Planet Minis

jkg2003 · 10-22-2009, 08:13 PM

I am needing to know what tooth engine sprocket for a factory 420 chain, I am putting it on a lifan 125cc, thanks Justin

jkg2003 · 10-23-2009, 01:17 PM

Anybody, it has a 15 tooth on it now and the sprockets are too wide for the chain, so I know I need a more toothed, if that makes since, sprocket I just dont know how many teeth

mexicanyella · 10-23-2009, 02:51 PM

I'm not sure I understand, but it sounds like you're not talking about how many teeth, but what size teeth. You can get sprockets for 420 chain in sizes from about 11 teeth up to about 17 teeth or so. What bike, what's your intended use, etc. will determine what to run. 15's probably a good starting point for an engine that size, since it will probably have plenty of torque to pull that ratio with a stock rear sprocket on a Z or CT. You may want a larger one if you ride on the street. Maybe what you have is a sprocket for 428 chain, which has the same spacing from tooth to tooth but the teeth themselves are too wide to fit a 420 chain on.

jkg2003 · 10-23-2009, 03:13 PM

Ohk maybe I dont understand what im looking for either, when I set my chain which is a 420 on my engine sprocket it fits a few of the teeth and then the teeth start to become too wide for the chain to fit, when I bought the engine it claimed to have a 420 14 tooth, but this one is a 15, so maybe I have a 428 sprocket???

jkg2003 · 10-23-2009, 03:15 PM

oh and it will be general use, trail and street, and it is a 72 ct70k1 with a lifan 125cc 4 speed manual

firepower354 · 10-23-2009, 03:22 PM

Watch (measure!) out, some Lifan's use a 20mm output shaft, rather than the more common 17mm one. Different sprocket, ya see.

jkg2003 · 10-23-2009, 03:38 PM

Quote:

Originally Posted by firepower354

Watch (measure!) out, some Lifan's use a 20mm output shaft, rather than the more common 17mm one. Different sprocket, ya see.

Ohk what do I need to measure, I know the stock sprocket on my engine does not fit the lifan, and if it is a 20mm what sprocket do I buy

mexicanyella · 10-23-2009, 03:41 PM

So your tooth spacing doesn't match the spacing between the chain rollers? Is it a new chain, or an old stretched one?

jkg2003 · 10-23-2009, 03:42 PM

new

jkg2003 · 10-23-2009, 03:55 PM

Quote:

Originally Posted by firepower354

Watch (measure!) out, some Lifan's use a 20mm output shaft, rather than the more common 17mm one. Different sprocket, ya see.

I went out and measured my output shaft and I now see what you are talking about the 20mm vs 17mm

dirtbkr188 · 10-23-2009, 05:19 PM

If your output shaft is 20mm, you can click on the pic below for other sprockets that will fit.

jkg2003 · 10-23-2009, 05:29 PM

Im not trying to b a pain but I just want to make sure that the sprocket you pictured will fit on my lifan 125 and also fit my tec 420 chain

dirtbkr188 · 10-23-2009, 05:34 PM

No, that is a sprocket designed to fit a 20mm output shaft and a 428 chain, a 420 chain will not work with it.
If you have a 20mm output shaft, and you think you need a 420 sprocket, click HERE

jkg2003 · 10-23-2009, 05:44 PM

how can I check and see if I have a 428 or a 420 sprocket

110streetlegal · 10-23-2009, 05:48 PM

if your sprocket wont fit your new 420 chain its a 428 sprocket just get a 420 sprocket and that should fix it
if its the right size chain for the sprocket you should be able to wrap the chain completely around the sprocket

jkg2003 · 10-23-2009, 06:31 PM

Ohk if I get a 420 sprocket for the engine, what tooth do I need, I have a 45 tooth on the wheel sprocket, its on a 1972 ct70HK1

110streetlegal · 10-23-2009, 06:34 PM

15t would be fine if you want more torque go down in the numbers and if you want top end go up

mexicanyella · 10-23-2009, 07:11 PM

I think stock for a CT70 is 15/35. Not 100% sure on that, but I think that's what's on my 1970 one, and if you've gone up to 125cc you could probably run a bigger one in front and still have plenty of power, plus more top speed...

...but...

...if you plan to ride it on trails at least some of the time, with the limits of off-road rideability and controllable speeds imposed by stone-age suspension and 10" wheels, you might want lower gearing, such as the stock gearing, so it's more nimble and easy to handle. Riding off-road on a bike with plenty of power but too high of gearing really sucks, unless you're a desert racer or something. But it's a tradeoff with top end speed vs. low-end woods trails riding. Back out to the Z50/CT70 forum page and check the sticky with the gear ratio calculator in it. Plug in your bike's numbers in the table (all the hard work is pre-figured) including that 45T back sprocket and look at the rpm/speed combos you'll have in the different gears.

You're probably not going to be in an rpm range that's much different from the stock motor, so if you had stock sprockets you'd still be revving it pretty hard once you get up above 45mph or so if you had stock sprockets. The Lifan will have slightly different internal gear ratios than the Honda motor, but not that much different.

10-22-2009, 08:13 PM	#1 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	What size sprocket I am needing to know what tooth engine sprocket for a factory 420 chain, I am putting it on a lifan 125cc, thanks Justin

10-23-2009, 01:17 PM	#2 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket Anybody, it has a 15 tooth on it now and the sprockets are too wide for the chain, so I know I need a more toothed, if that makes since, sprocket I just dont know how many teeth

10-23-2009, 02:51 PM	#3 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 976	Re: What size sprocket I'm not sure I understand, but it sounds like you're not talking about how many teeth, but what size teeth. You can get sprockets for 420 chain in sizes from about 11 teeth up to about 17 teeth or so. What bike, what's your intended use, etc. will determine what to run. 15's probably a good starting point for an engine that size, since it will probably have plenty of torque to pull that ratio with a stock rear sprocket on a Z or CT. You may want a larger one if you ride on the street. Maybe what you have is a sprocket for 428 chain, which has the same spacing from tooth to tooth but the teeth themselves are too wide to fit a 420 chain on.

10-23-2009, 03:13 PM	#4 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket Ohk maybe I dont understand what im looking for either, when I set my chain which is a 420 on my engine sprocket it fits a few of the teeth and then the teeth start to become too wide for the chain to fit, when I bought the engine it claimed to have a 420 14 tooth, but this one is a 15, so maybe I have a 428 sprocket???

10-23-2009, 03:15 PM	#5 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket oh and it will be general use, trail and street, and it is a 72 ct70k1 with a lifan 125cc 4 speed manual

10-23-2009, 03:22 PM	#6 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 10,989 My Mood:	Re: What size sprocket Watch (measure!) out, some Lifan's use a 20mm output shaft, rather than the more common 17mm one. Different sprocket, ya see. __________________ If it has my name on it I did it;) FirepowerMinis.com Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Pitster/Piranha/Thumpstar bikes, parts, engines and accessories.

10-23-2009, 03:41 PM	#8 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 976	Re: What size sprocket So your tooth spacing doesn't match the spacing between the chain rollers? Is it a new chain, or an old stretched one?

10-23-2009, 03:42 PM	#9 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket new

10-23-2009, 05:19 PM	#11 (permalink)
dirtbkr188 3rd Gear Member Join Date: May 2004 Location: New Jersey Posts: 2,972	Re: What size sprocket If your output shaft is 20mm, you can click on the pic below for other sprockets that will fit.

10-23-2009, 05:29 PM	#12 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket Im not trying to b a pain but I just want to make sure that the sprocket you pictured will fit on my lifan 125 and also fit my tec 420 chain

10-23-2009, 05:34 PM	#13 (permalink)
dirtbkr188 3rd Gear Member Join Date: May 2004 Location: New Jersey Posts: 2,972	Re: What size sprocket No, that is a sprocket designed to fit a 20mm output shaft and a 428 chain, a 420 chain will not work with it. If you have a 20mm output shaft, and you think you need a 420 sprocket, click HERE

10-23-2009, 05:44 PM	#14 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket how can I check and see if I have a 428 or a 420 sprocket

10-23-2009, 05:48 PM	#15 (permalink)
110streetlegal 1st Gear Member Join Date: Jun 2008 Location: central valley visalia california Posts: 236 My Mood:	Re: What size sprocket if your sprocket wont fit your new 420 chain its a 428 sprocket just get a 420 sprocket and that should fix it if its the right size chain for the sprocket you should be able to wrap the chain completely around the sprocket

10-23-2009, 06:31 PM	#16 (permalink)
jkg2003 PM Newbie Join Date: Oct 2009 Posts: 47 My Mood:	Re: What size sprocket Ohk if I get a 420 sprocket for the engine, what tooth do I need, I have a 45 tooth on the wheel sprocket, its on a 1972 ct70HK1

10-23-2009, 06:34 PM	#17 (permalink)
110streetlegal 1st Gear Member Join Date: Jun 2008 Location: central valley visalia california Posts: 236 My Mood:	Re: What size sprocket 15t would be fine if you want more torque go down in the numbers and if you want top end go up

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

10-23-2009, 07:11 PM	#18 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 976	Re: What size sprocket I think stock for a CT70 is 15/35. Not 100% sure on that, but I think that's what's on my 1970 one, and if you've gone up to 125cc you could probably run a bigger one in front and still have plenty of power, plus more top speed... ...but... ...if you plan to ride it on trails at least some of the time, with the limits of off-road rideability and controllable speeds imposed by stone-age suspension and 10" wheels, you might want lower gearing, such as the stock gearing, so it's more nimble and easy to handle. Riding off-road on a bike with plenty of power but too high of gearing really sucks, unless you're a desert racer or something. But it's a tradeoff with top end speed vs. low-end woods trails riding. Back out to the Z50/CT70 forum page and check the sticky with the gear ratio calculator in it. Plug in your bike's numbers in the table (all the hard work is pre-figured) including that 45T back sprocket and look at the rpm/speed combos you'll have in the different gears. You're probably not going to be in an rpm range that's much different from the stock motor, so if you had stock sprockets you'd still be revving it pretty hard once you get up above 45mph or so if you had stock sprockets. The Lifan will have slightly different internal gear ratios than the Honda motor, but not that much different.