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Bantam Trials Project #721387
01/07/18 3:10 pm
01/07/18 3:10 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
If I haven't got enough jobs on the go... Rebuild a D14 motor, re-fabricate a Honda 400/4 exhaust piece, an A50 Daytona racer and now a Bantam Trials project... oh yeah and finish the paintwork for my Honda 400/4 oh well nothing like having projects eh, the one thing that keeps us from insanity, well it would do but funding it is the problem most of the time... Anyway I digress....


So I have always been interested in trials riding (and having some off roading experience), especially following a loan of a bantam trials bike and how sure footed it was, followed by a go on my friends Grieves with leading link forks and dropping it down a ditch you can see why I took fascintation with the bantam.

So following the local purcahse of a frame (with swing arm and rear section) new hubs and a nice torquy D7 barrel I have most of what is needed for building one, I need to see if I still have my tiger cub swing arm (fingers crossed) something I bought an eternity ago for doing this project. I know that will need widening, I know the rear hub will need widening also plus other frame modifications (like moving the engine over to the left more and raising it also) modifiying the rake of the bike and basicly taking it from being anything like what the factory put out ha! But I have almost enough to be running with. Except the knowlege... What rake angle? And how would I best modify the swing arm? And questions like that. Doing it isn't an issue, but how to do it is the problem.

I also noticed the use of heavier A/B series forks being used with these bikes. I know the C15 used small spindles... But are the fork legs any different otherwise? And following a previous thread where someone had modified a set of aluminium fork sliders to fit in a set of Beezer sliders... I quite like that idea too.

My other (and probably biggest) question is which engine should I used, I can build up a 4 speed or a D10 3 speed motor (I bought the 4 speed cases for my D10 Sportsman project, but will hunt for another set) will the 3 speed be adiquete? or do you really need the well placed 3rd gear in the 4 speed box? (and what are the limiting chances of getting a 4 speed box from a bushman??? None im guessing)


All help and tips apreciated.... and I will update this as time goes on and hopefully I might get this built in a year laughing


beerchug
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Re: Bantam Trials Project [Re: Allan Gill] #721396
01/07/18 4:30 pm
01/07/18 4:30 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Photos of the frame

Attached Files Frame 1.jpgFrame 2.jpg

beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721429
01/07/18 10:38 pm
01/07/18 10:38 pm
Joined: Aug 2001
Posts: 1,974
Greensboro, NC
Alan_nc Offline
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The Cub swing arm will work without modification (it will hold a standard Trials Tire). Go for the 4 speed. The gap in ration between 1 and 2 in the 3 speed is just to wide. Plus you don't have enough speed when going from section to section. Your biggest problem is going to be over heating - I never did solve that. I went with a set of Yamaha front forks - the pogo sticks just won't cut it. Up turned exhaust is available but pricey. Your also going to need to work out some type of fold up foot pegs.

I took 2nd Here in AHRMA in the US one year but I've got to tell you that the bike is just to under powered. Also the brakes aren't up to the job (I chalked and sanded mine in but still never could stop as quickly as I needed to).

Keeping thinking of other things I changed: You will need to modify the frame under the seat, it's just to wide to stand up and ride the bike. This will require you to modify the seat. Also whichever model you use you will need to use the later tank - D7/D10 as it's narrow in the rear.

If you have a section with a fairly long up-hill or down-hill with a sharp turn at the bottom and then a return you sometimes can't complete the section.

If you have a Cub or Greeves available I go with either of them. You just need more power and a bike that was originally built for Trials.

I tried a Bultaco for a couple of seasons and then ended up with a TY250. Once set up the Ty Never gave me the slightest bit or trouble. I ran it for two full seasons without taking the head off. Good clutch feel, choice of several different flywheel weights. I had it totally under water and finished the section. A TY175 is probably the perfect bike (if you are under 200#), but over here they are expensive and the parts are hard to find.

If you have any questions email me directly. I have all kinds of pictures of modifications I made to the Bantam

Last edited by Alan_nc; 01/07/18 10:46 pm.

Alan
Cleared m out....left only
59 BSA Bantam (Trials)
78 Triumph Bonny (UPS)
02 Suzuki GS500
Re: Bantam Trials Project [Re: Allan Gill] #721462
01/08/18 9:34 am
01/08/18 9:34 am
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Thanks Alan, I'll drop you an email. I was hoping you would chime in...

I've added a photo of what I'm wanting to make it like, one chap has done a thread on how he did his Clicky Clicky I think it'll be a good basis to design it to, all of which i can fabricate.

Thanks for the confirmation on the 4 speed, it looks like the common thing to do is to swap 2nd and 3rd around also. I was hoping the 3 speed would be adequete as I have a complete bottom end I could use, so it would mean me buying another motor, or using the D10s motor in this.... and then keeping an eye out for something else (these bikes are becoming silly money now)

Didn't know the tiger cub arm wouldnt need modifying, what tyre size did you use? the guys in the UK generally use a 4.00-18..... even on the bantams.

Thanks again

Allan

Attached Files Target frame design.jpg

beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721518
01/08/18 8:43 pm
01/08/18 8:43 pm
Joined: Aug 2001
Posts: 1,974
Greensboro, NC
Alan_nc Offline
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Greensboro, NC
The Cub swing arm is 5/8" wider and will allow the 400x18 (if I remember you need to use the Cub wheel also), I think it is slightly wider. The pivot section is exactly the same width and the through bolt the same size. I had a devil of a time getting mine apart just because it had worn a groove in the bolt but once that was done it slid right in. Sent you a couple of pictures by email. You will get a kick out of the sprocket.


Alan
Cleared m out....left only
59 BSA Bantam (Trials)
78 Triumph Bonny (UPS)
02 Suzuki GS500
Re: Bantam Trials Project [Re: Allan Gill] #721525
01/08/18 11:51 pm
01/08/18 11:51 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Ahh ok, I should have a cub swing arm lying around somewhere, some of the late Bantam’s seem to have this and my old one originally had one which looked like a typical bantam unit but when I went to replace it with a similar one the other one was narrower at the spindle end. So a cub one got fitted into that.

I have heard of people chopping hubs to make them wider to give more strength to the spokes, again maybe the cub one is wider as you mention and solves this issue.

The pictures gratefully received. Yes the rear sprocket is huge, are you also using smaller crankshaft and gearbox sprockets? I have not found until recently smaller gearbox sprockets. One seller does 12, and 14t crank sprockets and now also does gearbox sprockets from 12t upwards, only found that today. He also does a 64 and 64.5mm piston for trials use, the transfer port cutaways look to be closer to the skirt, like having shorter cam dwell on a 4t engine.
He also has come Todd copy blank castings. Could be interesting... need to drill the 4 barrel stud holes and shape the combustion chamber (he gives milling instructions for his 64mm piston)

I see you have tried 2 exhaust systems, which did you prefer? I’m thinking of making something with an expansion pipe (similar to a modern bike) then with a small outlet after a muffler box.

Many thanks again for the photos, it’s great to see what you have achieved and on a great bike too.


beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721633
01/10/18 3:29 pm
01/10/18 3:29 pm
Joined: Dec 2004
Posts: 9,332
Scotland
kommando Online content
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kommando  Online Content
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Posts: 9,332
Scotland
On the C15 the heavy duty fork yokes fit in without mods, but you need to use the C15 head bearings not the heavy duty ones. The ID of the head stock is less but the stem OD is the same diameter as the heavy duty as is the length. Not sure if that's also the case for the Bantam but made it easy on the C15 to get heavy duty forks added.

Re: Bantam Trials Project [Re: Allan Gill] #721644
01/10/18 6:26 pm
01/10/18 6:26 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Rotherham - S. Yorkshire
Thanks Kommando, I’ll have to see what I can find. A lot of guys are using A/B series forks with the B44 style yoke (is the trail different with these forks over A65?)
A lot of people are suggesting using ally front end, mazochi etc and whilst I see the reason, the bikes I’ve seen are doing very well without them.

I may need to alter the headstock to suit other forks or bearings at least (can see me making a dolly for welding up a bigger bearing support)


beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721645
01/10/18 6:38 pm
01/10/18 6:38 pm
Joined: Dec 2004
Posts: 9,332
Scotland
kommando Online content
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kommando  Online Content
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Scotland
I will measure the B25/B44 offset and then you can compare to A65 yoke offset, there is more to the trail than the offset ie head angle etc but it will show you what if any difference it will give.

Re: Bantam Trials Project [Re: Allan Gill] #721649
01/10/18 7:30 pm
01/10/18 7:30 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Rotherham - S. Yorkshire
That will be great John. Thanks.


beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721651
01/10/18 7:45 pm
01/10/18 7:45 pm
Joined: Aug 2015
Posts: 1,134
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A
Joined: Aug 2015
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Bolton Lancs UK
The area around the swing arm spindle is very tight with a trials tyre. If you are using the bike on sticky clay mud, keep an old screwdriver on the bike to de-clog


1955 BSA B31 500cc "Stargazer"
1962 Greeves 200cc "Blue Meanie"
1962/67 Greeves 350
1967 Greeves 360 Challenger
1984 Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
Re: Bantam Trials Project [Re: Allan Gill] #721710
01/11/18 9:27 am
01/11/18 9:27 am
Joined: Aug 2001
Posts: 1,974
Greensboro, NC
Alan_nc Offline
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You are also going to need to alter (maybe remove) the stops for the forks. Any bike set up for the street doesn't have a tight enough turning radius. You may end up with fork tube dents in the tank - actually you may want to put them in before you start riding the bike.

OH and there is the question of a kick stand: Some people say never put one on a Trials bike. If you look at the pictures of mine you will see a kick stand coming off the swing arm. It ended up there after I road a Trial where there wasn't a tree in sight to lean the bike against while walking the sections. The Bantam center sand is useless (and in the way) on a Trials bike. You need all the clearance you can get.

Last edited by Alan_nc; 01/11/18 9:31 am.

Alan
Cleared m out....left only
59 BSA Bantam (Trials)
78 Triumph Bonny (UPS)
02 Suzuki GS500
Re: Bantam Trials Project [Re: Allan Gill] #721713
01/11/18 10:00 am
01/11/18 10:00 am
Joined: Dec 2004
Posts: 9,332
Scotland
kommando Online content
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kommando  Online Content
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Scotland
Offset for B25/B44 yokes is 1.375"

Re: Bantam Trials Project [Re: Alan_nc] #721783
01/11/18 10:13 pm
01/11/18 10:13 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Posts: 4,841
Rotherham - S. Yorkshire
Originally Posted by kommando
Offset for B25/B44 yokes is 1.375"


That’s the difference between the top and bottom yoke John? I’ll measure the A65 this weekend.

Originally Posted by Alan_nc
You are also going to need to alter (maybe remove) the stops for the forks. Any bike set up for the street doesn't have a tight enough turning radius. You may end up with fork tube dents in the tank - actually you may want to put them in before you start riding the bike.

OH and there is the question of a kick stand: Some people say never put one on a Trials bike. If you look at the pictures of mine you will see a kick stand coming off the swing arm. It ended up there after I road a Trial where there wasn't a tree in sight to lean the bike against while walking the sections. The Bantam center sand is useless (and in the way) on a Trials bike. You need all the clearance you can get.



I agree a side stand is a must, for the reasons you say. But it helps if they are on a clip to stop then dropping down. Often you see them dropping down and rarely they will cause someone to get a 5 because of it.

For lock stops I’m thinking of a threaded tube with bolt, each side of the neck, far enough back to allow a good lock and adjustable.

I’m also thinking of a bare build of the bike to check everything is where it should be, before going for paint.


beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721806
01/12/18 10:16 am
01/12/18 10:16 am
Joined: Dec 2004
Posts: 9,332
Scotland
kommando Online content
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Scotland
Quote
That’s the difference between the top and bottom yoke John?


No, its the offset, how far the stanchion hole centers are forward of the stem hole centre.


[Linked Image]

Re: Bantam Trials Project [Re: kommando] #721807
01/12/18 11:15 am
01/12/18 11:15 am
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Originally Posted by kommando
Quote
That’s the difference between the top and bottom yoke John?


No, its the offset, how far the stanchion hole centers are forward of the stem hole centre.


[Linked Image]


Sorry, I wrote my reply long, what I mean was is the offset the difference the offset of the top yoke compared with that of the bottom yoke. Thanks for the image, it confirms this.


Found (on the BSA Otter site) about widening the rear hub, looks within my remit, although I have to remind myself often that making these parts involves more times making the tools to do it. Alan mentioned to use a Tiger cub hub, after some research I noticed that the Cub used two hub sizes, the bantam size and a wider version. Unfortunately my search showed a couple of wider ones but each one bust in one way or another, so I will have a crack at making my own following the LINK. 35mm wider seems like quite a lot, but I have been told that trails is quite harsh on back wheels.

This looks like it will be my first task...I need to make my swing arm and rear frame section to suit this width.

Attached Files img_0507-edit.jpgimg_0516-edit.jpg

beerchug
Re: Bantam Trials Project [Re: Allan Gill] #721808
01/12/18 11:44 am
01/12/18 11:44 am
Joined: Dec 2004
Posts: 9,332
Scotland
kommando Online content
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kommando  Online Content
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Scotland
They are also using some KTM hub on the Cubs, on the B25/B44 the offset is the same for the bottom and top yokes so the stanchions are parallel with the stem.

Re: Bantam Trials Project [Re: kommando] #721817
01/12/18 1:10 pm
01/12/18 1:10 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Posts: 4,841
Rotherham - S. Yorkshire
Originally Posted by kommando
They are also using some KTM hub on the Cubs, on the B25/B44 the offset is the same for the bottom and top yokes so the stanchions are parallel with the stem.


Ahh, right this makes sense now, the A65 is different from memory, If you were to slide the top yoke so it sits against the bottom yoke, there is a marked difference in that the bottom yoke offset is greater. I beleive the pre unit models are the same.


beerchug
Re: Bantam Trials Project [Re: Allan Gill] #726761
02/25/18 1:06 pm
02/25/18 1:06 pm
Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Allan Gill Offline OP

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Allan Gill  Offline OP

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Joined: May 2013
Posts: 4,841
Rotherham - S. Yorkshire
Ok, some slight progress and some photos to follow, turns out the D14s yokes are identical to the B40 ones, only difference in the lower being the stem is of a different length... so a pair of old stanchions and I was able to mock up a front end with the B40 top yoke and the Bantam’s bottom yoke!! Great start!!

Feeling somewhat confident I then took to making an arbour to mount one side of the hub, having the drum mounted in the chuck, then parted the hub.

Today I’ll take my stock EN8 (pain in the ass to cut) 45mm steel shaft and turn it down to have 38mm width with 1” at either end to support in the hub... then try and drill a 29.5mm hole through the centre (can see that being fun) then if I have time, align it all up with th dial gauge and weld it back together. Then next project is to make the swing arm.

It’s anazing when you look at a lot of the one off trick trials bikes out there and you gain a lot of respect for what time other people have put in, how they have gotten their head around it and all the calucualting they had to do for it.


beerchug

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