Oil seals for Joe Hunt magneto behind cylinders

Some Commando owners set up a magneto behind the cylinders (standard with many Atlas owners). I've been using a magnetos for years. I hated the Lucas mag. Love the Neodymium magnet Joe Hunt mag (easiest starting of any Nort ignition) but I have had a problem with oil leaking into the points. The only way for it to get there is through the oil seal.

Renewing the seal didn't help. Then I noticed that the Hunt magnetos came with the seal installed backwards - So I installed the seal with the spring facing the oil side. It seemed impossible that it should still leak and maybe this isn't a problem for others. With an air pressure test it show no leaks - but normal riding oiled the points. Finally I got fed up and installed a DOUBLE LIPPED seal.

The seal is 15x35x7 #00607683 (motion ind) dual lip.

Then I went overboard and installed an aluminum collar (with loctite) and a 2nd seal 14x24x6. This seal can be a single lip because it rides on a tapered shaft. The 2nd seal probably isn't necessary but I went for it anyway.

I also cleaned the points with diamond sandpaper abrasive. It has a PSA adhesive so I folded it over on itself (back to back) and used it like a file to clean the points and nothing has ever worked so well. Sanding them down helped to align them and I think that also helped the performance.

Now the motor NEVER misses or farts and revves cleanly as high as I want to take it.










There are two other leaks you should know about. Joe Hunts come without sealer between the mag body and the adapter plate and sure as hell - oil leaks behind the cases there - a little sealer makes it all good.

But its not over. The four recessed conical screws enable oil to leak past the gasket. So 1/16" thick silicon rubber plugs cut with a .530" ID punch (sharpened KS brass tubing) are pressed by hand into the recesses and FINALLY - no more annoying mag leaks.



A fiberglass reinforced silicone gasket finishes the job. It may all seem like a big PIA but I love a Norton that is completely oil tight and this is the kind of detail that it takes to get there.



The rubber plugs aren't necessary with a Lucas mag but you might not be riding much with a Lucas anyway - more like pushing it up and down the street building up your cardiovascular system.

We havnt had any issues with Morris mags leaking. I left Hunt in disgust years ago after they defrauded my friend and I.

I think I gave you the full story some years ago Jim

johnm

Morris doesn't offer both the side mount and the rear mount for Norton. They do make the retard lever which is very cool and works on the side mount Commando for starting. I think they offer that MRA kit for the Hunt as well. From the pics I'm not sure if they have the seal on the right way either. But if it doesn't leak then it doesn't matter.

And yes I've heard the stories and I believe you. I could talk about it but I'm trying to solve problems rather than remember bad blood.

It seems like you would still need the rubber plugs because the recess of two of the countersunk screws runs all the way out to the edge of the triangular gasket.

Hi. I use a rear mount Morris on my 500 Dominator race bike and Morris have been very good working with us for mags for racing Velos. All rear mounted. It’s just a matter of making the correct mounting piece.

From memory I think I just filled those holes with high tempt red RTV but it was a while back now. The Hunt mag filling with oil was the least of our problems. The undersized machined shafts which had been needle punch ed so the bearing would have an interference fit was a more fundamental problem among others!!

I've had problems with Morris parts as well. Both Morris and JH have had to make corrections. So I'm not partial to one or the other. But they both seem to have tightened up their s**t. Neither brand supplies their mag with any special kind of seal (not even a dual lip). Weird things happen when riding hard in excruciating 105 deg Fresno temps. It took something extra to fix the problem and I made this post in case someone else has the same issue and needs the same solution.

I have had no problems with my side mount JH and have had no problems with dealing with JH when buying parts off them when needed.

Ashley

Lucky man. If they had been in NZ we would have taken them to small claims court. I have the photos and several people able to be witnesses

johnm said:

Lucky man. If they had been in NZ we would have taken them to small claims court. I have the photos and several people able to be witnesses

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One of the things they did was under machine a shaft so the bearing was loose on the shaft. Then they needle punched the shaft to increase the interference so the bearing would fit again. Brand new mag bought directly from Hunt. That’s not an error. That is purposeful deceit and shocking engineering practice.

Again I have photos and witnesses so if they want to challenge me bring it on !!!

Johnm

Which side of the shaft had the center punch for the bearing? The sprocket side or the points side? What years did you buy the mags you had problems with? I didn't notice any loose play between the shaft and the bearing on mine but I may take it apart YET AGAIN to check if it was loose enough to wobble and cause an oil leak at the seal.

I had a couple side mounts that were machined off center so the hex fitting was not aligned and was subject to excessive wear - I had to recall a couple mags from customers and make them right.

Hi Jim

I’m travelling for work so away from my computer. This was in the early 2000s when they were first changing to earth magnets. The rotor was a screwed together collection of pieces which basically fell apart.

The details are on my computer so I will get them when I return home.

John

The rotor is redesigned and simple now. They did have a short run of rotors that had too much magnetic power (four large magnets) and were overheating the plastic points arm (around 2011). The correct setup is two large and two small magnets.

I checked mine and the bearing is tight on the shaft. I bought it in 2009 and have been using it ever since. It has worked very well and there are no mistakes in the machining. The only thing has been the oil leak past the seal. It looks like a good seal with a spring - but I went to a double lip seal and flipped it so the spring faces the oil. I told them about which way the seal spring should face and added a 2nd seal for good measure.

Re; “ They did have a short run of rotors that had too much magnetic power”

Is that possible?????

Bernhard said:

Re; “ They did have a short run of rotors that had too much magnetic power”

Is that possible?????

Click to expand...

Yes - the points could overheat and melt the plastic points arm. They only made a few before they corrected it.

The new neodymium magnets work so well that my bike usually starts 1/2 way through the 1st kick. Plenty of spark.

This is a record of my experience with 2 Jo Hunt mags bought directly from Hunt in the USA around 2002. Yes it was years ago but as well as producing and selling a poor product they abused us on the phone and told us we were ignorant. Every company can screw up. Its how they fix it that counts. And Hunt did not fix it. They just abused us. This has been posted on the Britbike site about 15 years ago.

Quote

" I use a mag on my 500 Dommie used in classic racing in New Zealand. Nearly all of the race bikes use mags.

Hunt magnetos.

The first thing to say is that in the past say the 1980s and earlier these mags were wonderful. The guys who use Hunt mags made in this time are winning our races all the time. They are really excellent.If you look inside they are very very very similar to old Fairbanks Morse mags -in fact the parts must have come out of the Fairbanks Morse factory. Those mags were used on farm vehicles, catapilar tractors etc etc. Which means you can get some parts from your local friendly tractor dealer.

However I dont think Fairbanks Morse exist any more and I dont think they are making parts.

Because we were tired of repairing old Lucas mags and having them fail without warning in about 2002 a friend and I both bought new twin mags from Hunt. My friend races a Velo and wanted to twin plug it and I used mine on my Dommie. These mags have rare earth magnets and unlike the older Hunt mags the rotor is made up of several pieces screwed together. Previous the parts were cast together in aluminium.

These mags have been a real disappointment and in one year we had the following problems:

The timing was out between cylinders on both mags by 3 or so degrees. We asked Hunt and they said they had no problems with mags they checked. Latter we found the cam presses into the aluminium carrier for the magnets on the rotor. Depending on the alignment and machining interference you can sometimes get a perfect fit but often it will not be. We fixed this by stoning the cam. When Hunt said their cams were fine we set the mag on a bench and checked the cam with a dial guage and degree wheel. The cams were definitely off centre.

On one mag the bearing at the points end was loose in the housing and the rotor could be moved up and down.

The oil seal on one mag failed and oil filled the mag body.

Both of us had our timing slip several times.In 70 years of riding and racing between us we had each slipped a mag once. (When we were about 17 years old.)

Now it was happening every race ! We both cut key ways on the rotor shaft and sprocket so it couldn't slip but again the timing went proving something was moving inside the mag.

A condenser failed on one mag.

A coil failed on the other mag. This was latter tested by an aircraft registered magneto rebuilder who found it breaking down above 6000 rpm engine speed.

Finally the rotor shaft snapped on the mag on the Velo. When we looked at it we found the shaft was made of three parts. It had snapped where two pieces screwed together. We also think this was the reason the timing was moving. On a Norton or Velo the mag rotates in the direction to undo this thread which is loctited but very small in diameter (about 1/4 or 3/8
diameter)

When we pulled one mag down and removed the bearings we found the shaft had been machined undersize and the surface had been peaned with a needle punch to get enough interference fit for the bearing to stay in place.

For me this was the end of my patience with Hunt. Remember these were brand new mags bought directly from them in California. To needle punch a shaft to get the bearing to fit on a brand new mag is disgraceful.

Hunts response to these issues was that they had never had problems like this before. The snapped shaft was due to us tightening the sprocket nut too hard and that to send the mags back to them for inspection.

The guy who tightened that sprocket is not a kid. Bikes he built have won NZ titles. He has had World Road Race champions complement him on his machine performance. He is currently working on a new project with ex members of the Brittan team. (Added in 2019 - he has subsequently build a DOHC Velo 350 which in 2018 lapped the IOM in the Manx at 97 mph - the fastest Velo lap ever we think)

We chose not to go back to Hunt. It would have been a waste of time and money.

My mate made a new rotor for his mag using his own design. This mag has now run 4 seasons about 60 races with no problem. Previously it had failed 6 races in a row.

I'm not an engineer so I got Morris mags to make a rotor for me. http://www.morrismagneto.com

They do not make a mag specifically for Nortons but they made a rotor for me which fitted into the Hunt body. One issue is that the taper on their rotor is exactly the same as a Hunt or Lucas mag but about 3 mm shorter and therefore the standard sprocket does not fit very well. They asked me to update their CAD drawing so I am sure they could alter this . They also use a
different thread on the sprocket on than on the Hunt or Lucas mag.

(Added in 2019 - this Morris mag upgrade went on to run over 120 races without a single issue. Twice getting second in the NZ Classic Senior TT and winning several NZ club championships. With the Hunt mag I couldn't get it to finish a single race)

Morris Mags have coils and other spares.

So unless Hunt have changed their mag rotor design again since 2002 the my recommendation if you want a new mag is to go with Morris. (Added in 2019 - they have changed their rotor design. It now looks like the Morris one. But they were happy to use and abuse us with the earlier rubbish design and that tells me what sort of company they are)

Or else find an old Hunt mag which are excellent.

Also note. Morris make mags for V Twins (Harleys). For the Norton twin firing 180 deg apart on the mag they had to recast the rotor to match the parallel twin points openning. You cannot just use a V twin rotor because the firing angle is different. So if you buy one of their rotors make sure they know what you are using it on. "

End quote

Ok so it was 2002 and now they seem to have improved the product and clean up their act. But we wasted over $1000 on them and got verbally abused on the phone when we called them.

Australians have some extremely good descriptive words for what might be done to companies like Hunt. But I cannot put it on a forum. And if Hunt want to challenge me I'm very happy to see them in court. I still have the photos and witnesses. Bring it on.

The thing that really got me really mad was the under machined shaft with the peaning to get the bearing to fit. That's not a design error or faulty assembly. That pure straight up deceit.

You are never going to get things straight with Hunt - that's obvious - too much bad blood. Unfortunately there aren't many choices - Hunt or Pal. Morris doesn't make one for the Commando. I don't know anything about the Pal. Does anyone? I think Pal is finished.

A lot of things can change since 2002, I ran a early JH 2 rare earth maggie on my 81 Triumph for over 9 years without any problems with it the only thing I had to do is remover the cover every few weeks to lube the bearing, it didn't have sealed bearings in it, never changed the points in it, only cleaned the points with metho, I clocked up a lot of miles on that bike and it started first kick everytime.
When they brought out a 4 rare earth maggie for the Commando motor I didn't hesitate to get one, I brought mine from Lowbrows as it was $20 cheaper than from JH, as for parts I have brought a front cover and tune up kit from JH, I damaged the front cover and condenser from a lay down and was cheaper to buy the tune up kit than just condenser, the kit comes with new points, condenser and plug leads, so far have only used the condenser as the orginal one got crushed in the lay down, less than 9 days to get shipped from the US.
Like I have said a lot of things may have changed since 2002 better quility control, better machining, better people to deal with, sealed bearings lol, my mate runs a JH on his old Triumph and have ordered parts for him through JH and as I say have had no problems at all dealing with them and always quick response with emails to any questions and fast deliveries to Australia.
I can understand your anger and frustration but maybe things have changed and got rid of the bad addtude problems they may have had all those years ago, I for one proudly like showing off my JH hanging off the side of my Norton, to me its a peice of art of simplity for such a hot spark.

Ashley

Yes it was a long time ago and it doesn’t keep me up at night. ;-)

I only bring it up when Hunts name comes up.

My experience with Morris was all good and we have kept in with them over the years. They have built one offs for us for DOHC racing Velos and other projects. They sell a larger condenser which is much more reliable under continuous racing conditions.

jseng1 said:

You are never going to get things straight with Hunt - that's obvious - too much bad blood. Unfortunately there aren't many choices - Hunt or Pal. Morris doesn't make one for the Commando. I don't know anything about the Pal. Does anyone? I think Pal is finished.

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https://shop.morrismagneto.com/products/tpl-replaces-lucas

We use this on Norton engines pre Commando. Also modified for twin plugged Velos etc.

Its about who you want to talk to and who you learn to avoid talking to. When the wrong person answers the phone - ask for the right person or call back later. I've learned who is helpful and who is to be avoided when making calls to various vendors in this business. It saves a lot of aggravation.