Planet Minis

77 honda

Just lookin for a few answers to some sprocket questions i have.

I plan on riding steep switchbacks and trails, just to let you know what type of riding.

also i plan on upgrading the stock tires form a 8-400 to a 8-480.

im not sure what size the carb is but its air intake is 1.75 inches outer diameter (if that helps any) on a pitster pro four stroke 4 speed 125cc.

i searched the web and found bikes set up with a 16 / 41 tooth sprocket combination. They were pitbikes though and i dont know if the wheel diameters are close enough. couldnt find measurements.

again, im looking for nice tourque to get my 200 lbs up that mountain. Top speed is not an issue. it'll be fast enough.

if any of you could help me come up with some ratios i would greatly appreciate it!

thanks,

Steve

77 honda

z50 xl70

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LoudFastUgly

Stock gearing w 200Lb rider:

1st is for heavy towing / tractor pull or snow plow operation,
2nd is for learning wheelies,
3rd is intermediate wheelies,
4th is advanced wheelies.

Searching for a 16/17T 420 counterbalance as we speak. You'll want to ditch the 428 counterbalance from your pitster, too hard to find a 428 rear sprocket locally, (some of these guys could find the shell that killed jfk given enough time...).

Cdoublejj has done alot on this...

77 honda

1st gear = stump pulling
2nd gear = roost!
3rd gear = white knuckle hill ride
4th gear = yard sale!

im still running the stock 50 rim so ill have to find a rear sprocket that will match up to the 3 bolt pattern. I havent been able to find any in the 40s. should i loose a tooth or two on the front to compensate for the rear if i cant find one in the 40s and have to go with one in the upper 30s?

what do you mean by 420 counterballance?

thanks

LoudFastUgly

Should have said countershaft sprocket, not counterbalance (powered lift truck technician by day, mini enthusiast by night...).

420 is the chain size. 428 and 420 have the same pitch (pin to pin center measurement), but 428 is wider than 420.

So, you'll have to commit to one or the other, 420 vs 428. 428 would give you better life, but I have yet to find a rear 428 sprocket for 1968 to 1987 Z50.

Personally, I'm running a 15T on the countershaft and the stock 37T on the rear in the 420 size. I could probably use a little more gear on open fields, but have no problem on hills either. Might consider a 16T up front the max for off road. I don't believe I'll get more than 15 hours out of the set.
Rather than monkey with both sprockets at once, pick one side and go from there. If you ride it at all you'll have ample opprotunity to tune your own setup.

dirtbkr188

A 15/37 would be a good starting point for you.

77 honda

ive got a 16 tooth allready, so should i go with a 35 tooth to make up for the counter sprocket tooth gain?

thanks for the info

cdoublejj

14/30 has crap load of toruqe my dad is at least 150 even with him it was doing wheelies when you cracked the throttle. still searching for the right combo i'm gonna try out 12/26, 13/26 does about 50-51 on somewhat flat ground maxed out and 55.5 down hill maxed out. i'd say try 14/30 dratv has 30 thooth sprockets.

dirtbkr188

14/30 = 2.143:1
12/26 = 2.167:1
No appreciable change at all doing that, they are virtually the same ratios

cdoublejj

14/30 did about 47 mph down hill. then that means its not geared wrong any more it lack serious power. the dropping to 13 from 14 gave a few mph increase. any who i'm going for top speed he is going for toruqe. if thats being said why not stay at 14/37?

dirtbkr188

Normally, when you go down a tooth on the front sprocket, you go down in top end speed, all other things being the same.

You're saying that going down a tooth in the front gave you more top end speed, is that correct? Which means, according to your theory, if you were to drop the front sprocket down to 12T, your bike will go even faster?

You might want to rethink this a little, and then go over to HERE, enter the numbers for 12/30, 13/30, and 14/30 final gear ratios and check the results.

cdoublejj

if it is geared to tall then it will slow down!!! my 4th gear is also tall.

cdoublejj

the calculator just says nan i filled every thing out.

77 honda

is this suggestion coming from experience or are you just trusting in the conversion charts?

what motor are you entering / clutch?

I dont know if i trust the calculations.

dirtbkr188

The 15/37 will be able to suit all your offroad demands, whether its the steep switchbacks or the trails. It will also be quite capable of carrying you wherever you want to go. That is speaking from personal experience, not the conversion charts.

As an FYI, for those conversion charts, I used the information for a an XR/CRF50 US SPEC for Gearbox and Primary Gear Ratio selections, with a 3.00-10 rear tire. That information results in the following MPH at 10K RPMs:

12/30 - 40MPH
13/30 - 43MPH
14/30 - 46MPH

According to the conversion chart, the top end speed increases as the tooth number of the front sprocket increases.
If it is geared too tall, it takes longer to get up to top speed, you have less low-end torque.

77 honda

thanks for the help! ill let you know how it turns out!

77 honda

these sprockets are what my z50 came with when i bought it. 11/44 detuned?

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dirtbkr188

The previous owner use it at tractor pulls? With that kind of gearing, it's 3rd gear holeshots and never have to shift...

wearenet

Interesting. Post up results when you find a good combo. I have almost the exact same setup, haven't even messed with gearing yet though, still building.

Z

The calculations are balls on. The only variable that may slightly differ is the tire size of which you can measure your tire and imput your specific findings.

It doesn't factor in horsepower, just mechanical ratios. If you don't have enough HP to push the taller gearing, your bike will get slower.

I'm pretty confident in the math of the calculator since Brad and I coded it.

There is no chinese gearboxes in the calculator as we only deal with Honda stuff, but the principles are the same.