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Scott's D1/D7 Bitsa
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Scotto75
Bristol, UK.
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July 22, 2020 - 11:08 am
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Hello everyone,

I've just acquired a rather sorry looking Bantam from under a pile of junk in a corner of a barn, that appears to be made up of various bits and pieces over it's lifetime. Unfortunately the owner had no info or history regarding it so it's a complete unknown. Here's a photo of it after giving it a wipe with a soapy sponge.

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The frame is from a '52 D1 but the front forks, mudguard and headlight are from a later model. The frame and tank have a different red to the front end, which is slightly darker, but with green underneath all the paint. The engine off a '66 GD7 model, and the rear mudguard's been swapped out for an ali one. There's no battery or toolbox.

My first task is to assess the state of the engine. I'd like to see if it starts before I decide if I need to strip it. It has compression when kicked, the clutch moves and the gears change when rolled so it looks promising. It's missing its casings on the left side and the primary cover has a hole in it.

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I would guess that this is worn through from the nut and bolt holding the kickstart on. I'll drain any oil out of it which, judging by the hole I imagine is very little, and get the cover off to look for anything suspicious. Also, I'm going to remove the stator plate and see what lurks in there. Hopefully all I need is some new oil, points, gaskets and covers..... for now.

Please let me know if I'm missing anything. I'm no stranger to bringing old motorcycles back to dead, but I'm new to Bantam's and imagine there's a lot of dark art involved that I have yet to experience! Any advice is always welcomed. Thanks!

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cocorico
Central France
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July 22, 2020 - 11:37 am
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Looks as though it has been turned into a field bike at sometime. The hole in the case can be welded, or even patched using some thin aluminium and plastic metal. I wouldn't change the points yet - clean and set them, take the spark plug out and reconnect it, kick over and see if you have a decent spark. If not check plug, plug cap and capacitor finally a new mag coil (12£ on ebay). Then as you suggest, see if you can fire it up. I had an old D1 engine which hadn't been apart before which fired up easily and only got disassembled because there was a loose flywheel plate spinning like a turbine. Good luck with it.

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Scotto75
Bristol, UK.
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July 22, 2020 - 2:44 pm
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Hi cocorico. Thanks for the reply.

cocorico said
Looks as though it has been turned into a field bike at sometime.

That's what I thought possible. There's no centre stand either. But not sure why it's still got rear pegs on and why they're so high up??

The hole in the case can be welded, or even patched using some thin aluminium and plastic metal.

I had thought that. I've got some JB Weld, but was concerned that the nut would knock it out again. I check what the clearance is like with the kickstart lever.

I wouldn't change the points yet - clean and set them, take the spark plug out and reconnect it, kick over and see if you have a decent spark.

I've got some time tomorrow afternoon. Will give that a go! Cheers.

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Scotto75
Bristol, UK.
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July 24, 2020 - 12:48 pm
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Removed the plug and gave it a kick, but no spark. So I removed the stator plate and stripped the points, cleaned them and refitted, then tested the coil for continuity. Everything tested good, with the points breaking the continuity when open. I will try replacing the condenser with some I know work. I have an NOS Lucas Ford and old Intermotor one's off my Bedford CF.

Well in my quest for a spark, I've made another interesting discovery. The head has an 18mm size thread, and is currently using a 14mm Champion L82YC plug in an adapter.

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I'm unable to find a part number on the fins of the head to ID it, but the thread depth is 12mm, the same as the plug adapter. The plug seems to be sitting a mm inside the adapter, but at least it's not fouling the top of the piston. Looks like someone may have had a fight with a previous plug and lost and just tapped it larger, rather than helicoil it.

I also removed the 375/31 carb and stripped it down in order to run it through the ultrasonic cleaner, and made a couple more interesting finds. First off is the needle was bent just under the grooves.

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Maybe a previous owner had used a club hammer to get the clip back, or was trying to make a new groove? I was ordering a gasket kit anyway, so a needle has been added, along with a fuel filter.

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As it looks like the same gentle hands have been at work with this one as well!

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cocorico
Central France
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July 24, 2020 - 3:39 pm
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Oof, that lot could go in "The Black Museum"! Obviously not a mechanically sympathetic PO. I think I'd look at a helicoil or a replacement head. A new plug wouldn't come amiss, though it should still run using the adaptor (with a sealing washer). You may be able to gently straighten the needle, but new is best. Hope you don't find too many other horrors lurking. Your choice of capacitor should be fine, too.

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sunny
Norfolk
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July 24, 2020 - 4:14 pm
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the  Brass insert  was  serposed to  glued  and  staked to stop it  coming  undone        so  look  up  Stake   NUTS    for help 

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Scotto75
Bristol, UK.
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July 24, 2020 - 6:10 pm
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Hi cocorico, yes it doesn't bode well! The closer I get to it each time, the more I keep seeing other warning signs of botched work future me may have to deal with. I did try to straighten the needle but when I saw the state of some of the other bits, a repair kit was the only way forward.

Hello sunny and thanks for the info.

sunny said
the  Brass insert  was  serposed to  glued  and  staked to stop it  coming  undone

I was figuring that was the case after looking at pictures of other heads. On close inspection it would seem it has been fairly abused and may have come out a few times too often that it is now staked to the plug instead. I'll get the plug in a vice and see if I can either tap the insert off, or maybe file a couple of flats on it to use a spanner.

The thread of the insert looks metric and measures 17.9mm. I'm pretty sure the pitch isn't UNC. I can see on the internet there are 14mm to 18mm brass spark plug adapters, but they look quite wide around the nut end and can see it hitting the fins as it goes in.

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Scotto75
Bristol, UK.
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July 31, 2020 - 6:40 pm
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In my quest for the elusive spark, I have removed the stator plate and done some tests. To start I have a S55 WiPac stator type 1452 (SN:1269) with an AC/DC flywheel.

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Here's the test results....

Primary coil - 0.9 Ohms.  Secondary coil - 5.5 kOhms.  Spark plug - 5 Ohms.  Condenser - 55 kOhms.

I tested the continuity of the primary and points circuit and confirmed it broke when the points opened. I had a couple of other condesers and tested one and found the Lucas DCB703C condenser had resistance of 260 kOhms, so used that one instead, under the assumption that the higher the resistance the better....?

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Scotto75
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July 31, 2020 - 6:44 pm
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This all seemed promising so wasn't certain where the missing spark had vanished to. I cleaned up the flywheel and found TDC with a screwdriver down the plug hole and a degree wheel on the shaft. I then backed it off to 19 degrees BTDC. On the flywheel I marked where the magnetic neutral portion was between a S and N magnet. I then reinstalled the flywheel so that magnetic neutral had passed the stator finger, which was sat under the north magnet pole. This was based on this info, albeit a Lucas chart....

https://www.bsabantamclub.com/wp-content/sp-resources/forum-image-uploads/mike-p5xbx/2014/05/magnetic-neutral.png

I double checked the gap I had set previously was still okay, and then made a minor adjustment to get the points to open. Didn't have a fag paper as my roll-up smoking days are well and truly behind me, but used a thin bit of paper as a rough guide. Put the plug in the cap and turned it over with my hand. Hey presto!! A very faint and intermittent spark. Suspecting the cap had seen better days, I pulled it off and stripped some bare copper, which I attached to the top of the plug, by screwing the top terminal down onto them. Kicked it over and BANG!! Some big bright sparks. Happy days!

I will order a new cap. I'll also make a TDC tool so I can clearly mark TDC on the case and flywheel and then redo the ignition timing more accurately.... but I've established I have ignition, so now onto the fuel side!

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The 375/31 carb is now in pieces and in my ultrasonic cleaner. Luckily my mrs isn't in for the moment so I'm doing this from the luxury of my kitchen with a cuppa, but she and the kids hate the sound the cleaner makes and so I usually have to do this from my garage. I have a gasket kit, new needle, fuel filter, etc, so will hope to get this back together very soon.

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