125cc Fully Automatic Honda Clone

Adjuster · 01-31-2015, 04:09 PM

Ok I have my new engine installed and wow the difference in power from the original 49cc semi automatic is just crazy. I can't believe the entire engine is just held in place to the bike frame with 2 skinny cheap 6" bolts with no kind of reinforcement in the frame or motor mount of any kind. Oh well if its been working for Honda since the 1960's it will probably continue to work for me.

So here is my only complaint. As I feared in prior postings the fully automatic engine would be too 'torqueeeee' and that fear has come true. It would be great if this was a dirt bike but its a simple street Honda Cub clone made to ride easy. I don't know how fast it will go yet but at 35mph the engine is really screaming but still has lots of power left. So I guess I need to mess with the sprockets. The front sprocket is a real simple change out. It is currently a 14 tooth. Do I need to go up or down to make the bike not work so hard? I still need enough torque to get me away from street lights with the traffic but I want it to be able to cruise 35-40 much easier. I will have to deal with the back sprocket if changing out the front doesn't give me the desired affect. Thanks for the help.

Adjuster

Weldangrind · 01-31-2015, 04:33 PM

You need to either increase the countershaft size or decrease the rear sprocket size to lower the revs at speed. I'd try to fit a 16 or 17 tooth sprocket on the countershaft.

What size is the rear sprocket?

Adjuster · 01-31-2015, 04:37 PM

Quote:

Originally Posted by Weldangrind

You need to either increase the countershaft size or decrease the rear sprocket size to lower the revs at speed. I'd try to fit a 16 or 17 tooth sprocket on the countershaft.

What size is the rear sprocket?

It is marked 420-41T

/

Weldangrind · 01-31-2015, 04:43 PM

I presume that these sprockets are a match for your bike, but you'd need to measure to be sure: http://www.jtsprockets.com/catalogue/model/4943

You currently have a 2.93 final drive ratio, and you need to get that number lower, which is actually higher gearing. Confusing, I know.

A jump to a 17 tooth front sprocket would take you to 2.41.

Adjuster · 01-31-2015, 05:00 PM

I just took the sprocket cover off to confirm my front sprocket is marked:

SD420-14T

What does the SD represent?

/

Mudflap · 01-31-2015, 06:50 PM

Probably Spline Drive. There are 2 common size countershaft sizes on the Chinese horizontal engines, 17mm and I forget if it's 20mm or 22mm. In any case you'll need to get the right inside diameter for your engine.

Quote:

Originally Posted by Adjuster

I just took the sprocket cover off to confirm my front sprocket is marked:

SD420-14T

What does the SD represent?

/

culcune · 01-31-2015, 09:04 PM

I would guess a 17 front, combined with your 41 rear, should do the trick.

Adjuster · 01-31-2015, 09:21 PM

Thanks everyone I have ordered a 16t and a 17t. And I have an original 13t on my 49cc and a 14t on my new 125cc. They are only 9$ each for the new 16 and 17. I hope I have all my bases covered. This little 125cc motor amazes me.

/

Weldangrind · 02-01-2015, 12:30 PM

I wouldn't doubt if you're able to cruise at 55mph with the right gearing. The limiting factor will be the actual space available for the countershaft sprocket. IOW, if you had the space and an 18 tooth would fit (and is available), it might be worth a try.

You're probably gonna need a new, longer chain.

Adjuster · 02-21-2015, 03:21 PM

The sprocket change made a huge difference. Its a joy to ride now.

View My Video

/

Adjuster · 02-22-2015, 07:11 PM

My chain has that deal where as you spin the tire it has tight spots and loose spots. I have the tension adjusted correctly using the tight spots. The problem is the loose spots now have too much play in them. Is this something I can fix or adjust or does this mean I need a new chain? The bike and chain are brand new by the way.

/

Weldangrind · 02-23-2015, 01:56 AM

That chain symptom is due to a poor quality sprocket (most likely rear).

Adjuster · 02-23-2015, 10:11 AM

Thanks, is the sprocket out of round? They are cheap enough on Ebay but I would like to make sure I get a good one.

/

katoranger · 02-23-2015, 10:15 AM

I am willing to bet that a Honda part will fit. Try looking for a CT90 sprocket too.

Weldangrind · 02-23-2015, 01:28 PM

Quote:

Originally Posted by Adjuster

Thanks, is the sprocket out of round? They are cheap enough on Ebay but I would like to make sure I get a good one.

/

Yes and no. The sprocket is likely round, but the center hole is probably not actually centered. That's the problem with my quad rear sprocket. I'm thinking of cobbling together a chain tensioner to deal with it.

01-31-2015, 04:09 PM	#1
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	125cc Fully Automatic Honda Clone Ok I have my new engine installed and wow the difference in power from the original 49cc semi automatic is just crazy. I can't believe the entire engine is just held in place to the bike frame with 2 skinny cheap 6" bolts with no kind of reinforcement in the frame or motor mount of any kind. Oh well if its been working for Honda since the 1960's it will probably continue to work for me. So here is my only complaint. As I feared in prior postings the fully automatic engine would be too 'torqueeeee' and that fear has come true. It would be great if this was a dirt bike but its a simple street Honda Cub clone made to ride easy. I don't know how fast it will go yet but at 35mph the engine is really screaming but still has lots of power left. So I guess I need to mess with the sprockets. The front sprocket is a real simple change out. It is currently a 14 tooth. Do I need to go up or down to make the bike not work so hard? I still need enough torque to get me away from street lights with the traffic but I want it to be able to cruise 35-40 much easier. I will have to deal with the back sprocket if changing out the front doesn't give me the desired affect. Thanks for the help. Adjuster
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01-31-2015, 04:33 PM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	You need to either increase the countershaft size or decrease the rear sprocket size to lower the revs at speed. I'd try to fit a 16 or 17 tooth sprocket on the countershaft. What size is the rear sprocket? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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01-31-2015, 04:43 PM	#4
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	I presume that these sprockets are a match for your bike, but you'd need to measure to be sure: http://www.jtsprockets.com/catalogue/model/4943 You currently have a 2.93 final drive ratio, and you need to get that number lower, which is actually higher gearing. Confusing, I know. A jump to a 17 tooth front sprocket would take you to 2.41. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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01-31-2015, 09:04 PM	#7
culcune Join Date: May 2006 Location: Yuma, Arizona Posts: 9,056	I would guess a 17 front, combined with your 41 rear, should do the trick. __________________ "They say that life's a carousel, spinning fast you got to ride it well..." TGB Delivery Scooter 150 TMEC 200 Enduro--carcass is sadly rotting in the backyard
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02-01-2015, 12:30 PM	#9
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	I wouldn't doubt if you're able to cruise at 55mph with the right gearing. The limiting factor will be the actual space available for the countershaft sprocket. IOW, if you had the space and an 18 tooth would fit (and is available), it might be worth a try. You're probably gonna need a new, longer chain. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

01-31-2015, 05:00 PM	#5
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	I just took the sprocket cover off to confirm my front sprocket is marked: SD420-14T What does the SD represent? /
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01-31-2015, 09:21 PM	#8
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	Thanks everyone I have ordered a 16t and a 17t. And I have an original 13t on my 49cc and a 14t on my new 125cc. They are only 9$ each for the new 16 and 17. I hope I have all my bases covered. This little 125cc motor amazes me. /
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02-21-2015, 03:21 PM	#10
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	The sprocket change made a huge difference. Its a joy to ride now. View My Video /
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02-22-2015, 07:11 PM	#11
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	My chain has that deal where as you spin the tire it has tight spots and loose spots. I have the tension adjusted correctly using the tight spots. The problem is the loose spots now have too much play in them. Is this something I can fix or adjust or does this mean I need a new chain? The bike and chain are brand new by the way. /
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02-23-2015, 01:56 AM	#12
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	That chain symptom is due to a poor quality sprocket (most likely rear). __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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02-23-2015, 10:11 AM	#13
Adjuster Join Date: Dec 2014 Location: Deerfield Beach FL Posts: 1,410	Thanks, is the sprocket out of round? They are cheap enough on Ebay but I would like to make sure I get a good one. /
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02-23-2015, 10:15 AM	#14
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	I am willing to bet that a Honda part will fit. Try looking for a CT90 sprocket too. __________________ You meet the nicest people on a Honda Clone.
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