Author Topic: Triumph model P info needed  (Read 1405 times)

Offline john11668

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Triumph model P info needed
« on: April 17, 2023, 10:59:16 AM »
Hi  Folks !
Its a long time since I have been here  so please excuse my absence
Looking for help with a Triumph model P

Was trying to set the timing after my mate had fitted a refurbished Mag dyno ( He  was turning the engine while I looked for TDC on compression stroke)
Book we have does not have much detail so was going for 7mm before TDC on compression stroke with full advance . (points gap set at  .012)
Was surprised to see that  engine appears to run backwards ( clockwise as viewed from the contact breaker side )   Is this Correct??

The reason for the mag upgrade was due to its history .  Almost impossible to start.  When delivered the  seller started it with some difficulty,  and my mate has not managed to start it since.

We have exhausted all the usual possibilities  Carb. plug , mag, before delving deeper,   ie before  stripping the head and Cylinder so next step would be to test compression. Can anyone advise what figure is reasonable for such a longstroke sidevalve??
And then of course if   problem was lack of compression  are spares available  and where to search.

Many thanks     John



Offline iansoady

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Re: Triumph model P info needed
« Reply #1 on: April 17, 2023, 11:16:36 AM »
7mm full advance doesn't sound  much to me - but you can wrtite what I know about these bikes on a postage stamp.
Ian
1952 Norton ES2
1986 Honda XBR500
1958-ish Tre-Greeves

Offline john.k

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Re: Triumph model P info needed
« Reply #2 on: April 17, 2023, 02:50:23 PM »
Its going to be something like  5/8 before TDC on full advance (that is 16mm full advance) .......I used to use TDC ,but its quite difficult to determine with any accuracy.

Offline cardan

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Re: Triumph model P info needed
« Reply #3 on: April 17, 2023, 11:51:33 PM »
Was surprised to see that  engine appears to run backwards ( clockwise as viewed from the contact breaker side )   Is this Correct??

No, but the magneto does. Many/most magnetos are "anti clockwise" - by convention this refers to viewed from the drive end - so from the points end these magnetos turn clockwise. Usually the magneto drives at half engine speed from a camshaft, which, being gear driven from the crank shaft, runs "backwards". Common exceptions are most two strokes (run at engine speed off the crank) and some BSA models in the 1920s-30s (which drive the second cam by gear from the first, thus reversing the direction again!).

Timing about 35 degrees BTDC - about 10mm.

Leon

Offline cardan

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Re: Triumph model P info needed
« Reply #4 on: April 18, 2023, 01:30:31 AM »
Just had a thought - the engine in the model LS Triumph (unit construction 350 for the same period as the model P) is one of the rare engines that does run "backwards".

Leon

Offline john.k

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Re: Triumph model P info needed
« Reply #5 on: April 18, 2023, 02:31:41 AM »
Norton changed the rotation of the magneto three times in about 10 years ........oddly enough .it doesnt cause magneto confusion so much as generator confusion.

Offline R

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Re: Triumph model P info needed
« Reply #6 on: April 18, 2023, 11:43:22 PM »
Norton changed the rotation of the magneto three times in about 10 years

Not only that, but once you throw sv ohv ohc and twins into the mix, some ran one way and t'others ran t'other way !

Which has naught to do with a Model P, but it "pays to keep your wits about you".

Offline cardan

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Re: Triumph model P info needed
« Reply #7 on: April 19, 2023, 03:00:27 AM »
In the vintage years, the vast majority of four strokes ran the cams by gear from the crank, so the cam ran "backwards". If there were two separate cam wheels, usually (!) they each meshed directly with the half-time pinion on the crank, so they both ran backwards. (As mentioned above, occasionally one cam would drive the other cam, so one would run forwards, the other backwards.) Then usually the magneto drive was by chain from a cam shaft, so the majority of magnetos ran anti clockwise. Of course there were fancy bikes (eg Rudge) who even back then had gear drive to the cams and magneto - that's where all bets are off!!

The Model P Triumph was designed for simplicity: it had only one camshaft, which drove the magneto by chain, so mag is anti cw from the drive end.

Cheers

Leon

Offline john.k

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Re: Triumph model P info needed
« Reply #8 on: April 19, 2023, 04:18:29 AM »
My grandfather had a simple method of timing bikes.....remove the plug ,hold the spark lead in your hand and put your thumb over the plug hole ......crank the bike ,and you should feel the bite at the same time as your thumb is blown off the plug hole......then the timing will be pretty right.

Offline chaterlea25

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Re: Triumph model P info needed
« Reply #9 on: April 21, 2023, 12:04:13 AM »
Hi All,
For any new spares available the place to go is veterantriumph.co.uk

John