The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Ratchet Richard on 17.11. 2020 09:34
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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
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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
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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.
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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.
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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*
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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
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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.
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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
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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