Author Topic: A7 crankshaft end float.  (Read 344 times)

Online Ratchet Richard

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A7 crankshaft end float.
« on: 17.11. 2020 09:34 »
Hi just a quick one, I am in the process of doing the endfloat on my 1958 A7. I not on service sheet 208 that BSA state that end float on an A7 is taken up when tightening the sprocket but should be .005 to .010 ins before tightening the sprocket.  Is this right for the 1958 models?  I noted that the A10 has a maximum EF of .005 in.
Thanks

Offline muskrat

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Re: A7 crankshaft end float.
« Reply #1 on: 17.11. 2020 19:24 »
G'day Richard.
The end float is measured with the nut done up. Max 0.005" but 0.0015" is the one to aim for. The end float grows as the motor gets hotter.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
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Offline RDfella

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Re: A7 crankshaft end float.
« Reply #2 on: 17.11. 2020 21:01 »
Did the A7 have roller drive side main by then, or did they stay with ballrace? If the latter, that would account for the terminology and stated clearance.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: A7 crankshaft end float.
« Reply #3 on: 17.11. 2020 22:01 »
Richard. This is a classic case of a failure by the editors of the service sheets to update the copy  in the light of engine development. This was written when there were two similar but different engine types in production. The confusion continues with the description of the cam followers and rocker gear.

   The A7 model mentioned here is the early Longstroke design. The main bearing is a deep groove ball race, and as the race settles against the crank under the tightening of the crank nut the only float will be that present in the bearing by its manufacturing tolerance, in a word, zilch. Originally published in 1948, looks like no one thought to check  the copy was relevant  in later years.

   For your engine read the service sheet as for the A10, and it makes sense. The difficulty with the later design with a roller race is the need to remove the race from the crank to add or subtract the shims, tighten everything up and check again. The inner race and its cage are awkward to remove where bearing inner is a tight interference fit on the crank, many bearings have been wrecked taking off and putting on/off/on!!!!   Aim for Musky's figures, but be prepared for a bit of frustration, the theory is easy, doing it ain't. If the bearing is good I'd be tempted to leave alone unless its clearly wrongly set and at least it ran OK before. Even the thickness of any jointing must be taken into account, so make sure there are no lumps of old jointing holding the cases apart.

 This topic is well served, with numerous enlightened approaches to the problem. Pour yourself a relaxing drink and peruse the Forum. You'll nod off in next to no time.....

 RD.. All short stroke engines are roller. It's the service sheet that's wrong. They went back to the ball race on the early A50/A65, then returned to a roller as the power (and no doubt failures) went up.

 Swarfy.

Online KiwiGF

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Re: A7 crankshaft end float.
« Reply #4 on: 17.11. 2020 22:26 »
Hi just a quick one, I am in the process of doing the endfloat on my 1958 A7. I not on service sheet 208 that BSA state that end float on an A7 is taken up when tightening the sprocket but should be .005 to .010 ins before tightening the sprocket.  Is this right for the 1958 models?  I noted that the A10 has a maximum EF of .005 in.
Thanks

Just an observation, the endfloat on my engine was adjusted by a local expert as part of the job of correcting mis matched cases, whenI later assembled the engine I was convinced the end float was too much  *pull hair out* *problem* as the crank moved sideways perceptibly with a hefty clunk, after much messing about with a dial gauge I found it to be 002  *whistle* so John had NOT made a mistake  *red*
New Zealand

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Online Ratchet Richard

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Re: A7 crankshaft end float.
« Reply #5 on: 18.11. 2020 10:02 »
Thanks for replies.  That’s reassuring  that  the A7 figure was for the the long stroke model.  I bought a book of BSA A7 10 service sheets on line and they have been very helpful on the whole, just every now and then I get a bit caught out. 
Richard

Online TimK

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Re: A7 crankshaft end float.
« Reply #6 on: 19.11. 2020 03:49 »


Just an observation, the endfloat on my engine was adjusted by a local expert as part of the job of correcting mis matched cases, whenI later assembled the engine I was convinced the end float was too much  *pull hair out* *problem* as the crank moved sideways perceptibly with a hefty clunk, after much messing about with a dial gauge I found it to be 002  *whistle* so John had NOT made a mistake  *red*

I had a similar experience with Jack Croft who's a classic engine guru in this area. When I picked up my cases (and crank) that he'd skimmed after them being welded, Jack said "I've had a quick go at setting the end float, but you may want to check it". I did check it - 0.0015" - so I left well alone.
Tim Kerridge
Australia

Offline muskrat

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Re: A7 crankshaft end float.
« Reply #7 on: 19.11. 2020 20:26 »
G'day Tim.
I thought Jack had retired. He's getting a bit long in the tooth. He neglected to put the correct radii on two race cranks of mine. Both snapped at the crank pin. Nothing to do with 14:1 and 7500rpm  *eek*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online TimK

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Re: A7 crankshaft end float.
« Reply #8 on: 24.11. 2020 02:21 »
Musky

Unless he's fully retired in the last three months or so he's still doing a couple of days a week. Whenever I drop stuff off he always says he can't guarantee how long the job is going to take but then invariably phones back a couple of days later telling me it's ready to pick up.

Cheers
Tim
Tim Kerridge
Australia