Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Sept 30, 2009 19:53:01 GMT
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finally got enough of this done and together for it to constitute a project rather than a pile of parts- basically, its a 125cc bobber/chopper/boardtracker/whatever other names fashionable this week ...... it comprises of a BSA D1 bantam frame (hence the title  ), which although is fundimentally sound and has an I.D., was pretty mullered as it had been crashed, hard, and bent both front tubes quite a lot. plus all the plunger bits were missing, as was just about everything else id need to build a bike out of it (and to be honest, most bantam bits are horrible anyway) I decided to do something interesting with it. the first motor vehicle I ever owned was a 1950 D1 bantam I restored aged 15ish, with the aid of my grandad (will scan pics when I find em). ive always thought the shape of the frame lends them nicely to being hardtailed with relatively little work, its ive wanted to do it for ages and have finally got round to it. any of the bantam bits here are left over from that project. most of the other bits so far are from a '99 sr125 my mate crashed, also very hard, and seriously bent the frame and smashed various other bits, so much it was deemed not bothering repairing. ive used the 16" rear wheel, and the forks and headstock (which strangely are perfectly straight after the crash), and its currently got the front wheel too but I plan to change that for a 21". the next few posts will cover what ive done so far, and then what I plan to to. ive built this bike in my head quite a few times over now, so ive got some pretty definate ideas for it, but some bits are also totally up in the air still. more when the pics upload..... |
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Last Edit: Nov 17, 2009 1:48:40 GMT by Dez
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Stiff
Posted a lot
'kin 'ell
Posts: 3,021
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Sept 30, 2009 20:33:31 GMT
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Sounds good. Seen your skills and talent in a few other threads now so this should be no different. Lookung forward to this.  |
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Sept 30, 2009 20:41:48 GMT
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from humble beginnings....  notice severe bendingness at rear of head gusset, on both tubes. its steepended the head angle by about 5deg its that bad. this is what i want to slot in the back of it-  pirated from the yamaha SR125. has a decent size, well made drum, new sprocket, and a wide-ish 16" rim with good chrome. spot on really. no point lacing a frankly rubbish bantam hub into a 16" rim when i can just fit this complete instead. i will change the tyre eventually to something more appropriate, but itll do for mockup. what you need now, is a frame jig to mock everything up on. its far easier, cheaper and quicker of you know someone with one that you can knick, as i did. the guy in the workshop next door to me used it to build his trike frame, and then kindly donated it to me. its fully adjustable for length, head angle and height, and it also came with an extra attachment for doing hardtails from when he did his mates XS chop. its a jig that slots into the main jig and holds the dropout plates the right height and width, and parallel too. so, i chucked the frame on, set up the ground clearance and head angle (compensating for the bent front end) and set up the dropout jig to the right width, height and length. mockup dropouts were fashioned out of that custom builders favourite material, cardboard, to check it all looked right, as i find building bikes is mostly about looks, with function following second. in other words make it look right, then make it work around that!!  as you can see, the dropouts i wanted to make were quite stylised, flowing with the shape of the rear frame loop, which i didnt want to have to modify, for simplicitys sake. they are also quite long, but i think they look good and suit the bike overall. i decided the cardboard mockup was all good, so i penned round them onto some 1/4" plate, as a rough markout. notice i rattlecanned the plate white first so the lines show up well. youll see this come into its own shortly though  the first one roughed out-  notice the finer lines and the centrepunch marks going on here. this is where the painting the steel white comes into its own, as you can scribe very accurate lines onto it, that wont rub or burn off when working the material. here you can see ive pinned down the dropout axle slot a lot more accurately, with 30mm adjustment, and centrepunched the holes to be drilled. i then reworked the roughed out shape more accurately with constant dimensions around this. a lot of cutting, grinding, filing, holesawing and drilling later-  i couldnt resist a bit of holesawage to break up the big slab of steel and make it look a bit cooler. one note is that i had to drill the axle slots to 20mm or they wouldnt go on the jig, but the sr125 wheel uses a 16mm axle, so ile need to make/source a couple of step washers to overcome that issue. trying them on the jig, pre-drilling/holesawing  no going back now-  i chopped off and ground/filed the tubes up, which cleaned up nicely as the welds were soft as they were gas welded, unlike hard mig welds. |
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Sept 30, 2009 20:52:01 GMT
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Remember the time I took an angle grinder to a BMW R80/7.
Go for it Dez.
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Sept 30, 2009 21:52:37 GMT
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everything clamped up and ready to rock-  notice clamps holding dropouts to jig, and gauge on seat tube to make sure the frame is vertical. some weldage later, and we have the money shot. (only heavy-tacked for the mo, will seam later)-  those are the sr125 forks slotted in there, as you can see the bantam headtube is too short for them, so I will fit the sr125 one as part of straightening the front end out. the wheel is stock sr125, which is 17", but in my opinion is too small, need to be 19" minimum, preferably 21" ive also cleaned up and smoothed out the fork sliders and yokes, removing the mudguard mounts, steering lock, gauge mounts, headlight mounts, etc. ive left 2 mounts on the bottom yoke to construct a headlight mount off, but the rest have all been ground/filed/welded smooth.  |
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Last Edit: Nov 17, 2009 10:42:02 GMT by Dez
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Sept 30, 2009 22:03:51 GMT
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i cant do the front end til i have the front wheel- which i thought id got. i want a 21" steel rim one off a DT125 as the axle is the same size/fitment, and i won one on ebay, but the guy mailed me to say its been nicked out of his garage so i cant have it, which is a ballache. i need it to accurately set up the fornt end height, the fork length and the head angle before i weld in the new headtube, so instead i started making a seat. most people do this as one of the last things, but i think its quite important to the look and proportions of the bike, so i did it now. left to right is a notepad drawing of the shape (using sizing info gleaned from ebay auctions ), a full size cardboard template, and it roughened out in 2mm steel plate.  some more grinderage later-  the inner line around the edge if where I'm going to round over the edge, by cutting it into lots of little flaps as its too stiff to do by hammering and shriking/streching, then ile have to weld em all up. but before that, if need the 2 bends adding. one at the fornt to meet the frame/tank/mounting point, and one at the back to stop you slipping off when you gas it. like so-  it will have a single front mount made out of a leaf spring, so no unsightly chrome springs at wierd angles at the back of the seat, like most chops/bobbers. more on that once ive sorted the edges, and found a suitable bit of leaf spring to mount it. |
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Sept 30, 2009 22:17:16 GMT
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well, plans for it. it will have a stock bantam tank. it would be on there now, but ive left it at my parents 150 miles away. simple 5deg. drag bars. the headlamp i have is a vintage genuine ford one, which i believe is off a '30s ford ten (predecessor to the pop). single mini-speedo ina chrome pod made form a chav tailpipe tip (!), which i think i will mount to the fork leg rather than up-top. chrome rear mudguard (i have an a65 one i think will cut down just nice). single chrome bullet taillight on top of rear guard. tyres will be avon speedmaster II on the front, and probably a skidmark II on the rear. stock sr125 F+R brakes. i have a paint scheme sorted in my head, very, very simple but with one or 2 killer touches that will make is stand out. i even have little deatails such as the grips sorted....... the one glaring omission you may have noticed, is i cant decide what motor to put in it!! at first i thought bantam, but then i remember what pain in the ass they are regard oil leaks, the stator plate constantly adjusting itself, the low quaitly, inadiquately re-enforced, sort ally castings, and the rubbish bolts, plus id rather it was a 4 stoke, and i want it to have a top speed of more that 50mph. i have the sr125 motor, but its electric start, and beside the starter being it a awkward place, i hate leccy start with a passion, seeing as I'm not female or homosexual. aside from that and the gears being on the wrong side, not a bad motor. so, i basically want something british (so the gears are on the RIGHT side  ), kickstart, 4 stroke, and 125cc. not a hope in hell i don't think!! my best preposition so far is get a CB125 motor, as they fulfill all critera except britishness, and look quite good too. any other thoughts/suggestions? |
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this looks like it will be another epic build from you dez, looking forward to seeing the progress
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2001 Micra 998 - Daily
1986 Mini Mayfair 998 - Former Daily - Garaged
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Davenger
Club Retro Rides Member
It's only metal
Posts: 7,272
Club RR Member Number: 140
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BSA D1 bantam bobber.Davenger
@dminifreak
Club Retro Rides Member 140
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Looking good mate.
Have to pop round some time and take a look
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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feel free mate.
been so busy recently had no time for socialising, only people i see are the ones who come here!
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luckygti
Posted a lot
I need to try harder!
Posts: 4,912
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Another great looking project Dez! Can't offer anything else I'm afraid, I know next to nothing about bikes!!! But another of your projects I'm looking forward to watching as it progresses! |
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Looks like it's going to be an interesting build alright, I'll be keeping an eye on it.
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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update........ there wasnt any progress for a while, mostly due to the front wheel i wanted being rather elusive. as i decided I'm going for the 'digger' big/little look with short, steep forks, i will be using a 16"/21" combo, i was specifically after a steel-rimmed DT125 disc brake wheel, as id looked at one on a friends bike and determined the spindle is the same size (15mm), and they use the same speedo drive unit so mine slots straight on, and the rim matches the rear. i bought one off ebay, for it then to be stolen before the seller could post it! (i got my dorra back though so no loss), then, last week i spied another, very cheap too. i got the complete 21" wheel, with disc, tyre and spindle + spacers for £40 delivered. i don't want the tyre, or the disc, but i knew having the disc would help me fit the other one, so needed a wheel with one on really. same goes for the spindle, didnt really need it but it meant i got the spacers, which i do need. here it is slotted on, and the forks slid through the yokes a bit so it sits right again, with the bigger wheel. they will be shortened accordingly at a later date, once everything is set 100% right. youll also see the D1 bantam tank is fitted too-  here another shot, i love the look of these bantam tanks, a really pleasing shape and nicely made. it has a couple of small dents, need the pump mounts removing, and could do with a dose of tankliner as its a bit rusty inside, but is definately usable-  but first, i need to get the front wheel fitted properly, so i can set up the fornt ride height to then do the headtube swap. a bit of jiggerypokey with the 2 sets of spacers, and the spacer setup is sorted. but, the real issue is this-  the DT disc is about 2" smaller than the SR one, and obviously i want the larger road bike disc- dirtbike ones are smaller as your front wheel does less off the stopping in the loose stuff than it does on the tarmac. here you can see the difference-  all i need to do is make an adapter that pics up on the 2 bolt patterns here-  |
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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now i bet a lot of you think you need special machinery to do that don't you? well, you don't. you just need to be able to mark, cut, drill and allign accurately. heres our adapter marked out on some 2mm plate. the 4 rings are the outer diameter(170mm), the pcd of the SR disc (150mm), the PCD of the DT disc(103mm i think), and the inner diamter (86mm).  now, the tempting thing is to hump straight in and cut the centre out to fit it to the hub, especially as i happened to have a 86mm (3-3/8") holecutter. but you don't wonna do that, cos you want to have that centrepoint there for as long as possible to check everything is concentric, so you work from the outside inwards. so first, cut it out square, , then nib the corners off twice, and its not far off round-  then 5 mins on the bench grinder sees it round, and i quickly neatened up and chamfered the edges with a flapdisc, before carefully centering the SR disc on it. you simply lay it on and move it until the PCD circle marked on passes through the centre of all the bolt holes- its dead easy to get it very accurate simply by eye. then clamp the 2 together and drill the holes out.  then, same again using the DT disc. i tack welded this one on as i didnt need the disc and its a more foolproof way than clamping it as clamps can come loose, and welds cant. then i drilled it.  then cut off the welds, flapdisc em smooth, then boshed the big ol holecutter through the middle and then filed up the edges. then bolt it all together and check how round it is-  its less than 1/2mm out all i need to do now is file 2mm off the caliper mount studs to account for the 2mm offset the adapter adds to the disc, and its done. plus get some nicer looking bolts for it, allen head with dome nuts or something. next i need to get my new rubber as this plays a part in ride height/head angle, but i should be able to do the headtube swap just from sidewall height specs. this is what i will be running, 3.00x21 front- avon speedmaster and 5.00x16 rear- avon safety milage just over £100 the pair. i best get saving!! |
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What an awesome project, I'm really looking forward to seeing more progress on this! CB125 motor would be a good bet but it would be nice to have a more British set-up, like you say. Nothing suitable springs to mind though... I hate leccy start with a passion, seeing as I'm not female or homosexual. LOL ;D I'm not sure whether I look more gay pushing the start button on a Honda Bros or struggling to kickstart an Enfield in front of a crowd of people. |
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My fleet:
Suzuki GSX-R600Y SRAD with bald, melted tyres
A borrowed Mondeo
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Nov 17, 2009 11:28:22 GMT
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id like a bsa C15 motor. way over-capacity, but very 'hotrod' to had a larger capacity motor form the same marque and period in there.
enfields are lovely bikes to kick over, third kick every time on both the ones ive ridden. they make em with electric start too, which is rubbish and falls apart if you use it, so you still have to kick it anyway!
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BSA D1 bantam bobber.retrowagen1234
@GUEST
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Nov 17, 2009 16:00:52 GMT
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oooooo liking this alot.... think i prefer it with the smaller front wheel as the length of the wheelbase vs the hight of the wheel with the dt one looks a bit strange... but maybe thats because its got the knobly on and i cant focus past that..... either way looks great |
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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BSA D1 bantam bobber.Dez
@dez
Club Retro Rides Member 34
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Nov 17, 2009 17:01:13 GMT
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it is cos its got the knobbly on- i thought that looking at the pics myself, and was waiting to see if anyone said anything. its part of the reason i post these things on here, too see if other people see what i do it looks much better in the flesh, but i can get it to look right in a pic. i think its harder to 'ignore' seeing the knobbles in a pic. with a little less tyre on the front, and a bit more on the rear, it will take out that slight rake too. i deliberately want quite a short wheelbase- I'm not a fan of bikes with 4" or 6" over rear frames, i think they look too 'gangly'. the best way i can describe it is i want it to feel like a bmx to ride!! |
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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BSA D1 bantam bobber.slater
@slater
Club Retro Rides Member 78
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Nov 17, 2009 17:28:52 GMT
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ahh a proper project for once!
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Nov 18, 2009 19:43:35 GMT
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you need to ditch the disc for a true bobber |
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), which although is fundimentally sound and has an I.D., was pretty mullered as it had been crashed, hard, and bent both front tubes quite a lot. plus all the plunger bits were missing, as was just about everything else id need to build a bike out of it (and to be honest, most bantam bits are horrible anyway) I decided to do something interesting with it.
), kickstart, 4 stroke, and 125cc. not a hope in hell i don't think!!
