Can I Rebuild a 101 year old BSA Crank

Added: 2026-05-16

[00:00:04][music] Hey, this is Flat Tank Journey.

[00:00:06]I'm Chris. This is my round tank 1925 that I've been messing with for I think it's six or seven weeks now. I've had it in the shed for a few years and I'm getting it back together. Uh last week you saw the guards on and the pack rack and I didn't show you a lot of work.

[00:00:25]That's the way it is. Uh how do I feel about it this week? I feel a bit better.

[00:00:29]I think I was a bit downtrodden last week. So if I was a bit of a Debbie Downer, sorry about that. Pardon me. I had hoped that the guards would be a lot better than they are. And they're still better than what I thought they could be. I thought they could be really bad. So this week I'm a bit more positive about them and feel as though I've done a pretty fair job. to hark back to what a guy said to me in the comments. This is a rider restoration.

[00:01:01]I am no concoursy sort of restorer. I'm not nut and bolt perfect. I don't chase that. I don't think I'm capable of that.

[00:01:11]So, what I've got is what I've got. It's certainly a lot better than what I had 6 weeks ago. This week, I want to turn my attention to the engine. I'm not really sure why. Um, but I'm avoiding the wheels because I don't want to.

[00:01:33]I think the wheels will be about $1,500 to have new rims, new spokes, relaced, uh, paint or powder, plus tires and tubes. I suppose I'm avoiding it. It's not something I can do myself. The front rim is absolutely shot to pieces. The rear rim I actually think is savable and I actually think he's usable and I'm not sure what to do. So, I'm avoiding the rims. Maybe it's a good idea, maybe it's not. Motors not my thing. I don't really know what I'm doing. And this week I'm going to have a look at the crank and to see if I can put a crank together and then I'm going to attempt to balance the thing. come up the bench and we'll have a look and I'll tell you what I've got and what I think and maybe in the comments you can tell me I'm wrong.

[00:02:25]That' be even better. So, what have I got? A new bearing for what I'm calling the main case.

[00:02:32]And well, it's lovely, isn't it? So, that's a good result.

[00:02:38]I've got um what I believe and there's a lot of believing in this is a new old stock big end pin I'm going to call it [snorts] and it's lovely clean edges clean all over my cloths and it looks pretty good so I'm happy with that and you can see I've put down a white cloth >> [snorts] >> It's not the cleanest white cloth, I'll grant you. And I've got other pieces of cloth. And [snorts] as I go, I'm going to try and clean all these. I don't know what I'm doing. I've never put a crank together before in my life. I've watched some YouTube videos, uh, which is partially dangerous cuz, you know, you never know whether they're telling you the right thing. These people on YouTube, they're a bit reckless, some of them. [snorts] Uh, anyway, back to the story. I've got what I believe is a new old stock big end pin. I've got new roller bearings or yeah, that's what I'm calling them, roller bearings. Um, that cost me an arm and a leg. I've got a conrod that was selected by the engine builder from the wedge tank. Uh, and the piston and the gon pin and all of that.

[00:03:52]And then I've got the flywheels. And these are the flywheels that the engine builder picked for me [snorts] and said that they were good.

[00:04:00]Let's hope they are.

[00:04:02]And I have they've got the pins in them.

[00:04:07]Must have had the pins in them, I think, when I got them. They're going to get a little bit of a cleanup off camera. And they look all right. They look like they've been lightened or balanced or something. I don't know why. Here's the heaviest flywheels in the world that are all bolted together.

[00:04:30]um with a busted off conrod in it. And I was trying to get the little cheese head screws out that hold the securing plate, but I couldn't.

[00:04:42]So, they look all right. I've got the securing ring that goes over the nut that holds the pin in. And then you put a screw in that into the flywheel. I don't have those screws. Uh they're very beaten up on the what on what I've got.

[00:05:03]So I'm going to use a 1/4 in cycle thread bolt. Now someone will tell me if I can't use that. I don't know why I couldn't. It'd be easy to put in. It'd be easier to get out. So if I can't use that for some unknown reason, tell me why we are. Be good to know.

[00:05:24]What else have I got? I've got some grease and I'm just going to have at it and try and put this together.

[00:05:37]All right, I'm back with cleanish and I emphasize the isish flywheels. So, what did I use? Uh, I used a stiff brush and some workshop degreaser. I don't think you can see it on the end of the bench.

[00:05:51]It wasn't anything fancy. Um, I don't find the fancy ones work any better than the cheap ones, but that's just me.

[00:06:01]These probably would have benefited from a bead blast. This is how dirty they were.

[00:06:14]And one more. And they got cleaner as they went. And now I'm [clears throat] just going to give them another wipe to try and keep her hands cleanish. So, you know, bead blast would have been cool, but I don't have a bead blaster. And you know what? [clears throat] I'm not sure it's going to make a super amount of difference.

[00:06:36]I'm not putting together a race motor.

[00:06:40]Right.

[00:06:41]Let's have another look at it. So, here's the pin. The pin's got a woodruff key in one side. So, the only place the pin can go is into that flywheel right there. That That's all it can do.

[00:07:00]So, [laughter] I am a bit relieved um that that's the only place I could put that pin because at one stage I just thinking how do I decide where the pin goes? What does it do? And then I noticed the Woodruff key and thought, yeah, cool.

[00:07:21]That works for me.

[00:07:23]So, I did grab the right socket before.

[00:07:26]Of course, it's it's a Witworth fitting.

[00:07:29]And I'm just going to do that fingertight so the pin doesn't move.

[00:07:34]Now, the intriguing bit for me with these pins is the [snorts] flywheels don't necessarily run through um that way and that way and in a circle. They must when you put them together, they must run parallel to one another.

[00:08:02]But there's a giant shoulder on the back of the pin. So that's intriguing to me that they don't or they won't. And I don't really know how to do that. Right.

[00:08:16]There's that bit.

[00:08:18]And I'll put another on the back. And then into course the retainer would go over the top and you'd get that in the right place and that would look something like that.

[00:08:33]Not particularly worried about that. I am going to take the brass plugs out of the gon pin.

[00:08:44]Slide that out and disassemble that.

[00:08:48]Then I'm gonna put the conrod clean.

[00:08:55]I'm gonna hope to assemble it onto clean bearings with clean grease into a clean pin. So, I've got a little bit of grease here.

[00:09:07][snorts] And I've got a another cleanish cloth.

[00:09:11]And I've already wiped the gajon pin the pin over. Not the gudgeon pin, the big end pin. There's a gray hair stuck in there or a piece of cloth. Don't know.

[00:09:27]Now, I'm just going to shmear the pin with a little bit of grease.

[00:09:33]mainly to hold the bearings in.

[00:09:36]I sort of thought that the pin would splash in oil.

[00:09:43]Um, and that's how the big end pin would be lubricated.

[00:09:49]Well, that's what I thought. So, slippery little suckers.

[00:09:58]Now, I have fitted these in here before, one at a time.

[00:10:03]And they do fit, but boy, when they're coated in grease, they're not easy to deal with.

[00:10:15][snorts] Now, the sad thing is some of you are sitting there screaming at me, "Do it the proper way. Do it the easy way."

[00:10:36]I don't know what I'm doing.

[00:10:38]I'm just trying bugger. Listen, that's [clears throat] three bearings in there. I'm just going to do this off camera and bring it back when I'm putting the conrod over the top. Boy, I'm lucky I'm not getting paid by the hour.

[00:11:07]It probably only took a few minutes, but they were slippery little suckers.

[00:11:12]Really slippery little suckers.

[00:11:19]Question. [laughter] It'll all be too late when somebody tells me, [snorts] but wonder which way the conrod goes.

[00:11:27]Does it have a front? Does it have a back?

[00:11:30]It's got the same groove in each side, like a I don't know, an oil groove. It's got I think it's got a hole in it somewhere that I saw. Um, but I want that to go over there and fit really neatly.

[00:11:53]And if it doesn't, I'll be well pissed.

[00:11:59]Oh wow.

[00:12:01]Wow. It fits. Woohoo.

[00:12:06]And true to its word, I have one bearing left over. One $1120 bearing.

[00:12:14]Now, so that's really simple. And again, at this stage, I kind of got it wrong.

[00:12:22]And to hold everything together, again, that has to go over there. just logic says and it can't go anywhere else. So, the bearings now can't fall out. And I just want to snug that up a little bit.

[00:12:47]Get in there.

[00:12:55]And that snugged up a little bit. Not much. So, there's a little bit of sideways, more than I thought, but up and down is is in my books is non-existent.

[00:13:12]So, [snorts] currently the flywheels are not running. No, is concentric the right word to one another.

[00:13:22][snorts] Um, but they're together. That's a really promising sign. I'm really pleased about that. That's sort of made my day.

[00:13:33]It's a pretty shallow life. Alert. I was looking for a place to put that bearing.

[00:13:37]I do want to keep that bearing because it's brand new and this fly flywheel is likely to come apart again and again and again and I'm likely to lose one. I'm going to find a place for that and then we're going to come back and look at it a bit more. Been a pretty bizarre afternoon so far. And maybe I don't know, maybe an hour and a half has gone since you last saw me. But I've had VB blocks, the crank set up in VB blocks um on two large pieces of hardwood and it's sketchy. I'll I'll grant it all that.

[00:14:15]And I've been trueing the flywheels um so that they run concentrically to one another or in line with one another if you like and then getting the pinch out of them either way so they run parallel to one another. And I'm down to about um what am I down to?

[00:14:44]About five or 6 hundreds of a millimeter I think. [snorts] Um the dog caliper is not the best, but you know 56 hundreds depends the the the pins are a little bit nailed in places and and the the dog indicator will move around a bit.

[00:15:13]Uh because the pins are tapered uh and they have woodruff keys, you got to be selective about where do you put the the VB blocks and [snorts] how do you get them to run. Then the VB blocks will shift on me. So I readily admit to this being a sketchy setup, but I watched TwoStroke Stuffing.

[00:15:39]I don't know why anybody else watches him. I think he's a Norwegian guy. and he builds tiny two-stroke engines.

[00:15:46]And he's got a very simple video on explaining how this works. And so I've used a combination of a wooden mallet beating the flywheel and a wedge spreading the flywheel and a vice pinching the flywheel until I've got down to this measurement of, you know, 4, 5, 6, 7 hundreds of a millimeter.

[00:16:15]And to be honest, I reckon I'm going to call it good.

[00:16:20]Now actually right at the second it's running within a hundth or two.

[00:16:30]I will bring you down and show you that the doll caliper and see if we can get a look at it. You come in and have a look.

[00:16:41]This is all a bit sketchy.

[00:16:44]I've got you acutely zoomed.

[00:16:50]I'm trying to turn the flywheel so you can see.

[00:16:57]It's in touch and it just moves. It'll move slightly if you push the flywheel too hard.

[00:17:04]I'm going to take you back out of there and just I think I'm going to call it okay.

[00:17:13]I I really followed the instructions really closely and I have spent an hour and then you know sometimes when you push it too hard it'll move. Come back to the tripod for a second. So I'm having another go at this. I to be honest I keep expecting it to be wrong.

[00:17:31]I didn't think I'd get it this close like within let's call it 500s half of a tenth of a millimeter.

[00:17:44]You know, I reckon it's nearly close enough.

[00:17:48]What do people think?

[00:17:50]Am I close enough?

[00:17:53]You know, I keep turning it over expecting it to be wrong, but it's not.

[00:18:03]Um, I'll admit I did bang it and measure it and bang it and measure it and bang it and measure it and measure it and bang it.

[00:18:12]and then wedged it and pinched it. And I've watched the video from two-stroke stuffing about 15 times.

[00:18:19]I I can't see what else I'd have done wrong.

[00:18:24]I keep thinking I must be wrong.

[00:18:26]Admittedly, you can move the the um V blocks and that worries me that then the whole thing's not running parallel. But once I get them in the right place, everything sits off it just fine and everything kind of works. So, for now, I'm going to call it good and say that I may have balanced the crank. And [snorts] I have done the other side and it's running the same way. I may have balanced the crank to a level that it'll be okay. I'm going to leave it alone for a while and read a bit and watch a few more videos and see what I think.

[00:19:14]We'll leave it there. Bit of yelling in the shed again because I haven't got my microphone on. Had a mate shooting this footage. So, I'm heating up the drive side crank case and I've got the bearing shell in my hand. And after consultation with my engine builder, who's very glad he's not doing this, um I've I'm heating up the crank case and I'm about to drop the bearing in. And so, uh, I have got a glove on and [clears throat] I have got a wooden mallet.

[00:19:48]And I'm going to turn this off and get my wooden mallet.

[00:19:58][clears throat] I'm actually hoping that the lip goes to the outside.

[00:20:09]Doesn't quite go.

[00:20:27]And I actually thought that would go in smoother than that. So I might reheat and make myself a plug to get this in.

[00:20:36]I'll bring you back. All right. But while you were gone, I knocked it home.

[00:20:42]I used a wooden mallet upside down that fitted neatly and gave it a good smack and it dropped in. I think it's at the bottom of where it needs to be. I can't quite tell. Uh, and because I have nothing to reference it on, there's a little lip at the bottom and there is a groove at the bottom.

[00:21:09]So, on another set of crank cases, when I've looked at them, there is a raised portion of aluminum around the edge. Let me see if I can find one. You might not be able to see this, but around the edge of that bearing housing is a lip.

[00:21:31]A tiny little lip. And I think the bearing and I'll bring you back over now sitting on that lip. There's a tiny little gap underneath where I can slide the pick, but I can't get [clears throat] it onto the top of the bearing. So, I'm going to call it good because there's a step of aluminum that you just slide the pick up to there.

[00:22:01]Let's hope I'm right.

[00:22:03]I'm back with the crank. I have put the nut retainer on and I've used a bolt.

[00:22:13]One of you will tell me if I can't use that and that I should use some sort of cheese head screw. I can't see why I couldn't, but maybe I'm wrong. There's practically no movement in my hundreds dial indicator. And that's hundreds of a millimeter.

[00:22:35]So, the bearing's gone in the outside one. And then I need to put this onto the shaft according to the engine builder and then insert that shaft into the bearing housing that we've got and then put the other side on. And in theory the bottom end would be done late in the day. I really should stop but I'm not going to.

[00:23:01]So, I'll press the bearing into the housing. And then that bearing slides onto there like that.

[00:23:14]That goes back out through the drive side. And then the cush drive fits onto there.

[00:23:24]And there's a woodruff key that'll secure that in place. So, I know which side of the case that goes through. And this is all a process of elimination.

[00:23:33]Now, this piece, let's move my dial indicator. Oops. Let's not drop it on the floor. I've just taken the cheese head screws out. And so, inside is all that I suppose I'm calling it timing gear.

[00:23:47]It's all got copper grease on it. And somebody's gone to a lot a lot a lot of trouble.

[00:23:53]The crank will go through there.

[00:23:58]I'm just going to get a little bit of grease and pop that in there. Mr. BSA does say that you should use a lot of oil.

[00:24:11]When you're doing this, I'm just going to drop that in and hope for the best.

[00:24:18]Clunk.

[00:24:20]Clunkity clunk clunk. And there it is.

[00:24:24]You can see out the other side.

[00:24:27]And I'm obviously missing something.

[00:24:32]I'm missing a gear, a pinion gear. And that should fit back on, but doesn't look like it will.

[00:24:47]There's an awful lot hanging out there.

[00:24:49]It makes me wonder whether there's a spacer.

[00:24:53]Anyway, the crank's half in.

[00:24:57]And I'm missing the gear off there. So, I need to locate that. Let's call it a pinion gear. It probably has a woodruff key somewhere.

[00:25:12]Yep, there's the woodruff key. So, for now, let's call it quits. It's late in the day. I'm going to look for the pinion gear cuz I'm sure to have one.

[00:25:24]and I'm going to look for a woodruff key that fits. And then we'll come back and we'll have another look at it.

[00:25:32]So having a mate in the shed helps you a little bit more because you get excited and we want to do more stuff. So before I caught it stumps for the night, decided I'd have a look for the pinion gear. I'll turn that around. And there is the aforementioned pinion gear. And not only did I have one, but I had two and I had three. And it didn't take long before my goodie box revealed what I needed. I also found that Gary had left me a Woodruff key in a pill bottle.

[00:26:11]Now, I won't tell you what the pills are for. And that needs a little bit of a trim to get it to come down to fit. Now, it fits really well. And of course that shaft's tapered.

[00:26:23]So on looking for a nut to go on that timing gear, I remembered that it's actually castillated, a castillated nut. And there's a hole in it. So I have had this on and then my mate encouraged me to pull it off and show you. So that's not a bad thing to do.

[00:26:49]So remembering where the hole is in the shaft is helpful.

[00:26:53]And then weirdly, the first time I did this, it tightened up to exactly the right spot.

[00:27:02]I mean, exactly the right spot. So I gave that a snug. And when I went to offer up the pin, the pin went straight through. Of course, it's just a hair off. Now it'll be a hair one way or the other.

[00:27:22]And there it goes. So again, making the assumption that it requires a split pin that it's if it's castillated.

[00:27:34]I saw a guy who was so thorough with these split pins that he folded them round and tucked the ends in. Wow. I was super impressed. Chris isn't that good, but he is going to fold them right around and go like that. Now, that's pretty much done. Um, yes, I need a mag I've got the magneto and I need to find the right nut for that. But that crank's put in. I am going to let the other side cool down and the next time you see me, I'll be putting the other side on.

[00:28:08]I'm just lightly screwing the cover back on the timing gears, I suppose they are, and getting all that back together. But as we finish up the video, I need to tell you a funny story. [snorts] And I hope people are still watching. Be cool if you are. Uh, this morning I was reviewing the footage I shot yesterday.

[00:28:27]And of course, new day today. And I thought, gee, [snorts] I talk about putting the woodcraft, the woodruff key in the big end, but I don't see myself doing it.

[00:28:44]So, what do you do? Well, you have a little panic and you shoot an ending to your video that says, "I made a horrible mistake."

[00:28:54]When when you actually start pulling it apart and you take the big nuts off the end of it, you can see that the woodruff key is in fact in there. So, you've [clears throat] disassembled everything.

[00:29:12]Then you got to put it all back together. Look, fortunately, it wasn't a big deal, but it gave me peace of mind.

[00:29:20]It doesn't show me actually putting the woodruff key in. Um, but the, pardon me, the woodruff key was obviously sitting in there because I could I could see it. I could put a um probe in and there there it is. So, it was there. So, look, I don't know.

[00:29:43]There's the big end done.

[00:29:46]Now there's no up and down. There's there's movement side to side. I don't know. Somebody tell me how much of that we should have.

[00:29:57]How does it all look? Well, don't look too bad.

[00:30:02]I hope I've done a good enough job.

[00:30:05]Someone will tell me, "Hey, listen. You with good grace, if I'm really wrong and I've made a horrible mistake, can somebody just tell me? Don't call me names or tell me I'm a bad person. But just um let me know. Hey Quinny, you've made a mistake. That's not your thinking is not correct. Other [snorts] than that, look, I'm not unhappy with my efforts. I'm going to call that good for now. Until somebody uh lets me know that I'm not right, I'm just going to put that primary chain cover bolt in that I found and I'm going to call it good. That's this week's video. Listen, I hope you enjoyed it as much as me. I've had a hoot and a half. Um, it's been pretty cool. The things I thought would happen with the crank happened and I got it balanced quicker than I thought. Only took an hour, hour and a half. Um, of tapping, whacking, cajoling, and um, no, there was no pleading, but it was a good outcome.

[00:31:14]Hope you had a good time. Say good day from wherever you are in the world. Love to hear from you. Tell me I'm wrong.

[00:31:21]Love to hear that, too. In the meantime, have a good weekend. E [music]