bd125 Rear Sprocket Dimensions

Doubledown · 05-28-2023, 03:50 PM

Hoping someone can tell me the rear sprocket dimensions of my bd125-8. I want to drop a tooth in the rear with my bigbore kit. I see it is a 428 34t currently but hoping to get the bolt patttern, bolt diameter, center hole diameter etc. etc. so I can order without taking it all apart and ic an ride it until it gets here.

Thank you,

TominMO · 05-29-2023, 07:35 AM

I doubt that you will be able to tell a one-tooth difference in the rear. A one-tooth difference in the front, i.e. larger, would probably be noticeable.

Doubledown · 05-29-2023, 12:31 PM

Quote:

Originally Posted by TominMO

I doubt that you will be able to tell a one-tooth difference in the rear. A one-tooth difference in the front, i.e. larger, would probably be noticeable.

I have the 17 up front, dropping one in the rear is another 3% in speed approximately. Looking to have at least the same performance had with the stock motor and the 17 upfront with the added big bore and a tooth drop in the rear but gain a few MPH.

krat · 05-29-2023, 03:08 PM

You need to get out a calculator and discover what 3% of your top speed actually is!

If it is 65, and on a 125cc (even with a big bore kit) it probably is not that fast, you would gain 2mph. That means that a gentle head wind would wipe any gain out and humidity in the air and tire pressure could make more change in the performance.

It is very difficult to make radical change in RPM in a low horsepower engine and RPM is where you get your top end speed.

Doubledown · 05-30-2023, 01:29 PM

[QUOTE=krat;395556]You need to get out a calculator and discover what 3% of your top speed actually is!

If it is 65, and on a 125cc (even with a big bore kit) it probably is not that fast, you would gain 2mph. That means that a gentle head wind would wipe any gain out and humidity in the air and tire pressure could make more change in the performance.

It is very difficult to make radical change in RPM in a low horsepower engine and RPM is where you get your top end speed.[/QUOT

I checked a calculator before, that is where the 3% came from why I said a "few"!

Can't change the weather so all else equal, I can't get the extra (albeit small) extra mph without taching the motor unless I gear to it.

05-28-2023, 03:50 PM	#1
Doubledown Join Date: Jun 2022 Posts: 26	bd125 Rear Sprocket Dimensions Hoping someone can tell me the rear sprocket dimensions of my bd125-8. I want to drop a tooth in the rear with my bigbore kit. I see it is a 428 34t currently but hoping to get the bolt patttern, bolt diameter, center hole diameter etc. etc. so I can order without taking it all apart and ic an ride it until it gets here. Thank you,
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05-29-2023, 07:35 AM	#2
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,871	I doubt that you will be able to tell a one-tooth difference in the rear. A one-tooth difference in the front, i.e. larger, would probably be noticeable. __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
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05-29-2023, 03:08 PM	#4
krat Join Date: Nov 2019 Location: KY Posts: 260	You need to get out a calculator and discover what 3% of your top speed actually is! If it is 65, and on a 125cc (even with a big bore kit) it probably is not that fast, you would gain 2mph. That means that a gentle head wind would wipe any gain out and humidity in the air and tire pressure could make more change in the performance. It is very difficult to make radical change in RPM in a low horsepower engine and RPM is where you get your top end speed. __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
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05-30-2023, 01:29 PM	#5
Doubledown Join Date: Jun 2022 Posts: 26	[QUOTE=krat;395556]You need to get out a calculator and discover what 3% of your top speed actually is! If it is 65, and on a 125cc (even with a big bore kit) it probably is not that fast, you would gain 2mph. That means that a gentle head wind would wipe any gain out and humidity in the air and tire pressure could make more change in the performance. It is very difficult to make radical change in RPM in a low horsepower engine and RPM is where you get your top end speed.[/QUOT I checked a calculator before, that is where the 3% came from why I said a "few"! Can't change the weather so all else equal, I can't get the extra (albeit small) extra mph without taching the motor unless I gear to it.
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