I have built a stock Pan Motor for a 55 ridgid frame. It has Mechanical Drum brakes front and rear. I do not want a hole shot type bike, but would like to cruise on the highway and still have some response in the lower gears. I have a 51 tooth rear sprocket and I have heard there is a good combination for the tranny. I have heard 23, 24 and 25. I am leaning towards the 23 but wanted to see what was best.
Hey bud
Do you have a 23t or 24t motor sproc.? A 23t and 37t clutch shell sproc give you a 1.608 primary drive ratio... A 24t/37 is a 1.54...
A 51t wheel sproc and a 23t tran sproc is 2.217 drive ratio...
OK-- 1.6 times 2.217 = 3.547 OVERALL gear ratio, that's very LOW, no cruisin allowed... The stock 55 came with a 22t tran sprock, man that's unbearable,, a 3.7 overall, jeeeze...
If you have a 24t motor sproc, 1.54 times 2.217 == 3.414 OVERALL gear ratio, much easier on the RPM's when cruisin...
A 1.6 primary and a 51/24==2.125 will give you 3.4...
The wheel sproc remains 51t, the tran and motor sproc can be changed, now you know how to figure gear ratios and you can play...
I'm not sure you can fit a 24t tran sproc cuz there's very little room between the clutch arm and the sproc/chain/oilbag... The biggest I can fit on my shovel in a 52 wishbone with mousetrap and 4sp kick is a 23, also on the 120" with mouse and kick, a 23... Let us know how it comes out...
Great, thanks for the info! I am running a BDL 3" open Primary belt, is the ration caluculated the same way? I am going to try a 24 and if I run into clearance problems during mock up, I will drop down to a 23. I think a 24 will meet my needs as long as everything clears.
Yes the calc's are the same... If you're runnin the 47/76 the ratio is 1.61,, 47/72 - 1.53, that would be my choice...
Let me clear up the clearance statement-- even with the 23t I must be EXTRA careful with rear chain tension because just a little too loose the chain will flop and jump up and wear/grind away at the under-side of the clutch arm, sooo, I have never even tried a 24t, it would be waaay too close... That's just my experience...
Curious,,, which primary combo are you running.? 47/76 or 47/72..??
Built 2 Pan's in the 70's, very fond of em...
It is a 47/76 from BDL. Never really got a choice was either for Tapered or splined shaft. Primo was the same way. So it sounds like my final if I run a 23t tranny will be 3.6. So hopefully I can get a 24t to fit so I am closer to a 3.4. Just finishing getting the cases together, so hopefully next week I will have the motor finished and can then move on to this. I had my local shop order both a 23t and 24t. Figure If I can get a 24t to fit, I can alwqways swap when I ewant to go light hunting. I am not sure the exact yr of the frame, it is a straight leg, but no numbers, so hard to tell for sure the yr. best I can gather is a 55. I will let you know how it turns out, but it may be a little while.
Ok, allow me to jam you for a moment...
No disrespect here just wingin,,, I'm assuming you got the 3" just for the looks yes..?? The motor is stock or close to it yes.? Then a 3" is sooo totally unnecessy, except for looks of course...
In 28 years of using 1 1/2" 8mm belts I've broken only 3, 2 on the 120" and 1 on the 93",, this is doing literally hundreds of holeshots... Soo, why do I say this, IF you were to think about trading the 3" for a 1 1/2" 8mm, BDL or Primo, you can use, dig it, a 39, 40 or 41T motor pully and a 61 or 62T clutch shell sprocket for 4sp, tapered or splined... That is what I've done and I can change gear ratios in like 15 Minutes... From like 3.18 to 3.54... I run Alum primaries so I adjust the belt with a belt idler, you would have to move the tranny and then re-adjust the rear chain...
I never have to mess with the tran sproc, only the primary pulleys... And because I run disk brake wheels I have the added wheel sproc changes if I choose...
OK, I'm done, just wanted to pass that along, you know, give you some more to think about...
Cool thanks for the info. Went with the 3" cause I already had the engine Sprocket. so just went with it. Great info to have though, pretty simple change if needed. Thanks for all the knowledge, always good to hear from someone whos done it.
Hey Frisco, Due to other issues it took me longer than I wanted but the 55 is done, fired it off this past weekend. I was able to get a 24T tranny sprocket with enough clearance, but I am running a mousetrap eliminator. Hopefully getting a VIN issued tomorrow and will be able to do more than nieghborhood riding. Can't wait to get it broke in so I can get it up on the highway. Thanks for all your knowledge!
Oooh Man, I'm embarrased, I just now realized you are the same as the ramjet question Wideglide, jeeeeze, somebody just shoot me and put me outa my misery...
Tranny Sprocket for 4 Spd 
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