BSA B175 Bantam. . . . yet again


Yes - I've only gone and bought another one

    Having sold my B175, then also selling my D14/4S, it left a bit of a Bantam shaped hole in the garage.  I know I sold the other two 'cos I didn't use 'em enough, but I did rather miss the few occasions when I needed a "Bantam fix", and besides, I'd also miss the folks from the owners club on the national rally and other events.   Anyway, whilst looking on the forum of the Bantam Owners Club I noticed a B175 was up for sale.  OK, so it wasn't a running machine and it was over 200 miles away - but what does that matter ?  I don't mind travelling, in fact I quite enjoy it, and I do get pleasure from working on bikes as well as riding 'em.  If only I'd have known . . . looks like I will be getting a lot of "pleasure" with this one - still, time spent in the garage is always time well spent.  So on Tuesday the 5th of May, I hitched the trailer to the Bongo and set off for Kent - and by three o'clock in the afternoon I was back home with something Bantam shaped.

    Right, the first thing was to take a quick look around and see what obviously needed doing.  First thing was the gear lever spinning on the shaft.  Oh dear, those splines have seen better days.  Luckily I have a decent four speed gear change shaft in the garage.



    Next things to immediately jump out was the chrome ( or lack of ) on the headlight rim and the perished footrest rubbers.   Once again, an easy fix.




    I did rig up my remote fuel tank and have a quick couple of kicks when I got the bike home, but it showed no signs of wanting to start and the kickstart kept jamming when trying to kick it.  That will be looked at later.

Right, first thing is, take a look and make sure the carb is clean.  Oh dear - the inside of this carb has not seen daylight ( or petrol for that matter ) for quite a while.  The bottom of the float bowl was full of crap and there was what looked like a cover of some description over the main jet.  This cover turned out to be a fine gauze which had such a build up of crud on it that it gave the appearance of being solid.  I'd never seen gauze on a main jet before.  It was probably put on in the hope that it would somehow act as an additional fuel filter . . .but any restriction in the main jet will only cause the engine to run weak and most probably seize.  No wonder the bike wouldn't even attempt to run.




    When I sold my D14 last year, I also sold my spare B175 engine - and this engine was sat on an engine stand.  Seeing as I made the stand from bits and pieces from in the garage, I thought it would be a good idea to build another one before I go much further.  So a few bits were cut, drilled and welded, and I now have something to hold the engine whilst I work on it.




     Now that the engine is sitting happily on its stand ( can you sit on a stand ? ) it was time to dig further.  Next obvious thing was the up and down movement of the crank shaft on the alternator side.  Looks like a set of  main bearings will be needed - and if the mains have gone, you can bet the oil seals have gone too.  There was a bit of bluing on the main shaft, this could be down to the alternator rotor spinning because the woodruff key which prevents it from doing so was sat in the bottom of the casing.   I took the head, barrel and piston off next - it's a new +040 piston and the rebore has been done by PJ Engineering, a company local to me.  If PJ have done it, then that's one thing I won't have to worry about - they are good at what they do.  I spun the crank via the con rod, and you could hear the rumble of the worn main bearings.  I also noticed a lot of clean oil coming round with the flywheels, this also makes me think the oil seals are badly worn.



    Let's see what delights await in the other side of the engine.  First thing I noticed was the worn primary chain - it was also an endless chain, so both the clutch drum and the engine sprocket really need to come off together.  Now here's a little tip: When using a puller to remove the engine sprocket, put the points cam back on or you will stand a very good chance of breaking the end of the crank shaft - I know more than one person who's ended up with a broken shaft.  The clutch was next to be pulled apart.  The plates were well stuck together - it's been a long time since this clutch disengaged.  I used my home made clutch drum locking tool to remove the clutch centre nut - easy enough to make, just an old friction plate, a couple of nuts and bolts and length of steel strip.  The kickstart ratchet seemed ok - I'll have to find my spare quadrant and compare it with the one I took from this engine.  The leading tooth looks worn, but I'll leave judgment until I compare the two.




    Next job was splitting the crank cases.  This engine has been apart before because all but one of the fixing screws had been replaced by Allen bolts.  Luckily all of the bolts came out easily and none of the threads seemed damaged.  There was one bolt missing and one original cross head fitted.  I don't know what had been used as jointing compound, a barrel of tar springs to mind.  There was a load of the stuff.  It was in the gearbox and stuck in all the webs of the castings.  Cleaning that out will keep me entertained, or I might just get all the cases vapour blasted.  The gearbox seemed to change through all four gears easily enough, and although some of the gears looked worn, I don't think they will need replacing.  Once again, I have a spare four speed box living in a biscuit tin in the garage.  I tend to keep it as a reference when looking at other people's gearbox problems.

    Time to play with fire, and get the crank cases hot enough to make removing the bearings easy.  As I thought earlier, all the oil seals were badly worn, so they will be replaced along with the main bearings and the gearbox output bearing.  It makes sense to change it whilst the engine is apart . . . along with the gear change return spring.  A new spring costs less than five quid, but it's an engine out job to fit one.   Right, that's enough for now.  It's only taken a couple of days to get this far.  I'll press on with the rolling chassis whilst waiting for engine parts.




    A couple of little things today - first off was fitting a side stand.  The type that fits onto the front engine mounting bolts are not very good.  Being at the front of the bike means that there's a good tendency for the front wheel to lift off the floor and the whole plot to come crashing to the floor . . this is even more so if you have a carrier fitted and attempt to load camping gear or such like.  Fortunately those nice people at Kawasaki make a very nice side stand for their ZZR600 - which just happens to fit nicely on the pillion footrest mounting plates of a Bantam.  The other thing was the bike's log book arriving, not bad considering I only picked the bike up a week ago today.  Whilst working away I noticed something on the rear tyre.  Some lettering that someone in the past had tried to remove with sandpaper or similar.  I know the photograph isn't the best, but you can make out the words "Remould Quality"  Now I never knew they made remoulds for bikes - cars yes - I used to have 'em on my Land Rover many years ago.  As far as I'm concerned, tyres and brakes are something that I always fit new.  You don't know if that tyre has been rammed up a gutter, or run flat for any length of time.




    Whilst waiting for bits, I carried on with making the bike look generally nicer.  First off was all the tinware that was to be powder coated in whatever colour I fancy - there's a good chance it may be purple.  The rest of the bits will be gloss black.  I tend to make a numbered list of what goes to be coated, that way both you and the powder coating company have a list of what's what.



    As with every other old bike I own, this will be converted to 12 volts.  This improves reliability and give a greater choice when it comes to bulbs, plus most car spares places sell 12 volt bulbs, but very few stock 6 volt items. I tend to use a simple key switch for the ignition and a simple toggle switch for the lights - doing away with the "pilot light". . . . now a friend of mine wanted his bike converted to 12 volts but wanted to keep the standard switches in the headlight shell.  A few minutes messing around with my test meter and a few wires with crocodile clips on the end solved this problem.   Just to prove I practice what I preach, I will keep the standard headlight mounted switchgear - I will probably fit a "hidden" key switch if I can find a suitable place to fit one - as you know, there ain't a lot of spare room on a Bantam.



    When I bought this bike I was told that the kickstart sometimes locks and the bike has to be put into gear and rocked in order to free it.  I suspected the leading tooth on the kickstart quadrant had worn - and as it turned out, I was correct.  Looking at the quadrant it seems like it could be turned the other way round so the unworn trailing tooth now becomes the leading tooth.  I did ask the question on the Bantam Club Forum, and "BantamBaz" gave me the answer.  "No - there is an offset on the casting"  Ah well, time to buy a new one - they ain't expensive.

    Having sorted the kickstart quadrant out, it was time to carry on with putting the engine to rights.  By now my new bearings and seals had arrived, so armed with my trusty blowlamp I set about warming the cases up to make fitting the bearings easier.  OK - I could have bunged them in the oven for twenty minutes, but I like playing fire. 
    Now that the bearings and seals were fitted, I dropped the crankshaft in and made sure all was well. ( famous last words )  I didn't fit the gearbox internals - there's no point if you have to keep taking the two crankcase  halves apart to fit shims on the crank. . . . besides, I want to take a look at the gearbox internals before refitting them.



    Speaking of bearings - I next turned to the wheels.  The chrome on the rims is non existent and has been painted over.  The spokes are loose, and a few are bent . . . so I reckon there's a good chance that the wheel bearings ain't much better.  A useful tip in these days of smart phones and digital cameras is to photograph the components in the order they come off.  This makes putting it all back together again a less daunting task.  "Did that spacer go behind or in front of the bearing ? "  Refer to the photograph and all becomes clear.

      As you can see from the picture, one of the wheel bearings had started to break up.  Looking at the identification marks on the bearings, I wouldn't be surprised if they were the original fitment.  Another useful little tip is - buy a pack of plastic freezer bags - then put components which group together in a bag . . . and label it.





    Remember when I dropped the crankshaft in to make sure all was well ?   Well it wasn't - the right hand flywheel was running out of true by around.040"   Once again I just happened to have a spare crankshaft.  I'll get the other one repaired at my leisure.  The cylinder head was treated to a bit of very mild sand blasting - it cleaned up quite well, but there is a fair bit of pitting on some of the fins.  The combustion chamber is fine.

    Does this mean the engine is done ?  Indeed it does.  The only thing I could have changed were the clutch plates - they still have a lot of meat left on them, but I don't know how well the bonding will stand up.  I dare say I'll find out when the time comes - besides, changing clutch  plates isn't exactly an all day job.  The gearbox seemed ok - nothing too badly worn, so that went back in with a new return spring and a shaft with decent splines on it.  Main bearings, oil seals, primary chain, and kickstart quadrant are all new, as is the piston and bore.  I sat the engine outside in the sunshine, and showed it what it will grow up into one day.   The big egg and the little egg.



    Now here's a thing.  When it comes to undoing the bearing retaining rings in the front and rear wheels, why do people think a hammer and centre punch is the best way of undoing them ?  Get yourself an old spanner that's about one and a half inches wide and lash out on a couple of 3mm ( one eighth for us old buggers ) roll pins - you can get a set of assorted sizes for under a tenner, and they always come in useful.  Now take your retaining ring and file off the mess made by the centre punch wielding butcher, then drill the holes right the way through.  Using the retaining ring as a "drilling jig", drill two holes of the correct diameter for  your roll pins in the spanner.  Congratulations - you have now made a peg spanner.  No more hammering away at things that were never meant to be hammered on. . . .  and you can still use the spanner for its intended use ( at a push ).  This will come in useful later on when I get the rebuilt wheels back.



    Whilst other bits are away being sorted out, it's time to turn to the carburettor.  Ultrasonic cleaning is good, but an ultrasonic cleaner large enough for a carburettor body is a tad expensive.  Time for another little useful tip.  Get an old saucepan, fill it with water, then add washing powder . . .  and give the carb a good boiling.  The agitation of the boiling along with the cleaning of the washing powder will shift any nasty things which are lurking within the carburettor drillings.  A blow through with carb cleaner afterwards, just to make sure everything is clear, and all being well you should have a carb which does what it's supposed to.  With the ethanol in today's fuel, it's a wise move to fit a Viton tipped needle, and possibly the new "stay up" float.  Once again, these items can be fitted in fifteen minutes at a later date, should the need arise.

    Next on the list - front forks.  Oh dear, those stanchions have seen better days.  Being a B175, they have "heavyweight" forks.  I suppose they are heavier than the forks on the earlier models, but the forks on the Sport and Bushman are even heavier - in fact they are the same forks as fitted to the Starfire.  Anyway - B175 fork stanchions - virtually every dealer is showing them for sale, but none of them have them in stock.  This calls for plan "B".  Get the original ones refurbished.  Brook Suspension seem to have a good reputation, so that's where I've sent them . . . time will tell.  Speaking of refurbishment, the powder coating has now come back, and I must admit, I'm more than pleased with the result.  OK, it's a colour that can never be matched - it's a "made up" colour.  Silver was done first, then a fine coat of the secondary colour applied, this gives an almost metallic finish.
    Now for folks thinking that "doing up" a Bantam is cheap - it costs as much to build a wheel for a Bantam as it does for a Vincent.  OK, other bits may be cheaper, but so far the bill for this bike is up over £1000, and I ain't factored in the rebuild of the wheels and a new exhaust system yet.  Fortunately the rewire won't cost me much - I still have most of what I need from the last couple of bikes I rewired.

     I can't do much with the frame until the wheels are fitted - and I can't fit the wheels until the forks are fitted - do you see where I'm going with this ?  One thing I can fit is the swingarm.  The bushes don't show any signs of wear, and the spindle looks good.  I have a feeling the bushes and spindle are new items, mainly because the bolts which hold the spindle in place are cycle thread with a pitch of 26 threads per inch.  The correct spindle for a B175 should be a much coarser thread.  You can fit the spindle with a bit of persuasion with a large hammer, but a press makes things a lot easier.
   Having got the swingarm back in, the next item was the carburettor.  By now my new 180 main jet had arrived, so it was just a case of putting all the bits back where they came from.


    Time to take another look at the electrics.  It seems the rotor is an accident waiting to happen.  The centre has come loose, and if those bits start flying apart when the engine is running, then you could be looking at a big repair bill. . . so this "electric grenade" has to go.  I do not have a spare rotor, and it seems there are none for sale, so that leaves three options: 1 - try and make an adapter sleeve so I can fit a conventional ¾ inch rotor. 2 - try and obtain a new rotor. 3 - change the entire system for something more modern. 
    Whenever I've done work for other people, usually on the flywheel magneto Bantams, I've always advised them to fit Electrex World systems.  Other systems are available, but I've never had any problems with Electrex World units, and when I needed advice, I found them to be more than helpful - even to the point of trying different ignition boxes on a bike I trailered down to them.  So, after taking my own advice, I've ordered a new charging / ignition system.
    This new system means that the original switch gear in the headlight is no longer suitable ( OK, so the light switch is ) so I've reverted back to that old faithful - the keyed ignition switch and the toggle light switch.
    I've also made a start on fitting indicators to the rear using a stainless steel bracket which attaches behind the number plate.  This means that should you wish to remove the indicators and revert the bike back to original, then it's simply a matter of undoing a couple of bolts.  I also changed the rear light for something that actually fits the number plate mounting bracket.



    The petrol tap I normally use is one for an Indian Enfield - I've got one on my B31, and on my Guzzi,  and it works well.   Seeing as I had both the Bantam tank and the B31 tank on the bench following re-sealing with POR15, I grabbed the tap I'd used on the B31 tank and made sure there was no sealant left in the threads.  I then fitted the petrol tap back in place.  Seeing as I had the tap in my hand, I drilled out the Bantam tank and tapped the hole in readiness for the new petrol tap.  Oh dear, that seems a bit loose.
    It turned out that my new petrol tap had a ¼ inch BSP thread, but the other tap ( in the B31 tank ) is a 3/8 BSP.  Time for plan "B".  I've ordered a brass bush with a 3/8 BSP male thread and a 10mm hole in the centre - I've also ordered a ¼ inch BSP tap and a suitable tapping drill.  Hopefully it will all work out in the end.  It wouldn't be as much fun if you didn't make the odd cock up now and again ( or again, and again, and again, in my case )

    The Electrex World kit has now arrived, so it was off with the old, and on with the new.  It's a simple system to fit, almost as easy as fitting the standard rotor and stator.  With the piston at top dead centre, you just line up the two blue timing marks and it should be good to go.

   It might seem an expensive bit of kit, but if you price up a new stator and rotor, then add the cost of a regulator / rectifier, and add electronic ignition on top of that, you'll find there's not a lot of difference, price-wise.  Having fitted the new rotor and stator, I couldn't really test it without the engine being in the frame, and that isn't going to happen just yet.  I have no wheels and no fork stanchions, so until they arrive, there's not much I can do.


    Still awaiting forks and wheels, so let's get on with a few more bits.  First off was fitting the steering head, complete with 48 new ball bearings.  Whilst I had the frame up on the bench, I "dry fitted" the inner panels for the toolbox and air filter, along with the battery carrier - which has been modified to take the different shape of the new 12 volt battery.  Next up was fitting the rear mudguard, but not until I had fitted the rear light bracket and the number plate.  The whole mudguard / number plate / rear light assembly was then wired up, terminating in a six way plug connector.  This makes life much easier when it comes to wiring the rest of the bike up, plus it makes life simpler should you ever need to take the back end off again for any reason.  Now that the mudguard is in place, I next fitted the carrier.  A stainless steel item which actually fitted the bike without any modification, so well done "Classic Bike Racks".


    Remember that petrol tank that I messed up earlier on ?  Well after a bit of faffing about I finally got the hole down to the correct size for the petrol tap.  A quick test with a pint or so of petrol proved that there were no leaks, so it was time to try the tank on the frame.  Because of the lug for the steering lock, the tank has to be spaced out to the right otherwise the lug will hit the seam.  This isn't a problem with the earlier tanks, but the "jelly mould" tanks have the seam in a different place.  After a bit of fettling, I got the tank to sit on the frame with the bottom yoke of the steering head missing the seams on both left hand and right hand full lock.  So that can now be put on one side whilst I carry on with the rest of the bike. 

    Whilst waiting for the front end to come back, I carried on with wiring the rest of the bike up.  To make life easier, I sat the frame on a little trolley ( it used to be used for wheeling bread baskets about ) which means I can at least move the thing out of the way when I need to work on other bikes. The other thing about having the frame on the trolley meant I could bolt the engine in place.  With the engine in the frame, I rigged up my remote fuel tank and started the engine.  It runs with no rattles or bangs, and the charging system works . . so that's a big step in the right direction.

  The wheels have now come come back, so the first job was to get some new tyres and tubes fitted.  I've gone with Mitas - I've got them on other bikes and they seem fine.  Following that I did my rear sprocket bolt modification.  I've had the original BSA bolts work loose on more than one Bantam, so what I do now is to tap the bolt holes out to M6 and fit longer M6 Allen pins in.  It doesn't work if you use M6 bolts, the heads are too large and will foul on the brake plate.  New wheel bearings and brake shoes were also fitted - the peg spanner I made earlier came in useful again.



    Seeing as I now had the wheels, I fitted the rear one in place. Whilst I was working on the rear wheel, I might as well fit the chain and chain guard, which I did.  The frame was still sat on its trolley, waiting for the fork stanchions to arrive. . . .which they did.  Right - next job was putting the front end back together.  This is made a lot easier if you have a fork stanchion puller.  Not the most difficult of tools to make, providing you have an old fork top nut.  I made one of these a few years back when I had another B175 - take a look at THIS PAGE for details on how to make one.  Having got the forks fitted, the mudguard was next.  I'm afraid the rivet counters will not be pleased because I used stainless steel metric fasteners to hold it all together.  There again, as you will have gathered, I build bikes to be practical as opposed to factory original.  Next thing was the front wheel.  This too has had new bearings and brake shoes.  Of course, seeing as I'm using non-standard brake and clutch levers, new cables have to be made for both front brake and clutch.  I tend to make two of each - one to fit on the bike, and one to carry as a spare.


    Having done all the above, I wheeled the bike outside and started it.  Pulled the clutch in, engaged first gear and the Bantam moved under its own power for the first time.  The bike is almost finished now, but there are still little things to be sorted out.  A new exhaust system for one.  The decals for the side panels ( still waiting for 'em ) need putting on.  The little matter of insurance has to be sorted out, then an MOT test.  OK, so I know according to its age it doesn't need one, but I'd rather my friendly MOT tester spots something I'd missed.  There's a good chance the brake cams have worn the holes in the brake plate oval - I need to see how it behaves on the road before I go making bushes and sorting that out.  Hopefully the next thing I need to do is use the thing and run it in - staying local for a few "shakedown runs" before attempting any serious distance.  Still, this is all part of the fun in owning a Bantam . . . or so they tell me. 

    The bike has now been out on a few shakedown runs.  The brakes are working fine, so I won't be re-bushing the holes just yet.  The carburettor however is a different matter.  It's rather worn, rattles a bit and is running far too rich.  Time for a new Amal Premier I think.  I'm not happy with the shape of the indicators, they may look fine on a modern bike, but they just don't suit the Bantam at all - so they will be getting changed.

    Like I said, a new Amal Premier has been fitted.  It was a bit weak on the pilot side, so I fitted the next largest pilot jet, that's made things a lot better.  One of the things I try to do with any bike I intend using, is to find out how far it will go once the fuel tap is turned onto reserve.  I filled my one litre fuel bottle up and set off for a ride around the Severn Valley.  From going onto reserve to running out fully took 23 miles.  Funnily enough, the reserve capacity is also one litre.  This means the bike was doing 104 miles per gallon.  The new decals for the side panels arrived, so they got fitted too.  Now some of the more keen eyed folks will have noticed an earlier picture of the side panels with the decals fitted . . . go take a closer look . . . they are fitted incorrectly and would have been sloping down at around 30°.  That'll teach me to look before I fit next time.  The only thing I'm waiting on now is the new exhaust system.



December 2021

    The new exhaust got fitted - along with a GPS speedometer ( which you can't see during daylight hours, so that might be getting removed ) and a LED headlight unit.  I've also built a 185cc engine which is currently sitting on the bench waiting to be fitted.  I dare say I'll get around to that sometime next year.

November 2022 

     Well the 185cc engine never got fitted - although I've just bought another Bantam frame, so it might be going in that.  I did take the Bantam down to the Ace Café, in London, for their Bantams at the Ace day.  I made it there and back without any trouble at all.  I did call in at the old BSA factory on my way back home.