28 degree hole?

S

shedweller

Joined

Dec 1, 2006

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53

• Feb 5, 2008

• #1

I remember - vaguely - a reference in a thread by LAB, Norbsa or another of our more knowledgable brothers, to a "28 degree hole".
At the time I did not follow it up but I took it to be marked somewhere on the timing side of the bike and I am now wondering if this could not be used as a datum to check the timing index plate inside the primary (a lazy b........ds way out of doing the degree wheel thing).
As the cover on a Mk3 is dowelled, once you check/correct the index you should be able to rely on it from then on - yes?
Where is the fabled mark? Is it on Mk3's? Is it accurate?

 

Ron L

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Feb 27, 2004

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3,257

• Feb 5, 2008

• #2

The timing plug is on Mk3 crankcases only and is located on the timing side below the front curve of the timing cover. I have never used this hole or seen a timing tool that fits into it.

I can't remember seeing a hole in a Mk3 flywheel or crank cheek that would match up to this opening.

I have a set of Mk3 cases and I believe a crank up in the loft. I'll have to try to dig them out this weekend.

 

J

Jason Curtiss

Joined

Jun 14, 2003

Messages

747

• Feb 5, 2008

• #3

There is a machined slot in the cheek of the flywheel that corresponds with the threaded hole in the crankcase that Ron mentioned. I found a bolt with the same thread profile as the hole in the crankcase and turned down the nose to a diameter that matched the width of the slot in the flywheel.

 

L.A.B.

Moderator

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• Feb 5, 2008

• #4

Ron L said:

I have never used this hole or seen a timing tool that fits into it.

Click to expand...

A location tool isn't really necessary, as it is quite easy to do a visual check, unlike timing holes on Triumphs for instance.

The crank timing slot position can of course be checked with a degree wheel to verify that it is accurate, and mine was certainly OK.

 

S

shedweller

Joined

Dec 1, 2006

Messages

53

• Feb 5, 2008

• #5

So......if I follow Jason's lead, (do you have the details/dimmensions of your bolt, Jason?) and locate the crank using this, I will have an absolute check for the index plate - yes? You must be able to trust such a fixed mechanical datum. Surely it could not be incorrectly machined.

 

J

Jason Curtiss

Joined

Jun 14, 2003

Messages

747

• Feb 5, 2008

• #6

shedweller,

The timing plug was made from a 0.5" diameter X 1.0" long, 14 threads per inch bolt. The indexing pin machined on the end of the bolt has the following dimensions: 0.1845" diameter X 0.210" long.

Hope this helps!

 

S

shedweller

Joined

Dec 1, 2006

Messages

53

• Feb 5, 2008

• #7

Wow! How's that for service! Thanks Jason, I'll get one made up at my mate's workshop.
I was dreading having to go through the degree wheel thing - making up the "dead stop" tool etc, etc. This seems like a great solution.
Thanks again.

 

N

norbsa48503

Joined

Apr 7, 2004

Messages

1,691

• Feb 5, 2008

• #8

The mark will be good for points. Have your mate do a dead stop tool at the same time they are dirt cheap out of a spark plug base and a 10-32 long bolt. Don't fear a degree wheel they are friends man. The crank slot could also be used to double check your gage in the primary do some math and you could come up with the corrected number for an E.I.

 

S

shedweller

Joined

Dec 1, 2006

Messages

53

• Feb 5, 2008

• #9

Found this - /www.autotools.com.au/catalogue/product.php/10/460/2024
I thought for OZD28 it looks like a fairly handy gadget. Not sure if it will fit my old dial gauge but just being able to clamp a rod at different reaches would be very useful and can double as a dead stop tool.
Probably comes from the US anyway - $5 at Walmart?

 

N

norbsa48503

Joined

Apr 7, 2004

Messages

1,691

• Feb 5, 2008

• #10

That would work the 3/16 diameter is important on a Norton head. About an inch 1/4 stick out worked well for me. You would like to stop the piston about 30 degree each side of TDC. If you get the right degree wheel you can use it at the points location. Easy then just to jot down the numbers on the scale in the primary for future reference. An old plug with a tapped hole and a bolt works just as good and you will learn to like a rigid set up for this work. Before long we will be having you checking your cam timing and asking after vernier cam sprockets...

 

S

shedweller

Joined

Dec 1, 2006

Messages

53

• Feb 6, 2008

• #11

Uh-oh!! I can feel my "old dog..." syndrome copping a flogging if I don't look out!