irishjohn Posted October 15, 2008 Report Share Posted October 15, 2008 I recently purchase BSA 441 Victor as a basket case at a garage sale. The bike appears to be about 90% complete but at some time has had some modifications to use as a scrambler. I would like to build it back as a trials bike to use in pre-65 competitions. The frame is appears to be stock and it has a 19' front wheel. Any suggestions on frame or other mods and sources for BSA parts would be appreciated. Quote Link to comment Share on other sites More sharing options...
swooshdave Posted October 15, 2008 Report Share Posted October 15, 2008 Did they make 441 prior to 65? Or can you get away with "like design"? Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted October 16, 2008 Report Share Posted October 16, 2008 Hi Guy's, Yes my friend from the BSA competition shop said there was a victor prior to 1965, and as they are the same design as a C15 there is no problem in most cases. The seat tubes need pulling in to make for a better ride ,footrest positions need putting further back. and comprestion needs lowering on the engine. also gearing realy needs to be changed to wide ratio. then there are the tires etc to sort. These are just a few things off the top of my head. but it should make a good trials bike. Regards Charlie. Quote Link to comment Share on other sites More sharing options...
pat slinn Posted October 16, 2008 Report Share Posted October 16, 2008 I played about with a 441 motor during the mid 60's, converting it for trials use. I sleved the inlet port by turning up a alloy tube and sweated it in to the port, I used a compound called "devcon" ( I think) to mould the tube to the port and shaped and smoothed it using a rotary file. I think I reduced the port size to 1". I reduced the compression ratio ( I forget by how much now) by making up a simple compression plate from alloy plate to fit beneath the cylinder. I used a C15 trials camshaft and the C15 cam followers. I remember that I found finding a suitable "gearbox" difficult, but I played about with "Victor" and C15/B40 components. The motor was quite good, and I remember that it had very good low down talk, and did super "wheelies" !!. As Charlie has said the sub frame needs pulling in, and the footrests need to go back. I hung my footrests off the swinging arm spindle, and made up a new rear brake pedal & gear lever. It sounds like a super project with a lot of scope for development, loads of engine bits turn up on ebay. Please keep us updated on progress. Regards, Pat. Quote Link to comment Share on other sites More sharing options...
irishjohn Posted October 16, 2008 Author Report Share Posted October 16, 2008 Thanks for everyone's suggestions. This will be my over winter project as soon as I finish putting my KT250 together. Pat, any reccomendations on how thick of a plate you used to reduce the compression? On your mod for the intake track, did you continue to use the original carb or substitute something else? This engine now has a Mikuni carb installed, I believe it is a 38mm model. I wonder if you could acheive the same effect by suing a smaller model, such as a 32mm? It looks like it would be fairly simple to make an adaptor to do this. Regarding narrowing the sub-frame, think I can do a bit of a cut and paste to narrow it. I also wonder if I could graft a sub-frame on from a donor bike. I have a couple of spare frames, (TY and KT) which might be suitable but will need to take some measurements this weekend. IJ Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted October 17, 2008 Report Share Posted October 17, 2008 (edited) I've got a 441 project that has been "resting" for quite a while. Compression plates will ruin any squish clearances that you might have. Instead, try to find a flat-top piston that you can dish in the middle. I bought an OEM XL350 Honda piston with a flat top as the bore size is in the right range. Wristpin sizes don't match so I'll have to deal with that. Megacycle Cams does a trials cam for the unit singles. I'm not sure they have it in the catalog and I don't have it handy to give you the part number on it, but you might look into that. I'm going to start with a 26mm Mikuni on my XT400 Yamaha project bike, and sleeve down the intake as mentioned above. The 441 frame is really heavy. ETA: I am welding up the combustion chamber a bit around the edges so there will be some squish area with the flat top piston. The center of the piston crown looks thick enough to take a bit out to make a central bowl in it. cheers, Michael Edited October 17, 2008 by MichaelMoore Quote Link to comment Share on other sites More sharing options...
pat slinn Posted October 17, 2008 Report Share Posted October 17, 2008 I used a Amal monobloc 1", I have no experience of Mikuni carburetors on BSA singles. I still retain a Amal monobloc on my 1964 C15. I realy cant remember the thickness of the compression plate that I used, 40 years is a long time ago, I know I should have kept more precise records of what I did and used, but in thoes days people didn't. To day I keep records on my computer and photograph everything. But I can remember that I used a 441cc Victor GP "slipper piston". I do not know megacycle cams, however some C15, B40, & B44 engine parts are avaiable on ebay, a C15 camshaft was on there recently for Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted October 19, 2008 Report Share Posted October 19, 2008 Hi Guy's. Hi John. Just had a look in one of my books on BSA unit singles, and thought I was right. You need a plate 2.11.mm ( or just over 1/16 of an inch)on a B44 to give you an 8 to 1 comprestion ratio, if you want 6 to 1 you will need nearly 3mm.as on a B50. I would sugest using copper to make the plate out of. "Mr BSA", Pat Slinn, is your man for any tuning tips, etc. Should be an intresting project to get right. Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
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