Author Topic: Timing disc  (Read 933 times)

Online RichardL

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Timing disc
« on: 24.03. 2018 18:32 »
This seems the right topic for my question.

Just made the timing disc shown in the photo. It's ugly, but it was free and I think it will do. My question is: does anyone know, offhand, the thread size for the two holes in the cush nut? I thought it was 5mm fine (I don't know how many threads per cm.), but that didn't fit. Hopefully, I'll get right after just one more trip to the hardware store.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online muskrat

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Re: Timing disc
« Reply #1 on: 24.03. 2018 20:58 »
G'day Richard.
Lucky my cafe has an open primary. I had never looked at that thread. Best I can get to fit is 3/16" BSF = 32tpi. That might be hard to find in the US.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Muskys Plunger A7

Online RichardL

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Re: Timing disc
« Reply #2 on: 24.03. 2018 22:45 »
Muskrat,

Thanks. That was a big help. Before you responded, I had considered trying a common 10-32 (Unified National Fine according to ASME/ANSI) but thought, "Nah! No way would that fit on an SRM part." Lo and behold, it worked, and they came right out of my scrap screw bucket (keeping with the "free" theme).

Turned out my dip-stick graticule method had landed me right on 32 deg. BTDC. Yay!. Regardless, I see now that the degree disk is definitely the way to go (for me, at least) when timing with the primary cover off. Even though I had Richard's ("O") info on degrees versus inches, it helped to see the excel spreadsheet originally posted by Beezageezauk. Here it is again:

http://www.a7a10.net/BSA/ignition%20timing%20converter.xls

Richard L.






Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline coater87

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Re: Timing disc
« Reply #3 on: 25.03. 2018 00:00 »
 I remember when the parts stores gave cardboard degree wheels away for free. It was cheap advertising for them,  and they were kind of neat.

 Now ask for a degree wheel and they parts kid has to Google it. *sad2*

 
Central Wisconsin in the U.S.

Online muskrat

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Re: Timing disc
« Reply #4 on: 25.03. 2018 08:01 »
G'day Richard.
Now before you dismantle it all put a timing (strobe) light on it to see if it IS right and the same (or close to it) both sides. It's the only way I do'em now.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Online orabanda

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Re: Timing disc
« Reply #5 on: 25.03. 2018 10:21 »
If you intend to fit a SRM nut to a plunger / rigid cush drive arrangement, do a dry assembly without the spring and check that the SRM nut is not preventing the cush mechanism from working( sliding out, towards the nut). I have had to turn down the OD, for the sliding cush sleeve to slide back (only for semi-unit engines).

Richard


Online chaterlea25

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Re: Timing disc
« Reply #6 on: 25.03. 2018 22:14 »
Hi All,
Richard, 
10-32 UNF , 3/16BSF and 2BA are "almost" the same and will usually fit in each other's places   *eek* *eek*

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Rich B

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Re: Timing disc
« Reply #7 on: 27.03. 2018 00:43 »
Good info John, thanks! Helped me to sort out a GS with a parts bin special primary.

Now I need to print this out and put it in my BSA Book of Knowledge I have done a poor job keeping everything in one place.

Online RichardL

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Re: Timing disc
« Reply #8 on: 01.04. 2018 19:24 »
G'day Richard.
Now before you dismantle it all put a timing (strobe) light on it to see if it IS right and the same (or close to it) both sides. It's the only way I do'em now.
Cheers

Muskrat,

You were mistaken if you thought I remembered to test symmetry using the fag paper method before reporting my results. Testing both sides showed about 10 degrees difference.  I have now used a timing light for my first time ever on a motorcycle. The sad reality is that I do have about 10 degrees difference, but the high end is over 40. This is why I put the timing cover on with no sealant.  *eek*   First thing I'm going to check is cam ring wear, though our friend Groily at Brightspark says this is rare. Then, on to checking the housing and insulator washer as possible culprits. Any other advice gladly accepted.  *problem*

Curse you, Muskrat, for your good advice. I probably could have just ridden in blind bliss enjoying every minute until it blew up  *smile*

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: Timing disc
« Reply #9 on: 01.04. 2018 20:54 »
G'day Richard.
Sorry mate, the truth must be known. I try for the same amount advanced and retarded so if the ideal time is 35 and we have a difference of 10 then I set at 40-30. 40 may give you a bit of pinging, 30 may create a bit more heat. Those little infrared temperature guns are great to measure pipes.
At the end of the day the imbalance should be addressed. Sorry I know bugger all about magies (both mine electrick), camring would be my guess.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Muskys Plunger A7

Online chaterlea25

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Re: Timing disc
« Reply #10 on: 01.04. 2018 21:05 »
Hi Richard,
Before you pull the mag to bits
Is there any in / out play on the mag armature?
Are the max points gaps the same on both sides? the end cover on the mag may be off to one side
The rotating contact may also not be seating evenly in the armature taper
You could try swopping bits from your project bike mag ?

John
1961 Super Rocket
1963 RGS (ongoing)

Online RichardL

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Re: Timing disc
« Reply #11 on: 01.04. 2018 23:52 »
I actually misspoke about the difference when using the fag paper. That was only about 5 deg. Using the timing light looked like about 33 on one side and 42 on the other, or thereabouts, but my technique is bad. Doing it by myself, I have to juice the throttle, hold the light, read the disk and steady the bike from walking all at the same time. All this in daylight, making it hard to read the black graticule against the muddy background of my home made disk. Now I see why the commercially available disks have light graphics on a dark background.

John, I will check the armature in/out and seating of the rotating contact, and recheck the gaps. Cover is seated correctly.  I wouldn't be able to swap out the whole mag from the basket case because it needs its own rebuild, but you reminded me that I could swap housings and/or cams.  The last time I rotated the housing on the mag in question gap difference got bad.

Thanks for you advice (and more, if you have it).

Richard L.

Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline coater87

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Re: Timing disc
« Reply #12 on: 02.04. 2018 13:40 »
Richard,

 Mine was way off also, 12 degrees. I found it very hard to "chase" degrees to make them equal.

 Right or wrong, I chased the gap to get them as close as I could and the degrees followed if that makes sense.

 I ended up installing two narrow pieces of .001 shim stock between the cam ring and housing (not stacked up and not right next to each other). You would think you need thicker, but you don't. A little went a long way for me.

 This got me to 32 and 34 degrees. I don't know if it will work well, but it looks good with the disk and feeler gage.

Lee
Central Wisconsin in the U.S.

Online RichardL

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Re: Timing disc
« Reply #13 on: 08.04. 2018 03:47 »
Does anyone know if K2F bodies were matched to their cam-ring housings at the factory? When I rotate mine 180 the gap difference is wild. I'm going to try one from a different mag.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online duTch

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Re: Timing disc
« Reply #14 on: 08.04. 2018 05:32 »
 
Quote
..., I have to juice the throttle, hold the light, read the disk and steady the bike from walking all at the same time....

  I don't have this problem worth the Gutzzi,  but definitely do with the Beeza, mostly when tuning the regulator... but after a comment from GB a while back started me thinking (dangerous move),  I've been trying to figure a way to utilise the wheels from a hand truck to use as outriggers for this purpose, but not as easy as it may seem...

Quote
... All this in daylight, ....Now I see why the commercially available disks have light graphics on a dark background.....

  *idea*  *conf2* *bright idea*
I have a fair notion that there's a readily available product known as 'white paint' which may help...*whistle**bash* *bash*
 
 
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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