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triumph 500 pre unit ignition timing #408108
12/10/11 8:33 pm
12/10/11 8:33 pm
Joined: Sep 2009
Posts: 198
East Sussex UK
db133 Offline OP
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db133  Offline OP
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Posts: 198
East Sussex UK
Triumph pre unit 500's ingition timing. The only information I can find is for 1945-55's.

5t = 7 degrees BTC (full retard and a distributor)
TR5 = 41 degrees BTC (full advance/magneto)
T100 = 37 degrees BTC ( full advance/magneto)

I have a knackered 5t (#5t 58413) with the generator head and barrels thats been used for trials and this appearsto be set on full advance/magneto at 22/25 degrees BTC.

I do not know what cams are inside as yet. I wanted to find out how it has been set up before I take it apart. Any information will be most appreciated.......Regards

Last edited by db133; 12/10/11 9:10 pm.
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Re: triumph 500 pre unit ignition timing [Re: db133] #408133
12/11/11 12:03 am
12/11/11 12:03 am
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
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41 BTDC looks realistic. 37 BTDC looks possible.

25 is wrong.


Amateur Loctite enthusiast.
Re: triumph 500 pre unit ignition timing [Re: db133] #408157
12/11/11 2:11 am
12/11/11 2:11 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
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Most likely,the idler timing wheel has been dis-engaged since the engine last ran.
The intake cam and the magneto could be retarded one full tooth from where they were last happy.That's 14.4 degrees.

36.4/39.4 degrees advance could be what it was last set at.

Re: triumph 500 pre unit ignition timing [Re: db133] #408208
12/11/11 12:18 pm
12/11/11 12:18 pm
Joined: Oct 2005
Posts: 568
Surrey UK
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Mattsta Offline
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Remember to check the valve timing before you time the ignition. And yes, I would check which cams are fitted too because this may effect the standard valve timing.

I'm very wary of using the marks on the camshaft pinions because often they aren't original or they have been reinstalled on a different keyway or non original cams have been fitted. It's worth double checking the valve timing with a degree disc before you time the ignition and refit the magneto pinion

On my engine, the inlet camshaft was 1 tooth out synch when the pinions were aligned with the markings in the correct position so my inlet camshaft was opening 3.6 degrees too late.


Last edited by Mattsta; 12/11/11 12:20 pm.

1952 Triumph T100 in a BSA A7 Frame
Re: triumph 500 pre unit ignition timing [Re: Pete R - R.I.P.] #408209
12/11/11 12:23 pm
12/11/11 12:23 pm
Joined: Oct 2005
Posts: 568
Surrey UK
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Mattsta Offline
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Quote:
Most likely,the idler timing wheel has been dis-engaged since the engine last ran.
The intake cam and the magneto could be retarded one full tooth from where they were last happy.That's 14.4 degrees.



The crank pinion has 25 teeth and the cam pinions double that (50) so I believe that being one tooth out on a camshaft pinion is equivalent to 1/2 tooth or 3.6 degrees of crank rotation

Last edited by Mattsta; 12/11/11 12:23 pm.

1952 Triumph T100 in a BSA A7 Frame
Re: triumph 500 pre unit ignition timing [Re: Mattsta] #408213
12/11/11 12:48 pm
12/11/11 12:48 pm
Joined: Jul 2009
Posts: 3,549
Vic. Australia
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Pete R - R.I.P. Offline
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When the crankshaft has turned 25 teeth (360 degrees),the camwheel has turned 25 teeth.50 teeth on the camwheel = 720 crankshaft degrees.
360/25 = 14.4 degrees per tooth.
720/50 = 14.4 degrees per tooth.

Re: triumph 500 pre unit ignition timing [Re: triton thrasher] #408228
12/11/11 2:52 pm
12/11/11 2:52 pm
Joined: Sep 2009
Posts: 198
East Sussex UK
db133 Offline OP
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db133  Offline OP
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East Sussex UK
Originally Posted By: triton thrasher
41 BTDC looks realistic. 37 BTDC looks possible.

25 is wrong.


Your right 25 is wrong ! I was on full retard not full advance (sorry no adv/retard cable fitted ) revised now at 54 BTDC. As I say it was used for trials and the manual advance /retard set via a bolt no cable in the 3/4 to full retard position. If that makes any sense ?

Last edited by db133; 12/11/11 2:57 pm.
Re: triumph 500 pre unit ignition timing [Re: db133] #408230
12/11/11 3:19 pm
12/11/11 3:19 pm
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
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Originally Posted By: db133
Originally Posted By: triton thrasher
41 BTDC looks realistic. 37 BTDC looks possible.

25 is wrong.


Your right 25 is wrong ! I was on full retard not full advance (sorry no adv/retard cable fitted ) revised now at 54 BTDC. As I say it was used for trials and the manual advance /retard set via a bolt no cable in the 3/4 to full retard position. If that makes any sense ?


Yes I get it. Someone did the adjusting with the cam ring and jammed it at their favourite setting.


Amateur Loctite enthusiast.
Re: triumph 500 pre unit ignition timing [Re: triton thrasher] #408342
12/12/11 12:45 pm
12/12/11 12:45 pm
Joined: May 2006
Posts: 509
melbourne, australia
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76degree-triumph Offline
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54deg BTDC aint a favourite setting!


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
Re: triumph 500 pre unit ignition timing [Re: 76degree-triumph] #408491
12/13/11 11:18 am
12/13/11 11:18 am
Joined: Sep 2009
Posts: 198
East Sussex UK
db133 Offline OP
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db133  Offline OP
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East Sussex UK
Originally Posted By: 76degree-triumph
54deg BTDC aint a favourite setting!


I have re checked it and it is 55/57 deg BTDC on full advance. I understand its an unusual setting. The only two things I can think of is its been set up this way for trials or I've messed up. Is it possible it was set to 55/57 BTDC for trials ?

Regards.

Re: triumph 500 pre unit ignition timing [Re: db133] #408497
12/13/11 12:56 pm
12/13/11 12:56 pm
Joined: May 2006
Posts: 509
melbourne, australia
7
76degree-triumph Offline
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melbourne, australia
55/57 full advance at trials speed/revs dont work.
34/36 much better.
Cheers. Chris.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
Re: triumph 500 pre unit ignition timing [Re: db133] #408652
12/14/11 4:09 pm
12/14/11 4:09 pm
Joined: Sep 2009
Posts: 198
East Sussex UK
db133 Offline OP
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db133  Offline OP
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Posts: 198
East Sussex UK
Full retard was 25ish btdc full advance 56ish btdc. I'd like to think the PO had the bolt wedged in at 35ish. Thanks for you input, cams next methinks.

Kind regards to you all take care db


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