish. Results are no clutch slippage (provided everything else is adjusted correctly), no clutch grabbing, and less tendency to stick. Try it, you'll like it.

I see your theory...but I will reserve judgement as to whether it is better for me...never had a bit of slip with those nice after-market plates I have had for 30 years...with the tranny shaft seal from Dyno Dave, they no longer stick, and grabing...not since I put the seal in......not had to do the normal twice a year clutch clean yet and you know how it is...old dogs new tricks. Why change if what you got works... If I was a habitual "change for the sake of changing" type...the bike would have been sold in 75 and the wife....:lol:
And I do think blasting would make my nice old cork plates wear a bit faster than they have to. So...I will stick to the old glazed things and let you now if they still are ok in another thirty years. Have we got a Date? :wink:

Checked in with my pal last night who has quite a stock pile of Commando parts. He gave me a box of clutch plates - literally 35 lbs of the things - to go through and use whatever I want. In the box we found another set of the mystery friction plates, altough his set is not gummy as the set I found in my Mk III. He changed them out because he thought they were getting a bit thin, but confirmed that he had good luck with them. I printed out the data that Dyno Dave has posted on his website with respect to clutch plate thichnesses & stack-up height. His thickness dimension for the 850 friction plates is .125"; my pal's mystery plates measured .124". There were also numerous bronze plates in the box, all measuring about the same at .123" - .124". I'm a bit hesatant to run the bronze plates for fear that they will slip - I'll figure out what I will do once I take my clutch apart again & do a better inspection.

Thanks for all your responses! I'll keep you posted.

With reference to clutch drag after fitting a pushrod seal.

I fitted a longer pushrod, in my case 5mm longer the thickness of the seal I made up. I forgot I had to do that.

Is this the reason why others are getting clutch drag? If so a short length of 6mm dia silver steel bar is only a couple of quid, cut it and face it to length. Heat the tips cherry red and quench in salty water, or, RGM will make you one to suit.
Cash

Hey hewho...

My years of experience has taught me to never argue with tested and proven success, but to listen and learn. Maybe I'll try it your way

Later dude (30 years) :lol:

Good advise for both of us...actually.

On another angle to the question....the old bike I have...1941....small (2.5 PS) but a real rush at a top end of 35 MPH.....has cork plates too ..the neat old hand-made type where some kid took a wine bottle cork and sliced it into several pieces and glued them on the plate. evidently not that bad an idea, as they seem ot work just fine still and they must be in there for a while...since maybe the early fifties at least. Still gets it up the mountain.... and that's the main point...or?
Peace!

Cash wrote;

I fitted a longer pushrod, in my case 5mm longer the thickness of the seal I made up. I forgot I had to do that.

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Cash this is the first time I've heard of this, and I have fitted a push rod seal to my MK3. I don't have drag anymore, but selecting neutral at standstill is a bit hit and miss.

Whats puzzling me is why you would have to put a longer push rod in? If the rod clears the seal, then surely the geometry remains satisfactory left as original. What advantage does the longer push rod give? If there is an advantage, I'll get a longer push rod for mine.

MK III Sticky Clutch Follow-Up

Last night I disassembled the sticky clutch on my Mk III. As I was pulling out the plates I noticed that the first few outboard plates were free from each other. But the deeper I went, the more they were stuck together. Recall that I had broken the clutch free numerous times by pulling in the lever & kicking it through. I presume that these friction plates (bike out of service since '93) have absorbed some oil and now just have a tendancy to stick. The inside of the basket had a few drops of oil present, and only a slight spotty film of oil was present between the plain & friction plates. The splines in both the basket and on the hup were pretty much dry and without any notches.

After visual inspection I took some measurements. Per Dyno Dave's data the friction plates should be .125" and the plain plates .080". All of my friction plates were .004" - .005" thinner than the spec, but the plain steel plates were all within +.002", -.000". The pressure plate was about .006" thicker than his spec, so all in all the clutch pack measured about nominal.

I decided to go back to the OEM sintered bronze friction plates. I was easily able to locate 5 plates in my buddy's stash that measured nominal, showed negligable wear on the splines, and still had the factory grinding marks in the friction area. I cleaned them up with simple green, steel wool, and hot water. After a dry reassembly I checked the action - absolutely no sticking while kicking through and a totally foo foo effort required at the lever, mostly due to the new cable that I installed at the same time. I just hope I don't experience any slipping!

Prior to reinstalling the primary cover, I decided to inspect the gear shift shaft seal. As you may have already guessed, it was in sad shape and may have been the source of a primary oil leak I noticed after the first ride. A standard lip seal, dimensions cast into the seal it self; simple enough, eh? I don't think so! First off, the parts manual doesn't show the seal, so no part number. The Andover site shows the same exploded view and lists no seal. Calling three bearing houses locally revealed no listing for those dimensions; a 17 x 25 x 4 is available (special order) but not the 17 x 25 x 3. Had the exact same experience trying to locate a replacement seal for the electric starter shaft. Old Britts had a seal for the starter, but their web page says they are closed until Monday so no joy there. A fourth supply house found a listing for a 17 x 25 x 3 and has ordered it in for me; they expect delivery late next week.

While I was poking around inside the primary (looking for the source of the leak) I noticed a rather loose fit of the gear shift cross shaft to the seal located in the inner primary case. I can see the seal's ID is loose on the shaft, but feeling around the shaft on the inboard side of the inner case revealed no great leaks past the seal. Is this a double seal? Can it be removed without dismantling the complete primary drive & removing the inner case?

Thanks for your time & patience,

Re: MK III Sticky Clutch Follow-Up

jumpjg said:

First off, the parts manual doesn't show the seal, so no part number. The Andover site shows the same exploded view and lists no seal.

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Isn't the seal you need the one in the Andover parts lists shown here (if you mean the seal for the "shaft-gear pedal (=066810)" in the outer cover (item marked *10*)?: http://www.bsa-regal.co.uk/norton/parts ... 10&Part=10
and is also shown in the parts book?

If there is any notiecable play in the gear pedal shaft and bush I would consider replacing the bush (BUSH - PEDAL SHAFT Part Number: 066189) as well as the seal, and also the cross shaft bush (BUSH - G/C CROSS-SHAFT Part Number: 065185) as it should help to eliminate some of the gear pedal play.

Re: MK III Sticky Clutch Follow-Up

L.A.B. wrote...
"Isn't the seal you need the one in the Andover parts lists shown here...."

Yes, you're right! I was looking at the next sheet that shows the gear linkage. I'll have to look twice next time before I open up my yap. Thanks for the heads-up!

Would you have any insight into the construction and removal/installation of the oil seal, P.N. 065183, item 1 on the following sheet (gear linkage) of the parts book?

Thanks for the help!

Sorry I can't remember, but I don't think there should be much of a problem removing it with the inner cover in place.