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timing gear #367758
04/12/11 12:46 am
04/12/11 12:46 am
Joined: Sep 2009
Posts: 626
SEATTLE WA
S
SEATTLE GS Offline OP
BritBike Forum member
SEATTLE GS  Offline OP
BritBike Forum member
S

Joined: Sep 2009
Posts: 626
SEATTLE WA
Does ANYONE have a cure for the mag gear slipping on its shaft? I have tried lapping and red locktite. I have cracked two gears. No real luck. I finally went to a Boyer crank triggered ignition. My problem now is a Matchless G80 with twice the problem. The locktite worked for a few months then I began closing the points gap trying to keep it in time. This is extremely agravating. Any suggestions accepted.

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Re: timing gear [Re: SEATTLE GS] #367890
04/12/11 10:15 pm
04/12/11 10:15 pm
Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
Dave - NV Offline

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Dave - NV  Offline

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Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
It seems like we've discussed this issue before... I or no other GSr I know of has ever had this problem. And for sure no one uses LokTite!
Wasn't your initial problem with a SRM shaft?
Did you ever us 'Dykem Blue' to check the fit of the tapers?
The problems must be with the magneto shaft but then repop gears could have a bad taper I suppose.
I assume the dynamo or alternator turns free and the gear isn't slipping now? If it is slipping the tapers are prolly junk

'I've been told'.. An old machinist trick to make tapers work better is to clean and dry the parts and then dust the tapers with chalk dust before assembly.

The correct way to install the GS mag gear is to of course clean and dry the tapers well. A spritz of carb cleaner works nicely.

*First* bring the piston up on TDC with 'a stick in the plug hole' check.

Then slip the gear onto the shaft with the breather peg aligned with the case/cover screw hole. Remember ... time the breather at TDC, not at the timing point!

Now rotate the engine for the correct timing BTC. Do it accurately using a properly calibrated degree wheel or 'it will be OK' using the 'stick in the hole' method.

With the mag shaft nut removed, tap the socket against the face of the gear with a small hammer, seating the taper. Now crefully fit and tighten the nut.

Recheck static timing. Repeat as required.
Using a timing light and degree wheel check/set the timing with the engine running.

A question .. Now that you are using the crank triggered ignition what are you using for a generator?

Last edited by dave - NV; 04/15/11 7:16 am.

Dave - NV
Re: timing gear [Re: SEATTLE GS] #367902
04/12/11 11:26 pm
04/12/11 11:26 pm
Joined: Feb 2011
Posts: 3,255
Orygone
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Boomer  Online Happy

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Posts: 3,255
Orygone
As Dave says, super clean taper and chalk. I use a socket on the gear to tap with the hammer to seat the taper as evenly as possible. When I was vintage racing a Goldie, retiming before each race was critical. It seemed that every time I seated the mag gear and rechecked with a degree wheel I would be one or two degrees off. It got to the point of timing it off those one or two degrees before seating the gear that way I could get it spot on. Never had a prob with the gear slipping.


Boomer
Re: timing gear [Re: SEATTLE GS] #367932
04/13/11 1:03 am
04/13/11 1:03 am
Joined: Aug 2001
Posts: 1,847
California
Ron - in California R.I.P. Offline
In Remembrance
Ron - in California R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 1,847
California
I have seen crack gears... I even had one that someone tried to weld up to no avail...

I suspect the two tapers are not the same.. Also keep in mind those gears are very hard, so either to much tightening or too hard a hammer hit could crack one...

The "clutch" for the dynamo should help prevent slippage. Also make sure there is enough gear clearance, or that will mess things up as well...

Lastly, be sure the gear is not contacting the fancy nut for the dynamo clutch.. seen that before, and it won't allow for the gear to get seated on the taper...

Ron

Re: timing gear [Re: SEATTLE GS] #367941
04/13/11 2:07 am
04/13/11 2:07 am
Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
Dave - NV Offline

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Dave - NV  Offline

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Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
And I've remembered something that caused me a problem once.
If the mag shaft seal in the case is too thick, the seal lip won't allow the gear to fit properly on the shaft.

So you say, merely shift the mag in the case slots for more exposure of the mag shaft. Careful!

If the mag is shifted too far, this will put the mag gear peg too close to the rotary breather, sticking past the slot, causing those terrible gouges we've seen in some outer timing covers. You can easily shorten the peg with your bench grinder if required.

The correct mag shaft oil seal is 5mm thick. I've been using available 7mm thick seals which just barely work. Brit Only once sent me 9mm seals at one time. NFG.


Dave - NV
Re: timing gear [Re: Dave - NV] #367950
04/13/11 3:03 am
04/13/11 3:03 am
Joined: Sep 2009
Posts: 626
SEATTLE WA
S
SEATTLE GS Offline OP
BritBike Forum member
SEATTLE GS  Offline OP
BritBike Forum member
S

Joined: Sep 2009
Posts: 626
SEATTLE WA
Yes, I have asked this question before and everyone has said the same thing..never even heard of the problem. If I had a nickle....I could buy another Goldstar. The Matchless is the problem now. The nut holding on the crank sprocket is puny so I am very careful about tightening it. Both sprockets seems to make a good fit. The locktite has worked the best. I will try the chalk this time but I don't see how it works. I have even thought of using super glue but I don't know if I can break it loose with heat. I really don't want to heat the mag armature with a torch.
The problem on my GS was with the stock and SRM shaft.

Re: timing gear [Re: SEATTLE GS] #368173
04/14/11 1:42 pm
04/14/11 1:42 pm
Joined: Aug 2001
Posts: 101
N.E England
HARRYKUK Offline
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HARRYKUK  Offline
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Joined: Aug 2001
Posts: 101
N.E England
Hi SGS
Yes! do lap the gear to the shaft, make sure there is no shoulder occuring from the lapping, dismantle and clean thoroughly then apply "blackboard" chalk to the taper and reasemble, making sure you have a (spring) washer between the shaft and fixing knut.
Do ensure breather is timed correctly before seting advance point and tightening up.
Works for me ;O)

VBSTRGDS HarryKUK

Re: timing gear [Re: HARRYKUK] #368266
04/15/11 1:35 am
04/15/11 1:35 am
Joined: Sep 2009
Posts: 626
SEATTLE WA
S
SEATTLE GS Offline OP
BritBike Forum member
SEATTLE GS  Offline OP
BritBike Forum member
S

Joined: Sep 2009
Posts: 626
SEATTLE WA
several people recommend chalk. I would like to know why this works. Any ideas?

Re: timing gear [Re: SEATTLE GS] #368270
04/15/11 1:49 am
04/15/11 1:49 am
Joined: Aug 2009
Posts: 1,072
gastonia .. NC
L
limeyrider Offline
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limeyrider  Offline
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L

Joined: Aug 2009
Posts: 1,072
gastonia .. NC
Chalk dust, in this application,becomes a fine anti-slip agent,if you have ever have a quantity of chalk dust on your skin you will experience a drying of the surface moisture and oils .. same principle applies here.
James.

Re: timing gear [Re: SEATTLE GS] #368298
04/15/11 7:06 am
04/15/11 7:06 am
Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
Dave - NV Offline

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Dave - NV  Offline

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Joined: Aug 2001
Posts: 1,861
Elko, Nevada USA
And slipping a bit off topic, but still Gold Star emgine taper issues ... Please excuse my longish spiel.

One of the most poorly engineered issues on a GS is/was the @#$% crank shaft flywheel design. Okay okay the design worked just fine for M20s and even B33s. it takes a strong imagination to picture the crank pin taper to be seated at the same time the flange on the pin fits tight against the flywheel face.

We've all seen the fret marks on the pin and flywheel tapers when you disa a crank assembly. This is evidence of the flywheels flexing, 'breathing' as Phil Pearson describes the problem. To add insult to injury, we've been told the timing side wheel was made of a softer alloy to save a few pennies. Good grief.

A story for you ... One sunny day on a Club ride both mine and Ron Halem's GSs broke a crank pin. Luckily we were both able to truck home. And double lucky to only have damage to the crank and not the cases. The pins broke in the classic manner, across the oil feed hole to the timing side wheel. Here's what happens.. Prolly due to a bit of over rev sometime earlier causing the wheels to flex which bends the pin, causing metal fatigue. My pin broke at ~4k revs going easy on a new piston. sheeze.

Ok continuing on ... While awaiting a pressed up cro-mo crank from Pearson, I built up another crank assy with a new OEM pin but with used wheels. The crank that had broken the pin also had damaged wheel.
Now being double paranoid, having once destroyed a good GS racing engine with a broken rod. I hand lapped in the tapers of the new pin into 'good' used wheels. This seemed to take near forever. I was amazed how much lapping was required to correct the distorted taper bores, especially on the timing side. I had removed enough metal it was required to have the rod journal ground for side clearance.

The crank worked just fine until my new Pearson pressed up crank arrived, a work of metal art. With a US Carillo rod on a GM speedway engine pin. Nice. Hand delivered by GStarRon no less!
BTW, the crank with the lapped pin is still in a box on the shelf.

I'm told some a Goldie dirt track race bike builders secret from The Era when the tracker was routinely revved to 8k+ weekly. They would knurl the pin tapers and press up and assemble the crank in a jig. I have such a jig but never tried the knurling. hmmm Many/most of those tuners would fit a new crank assy at least twice a season as recco by BSA. I only did it once a year... with the help of my 'friendly' dealer.

Again my apologies for being both difty and a bit wordie

Last edited by dave - NV; 04/15/11 7:27 am.

Dave - NV
Re: timing gear [Re: SEATTLE GS] #368320
04/15/11 1:28 pm
04/15/11 1:28 pm
Joined: Feb 2011
Posts: 3,255
Orygone
Boomer Online happy

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Joined: Feb 2011
Posts: 3,255
Orygone
I asked a local retired BSA dealer and racer once why do you see more used barrels, heads, pistons, ect, but not many cranks. He said they would run two races and throw away the crank for scrap. If they tried to run a third they would have every toe, finger, and hair on his head crossed hoping the engine wouldn't break.


Boomer

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