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Brinky 
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Location: Uk
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 Topic: Allis B timing
Posted: 22 Apr 2025 at 11:42am |
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Just wanted to check what I read for the timing is correct.
When the magneto came back I turned it until it sparked on plug one. I then turned the engine over until I got compression on cylinder one and fire mark in the hole, I then advanced it to TDC and put magneto back on. Does that sound about right ?
Edited by Brinky - 22 Apr 2025 at 12:14pm
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steve(ill)
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Posted: 22 Apr 2025 at 12:42pm |
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Normally you get the engine rotated so it is coming up on compression,, maybe the FIRE mark for #1..... then you rotate the MAG by hand and watch it fire on 2 -4 -3 .. then its ready for #1 NEXT... So you install the MAG and snug the bolts... as you rotate the motor to TDC you will see #1 SPARK... If its off a little, then loosen the mount bolts and rotate a few degrees one way or the other untill you fire at TDC.. You will need to rotate the engine 2 revolutions each time to RETEST for FIRE at #1 TDC.
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Like them all, but love the "B"s.
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Les Kerf
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Posted: 23 Apr 2025 at 2:05pm |
I just went through this with my B-125 engine.
Get the engine rotated to TDC #1 compression (the magneto coupling should be horizontal), then rotate the magneto until #1 fires, then rotate the magneto slightly backwards enough to engage the impulse, then rotate it forward just enough to get the coupling horizontal, then install the magneto with the top of the magneto rotated toward the engine.
Tighten the magneto bolts lightly so as to allow the magneto to still turn. Then CAREFULLY rotate the top of the magneto away from the engine until the impulse trips. If all went well this will be correct, then re-test and fine tune as needed. If you are able to rotate the engine backwards with the fan about a half-turn then you won't need to go forward the full two revolutions. I like to go forward a half-turn and, using a spark tester, check #2, then #4 and #3 in sequence and finally back to #1 just to verify that sparks are indeed happening when and where they should.
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Brinky
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Posted: 18 hours 36 minutes ago at 11:58am |
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Thanks for all the advice, I have done the timing, managed to start her and take her for a run.
I now have a problem with the starter barely turning the engine over.
According to my charger the battery is 100% charged at about 6.5v, I have new 50mm cables. When the start button is pressed I have 4.5v at the starter is this too low?
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Les Kerf
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Posted: 16 hours 41 minutes ago at 1:53pm |
 Brinky wrote:
... I have new 50mm cables. When the start button is pressed I have 4.5v at the starter is this too low? |
Did you perhaps mean 5mm cables? 4.5v is a bit low but 5mm cables are pretty small, 50mm is huge.
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ekjdm14
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Posted: 16 hours 32 minutes ago at 2:02pm |
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Not sure why but over here we measure our cables by some kind of cross section or area of the strands added up do 50mm nominal does seem legit for 6v cables.
Why we can't go by wire gauge, I don't know. Works so much more intuitive for me at least.
4.5v is a little low but 6v starters never spin over like a 12v one anyway, as long as it can push through compression it should start well enough.
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Stuck Farmer
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Brinky
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Posted: 16 hours 32 minutes ago at 2:02pm |
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50mm² , 345 amp
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steve(ill)
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Posted: 14 hours 22 minutes ago at 4:12pm |
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50 mm divided by PIE ( 3.14) = 16 ( r**2)... so r = 4 or the diamter = 8 mm .... that is half way between gauge 1 and gauge 0 in the US... ( .311 inch dia).... most people would go a size or two BIGGER on a 6 v system.... If it starts OK, thats fine.. If it is COLD, WEAK BATTERY, WEAK MAG.. etc, etc... You "might" need larger cables..
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Like them all, but love the "B"s.
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mdm1
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Posted: 12 hours 26 minutes ago at 6:08pm |
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Just did my 2 B's. Similar to what Les said. Bring the engine to TDC, compression stroke on #1 cylinder. I couldn't find any marks on my flywheels but the engine is TDC on compression when the set screw- bolt on the crank shaft pulley is at 12:00 O clock. Snap the mag on #1 and back it up to line up with the coupler. Should be horizontal. Mount it straight up. The next cylinder to fire will be #2. As far as the starter goes. Did you load test the battery? I just had one that wouldn't turn over ever though the starter would function on another battery. My battery was bad. Make sure all your connections are super clean especially the ground. Clean the area where the starter mounts to the engine. Welding wire size cables. I think you may be looking at a new battery. Good luck.
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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!
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Les Kerf
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Posted: 10 hours 46 minutes ago at 7:48pm |
Brinky wrote:
50mm² , 345 amp |
Ah, thank you for the edification, I missed the little 'square' symbol  We do some things a bit differently on this side of the pond 
Those cables should be adequate; you could do a voltage drop test on them to verify.
Put one test lead of your voltmeter directly on the battery terminal and the other lead directly on the terminal stud at the starter. While cranking, read the voltage drop, it should be a tenth of a volt (0.10 Volt) or thereabouts. This will test the conductivity of the entire cable and the the connections.
Do the same on the ground cable, testing from the actual battery terminal to a good ground near the battery. The voltage drop needs to be very low on this one too.
Edited by Les Kerf - 10 hours 44 minutes ago at 7:50pm
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