Sheds Moderator Posted March 18, 2011 Share Posted March 18, 2011 It occurs to me I know nowt about bikes or bike gearboxes. (Some would say or about owt else...) I don't want to hijack the thread about Blackbird gearbox wear, so what's the deal with BEC boxes? On bikes they last for yonks and other than being operated by a foot I can't see the difference. I can appreciate why it's better getting them engaged and the clutch back out stoips the dogs wearing. Why though does a Nova box with undecur dogs (whatever they are) solve the problem? Link to comment Share on other sites More sharing options...
neilg Posted March 18, 2011 Share Posted March 18, 2011 Well, it's really a case of bike gearboxs being very small , with tiny cogs , and having to cope with all the work of suddenly slowing down and speeding up 500 kg rather than say 250 kg . On a Blackbird the gears have straight cut dogs, like the castellations on a castle turret. After a while the corners wear and the dogs slip out when engaged. On a Nova gearbox the dogs are undercut which means that when the two dogs engage they pull themselves together. Hard to explain without pictures but if you imagine the dogs being narrower at the bottom than at the top you'll get my drift. Or not *confused*. On a Busa, the gears come undercut as standard and as such there is less of a problem with them. A Nova gearbox , like wot i've got, is a massive improvement over the standard gearbox and sorts the problem. I don't know what Fireblade and R1's have so unsure as to their longevity. Cheers Neil Link to comment Share on other sites More sharing options...
Myles Posted March 18, 2011 Share Posted March 18, 2011 Well my BB box is still going strong as far as I know I always use the clutch though - not sure if this is good or bad with a bike box! Also a bit unsure as to whether I should pull the clutch next time I change the oil - I'll have a chat with my long-term BB-Bec buddy tomorrow (one of the earliest to convert so has mega experience with them). We've got a long international tour later in the year so I suspect the answer might be 'yes' to check wear. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted March 18, 2011 Author Share Posted March 18, 2011 That makes sense Neil, thanks. The dogs are what locks the gear to the shaft then, given that bike boxes are constant mesh IIRC(is this right?). Your explanation of undercut dogs does indeed make sense. Link to comment Share on other sites More sharing options...
neilg Posted March 18, 2011 Share Posted March 18, 2011 This helps i think Link to comment Share on other sites More sharing options...
neilg Posted March 18, 2011 Share Posted March 18, 2011 Or here Still tricky to understand right. Link to comment Share on other sites More sharing options...
Badger Bill Posted March 19, 2011 Share Posted March 19, 2011 Well i drove my blade engined car for around 18k road miles, very carefully, without issue. Generally didn't use clutch for upshifts, and just a dab on the way down. BB. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted March 19, 2011 Author Share Posted March 19, 2011 Thanks gents, a bike box isn't that much different from a car then. Selector arrangements differ of course. Good stuff, this is what TechTalk is supposed to be about! Link to comment Share on other sites More sharing options...
blade_runner Posted March 19, 2011 Share Posted March 19, 2011 Neil hit the nail on the head, the tips of the dogs wear causing the cog to 'throw out' when power is applied. as far as i'm aware, the undercut dogs are tampered rather than straight cut, and as more power or torque is applied these pull in tighter to each other. Link to comment Share on other sites More sharing options...
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