Jackpiner gearing

[wfopete]

My CC race bike is a '73 175 Jackpiner which is running 12/52 gearing.  This combination has seemed to work ok for general racing conditions but I was thinking that a larger rear sprocket would tighten up the ratios and give me more "usable" gearing.  First through third gear are ok, but fourth gear and above seem to be widely spaced out. At the Evansville CC I didn't even get the 'Piner fully wound out in sixth gear on the generous pavement section. Also, when climbing steep, technical hills, first is not low enough and I end up abusing the clutch to the point that it won't fully disengage, resulting in a stalled engine. All this makes me wonder if I shouldn't consider going to a 57T or larger rear sprocket for more efficient use of my gearbox.  Is anyone running this type of lower gearing and if so, how is it working out?

Pete Petrick
Slow but Good

[Lew Mayer]

I run 12/55,Pete. I would think 57 on the rear may be too low gearing.

Lew Mayer

[brian kirby]

I dont have a Jackpiner, but my Can-Am 175 was similar when I got it. First gear was too tall and sixth would do about 80mph, I hardly got to the top of fifth much less sixth. You know from the races we do that second and third are gears we use the most and are much more important than sixth. I would say even if you loose a bit more top speed than you wanted with the 57T you would still run faster overall lap times because of the more usable first, second and third gear. For my Six Day I am going to gear it to maximize second, third, and forth even if I loose some top speed, since we rarely get top gear open stuff like the dirt roads at Marion or the paved road I heard about at Evansville.

Brian

'72 Six Day (on loan from Ernie P.)

[Dennis Jones]

I have found 12/56 to be the perfect combo for my Piner.
1973, stock pipe, bing carb, S12's, 520 non O-ring chain.

Dennis Jones

[Rain Man]

I'd run that 52t rear, if it was a road bike  [8D]

Raymond
 Down East Pentons

[wfopete]

Thanks guys. I think I'll try the 12/56T. Maybe it will makes second gear more useful in the tight stuff too. With a dead engine start on CC events the 12/52T combination gives me a slight bog off the line but that is quickly remedied with a fan of the clutch lever. Still it could mean the difference of losing/winning the holeshot and I know with guys like Dennis and Lew on the line with me there is little room for mistakes.  Quite frankly, I'm often surprised at the success I have had with dead engine starts without the advantages of a primary clutch system.

Pete Petrick
Slow but Good.