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timing gear location #718948
12/16/17 12:40 am
12/16/17 12:40 am
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Posts: 630
SEATTLE WA
S
SEATTLE GS Offline OP
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SEATTLE WA
If you were to place a straight edge across the timing case (with the cover removed) and across the timing gear, would the gear teeth be flush with the case or inset a little bit? By how much? I have to manufacture a part so this info is important. thanks

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Re: timing gear location [Re: SEATTLE GS] #719085
12/17/17 12:02 pm
12/17/17 12:02 pm
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Bolton Lancs UK
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Andy Higham Offline
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The rear of the timing gear support plate is on the case joint face, the outer edge of the camshaft gear is 4.6mm inboard of this face


1955 BSA B31 500cc "Stargazer"
1962 Greeves 200cc "Blue Meanie"
1962/67 Greeves 350
1967 Greeves 360 Challenger
1984 Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
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Re: timing gear location [Re: SEATTLE GS] #719159
12/17/17 9:53 pm
12/17/17 9:53 pm
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Seattle .. If you are asking about the "timing gear", meaning the gear on the magneto .. Make doubly sure that a straight edge across the timing chest face clears the end of the rotary valve drive pin. Many timing covers have been gouged by this pin protruding against the face of the cover. Position the mag on the platform to insure you have clearance.
I don't doubt some of the gouges on the covers were/are caused by the @#$% ill engineered mag clamp strap method coming loose allowing the mag to move around. This can be prevented by drilling and safety wiring the head of the clamp bolt.

Adding to this discussion of the mag mount ... Fitting a 50 thou alu shim between the base of the mag and the cylinder flange will help maintain the correct gear lash when shimming the mag base by shifting the mag rearward in the case slots.
BTW, I've found the alu 'peel type' mag base shim, like the head gaskets, to be ideal when setting the gear lash. A GSr friend in Reno has had these shims made and he may have more to sell.
Make sense?

Last edited by dave - NV; 12/17/17 9:55 pm.

dave - NV
Re: timing gear location [Re: SEATTLE GS] #719278
12/18/17 8:04 pm
12/18/17 8:04 pm
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Posts: 630
SEATTLE WA
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SEATTLE GS Offline OP
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My electrical/ignition problems have been plaguing me since I bought this CB in the early 70's as a dirt bike. To make a long story much shorter, I could never keep it running for more than a day or two because I could never keep the mag gear from slipping on the magneto shaft. Yes, I did all the tricks short of replacing the magneto armature. This went on for about 30 some years until I discovered the Boyer crank triggered ignition. Problem solved in that dept. To power it I installed an Alton generator in the magdyno and was happy to gain 12V lighting. However, I could not keep the battery charged. The magdyno was always wiggling around on the platform,, the top strap has broken out some of the casting and has little hope of holding anything in place. It is for decoration only. Even in good condition it takes hours to shim the magdyno this way and that to ensure good gear mesh...then I quickly lose that in a days ride. On top of that I discovered that the Alton was causing the big fiber gear to skid on the four lobed tensioner device...I didn't discover that for years because of my reluctance to R&R the magdyno and get it set up again.
Fast forward a couple of years.....I bought a new crank and it is time to install. I want to machine a new magdyno base and BOLT it to the cases ONCE AND FOR ALL. I have the innards from an old Boyer ignition which gives me a mag shaft and two bearings, I have to make the housing and a platform for the generator. The motor is sitting in a stand so I have great access all around.
What I don't know is how deep to mesh the gears, especially the timing pinion to the driving gear in the case. I have always used a sewing needle placed between the gear teeth as a gauge. anybody know the exact measurement?

Re: timing gear location [Re: SEATTLE GS] #719289
12/18/17 9:01 pm
12/18/17 9:01 pm
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Magnetoman Online content

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Originally Posted by SEATTLE GS
anybody know the exact measurement?
Somebody who pretends he knows what he's doing claims the correct backlash is 0.007" and shows how he arrived at that figure here. Standard photocopy paper is ~0.0035" thick so if you trap a strip of paper between the pinions when you tighten down the magneto the backlash will be 0.007" after you rotate the engine to cause it to spit the paper out when you're done.

Last edited by Magnetoman; 12/18/17 10:00 pm. Reason: paper thickness
Re: timing gear location [Re: SEATTLE GS] #719343
12/19/17 3:57 am
12/19/17 3:57 am
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SEATTLE WA
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That was a good jump to a lot of good info.....

Re: timing gear location [Re: SEATTLE GS] #719344
12/19/17 4:08 am
12/19/17 4:08 am
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SEATTLE WA
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SEATTLE GS Offline OP
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that was a good jump to a lot of good info...and it shows I have a lot of company with this problem. Someone in the bike's past installed a brass oil seal holder which is somewhat permanent in the timing chest. The flange sticks out about 1/16 + on the magneto side which I have to take into account. It was also placed off center and I had to cut an eccentric ring in order to get the oil seal to fit the mag shaft correctly. I am lucky that the cases are apart so I can drill a pair of holes, probably 1/4", and tap them. The holes will have to go into the crankcase in order to get enough thread but it looks very possible. The straps will be just for looks.

Re: timing gear location [Re: SEATTLE GS] #719349
12/19/17 4:55 am
12/19/17 4:55 am
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Sure seems like a lot of expense and effort to make something work when if the expense and effort was spent on repairing the engine back to original you'd be just as well off.



Bill B...


Boomer
Re: timing gear location [Re: SEATTLE GS] #719411
12/19/17 7:55 pm
12/19/17 7:55 pm
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Magnetoman Online content

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Originally Posted by Boomer
if the expense and effort was spent on repairing the engine back to original you'd be just as well off.
+1

I won't defend BSA's design of the magneto mounting system, but it could be worse for a system that allows for interchanging Magdynos and various magnetos. That mounting system was used for the tens of thousands of singles that rolled off the assembly line at a fairly rapid rate, each with the timing having been set and the pinions reasonably meshed. The system that was good enough for BSA back then is good enough for me now.

The fore-aft position of the slots machined in the engine case ensures the pinion is set so it properly meshes with the mating gear and at the same time is centered in the oil seal, while the use of slots rather than holes allows the magneto to be moved left-right to compensate for later wear in the tapered shaft that results in the pinion moving closer to the magneto body. A strong strap then holds the magneto firmly in place so it can't move from its set position. All of this is great "in theory" (in the popular use of that term), but not quite perfect in practice. But, its defects can be dealt with.

At the risk of jinxing myself by writing the following, I haven't had the problems with this that others have had. I'm not saying others who have owned Gold Stars much longer than me are doing it wrong. I'm just saying I haven't (yet?) experienced problems despite quite a few thousand miles on the various Gold Stars. That's not to say I love fiddling with the mounting system each time I need to install a magneto, because I don't, but the system gets the job done.

Addressing the strap first, the way it comes around the back of the Magdyno on my BB does not allow the Magdyno to move backward even if the strap hadn't been properly tightened. Its metal-against-metal from where the strap is bolted to the case to where it bends around the base of the Magdyo so only if the strap somehow stretched could the Magdyno move to the back. However, there is a ~1/8" gap at the base of the Magdyno at the front that certainly would allow for fore-aft movement to let the pegs "worry" themselves into the metal at the edges of the slots if loosely clamped and left as-is. So, I inserted a ~1" high piece of 1/8" Al the width of the strap that completely fills the space between the base of the Magdyno and the strap. With this "shim" in place, even if the strap were only somewhat tightened it would be physically impossible for there to be any fore-aft movement of the magneto. Due to tolerances and differences in the body shapes of Magdynos and magnetos I have similar "shims" in gaps that are in both the front and back of the magneto bases of the DBDs that won't allow them to move fore or aft, either, irrespective of the 40 h.p. worth of vibration hammering on everything.

Turning to the fore-aft location of the magneto or Magdyno, unless the slots were machined in the wrong position at the factory they will place the shaft pretty close to the fore-after centerline of the hole in the timing case. Wear in the base or the platform area (or production tolerances) that cause the shaft to be below the up-down centerline can be easily addressed by a shim of the necessary thickness under the unit. Of course, it's much faster to write this paragraph than it is to do the work required to center the magneto, but this should be a once in a blue moon task.

Unfortunately, due to production tolerances, when you slip the pinion on you might find too little or too much backlash. The teeth mesh at a steep angle of 20o from the vertical so every 0.010" the pinions move with respect to each other changes backlash by just 0.0036". Vincent addressed an issue of the meshing of gears in their timing cases by supplying one of the pinions in over- and under-sizes. In their case the gears were on shafts inserted in machined holes so there was no other possibility for adjustment. However, BSA didn't supply magneto pinions in a range of sizes at the time, and aftermarket suppliers haven't done it for us now, so a compromise will have to be made between perfect centering of the shaft in the oil seal, and perfect backlash of 0.007".

If the pegs were an interference fit in the slots the use of shims under the body would be the only means of adjustment. If the shaft were perfectly centered in the oil seal but the backlash was, say, 0.000" it would require moving the pinions apart by 0.020" to get the backlash correct. However, the gears are at ~45o with respect to the magneto base so it actually would require raising the magneto by 1.4x this amount (1/cos45o), or 0.028". Thus the shaft would be off center in the oil seal by 0.028".(*) However, if there is some fore-aft movement possible the magneto could be raised by half this amount, 0.014", and also moved horizontally the same 0.014" to get the required 0.007" backlash, resulting in the center of the shaft being off center by only 0.020" (square root of 2 x 0.014").

So, in summary, "if the expense and effort was spent on repairing the engine back to original you'd be just as well off." Unlike a "solution" that damages the cases and that might or might not work in the end, the original BSA system will work.

(*)A Timken Seals Catalog says their Model 87 spring-loaded lip seal of the type sold for our timing chests can tolerate a shaft misalignment of as much as 0.100" at over 3500 rpm (7000 rpm engine). The catalog says it has "Aggressive shaft-to-bore misalignment capability."

Last edited by Magnetoman; 12/19/17 10:13 pm. Reason: (*)
Re: timing gear location [Re: Magnetoman] #719418
12/19/17 9:17 pm
12/19/17 9:17 pm
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Posts: 417
Cork Ireland
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chaterlea25 Offline
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Hi All
The alternator equipped B31/33 models had the top three timing cover holes drilled through the case so long screws and nuts clamped the contact breaker housing to the crankcase,
If you were machining up a "dummy" mag to mount the Alton on it could be further held by modifying as B31/33 alternator?

A useful gadget to aid lining up the mag dynamo is a valve spring top collar from a B31/33
This sits nicely into the oil seal recess and a clearance fit around the magneto shaft
eyeballing the shaft in the clearance hole is surprisingly accurate, A similarly sized "washer" could easily be made up if needed ?

The fit of the original fixed dowels in the mag base are the root of the problem
A round peg in a rectangular hole is not too clever :-(

On a couple of BSA's I have substituted magneto bodies from other models that have four threaded holes in the base
These bodies usually do not have the wear problems associated with BSA fitted mag's
I get short 3/8 x16 hex head bolts and relieve the thread a little near the head so the bolts screw in fully and the head sits tight to the base
Some careful marking out later I machine the bolt heads to the width of the slots in the crankcase, then the remainder of the bolt head is shaped
to fit the crankcase slot , (imagine an upturned woodruff key shape)
Shim gear mesh as MM's post

John

Re: timing gear location [Re: SEATTLE GS] #719434
12/19/17 11:27 pm
12/19/17 11:27 pm
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Posts: 630
SEATTLE WA
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SEATTLE GS Offline OP
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The slots in the case for the mag are well hammered. As I said before, the top strap is halfway broken out so it's ability to hold is poor. For the last couple of years I have watched the mag wiggle as I kick it over, as if the mag gear was being thrown off the mating gear. It settles down in running but definitely worrisome. I have fought this problem since I bought the bike in the early 70s and it is time to solve it while the cases are apart. I really enjoy the bike, I have made it a good runner, now to solve the magneto and charging problem. I am sure there are several ways to go about this, this is what I have come up with. I am leery of welding up the case 1/2" from the cylinder hole because of distortion, and it is right next to the crankcase seam. In 1994 Neil Keene had the motor at his place and machined the mag platform flat, it was really beaten up before. So now I have a distance different from stock. Not unsolvable but great care will be needed to get things dead on.

I have thought of using the top 3 timing case screw holes for through bolts to anchor the mag to the back of the timing side. I have a very good machinist who could true up the back of the case to the mag platform. That system would be ideal but there is very little material to machine.
Ideally I would buy new cases and that would solve a number of problems.

Re: timing gear location [Re: SEATTLE GS] #719445
12/20/17 1:57 am
12/20/17 1:57 am
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Magnetoman Online content

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Originally Posted by SEATTLE GS
As I said before, the top strap is halfway broken out so it's ability to hold is poor.
For the last couple of years I have watched the mag wiggle as I kick it over,
The slots in the case for the mag are well hammered.

machined the mag platform flat, it was really beaten up before. So now I have a distance different from stock. Not unsolvable but great care will be needed to get things dead on.
I have a very good machinist who could true up the back of the case to the mag platform. That system would be ideal but there is very little material to machine.

I am leery of welding up the case 1/2" from the cylinder hole because of distortion, and it is right next to the crankcase seam.
Taking these reordered points in order, of course the magneto wiggled when only held down by a halfway-broken strap. Which is why the slots are hammered. Although that cow is already out of the barn, in the future any component that should be rigid but that moves is cause for immediate attention.

It would be straightforward and fast to determine by how much the magneto needs to be raised because of the machined platform, and to make a spacer of the correct thickness.

A picture would help a lot, but I imagine the portion of the case for the stud that holds the front of the strap is broken. The heat from TIG is well localized. If the cases were mine I wouldn't hesitate to weld them. I'd probably bolt plates to the two surfaces just to be sure nothing could warp.

Re: timing gear location [Re: SEATTLE GS] #719452
12/20/17 4:09 am
12/20/17 4:09 am
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SEATTLE WA
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SEATTLE GS Offline OP
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I have no other Goldstars to compare to or to closely inspect.
Currently the mag gear seems to be fairly well placed but I have a question...another one. Imagine a flanged bushing pushed into the timing case mag hole from the left side, so the flange is proud of the case on the mag side, about 1/8" or slightly less and holds the mag/dyno off by that amount. I am sure it was not a stock BSA part (it is actually a seal holder) but did BSA provide a seal of some sort between the mag and case about the same thickness?
I used to have the good Goldstar book, black and white, but the dog, as a pup, chewed on it then peed on it.

Re: timing gear location [Re: SEATTLE GS] #719479
12/20/17 1:27 pm
12/20/17 1:27 pm
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Magnetoman Online content

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Originally Posted by SEATTLE GS
did BSA provide a seal of some sort between the mag and case about the same thickness?
I used to have the good Goldstar book, black and white, but the dog, as a pup, chewed on it then peed on it.
OK, you must be trolling us. Surely no reasonable person would work on a Gold Star, let alone consider making permanent modifications to it, without even a parts manual to refer to.

Re: timing gear location [Re: SEATTLE GS] #719634
12/21/17 6:06 pm
12/21/17 6:06 pm
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Kent, England
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John Alexander Offline
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Hi Seattle, you have explained why this happens yourself, your timing chest has been modified with as you say a brass seal holder. what i understand is normally the oil seal goes into a recess behind the mag pinion and it appears that your modification, which you have inherited is causing the pinion to be slightly , proud hence the pinion not staying on the magneto shaft for not longer than a day. Also crankcase magneto mounting base holes appear to be elongated which does not help. I know these holes can be re-welded professionally but i've heard that these mounting holes can be filled out with epoxy resin, with the magneto mounted till it sets, but obviously your problem is the steel modification plate
Goldie John

Re: timing gear location [Re: John Alexander] #719761
12/23/17 12:09 am
12/23/17 12:09 am
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SEATTLE WA
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SEATTLE GS Offline OP
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one possibility of the mag pinion problem is the pinion is too long andbumps up against the large nut holding the 4 lobed spring in place. I have already ground off the end of the gear to make sure there is a good fit. Still did not solve the problem. It is not a problem anymore because the ignition is driven off the crank. All I need is the gear to work somewhat and drive the generator. I gave up 10 years ago trying to make the gear stay put on the shaft. I went through three gears and two shafts, lapping, grinding, and any other possibility. Now, let it skip from time to time, I don't care. It's crank driven. I know many other people will claim to never having this problem. Good for them. I fought it for 30 some years with no luck. At one point I was so frustrated I even considered welding the gear on to the shaft.

Re: timing gear location [Re: SEATTLE GS] #719783
12/23/17 11:34 am
12/23/17 11:34 am
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John Alexander Offline
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I sympathise with your frustration, had a problem starting my Goldie when hot till i eventually adopted a different starting technique, great it's no longer a problem, enjoy the bike.
Goldie John

Re: timing gear location [Re: SEATTLE GS] #719939
12/24/17 6:44 pm
12/24/17 6:44 pm
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Elko, Nevada USA
dave - NV Offline
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Seattle .. I have no idea if this applies to your issue, but ... Some years ago I ordered up some timing chest seals for the mag shaft from a US supply house. They no longer carried the 5mm wide seal but had had 7mm widths. 'It'll be OK', wrong. The added 2mm thickness was enough to space out the mad gear enough to prevent the mag from moving back far enough for proper gear clearance.

BTW, I'm excited to find some of those 'self aligning' mag seals MM has mentioned as '59 GSs has a serious mag alignment issue that causes the mag seal to wear out quickly.

Regards the question of a 'seal' between the mag and the timing chest to prevent water/dirt from entering the @#$% magdyno.... I believe BSA included a cork spacer in their gasket set. I've found it too thick. I tried slicing one in half unsuccessfully. So I've been using a thick 'O' ring gooped into place. sheeze.

I strongly feel crank trigged ignition as Seattle has fitted is the way to go. As I've mentioned we have that set up on our GS dirt tracker running total loss. A great system design that I may fit to my current '58 GS project bike. But then you still need a dyno/alternator. OEM generator on 12V, Alton alternator? But ... bolting in a Power Dyno unit is so sensible. hmmm


dave - NV
Re: timing gear location [Re: SEATTLE GS] #720977
01/03/18 8:48 pm
01/03/18 8:48 pm
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As always, another interesting discussion.
Seattle, having occasionally had mags come loose etc I can sympathise with the problem. When I first had a BSA single with mag I had trouble getting the timing right & to stay right, luckily an old hand showed me to give the mag gear a sharp tap to "seat" it having set the timing & before tightening the nut. I never had trouble after that, otherwise I might have given up with having a Brit bike! It does seem that you have had an unusual lot of trouble. I wondered whether it could have been the balance factor of the engine & vibration causing the constant loosening of the gear? Obviously the broken strap mount is an added problem. I can imagine (never having done it) that really heavy off road use - motocross withreally rough ground / big jumps / heavy landings could rattle a mag on it's mounting.
I don't quite follow the issue here;
Originally Posted by SEATTLE GS
one possibility of the mag pinion problem is the pinion is too long andbumps up against the large nut holding the 4 lobed spring in place.
A typo I suspect or have I missed something!?
The description of the special seal holder / flange fitted into the back / mag side of the case certainly shows it's been oddly modified. I think I would consider stripping all that out & getting the timing case tig welded & machined to correct specs. or specs that suit your needs.. However now you've got crank triggered ign it is kind of irrelevant except where that might affect the Dyno fitting. As with Magnetoman, my experience of having cases etc tig welded is that disortion, even on relatively delicate parts, has not been much of an issue.

The issue does remind me that years ago I had a motor that I could not get the mag to sit correctly in the seal / mounting hole & still maintain acceptable backlash. Every time I had the timing cover / mag gear off the seal would be distorted off centre & not doing it's job.
I went thru a lot of seals. All I could think was the mag platform hadn't been machined to the correct relationship to the timing case opening. In the end, not having any serious machineing eqpt. I made up a press fit eccentric aluminium seal holder for a smaller seal. It cured the issue. The mag had previously been on another BSA single & fitted fine.
Like Dave NV, having run crank triggered ign. on race bikes I think it's great except for the total loss battery issue & lack of lights...


na
Re: timing gear location [Re: SEATTLE GS] #721002
01/04/18 12:13 am
01/04/18 12:13 am
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Posts: 40
city island ny
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hunter h Offline
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cheers last year there was a thread on this . they used a face seal in the old oil seal hole . this type of seal works with shafts that at not in the center of the bore . maybe someone saved that thread. hunter


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