Pre-65 Bikes

Just finished rebuild of Bantam D7, with a couple of running issues. Takes a good while to start - seems when you put some petrol down the port and heat the plug it will start, then run ok - changed plug cap and new plug. It will then tick over and rev out, but when you ride under load it bogs after about quarter throttle - sounds like it is pulling a load of air in. Any thoughts ? (crank seals ??) cheers guys John

Hi Guy's Just on with changing the fork seals on my Sprite , so while they are in bits are there any mods that can be done to improve the forks , also anybody know of other springs that will stiffen the front end up .. Any info grateful

What is the general consensus re heat dissipation. I am building a B175 engine for trials, I am using a modified Fantic 200 cyl head which has a larger finned area etc, they can get hot during trials in the warm months and they are centre plug head. On the Fantic they were black, just wondering is it best to paint or get blasted to bare ally. ?? I will be painting the barrel and using a Suzuki TS185 piston. Thanks in advance....

Guys, Got a centre casing on my Cub that’s past it’s sell buy date. Im looking for a replacement, the replacement I’ve found has the same E4087 number as mine , but mine is stamped underneath that as AM 1, the replacement is AM 2. They look identical but that’s from a comparison of photos , not in person. Will the casings be the same, I’m assuming the AM number is probably a casting batch and the part number is the E4087. Thanks.

Couple of Bantam build questions please, Is it a good idea to swap around the existing 2nd and 3rd gears, I found a diagram of how to do this on the web but if that lowers second then what happens to third gear. Is it instead better to buy the aftermarket second gear set which is I believe 20/27 ? Which ignition system and crankshaft weight is the one to get All BSA Bantam engine build hints and tips welcomed

working on a cub to replace the seals ( i think the forks are actually bsa perhaps from a c15) i put 150ml of 15wt oil in and they 'sag' for fun (maybe an inch and a half under the weight of the bike and another inch when lardy boy climbs on board..) to stiffen them up do i put more oil in put thicker oil in put a longer preload spacer in put 'fresher' longer springs in ..

Hi All, have a small oil leak from top of push rod tube so decided so that bike can stay running I would refurbish a spare head that came with it, so I could upgrade when I get round to repairing the leak. On inspection of the spare head and the removal of the valves (guides came with them) it turns out both valve guides were loose in the head, exhaust guide snapped in half at the line of a spring clip and the inlet valve spring broken. Looking down the inlet port it has been reworked with all of the aluminium boss for the guide removed and the guide was tapered to increase flow. This is a suggestion I have read in Rupert Ratios book but he did have a warning caveat rega…

in advance of Scotland i have just fitted a bicycle digital speedo, having heard that the ignition plays havoc with the wireless types, i fitted a wired one. all works well if freewheeling with a dead engine, but once the engine is running the speedo displays random numbers.. i guess the PVL coil is causing the problem... any one have a solution????

I need some help with my b40 engine! Im in the middle of rebuilding my engine and Im not sure about the crank shaft bush in the outer casing. It looks like a steel insert within a piece of rubber and is'nt a very good fit with the crank. Drawings only show an oil seal. Is this correct or has some one played with it? would be very greatful for any info.

i have heard there is a guy in the midlands who builds and prepps them to a high spec. Anybody got any info. As in my wanted add, I have a crazy german who wants to buy a high spec beezer.... if I wanted a fanny , i would ask Bill Pye... Whos the beezer guru in the UK?

Hi all can anyone help me to locate a 15mm alloy spindle about 230mm long as i broke my bantam one today at a trial and now want to fit a knock through one , i think wrighty was selling them at telford ? or failing that what sort of alloy would i need so i could get the local guy to turn me up one , need it quick as pre 65 champ round next sunday CHEERS FOR ANY HELP

Well the sows ear project is progressing very slowly and i am now at the point where i am looking to fit sprockets. Got a 12 tooth crankshaft sprocket fitted so what is the best combination gearbox and rear sprocket that people have found

I have seen some pictures of a few trick ARMAC frames for Cub's and was wondering if anybody does something similar for BSA's. I have always had BSA's and have plenty of bits to build a C15G or a B40 up. I am sorting out a bike at the minute to have a go again as not rode a trial for over 11 years!!! Would like to have a fairly standard one and a really trick one to cover all options. Anyone know what forks Thorpey has on his ? Certainly look pretty modern.

Hello all Why do we have this so called pre 65 rule book which i hear quoted at every trial when clearly most of the bikes do not fit within the so called rules! Mcdonald cubs that do look the bizness and brand new dots that are 2010 made..how are they pre-65? frames are nothing like the originals front loops. there not meant to be altered are they. but all the trails i have been to recently the organisers havnt battered an eyelid. it seems ok to run these trick extra light engineering genious machines..but its not pre 65. How do the dots get into the scotish? there not pre 65/67. Am i loosing the plot bringing this up does anyone else seem to be bothered this all happe…

I have just finished building my dream Armac Cub but am slightly frustrated at not being able to stop a minor oil leak from the gearbox side. I cured the clutch side by fitting a belt drive primary and diaphragm clutch I had a spare gearbox cover, a lathe and a mill so decided to try the Armac conversion and do away with the outer cover, however, I only have a photo to work from. I don't have access to ally welding equipment so am trying to avoid welding if possible. I have machined the flanges off the edges of the side cover, modified the case for a clutch lightener (I'll be using my original Armac clutch lightener on the bike), machined the selector ho…

A while back I bought a BSA Bantam 175 as an unfinished trials project, its a D7 frame but the rear tyre (4.00 x 18) catches the swinging arm. Does anyone know the best mod? Is is a case of extending the swinging arm behind the shock mounts or is their a better way? Cheers Eiger

Is there any reason why this system cannot be shortend so that the silencer sits tucked away where the oil tank was sited. Does it affect running to shorten the manifold pipe? Also how do you get a lighter clutch? apart from the right cable/routing what other mod's are there to get a lighter action?

Thanks to Jim Evans and John Robertson we found this Greeves TFS Scottish for a very reasonable price. It will be my next project for this summer. Will upload some pics with the progress and when finished. Any advice is wellcome. My idea is to paint frame and tank in a metallic blue (not the original) and make the seat in dark grey.

My air filter assembly has a potential leak near the front. See the picture. Am I missing something? Should there be some sort of cage?

Dear all, Do need some advice here, where to search for proper black full lenght, ~180dg, polymer compound 5" mudguards similar to all OEM, Acerbis, UFO... mesaurements and shapes identical to 5" alloys = accurate diameter for 18 x 4.00 for "periodic 50´ rigid look:-) Were naive enough assumed no one offering rear 5" full lenght with smaller radius than required for 18 x 4.00.... should match what?? 17 x 3.75 is it even possible to find for OEM Cota 125?? And China compound not at all corresponding to all trials / motocross panels, tanks, mudguards..Ive ever seen from -75 up to date. M G.. Cheers,