The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: jachenbach on 01.02. 2016 03:02
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Couldn't find the old thread, so started a new one. Anyway........... I had assembled an engine with Yamabond between the case halves and the endplay was excessive (.025"). There was some question as to what if any effect the Yamabond had. Well, I finally got around to taking it apart, cleaning it up , reassembling (dry), and the answer is......... none. Still had .025" (no shims). Shimmed the timing side bearing and now a bit less than .003". Should be able to get back to it and finish assembly in a couple days.
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Don't think it is a good idea to shim for crank end float on the timing side, others may disagree http://www.a7a10.net/forum/Smileys/default/icon_confused.gif
The shims are not held tight and are free to turn, can cause problems!
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Don't think it is a good idea to shim for crank end float on the timing side,
I daresay it's a dummy run-simulation type thang...seems a reasonable way to get an indication... others may disagree *eek*
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I'm goint to take a guess that Jachenbach just misspoke. Shims on the timing side are sure to lead to more practice in dismantling and reassembly under bad circumstances (that is, after the bike is completely back together and you are imagining you won't have to do that agian for a long time).
Richard L.
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I'm goint to take a guess that Jachenbach just misspoke. Shims on the timing side are sure to lead to more practice in dismantling and reassembly under bad circumstances (that is, after the bike is completely back together and you are imagining you won't have to do that agian for a long time).
Richard, maybe you didn't properly read what I wrote; from memory, Jacho's a BMWhatzit muckanick, so I think... I daresay it's a dummy run-simulation type thang...seems a reasonable way to get an indication...
... is a fair way to evaluate the shims needed- to be added in the correct place- behind the drive bearing...?
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Dutch,
I did understand what you meant but took a guess that that was not what Jachenbach had done. My assumption is due his saying he had "shimmed the timing side bearing." Now, I am not going to stand so strongly on this idea that I will need to break out the pointy yellow hat if I am wrong.
Richard L.
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Yes, it's an easy way to evaluate what shims are needed, as the crank and cam can stay in place and it's easy enough to remove the timing side bearing. Figured it shouldn't matter which side they're on to get a measurement. Somehow it just doesn't always seem to work quite as simply as I'd like. After the first measurement, I installed what mathematically should have been appropriate shims and found no endplay. Took out a .002" and it came out fine. Go figure.
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Let me try again. Yup, you're right, it's the drive side that's left in the case so the shims are on the correct side. I probably shouldn't try to make sense on little sleep. Been up since 3 AM and spent most of the day at the hospital with the wife in surgery (all fine, it was a scheduled event). Got home and immediately logged onto this forum (it's my favorite internet site). Anyway, the main point was just to verify that sealant between the case halves didn't effect the endplay measurement. Nevertheless, I didn't use it on reassembly. Now I'm going to get some sleep and hopefully be more alert and making some sense later on.
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Important thing: wife OK.
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Don't think it is a good idea to shim for crank end float on the timing side,
I daresay it's a dummy run-simulation type thang...seems a reasonable way to get an indication... others may disagree *eek*
I think you were right duTch He was just getting the shims required for final assembly, I will go back in my box!
Peter
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The jury may still be out. It's a bit tricky (for me at least) to interpret what Jachenbach has going on. My thinking is that he's got the engine in the frame and the drive side pulled off and is fitting the shims behind the drive side bearing, as we know is the prescribed (granted, not only) location for them.
Richard L.
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Is Jachenbach fitting the shims BEHIND the timing side bush? (which involves removing it first).
Wouldn't that also be OK as a place to fit them? (Provided the bushes oil supply holes remain ok)
I confess I did not do the shim job myself, my engineer made a single thick shim of the correct thickness for me, for fitting on the crank, drive side, all I had to do was fit it when assembling the bottom end, and double check the end play was 0015".
I was surprised at the loudness of the clunk the crank made when pushed to one side, even with such a small clearance *conf2*
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I was surprised at the loudness of the clunk the crank made when pushed to one side, even with such a small clearance
does seem a little strange but if it's on an engine just assembled (dry) and metal to metal maybe not so strange, a cushion of oil in the 0.0015" will damp it down a good bit
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Got a good night's sleep, so....... shims are on drive side, not timing side.
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Several times in my many years of A10 building I have found that occasionally the shims get eaten up and deposited in the sump. Yes they were under the main roller bearing. Om my last 2 rebuilds I used Loctite bearing retainer on each shim (after I was POSITIVE I had the correct measurement). Then installed the bearing with the same retainer fluid. After several years they are still in place. On my latest rebuild, I used an old bearing where the center bore was slightly larger than the crank (.001 approx.) that way I could easily get the bearing on and off while checking measurements with the shims. The sacrificial bearing must be EXACTLY the same thickness as the new one that will go in.
Greg
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Greg,
Welcome to the forum. *welcome* I won't embarrass you for wanting to slip in quietly with no introduction. Seems that in those years of building A10s you might have taken some photos that we would all love to see in any state of build, sometimes the grittier the better.
You have definitely dived in on one of our favorite topics. If you have been watching the forum for a while you might already know that. Personally, I really appreciate knowing that the bearing-hold Loctite has worked for you, because I am currently depending on that method myself. I will assume that your previous shim disintegration occurred regardless of a well-tightened cush nut.
Richard L.