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stuffing a BT in a 45 frame

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Post Thu May 06, 2010 9:19 am

Posts: 74
Location: Wichita, KS
seen a couple of BT shoehorned into 45 frames ( always a OHV never a UL ) , don't have the parts to play with and was wondering if any of y'all have actually done this ? motor mounts welded and re drilled ? spacers under motor mounts for case clearance from skid plate ? etc .

Post Thu May 06, 2010 11:44 am

Posts: 1606
leaving aside the question of why you would want to do this at all, the 45 frame being apparently designed for the maximum weight combined with the minimum strength, Panic's reply to a recent thread would indicate that the BT flathead is a very tight squeeze.

This suggests that an ohv BT will not fit without fairly major frame surgery. The "45 magnum" certainly doesn't fit, nor does the British variant of fitting ohv Matchless heads and barrels. I've never seen an ohv BT in a 45 frame; I've seen occasional VLs, which look similar in some respects, fitted with knucklehead engines, but this also requires considerable surgery

The next problems would be;

(1) the primary drive doesn't match, for alignment or size
(2) the 45 transmission is highly unlikely to be able to handle the power
(3) the BT transmission probably won't go into the available space

apart from that you should have no problems.....
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu May 06, 2010 12:01 pm

Last edited by panic on Sun Nov 28, 2010 12:15 pm, edited 1 time in total.

Post Mon Oct 18, 2010 11:43 pm

Posts: 1538
Bsatom did it, look in the search box for something from him..

Post Tue Oct 19, 2010 1:18 am

Posts: 1606
bsatom's bike seems to bear out panic's assertion, that you can do it with a BT flathead if that's what you really want to do, but quite what you gain by it is a good question. Photos certainly indicate that an ohv engine will not fit without major surgery. There was a thread about the converse, a 45 engine in a BT frame, and the consensus appeared to be that the BT is a superior frame in all respects and not significantly heavier.

I'd suspect that the 45 transmission ratios would not suit the larger motor, quite apart from alignment issues, and the ability of the mounting and cross-over drive pattern to cope with the increased torque would have to be suspect ( best configuration is the primary and secondary drive on same side with all 3 hubs in a straight line, as per raised gearboxes on BTs as a racing mod )

given that very few custom bikes do any serious mileage or real work, you could probably get away with pretty much anything if that's what you really wanted to do... but it would be a shame to cut up increasingly rare and expensive parts for that sort of reason IMHO
Shoot, a man could have a good weekend in Dallas with all that stuff...

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