BD250-7 Rear Sprocket

aZ3R0n · 06-16-2023, 10:07 AM

I'm in a bit of a bind.

I've owned my bike for about a year. Love it, put a lot of miles on it, so naturally it's time to replace the sprocket and chain. Chain size was easy enough to figure out, but the sprocket not so much. Did some measuring and found an equivalent from JT Sprockets and ordered it from Amazon: https://www.amazon.com/dp/B0068O2W8U (JT Sprockets link http://www.jtsprockets.com/catalogue/part/JTR486)

Took the bike and the replacment sprocket to the mechanic. Few hours later, I get a call from him and he says the inner diameter of the sprocket is about 1/8 inch too big (maybe about 3 or 4 millimeters) and so it's not going to fit. Problem? We were so sure it was going to work, and in order to get the old sprocket off he had to beat it up pretty hard. I'm basically without a motorcycle until I find a replacement sprocket.

I've been scouring the JT Sprockets website to see if I can find one with a slightly smaller inner diameter and pitch circle diameter (distance from bolt hole to bolt hole), but so far no luck. I've reached out to the manufacturer, and so far they have been no help.

Does anyone know a sprocket that will match?

**JerryHawk250** · 06-16-2023, 11:06 AM

what is the actual hub diameter? Is it a 6 bolt pattern? Does the bolt circle diameter match the one you linked? 520 chain?

aZ3R0n · 06-16-2023, 11:12 AM

Quote:

Originally Posted by JerryHawk250

what is the actual hub diameter? Is it a 6 bolt pattern? Does the bolt circle diameter match the one you linked? 520 chain?

I don't know the actual diameter of the hub, I was trying to measure the actual sprocket itself. It is a 6 bolt pattern. The inner circle diameter of the sprocket I bought is 110, and bolt to bolt is 130. So if 1/8 inch is 3.17~ millimeters then the sprocket I'll actually need will be 106 or 107 inner circle diameter.

I actually just got an update from the mechanic and he said he's putting the old sprocket back on, reversed, so I can get a little more from it. We both looked and called some places but couldn't find anything.

**JerryHawk250** · 06-16-2023, 12:25 PM

I tried searching myself but didn't come across any either. Try contacting JT Sprockets. Give them exact dimensions and I'm sure they will find it.

aZ3R0n · 06-16-2023, 01:03 PM

Quote:

Originally Posted by JerryHawk250

I tried searching myself but didn't come across any either. Try contacting JT Sprockets. Give them exact dimensions and I'm sure they will find it.

Thanks for at least taking a look! There are other riders that have this bike so we'll all need this info eventually. Can't ride a bike without good working parts!

VTitan · 06-16-2023, 11:23 PM

I know it might be a pain but your best bet may be to pick up a cheap digital caliper from Harbor Freight or somewhere similar. The accurate measurements will help a lot with your search and if you absolutely can't find one there are companies that will custom make one for you for less than $100. I just went through this with my Vitacci Titan. I found that my sprocket actually matched what goes on older Dymag wheels. I am waiting for it to arrive to make certain. It may take a bit of patience but it's out there.

JCblue · 06-17-2023, 02:52 PM

I have the same bike and it needs new chain and sprockets too. Do you know the front sprocket size? Thank you for sharing your experience.

aZ3R0n · 06-18-2023, 01:50 PM

Quote:

Originally Posted by JCblue

I have the same bike and it needs new chain and sprockets too. Do you know the front sprocket size? Thank you for sharing your experience.

Take a look at this: https://www.amazon.com/dp/B0BVYSC9B8

The bike's front sprocket has 13 teeth. I strongly advise double checking the measurements on the chart in the product pictures before buying it. I was going to order it for my bike, but the front sprocket is still in pretty good shape so I haven't actually tried to put one on just yet.

Despite what any listing might say about the BD250-7, it does NOT have 17 teeth on the front sprocket. It has 13. I have thought about trying a 14t front sprocket to change the ratio a bit, but after looking in the case I don't think there would be room for it unless you shaved down the case by a few millimeters. When I do eventually need to change the front sprocket I'll buy both the 13 and 14 to see if a 14 will fit and then report back here.

aZ3R0n · 06-20-2023, 12:42 PM

Got an update that may help anyone else with the same bike.

While I have not found a sprocket yet, my mechanic took measurements while he had the stock sprocket taken off and shared them with me. The inner diameter is 103mm and the measurement across the center from bolt to bolt is 127mm. The measurement between each bolt hole is 62mm. Remember that this sprocket has 6 bolt holes, and 38 teeth.

**JerryHawk250** · 06-20-2023, 01:43 PM

Quote:

Originally Posted by aZ3R0n

Got an update that may help anyone else with the same bike.

While I have not found a sprocket yet, my mechanic took measurements while he had the stock sprocket taken off and shared them with me. The inner diameter is 103mm and the measurement across the center from bolt to bolt is 127mm. The measurement between each bolt hole is 62mm. Remember that this sprocket has 6 bolt holes, and 38 teeth.

520 pitch or 428?

aZ3R0n · 06-20-2023, 01:56 PM

Quote:

Originally Posted by JerryHawk250

520 pitch or 428?

520 pitch

For those that are curious about the stock chain length, it's 120 links.

**JerryHawk250** · 06-20-2023, 02:03 PM

You can always get a custom sprocket made if you can't find an off the shelf fit. I had to do that with my X22R. Here are a few places that do it. PBI sprockets stopped making custom sprockets a couple years ago. That's who made mine.

https://sprocketspecialists.com/custom-builds/
http://www.rebelgears.com/sprockets/...sprockets.html
http://www.custommotorcyclesprockets...ontact-us.html

aZ3R0n · 06-20-2023, 02:10 PM

I called the US location of Boom International, I believe I found the number on this forum.
It's 1-800-916-3381

They said they are moving warehouse locations right now, but if I call back next week they should be able to help me get a replacement sprocket.

aZ3R0n · 08-23-2023, 02:16 PM

UPDATE:

I called Boom International again, and this time they said that they cannot sell parts directly to a customer since they are a wholesaler. They said I need to contact a dealer and buy the parts from them, so now I am back at square one.

06-16-2023, 10:07 AM	#1
aZ3R0n Join Date: Jun 2023 Posts: 9	BD250-7 Rear Sprocket I'm in a bit of a bind. I've owned my bike for about a year. Love it, put a lot of miles on it, so naturally it's time to replace the sprocket and chain. Chain size was easy enough to figure out, but the sprocket not so much. Did some measuring and found an equivalent from JT Sprockets and ordered it from Amazon: https://www.amazon.com/dp/B0068O2W8U (JT Sprockets link http://www.jtsprockets.com/catalogue/part/JTR486) Took the bike and the replacment sprocket to the mechanic. Few hours later, I get a call from him and he says the inner diameter of the sprocket is about 1/8 inch too big (maybe about 3 or 4 millimeters) and so it's not going to fit. Problem? We were so sure it was going to work, and in order to get the old sprocket off he had to beat it up pretty hard. I'm basically without a motorcycle until I find a replacement sprocket. I've been scouring the JT Sprockets website to see if I can find one with a slightly smaller inner diameter and pitch circle diameter (distance from bolt hole to bolt hole), but so far no luck. I've reached out to the manufacturer, and so far they have been no help. Does anyone know a sprocket that will match?
	0

06-16-2023, 11:06 AM	#2
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,562	what is the actual hub diameter? Is it a 6 bolt pattern? Does the bolt circle diameter match the one you linked? 520 chain? __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	0

06-16-2023, 12:25 PM	#4
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,562	I tried searching myself but didn't come across any either. Try contacting JT Sprockets. Give them exact dimensions and I'm sure they will find it. __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	1

06-16-2023, 11:23 PM	#6
VTitan Join Date: Apr 2023 Posts: 7	Measure I know it might be a pain but your best bet may be to pick up a cheap digital caliper from Harbor Freight or somewhere similar. The accurate measurements will help a lot with your search and if you absolutely can't find one there are companies that will custom make one for you for less than $100. I just went through this with my Vitacci Titan. I found that my sprocket actually matched what goes on older Dymag wheels. I am waiting for it to arrive to make certain. It may take a bit of patience but it's out there.
	0

06-20-2023, 02:03 PM	#12
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,562	You can always get a custom sprocket made if you can't find an off the shelf fit. I had to do that with my X22R. Here are a few places that do it. PBI sprockets stopped making custom sprockets a couple years ago. That's who made mine. https://sprocketspecialists.com/custom-builds/ http://www.rebelgears.com/sprockets/...sprockets.html http://www.custommotorcyclesprockets...ontact-us.html __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	0

06-17-2023, 02:52 PM	#7
JCblue Join Date: Jul 2022 Location: Bellevue WA Posts: 5	I have the same bike and it needs new chain and sprockets too. Do you know the front sprocket size? Thank you for sharing your experience.
	0

06-20-2023, 12:42 PM	#9
aZ3R0n Join Date: Jun 2023 Posts: 9	Got an update that may help anyone else with the same bike. While I have not found a sprocket yet, my mechanic took measurements while he had the stock sprocket taken off and shared them with me. The inner diameter is 103mm and the measurement across the center from bolt to bolt is 127mm. The measurement between each bolt hole is 62mm. Remember that this sprocket has 6 bolt holes, and 38 teeth.
	1

06-20-2023, 02:10 PM	#13
aZ3R0n Join Date: Jun 2023 Posts: 9	I called the US location of Boom International, I believe I found the number on this forum. It's 1-800-916-3381 They said they are moving warehouse locations right now, but if I call back next week they should be able to help me get a replacement sprocket.
	0

08-23-2023, 02:16 PM	#14
aZ3R0n Join Date: Jun 2023 Posts: 9	UPDATE: I called Boom International again, and this time they said that they cannot sell parts directly to a customer since they are a wholesaler. They said I need to contact a dealer and buy the parts from them, so now I am back at square one.
	0