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LUCIFER
12-16-2009, 3:42 AM
I have a 1982 CB750K and am gonna put a small speedometer on it. But while looking for one I came across a lot of differend Ratios 2:1, 1:4, and a bunch of other shit. I have stock size wheels on the front and back. What ratio should I be looking for? Or does it make a difference? Thank a Lot

revmike
12-18-2009, 12:46 PM
I have a 1982 CB750K and am gonna put a small speedometer on it. But while looking for one I came across a lot of differend Ratios 2:1, 1:4, and a bunch of other shit. I have stock size wheels on the front and back. What ratio should I be looking for? Or does it make a difference? Thank a Lot
Lucifer... I stole this - Most Japanese bikes use 1:2 and 60:2240 for 21 inch wheels

From here....

CRC2 (http://www.crc2onlinecatalog.com/chopper.htm) They have some Mini speedos for sale there too, but I'm not pimping them, I don't work for them and I've never bought from them, that I remember or USED their products.

~Rev Mike

LUCIFER
12-18-2009, 2:14 PM
Lucifer... I stole this - Most Japanese bikes use 1:2 and 60:2240 for 21 inch wheels

From here....

CRC2 (http://www.crc2onlinecatalog.com/chopper.htm) They have some Mini speedos for sale there too, but I'm not pimping them, I don't work for them and I've never bought from them, that I remember or USED their products.

~Rev Mike

Cool, sounds good. Thanks a lot Rev Mike

rustrocket84
12-18-2009, 2:36 PM
I've got the original honda manual for the DOHC 750's and can't find shit in the manual about speedo drive ratio. Go figure. I'll keep digging through it to see if anything comes up.

LUCIFER
12-19-2009, 2:56 AM
I've got the original honda manual for the DOHC 750's and can't find shit in the manual about speedo drive ratio. Go figure. I'll keep digging through it to see if anything comes up.

Sounds good. Thanks

jpswino
12-20-2009, 3:40 PM
Your bike has a 19 inch front wheel, right? Unless you changed it to 21.........

LUCIFER
12-20-2009, 7:20 PM
Your bike has a 19 inch front wheel, right? Unless you changed it to 21.........

Yup, has a 19 inch front wheel.

Rabbit
12-21-2009, 10:46 AM
I have used CRC before... great place to get parts and decent ship times. sometimes their parts are a little higher than other places, but then again, they have a bunch of things that are hard to find for metrics. I'd recommend them to anyone.

revmike
12-21-2009, 10:59 AM
I have used CRC before... great place to get parts and decent ship times. sometimes their parts are a little higher than other places, but then again, they have a bunch of things that are hard to find for metrics. I'd recommend them to anyone.
I saw a couple things on their webalog that I think I'll buy. Stuff I thought I might have to make myself and the prices are pretty good. I also started using Z1. I've been happy with them so far, but I don't know how deep they go with the harder to find older metric stuff. One thing I like about metric bikes and the Universal Japanese Motorcycle is the parts are SUPPOSED to be made in Asia... always look for the 'Made in Japan' label... lol, just kidding. Oh, god, let the games begin....

~Rev Mike

gr8paradox
12-22-2009, 12:06 AM
I think there may be a typo on the ratio. I believe 2:1 is correct for your bike.There are a lot of different sellers of the same speedo.Or at least it looks the same. I just had to replace my mini because the pointer broke some time back.and now the pointer fell into the odometer and has it bound up. I run a mini with 4 indicator lights. Wire up is easy but you need to install a diode on both sides of the turns to avoid feedback. I just bought off e-bay $ 77.95 shipped.
http://www.chcustom.com/ebay/bc/490291.jpg

http://stores.ebay.com/courthousecustom

revmike
12-22-2009, 5:00 AM
I think there may be a typo on the ratio. I believe 2:1 is correct for your bike.There are a lot of different sellers of the same speedo.Or at least it looks the same. I just had to replace my mini because the pointer broke some time back.and now the pointer fell into the odometer and has it bound up. I run a mini with 4 indicator lights. Wire up is easy but you need to install a diode on both sides of the turns to avoid feedback. I just bought off e-bay $ 77.95 shipped.

I saw the ratios listed both ways which, while technically wrong, isn't too uncommon. I believe the correct answer is 2:1, and that there really isn't a 1:2. I know on CRC's page they had 60:2240 listed that way and 2240:60. I dont think there really is a 1:2, although there are 1:1 speedos. So yeah, I think we are really talking 2:1.

LUCIFER
12-27-2009, 4:18 AM
I think there may be a typo on the ratio. I believe 2:1 is correct for your bike.There are a lot of different sellers of the same speedo.Or at least it looks the same. I just had to replace my mini because the pointer broke some time back.and now the pointer fell into the odometer and has it bound up. I run a mini with 4 indicator lights. Wire up is easy but you need to install a diode on both sides of the turns to avoid feedback. I just bought off e-bay $ 77.95 shipped.
http://www.chcustom.com/ebay/bc/490291.jpg

http://stores.ebay.com/courthousecustom

H6LY SHIT!!! That's the kind I wanna get. With the lights and all. THANKS. But the ratio is STILL up in the air to me. I think the 2:1 is for Harley's. I read somewhere it might be 1:4 BUT... STILL not 100% Fuck it, it'll come out of hidding

jpswino
12-27-2009, 5:48 AM
Okay, this may boggle your mind so pay attention.

Good news is that you are running a stock wheel. The ratio speedometer you need is 2240:60 which is stock for Honda CB750 on a 19 inch wheel.

If you decide to run a 21 inch wheel the wheel will turn slightly less amount of times to go the same speed since the wheel is taller. This means if you are using your stock speedo the guage will read that you are going slower than you actually are truly. So watch out for the Popo!

And if you switch to a smaller front wheel, then the speedo will actually read that you are going faster than you really are truly.

Follow? Thats why I asked about your 19 inch wheel. I hope this helps. And atleast you now know the "stock" ratio.

Cheers, jp

jpswino
12-27-2009, 5:58 AM
Oh and one more thing. The key to best accuracy is to match the speedo with the gear on the wheel from the same application. So if you switch to a 21 up front, you really should run a hub/speedo gear that was geared for a 21 wheel. You can lace a Honda hub to a 21 inch wheel. Many have done it, including me. But you would need to be using the Honda gear on the hub. Simply changing the ratio in the speedo will not do the trick to adjust for the 21 inch wheel. The gear at the wheel must match the speedo. So in that case most guys still run the stock ratio at the speedo to keep the whole deal matching knowing the speedo will be off slightly.

Hey, they're choppers, right? lol

gr8paradox
12-27-2009, 5:06 PM
Okay, this may boggle your mind so pay attention.
Good news is that you are running a stock wheel. The ratio speedometer you need is 2240:60 which is stock for Honda CB750 on a 19 inch wheel.
Cheers, jp

ROTF LMAO Maybe this is why my speedometer is off about 10% ? I thought the ratio was 2:1. And damn if I didn't just buy another 2:1. WTF

jpswino
12-27-2009, 5:41 PM
ahahaahahahahaahahahaahahahaaha

Yeah, I feel for ya. I'm speaking from experience as well!!!!

revmike
12-27-2009, 11:41 PM
ROTF LMAO Maybe this is why my speedometer is off about 10% ? I thought the ratio was 2:1. And damn if I didn't just buy another 2:1. WTF
Interesting, I read the actual ration was 2.1 to 1. I wonder if that would produce a 10% difference. I read A LOT of people had problems with 2:1 speedo being off. Seems like 2240:60 (37:1) would be a lot diff than 10%. Best advice I heard was pull the stock speedo cable and spin the wheel and count the revs of speedo cable per wheel revs. Although someone could open up a stock speedo gear and count the differential I would think, too.

I don't know because like Lucifer, the more you look into this, the murkier it becomes.

Shoot I should have added that I meant the subject is murky on the net, I don't doubt jpswino's experience

~Rev Mike

jpswino
12-28-2009, 11:27 AM
Nope, you are completely WRONG! ........................


Its murky for me too! ahahahahahaahaha



Yeah, I know guys that run 2:1 as well and its off. I think our friend here is simply estimating 10% and not necessarily meaning exactly 10%.

Again, what has been common knowledge among hondachopper guys is to keep like speedo with like speedo drive for best results. So if accuracy is important when running a 21 up front then your best results will be using a 21 with a HD (or comparable) hub in the wheel so that you can use the proper drive set up for a 21 and the matching speedo.

It gets tricky when you lace a Honda hub into a non-stock scenario (21 inch rim) because you have to make a choice somewhere. I know I have to use the speedo drive that fits my hub so do I use the matching speedo to the hub or do I use the matching speedo to the rim size? Most use the matching speedo to the hub finding closer accuracy than matching to rim size.

So to sum it all up, 3 points to match for accuracy, rim size, speedo drive, and speedo.

Hey, its a little clearer to even me now! Thanks yall for making me think about it more...lol

gr8paradox
12-28-2009, 12:04 PM
Well to add to the muck and misinformation, I will tell my story

I also did alot of searching to try and find out the correct ratio. At the time I bought my first speedometer I felt that 2:1 was the correct ratio. I have the stock 19" wheel and drive unit so it was just a matter of the speedo ratio. After the install and test run it seemed to me that the speedo was telling me I was going faster than I really was.(about 10% give or take)

Given the options of 1:1 - 2:1 or 2240:60 I still felt that 2:1 was correct and it was just a matter of poor quality of construction. Like Mike I felt that 2240:60 was a ratio and that was almost 7 to1, no way that could be it. And 1:1 would be twice what the 2:1 was. So 2:1 must be it.

The bottom line is. I more or less use the speedometer as a gauge/guide. I don't rely on it to tell me for sure how fast I am going. If I can go 120 miles on the trip gauge between tanks that is all I need to know. It doesn't matter if 120 is really 120 miles or only 110. I just found a post at Old Bike Barn that says 2240:60 means when the cable spins 2240 rpm it = 60 mph.And old bike barn does say 2240:60 is correct for jap bikes.Who knows? If a poster says I am running a 2240:60 and it is close to correct and I say I'm running a 2:1 and it is about 10% off.Seems to me that maybe the 2240:60 is the way to go.

As it stands I just ordered a 2:1 and will keep it till it busts then try a 2240:60. What the hell? You know if you are speeding or not anyway right ? For what it is worth it doesn't matter if your gauge is 100% correct or not. If the cop wants to ticket you they are going to. And given the bikes we ride speed may only be the tip of the ticket..

Thats my story and I'm sticking to it.. Have a happy new year....

jpswino
12-28-2009, 6:11 PM
I know a guy that made a new plate for inside his speedo. He and a friend calculated at what speeds on his speedo were actually 40,45,50,55,60,65,70,75 by riding side by side. Then he made a new faceplate for his speedo with the numbers in the correct position. All he had to do was pull the speedo apart and glue the new faceplate over the top of the original. Voila!

LUCIFER
01-01-2010, 2:07 AM
Aaaaaaaahhhhhhhhhh!!!!!!!!!!!!
TOOOOOOOOO much info!!!!!!!!!!!!! LOL!!!!!! BUT... that's GREAT!!! Thank You EVERYONE. Thanks a mill. Everything sounds great.

JuanCarlito
10-07-2014, 3:31 AM
I think there may be a typo on the ratio. I believe 2:1 is correct for your bike.There are a lot of different sellers of the same speedo.Or at least it looks the same. I just had to replace my mini because the pointer broke some time back.and now the pointer fell into the odometer and has it bound up. I run a mini with 4 indicator lights. Wire up is easy but you need to install a diode on both sides of the turns to avoid feedback. I just bought off e-bay $ 77.95 shipped.
http://www.chcustom.com/ebay/bc/490291.jpg

http://stores.ebay.com/courthousecustom

I just bought this! How do I wire it up to my 79 CB650?? Any help is appreciated.