Metal in Primary Chaincase Oil - stumped

Hey everyone, I'm sort of stumped with an issue I just discovered in my primary case and hopefully a discussion can help me find the cause of it.

A little background...

I just had my inner primary off to replace the felt seal, mainshaft seal and spacer at the gearbox, as well as to replace the inner clutch hub due to some heavy notching. Everything went back together fine and I didn't have any issues. My stator seemed to have an air gap tight spot of about 0.007" in the 1 o'clock position but was approximately 8-10 thousands in all other areas. Replacing the stator studs showed no change in gap or position of this "tight" spot (its all tight if you ask me). This gave me the assumption that the stator was causing the discrepancy and crank runout was OK. I decided to run it for a few miles with the tight spot of 0.007-0.008" to see how it faired. I filled the primary with ATF type F.

After riding a few miles and coming home I noticed I had a ATF leak from the primary. Fast forward a couple days later, tonight, and I put the bike up on the lift to try and get a better seal around the primary. When I dropped the ATF I noticed black spots in the oil. Had this been regular motor oil I may have not noticed. At first I thought it was burnt ATF but upon closer inspection saw that it was magnetic. I didn't see any noticeable wear on anything. I removed the stator and rotor to inspect near the engine sprocket. Nothing out of the ordinary.

However, the stator sort of looks like its deteriorating. Voids were noticed in the stator insulation (all around the inner diameter in various locations, not just the air gap tight spot). They may have been there for some time and were just noticed now. who knows. Like I said, Im not really sure what would be causing this. Any input would be greatly appreciated. I'm wondering if replacing the stator would eliminate the problem


ATF with metallic fuzz


Has a paste-like consistency. Almost like anti-seize.


Found a good bit of it behind the stator holes.


Voids and cracking in the stator


More stator voids

I forgot to mention that there is not any noticeable wear or markings on the rotor from rubbing against the stator.

Patrick M said:

I just had my inner primary off to replace the felt seal, mainshaft seal and spacer at the gearbox,

Click to expand...

Then I think that would be the first place I'd look.

If you were using motor oil and now switched to ATF, the higher detergent ATF is cleaning the components and interior of your primary.

You report the stuff in the ATF is magnetic. The stator is iron (magnetic) and the rotor magnets are possible sources of magnetic chaff. You report the stator insulation is deteriorating, but such insulation is non-magnetic.

The stuff in the pics looks like aluminum (the anti-seize like stuff you report). This could come from chain slap against the stator MOUNTS. Look for chain grooves on the mounts.

The factory spec on rotor-stator clearance is 0.005". You report 0.007 to 0.010. This clearance could be the result of rotor contact with the stator that has worn down the rotor magnets (magnetic) and the rotor magnet encasement (aluminum), producing both a magnetic, and non-magnetic aluminum paste. Such rotor-stator contact occurs when the main bearing or the bearing housing is bad. You report no crank runout, but the rotor stator contact will occur ONLY under a load.

Hope this helps, and also hope it is not a main bearing problem.

If it is a main bearing fault, replacing the stator is not going to solve anything.

Slick

Chain, sprockets, steel clutch plates, clutch hub splines

texasSlick said:

The factory spec on rotor-stator clearance is 0.005".

Click to expand...

http://www.classicbike.biz/Norton/Repai ... mmando.pdf
According to the factory manual, section C34, 26: "Check the gap between stator and rotor which must give a minimum air gap of 0.008 in. to 0.010 in."

Personally, I wouldn't want it less than 0.008".

Thanks for the replies. I will check the stator posts for any possible wear from the chain. I've had the Norton for only 4 or 5 months so excuse any dumb questions about it's nuances.

LAB, I mentioned removing the inner primary to replace the gearbox mainshaft seal and spacer ring as well as the felt seal on the inner primary. There's no gear oil intrusion nor any indication that the felt seal is failing. The area surrounding the clutch basket and the backside of the inner primary are completely clean. Though removing the inner primary again may be in my future as I try to pin the problem down.

Slick, your comment about a main bearing problem definitely made me lose some sleep. I suppose there's real no way for me to inspect them without a total tear down.

I concur with the above notes concerning rotor-stator clearances all around. You have to get the gap even all around using a feeler gauge to check . A trick :wink: is to use a strip of plastic milk jug material temporarily wrapped about the rotor then tighten down the stator ,then pull out the strip ,then do a final feeler gauge check. Also with the sparkplugs out kick over the motor and check clearances all around again. I doubt the main bearing is going south.

I've found that adjustment of the gap for uniformity is a issue. Having replaced the rotor studs with new ones, and still finding the same discrepancy of the gap (<0.007") in the same exact location makes me wonder if the stator is not concentric with the rotor. In other words, It seems that the stator may be the slightest bit out-of-round.

Thanks for the tip, Torontonian. I'll give that a try to see if I can get a more consistent gap all around.

Sometimes overlooked is the need to check how the inner primary sits against the central mounting stud. It may be necessary to shim it so it doesn't distort when the outer cover is tightened down. This can lead to leaks and general distortion.

Shimming the backside of the clutch basket properly is also a MUST.

Chain misalignment contributes to any number of woes.

I second the proper chainCASE alignment which leads to many a cracked inner case (as does over-tightening the outer nut)'

L.A.B. said:

texasSlick said:

The factory spec on rotor-stator clearance is 0.005".

Click to expand...

http://www.classicbike.biz/Norton/Repai ... mmando.pdf
According to the factory manual, section C34, 26: "Check the gap between stator and rotor which must give a minimum air gap of 0.008 in. to 0.010 in."

Personally, I wouldn't want it less than 0.008".

Click to expand...

My information comes from a Norton Factory Publication. While it is a pre-Commando manual, I would think it appropriate for the Commando. The manual calls for 0.005" minimum which of coarse allows for more clearance. On my Atlas, a 0.005" gauge is snug all around.

One way, without a tear down, to check if it is indeed the rotor making contact with the stator that is producing the "anti-seize" looking slurry, is to paint the stator poles with machinists blue. Put the engine under load, then check to see if the blue has been taken off. I hope not, but then you must find where the anti-seize stuff is coming from.

Slick

In my limited experience since the very early 1960s I have found the gap between the stator and rotor of my genuine made in the UK Lucas alternators to be 0.008 - 0.010 inch and that there is enough clearance in the stator mounting holes so that with the nuts 'less tight' and with a big hide hammer being applied to the outer edge of the stator an equal gap all round is usually obtained. With later encapsulated stators (Made in China / India ????) I have noticed the steel core laminations are sometimes not as well aligned with the odd lamination slightly proud in the mounting holes and the application of a round file helps so as to obtain the stator movement required ......... Also the encapsulation often requires to be errr....modified as the fixing nuts are fouling it plus when fitting belt drive systems the encapsulation raised outer edges on the alternators now available can foul Triumph and BSA unit construction motor chain case outers and require a bit of a shave!!.

triumph2 said:

Sometimes overlooked is the need to check how the inner primary sits against the central mounting stud. It may be necessary to shim it so it doesn't distort when the outer cover is tightened down. This can lead to leaks and general distortion.

Click to expand...

+1

It may be necessary to shim the central fixing stud, but is ALWAYS necessary to check it; probably the larges single source of a leaking primary chain case.

Also, there is a surprising amount of "wiggle" room amongst three (pre Mk3) 1/4-20 hex bolts that fasten the inner primary to the engine and the central fixing stud. The hide hammer should be the last resort, but if applied correctly can be very satisfying...

I appreciate the replies. I'm with you on getting an idea of where this fine paste in the oil is coming from, Slick.

I pulled the primary apart last night, and again, nothing seemed out of the ordinary. Primary chain alignment is OK. My inner case has been shimmed prior to me getting the bike, however, I'm going to inspect it further. There's a possibility it may not be sitting outboard further enough. I see a little bit of drive chain contact on the rear of the inner. However, this is OLD damage that may have been mitigated by the previous owner. Waiting on some parts from OldBritts, including some shims.

I'm hoping that adjustment of the inner primary case will possibly bring my stator and rotor gap more consistent. I'll try the machinist's blue as well. Button it all up and take it from there. Someone mentioned the detergents in the ATF cleaning out the internals of both cases, I think there's a lotmore paste than I would expect that type of cleaning to show. I had cleaned it pretty thoroughly before my previous reassembly. I also don't see the need to be hammering on my 40 year old stator just yet.

My clutch ( with Barnett plates) generates the grey paste, never to see if it's magnetic. I wrote it off as the alloy host plates peening over on the hub and giving up some material.