Author Topic: A7 Plunger Timing  (Read 2671 times)

Offline bsarider

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Re: A7 Plunger Timing
« Reply #15 on: 16.04. 2010 17:56 »
http://www.bsawiki.co.uk/index.php?title=Chapter03 Brian if you open up the link it says the A7 before engine number before is 3/8" advanced. my engine is 4414 ? alan

Online Brian

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Re: A7 Plunger Timing
« Reply #16 on: 17.04. 2010 06:37 »
Alan this has just got a little confusing. I have looked back through some of my workshop manuals and handbooks, all genuine BSA literature, and it seems even BSA couldnt make up its mind. However the majority of them seem to say that 3/8" is correct for all the longstroke, Z prefixed engines. It seems 5/16" was introduced with the newer shorter stroke engine, AA7 onwards. However depending on which particular piece of literature you have it could say 5/16" for the standard ZA7 motor. Nothings ever straight forward in the world of old bikes.
I have timed my Star twin to 3/8" and it goes well, not a hint of pinging

Offline bsarider

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Re: A7 Plunger Timing
« Reply #17 on: 18.05. 2010 10:34 »
At last the Magneto is back  and FTW in Sheffield made a nice job of it, prior to fitting the Mag I did some more work on the Plunger timing.
   With a degree disc fitted to the timing side mainshaft nut,I found TDC using an old plug with a piece of screwed thread ,took the difference from one rotation and achieved TDC.I also rigged up a DTI and again checked that TDC was correct.
 taking readings from the DTI I wound the engine back from TDC and then forward to 5/16" BTDC and the degree disc read 30 degrees, Doing the same for 3/8" the disc read
33.8 degrees which is not what was expected. I have timed the engine up at 3/8" so hopefully it will start,I will let you know.
Just tried the bike and it kicks up first time and ticks over just need to give it a road test next
to see if it has any power. The bike runs and pulls well,whats next .Alan