Pre-65 Bikes

Can this seal be changed from the primary chain side ? Its a GB engine. Thanks Ross

Hello I have a nice rear wheel built on a D10 half width hub that I used to run in a C15 frame and swinging arm. I was thinking about using it in a B40 WD frame and swinging arm I have for a vintage Mx build. The spindle is obviously a little short in the B40 WD swinging arm, are there any other longer spindles that fit the Bantam hub to help with this?

Hi folks, just a question for future sprocket alternatives. I have a motor which is B40 cases, with B44 crank and top end, 23 eng sprocket and 52 clutch....gearbox is 11 teeth with 55 on rear. I'm guessing standard side point motor gear box ratio's, but no clue realy. So bike handles sections in first gear reasonably well if not realy tight, and second good for hill climbs, so quite usable. Was just wondering if I went to a 18 tooth engine sprocket....I may be able to go up a tooth or two on the gear box and less teeth on the rear and shorter chain, and still lower the overall gearing slightly. Sounds feasable to me, but any input welcome. My biggest wor…

Hello all, Just joined the pre65 brigade after purchasing an otter framed B40. Is there a service manual available that could give me information such as oil types/quantities, servicing tips etc? The bike is in good condition but needs a few sessions in the 'Cosmetic department' and a good checking over...any help would be appreciated. Thanks in advance, Mark.

Hi I have a problem with my B40 trials, I went to fit a pvl ignition and found the primary chain had been rubbing the crank seal. Is this common and how can I sort it? I also need to get more ground clearance from a c15 frame b40 engine . Been having problems with getting hung up all the time. Are there any common mods that were done? Also how easy is it to replace the conical hub with a cub hub, I have b50 front forks four studs Any help would be much appreciated

How much wider is a B40 swingarm than a C15?

Hi I've been trying for some time now to get some details on enlarging the capacity of my B25. It's had several mods already done, including changing the cam, and it now plonks and pulls pretty well. I would like to know the easiest way to get it out to say 280 ish ideally without having to bore the crankcases. I did hear a 650 triumph piston would do it? But which model and compression, is there enough on the standard liner to go out that big, if not what liner will I need? thanks Paul B

Hi, Recently retired so am relatively new to old bikes. Just finished rebuild on !961 B40 which took 18 months. My question is regarding the oil feed to the rockers. It would appear they are not pressure fed due to returning oil pressure being vented into the tank. It obviously works but should I put in a pressure relief valve on the tank return to ensure a pressured feed to the valve gear.

Hi there I have been given a Bantam (Ihave been told a d14) not sure though which is in alot of bits. I have been thinking of converting it into a trials bantam. Has anyone have done this before and what should i need to know or consider before i start the wheels need new rims and spokes anyway

I need help with a project I have bought which I was going to use for spares but after giving it a look over I think it might have a bit of history to it.My thoughts are that it has been built rather well,its frame has been modified with twin rails under the motor (the frame number is d10***)and is clearly bantam and the rest of the bike has been built with a lot of thought,does this ring any bells with anybody.Thank you.

Asking for a friend. Anyone know where to get a con rod & big end for a MZ 150. Apparently they can be machined to fit the Bantam. Thanks in advance. Ross

When up at the Two Day pre 65 Trial I saw some Bantams which looked 3 speeders but were definitely not. Am I correct in thinking it is a simple (!) case of fitting a 3 speed crank in a 4 speed c/case to get the ignition on the ‘correct’ side and using 3 speed outed casings? Our son has a B175 based trials bike and we were thinking of converting a spare engine to a 3 speed look-a-like over the winter just for something to do. Any suggestions on what to replace the old Amal carb with – make (Mikuni ?), bore etc? He will never be competing in any restricted specification events so no worry on that issue. Jim

Hi all, I'm about ready to embark on my bantam trials machine. I've had her tucked away in the garage a good few years now. Someone has had a go at her before but a bit cowboy'esque !! She has what I believe are Montesa adjustable damping forks and wheel set up. With (somewhere) the swing arm and adapters to fit this also. But it doesn't seem entirely British, I'm all for using what works the best but I think I would like to keep it at least looking like it could have come out of the BSA factory. So then questions....heaps of them if anyone could help. Just a few for now: - Where do I start with frame mods, lifting the reas sub doesn't seam too difficult but I'm conce…

Just about to lengthen the swing-arm on my bantam project, anyone know how much I should lengthen it by? It’s a wider type sports cub swing-arm

Hi all. I am rebiulding a new Trialsbits WM1 21ins 40 hole non-valanced alloy rim, onto a standard Bantam front hub and would appreciate help with the spoke lengths I require, if anyone has the info available. I believe they are 10swg, but am not sure of the length and the hub was not in a wheel when the project was purchased, so I cant even have a stab at it The nipple holes on the rim are 7mm and i'd like to use stainless spokes if they are available. I hope to lace it myself, as I have rebuilt plenty of British iron, but never done my own wheels. I will have it trued by someone professional just to be safe, but I'm determined to have a bash at it. Thanks. Steve

I'm not sure whether the 2nd and 3rd gears on my bantam engine have already been swopped over. If you want to lower the gearing on a transmission then you go for less teeth on the driving end and more on the driven end. So, in the gearbox, am I right in assuming I should end up with the 22 teeth cog on the output shaft, and 21 on the other shaft ?

Just wondering if anyone is using any after market ignition other than the popular PVL on a Bantam 175 and if so any advantages (other than price) Thanks in advance.

does anybody know who produces alloy barrels for the 4 speed bantam engine please.

Hi All, Project Bantam is coming along very slowly. I'm now looking for a 3rd Kickstart after the first 2 i made failed. I've seen several pre65 Banatms with spangly folding kickstarts (usually off other bikes). Anyone got any ideas as to what fits? I'm struggling to find a 3/4" splined version of anything Cheers Chris

Hi Guys I am new to this forum i have a cub frame and modified subframe i am basically building a cub rolling chassis with all cub parts then putting a bantam engine in as that is all i have spare any bantam engine modifications or tiger cub parts that i should buy though they will have to be cheap as i am only 15 Cheers Sam Photos so far