Author Topic: Small Journal timing side bush dimensions ?  (Read 1477 times)

Offline Josh Cox

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Small Journal timing side bush dimensions ?
« on: 06.08. 2009 12:17 »
Hello,

Trying to find out what the diameter of the inner lip ( that the crank rests against ), on the inside of the engine case, that mates hard against the case inner.

My present bush has a diameter of about 3.18-3.2mm, it also has a .3mm shim wedged between the bush and the case, trying to work out if there is a reason why the shim is there and if the bush lip is standard diameter ?.

Thanks,

Josh
Black 1953 Golden Flash Plunger

Online RichardL

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Re: Small Journal timing side bush dimensions ?
« Reply #1 on: 06.08. 2009 13:23 »
Josh,

If I understand you correctly, you are looking for the thickness of the lip (or "flange") that is between the case and the crank. Measuring a new one that I have, using a good but inexpensive electronic caliper that reads to 0.01mm, I get 3.17mm +/- 0.02 mm (variation around the lip).

I believe the shim was probabaly put there by someone believing the crank must be shimmed on both ends, else, they had machined the landing for the bush and were making up for what was removed. Plus or minus 0.3mm (corrected from inches) on the shimming between the crank flange and and the roller bearing should not be an issue. Keeping all the shimming in one place simplifies the matter and is as BSA intended, to the best of my understanding.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline Josh Cox

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Re: Small Journal timing side bush dimensions ?
« Reply #2 on: 06.08. 2009 13:52 »
Richard,

Thank you, on my inexpensive but also very reliable electronic caliper I also measure 3.17mm, thanks for clearing it up, was wondering if the reason for the shim was to replace removed material, it would appear they have shimmed both ends as you say, might explain some horrid wear marks in the cylinder.

Incidently this is by the jackass that had the big end bearing with the hole on the bottom right position, I feel it safer to ask than to assume, thanks again.

QUESTION: What is the "normal" amount of shimming one will generally require on the crank, ball park figure ?.
Black 1953 Golden Flash Plunger

Offline muskrat

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Re: Small Journal timing side bush dimensions ?
« Reply #3 on: 06.08. 2009 21:23 »
G'day Josh,
               My '51 A7 is using 0.005", '57 A10 has none just 0.001" end float. A friends A10 has 0.012" shims. So you must assemble and measure the end float and shim to give 1 to 3 thou float.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online RichardL

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Re: Small Journal timing side bush dimensions ?
« Reply #4 on: 06.08. 2009 21:27 »
Josh,

In my previous post, when I said that 0.3mm shimming was not an issue, I had inches in my head, as in 0.003" (which I then corrected to millimeters in the text but not in my head). Sorry for the confusion. The actual 0.012" of shim is, indeed, significant and makes me guess, (and it is just that, a guess) that the previous builder was trying to split the differnce of the total required shimming in order to place some on both sides of the crank. I can't recall exactly how much shimming I required, but I seem to recall it being more than 0.024". I will look for some note I may have made, then I would be able to give you a better answer on this.

It would be very interesting to know how much shimming was between the left-side crank web and the roller bearing. It would also be interesting to see what the bush landing looks like.

 I never forget that there are plenty of members here with considerably more exerience than I and can probabaly cite, from memory, a working range for total shimming. Boys, jump in.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline coater87

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Re: Small Journal timing side bush dimensions ?
« Reply #5 on: 06.08. 2009 22:49 »
 Hello Josh,

 Before I split my cases I set up an indicator, and got a 15 thousandths reading. Lucky enough for me there were NO shims inside the cases, as these were deemed unimportant to the last guy (along with cleaning the trap, gaskets, tight bolts, etc. etc.).

 From the sounds of this thread, it could all come down to the batch the cases were cast from- and the only thing that matters is the end float as measured once the shims are in place.

 Lee
Central Wisconsin in the U.S.

Offline Josh Cox

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Re: Small Journal timing side bush dimensions ?
« Reply #6 on: 07.08. 2009 08:28 »
Final numbers on the fitted shims:
Timing side: 14 thou
Drive side: 19 thou
Total: 33 Thou, this was with a Hoffman Roller journal.

Will be putting the cases together and measuring end play as per the maintenance manuals.

Manosound, the bush landing looks normal, do you want me to post a photo ?.
Black 1953 Golden Flash Plunger

Online RichardL

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Re: Small Journal timing side bush dimensions ?
« Reply #7 on: 07.08. 2009 14:21 »
Josh,

While the 0.033" is more than some folks here are experiencing, I think it is roughly where mine ended up. As far as I can tell, the  physical limit to the amount of shimming on the left side (between crank web and roller bearing) is based on the amount of play the small end of the rod has riding to the right on the piston gudgeon pin. Meeasuring an old rod and piston, this looks to be around 0.068" assuming center being the perfect position requirng no shims. I haven't heard of anyone getting close to this amount and I suppose it would be reason for a bit of concern if they did, but 0.033" is less than half of it and should allow plenty of clearance between conrod and piston while running.

One thing that can be a pain is if you must make changes after the first attempt at fitting the shims. If so, you will be pulling off the bearing multiple times. To do this, I fashioned a puller specific to the purpose. I can't say it is the best possible method, but it worked for me. You can see it at


http://www.a7a10.net/forum/index.php?topic=368.msg1717#msg1717


Be sure, also to read the three posts following.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline Josh Cox

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Re: Small Journal timing side bush dimensions ?
« Reply #8 on: 07.08. 2009 14:46 »
Bearing puller, great idea.

Orabanda Esq had given me the other idea previously, I have dremeled the ID and OD of my old bearing which I plan on using for the initial fitting and measuring....

Thanks again.
Black 1953 Golden Flash Plunger