The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: jhg1958 on 25.05. 2025 09:07
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A bit more useless information
I have seen it written recently and many times before that once the engine has turned after you have set the valve timing marks it takes a few turns to get them to realign.
As I was fastening up my timing chest I thought I would see how many.
20 turns (of the crank) and the marks were close but one out on both sides. I must have set them wrong so I lifted the idler pinion and rest the marks by one tooth. Once again 20 rotations and it was out by one tooth. So I carried on. After 40 turns it as out by 2 teeth. By my reckoning assuming there is 20 teeth on the idler pinion I would need to rotate the engine 400 times to get the marks to align.
John
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https://www.a7a10.net/forum/index.php/topic,789.msg5039.html#msg5039
was where I think this hunting tooth thing last got seriously pondered.
Richard L reckoned 98 turns. With 98 over 2 giving the 49 T of the intermediate pinion that sounded good . . .