E: Engine Strange Comet engine.

Bill Thomas

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Anybody seen a Comet with a Sump Plug half way up the rear of the cases ?,
Now if it were on the front !, It might be Brian Chapmans " Mighty Mouse " :) .

The only thing I can think is an electronic pick up, With maybe a magnet on one flywheel ?.
Still learning all the time !.
 

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bmetcalf

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BSA A65s had a plug in that vicinity to insert a rod into a hole in a flywheel to establish TDC. (Disclaimer: memory from 50 years ago and the 1965 A65 I had then didn't have the plug.)
 

Bill Thomas

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Another thing I found interesting, The Flywheels with this Engine ,
I thought I would try and check the run out,
Been playing on the lathe with centres,
Didn't think the results were right, Had bad readings with just some other shafts !,
Anyway I got 4 thou out on one side and 3 on the other,
Then put it on my Jig I made up after talking with "Cyborg" a long time ago,
And got less than a thou both sides !,
So now have a good way of checking anything I may do with another Job I am doing.
 

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oexing

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Bill, you better bin the between-centers-check on the lathe. Looks impressive but you cannot know what the crank does when assembled in the engine when supported by main bearings. That is why I recommend to put crank on main bearing places on little bearings or on V-slots made of plywood or alu, perfectly OK for checking runout on crank ENDS. No use to put the clock on same place above the bearings, you always get zero in that case.
Look into my youtube clip below to see how I do for decades, no questionable procedure using centers in shafts and meditating after this what you will get later in the engine .

Vic
crank check clip:
HRD crank
 

Bill Thomas

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I thought Dan Smith says between centres ?,
But I think he said sometimes you have to re do the centres,
My stuff is not that good, And I don't really know what I am doing.
 

Bill Thomas

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Some of the H.D. youtubes you can see by eye how far out they are !,
After I weld and bore the flywheels on my 560 cc,
I want to know how far out, Will be good enough for me !.
Maybe 3 thou I could get away with.
 

oexing

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Yes, Bill, another thing of religions. My logic is to support the crank exactly like in the engine, on mainshaft bearing places. And only then check ends for runout. No pondering later from between-center results about what that means when assembling the engine.

Vic
 

Bill Thomas

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With Vincent's, I have never seen a big end quill ,
Without rubbing on one side, So to me there is always some runout ?.
My L/ning was super smooth after building, But after one race It must have settled ?.
You put your meter on the outer bearing on the t/side ,
What do you put it on the drive side ?.
Cheers Bill.
 

oexing

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There is another clip of the drive side , link below, well, you cannot go more than to an uninterrupted diameter for checking. At least you get all diameters for checking where ball or roller bearings go. Vincent S. says you better get runout below 1 thou for avoiding bellmouthed outer race seats in engine halves. You can have minimal runout by bashing the webs when from twisted runout. In directions of crankpin and 180 degrees opposite you may tweak it in the vice or wedge it apart depending on what sort of runout - and hope it stays that way when in operation.

Vic
crank check
 
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