What is my speedo ratio?

According to my service manual, all of the KZ650 models came with 19" diameter front wheels. The SR used a slightly wider tire, 3.50" vs. 3.25", than the B and C models. These days the tire manufacturers offer this width with one tire. The B and C models have 18" rear wheels while the SR has 16".

So, with a stock drive gear at the front wheel, the speedometer will be as close as they get with a 19" wheel (somewhere less than 10% error usually). BTW, the FSM is mum on any mention of a speedo or tach ratio.

HTH,

- Nate >>

Post edited by: n0nb, at: 2006/03/23 21:36

Well I am going to use an aftermarket speedo & tach so that still doesn't help me as I don't know what the ratio is. Are you saying if I put on any 19 inch front that the ratio will still be the same? I have a KZ650 B which has an 18 inch rear but I am changing it for a 16 inch. I am going to use a 4.00 x 19 on front & 5.00 x 16 on back for tires.

Here's an idea. Maybe the ratio they're asking for is the number of revolutions the speedo drive cable makes for each revolutions the front wheel makes.

Jack up or suspend the bike so the front wheel is off the ground.

Remove the speedo drive cable at the speedo end and use a piece of tape or a zip tie as a flag so you can count the revolutions.

Slowly rotate the front wheel one revolution and count the turns the drive cable makes.

Changing the rear wheel to a 16" may have an effect on your engine RPM compared to the 18" wheel, so you may want to change your final gearing. On my SR with a 130/90-16 tire, I have a final drive ratio of 16/38. The stock final ratio is 16/41 (front/rear).

HTH,

- Nate >>

The speedometer ratio you are looking for is 2240:60.

Post edited by: twowheeledterror, at: 2006/03/24 10:30

the thing that gets me is he cant wait to get an answer. i have seen this same question at other forums also. i found it in the archives along with alot of the info he has been asking.

yes i'm new but for gods sake man spend some time looking for a answer in the archives over asking it on every forum you are signed up for.

Thanx Timber. And I did do a search & found nothing. I did not know about doing a separate search in archives as every forum I have been to has one area to search in (I just searched the archives & did not find one definitive answer on this with my setup). Isn't that what this forum is for? Asking questions? If you don't like seeing my posts, then put me on ignore. Everyone thak you for your help...

Post edited by: elcid, at: 2006/03/24 13:13

Post edited by: elcid, at: 2006/03/24 13:14

Curious about how TWT came up with the 2240:60 ratio. That is the ratio used on a Sportster, I believe. I have used mechanical mini-gauge speedometers on various Kawasakis and always used 2:1. If you look in JP Cycles catalog, they will have the 2240:60, 2:1 and a 1:1 set of ratios for some of the mini-speedometers.

The mechanical tach has no ratio associated as near as I can remember.

Oh fellas... speaking as a site moderator...

The search function is OK... but not great. I personally dislike using it as it is awkward and can understand why some folks wouldn't use it. I am not suggesting you don't try looking things up as there may have been some super-duper comments made on a subject in the past.

The point of our new site is to put technical subjects in places where they can be recovered easily so that folks don't have to answer the same questions over and over. This means, if you know a bit about a subject and think it is worth sharing, put it in an ARTICLE or put it in the FILEBASE! If you haven't done that, don't scold others for asking a question that isn't covered in one of those two areas since the search feature we do have, is on the primitive side and cumbersome.

I am disappointed that more folks have contributed to the FILEBASE and ARTICLE sections. A good selection of tech articles would sure go a long way to improving the site.

Thanx wiredgeorge. I actually work for a website that has a discussion forum & I am on there everyday so I agree with searching before you ask. I always do & will continue to. Do you think changing the wheel sizes affects the ratios? I want to use a 19 on front (same as stock) but change the rear to 16. I will just wait until I have my new wheels & tires installed & then call the guys at JP & ask them.

wiredgeorge wrote:

Curious about how TWT came up with the 2240:60 ratio. That is the ratio used on a Sportster, I believe. I have used mechanical mini-gauge speedometers on various Kawasakis and always used 2:1. If you look in JP Cycles catalog, they will have the 2240:60, 2:1 and a 1:1 set of ratios for some of the mini-speedometers.

The mechanical tach has no ratio associated as near as I can remember.

TWT got it because 2240:60 is the universal speedo for japanese bikes. That's a proper ratio for damn near any bike with a mech. speedo that rolled on out of Japan.

Oh, and 2:1 will also work, but to be precise 2240:60 is the proper speedo.

Post edited by: twowheeledterror, at: 2006/03/24 16:24

Elcid... I sort of promote searching but I think it would be far easier to search the Filebase / Articles and not muck around looking at old threads. Most folks who post a thread use terrible names to search on... I just hope folks stop ragging others for not searching. If we had a strong Filebase/Article section, then this would elminate a lot of the irritation of looking at the same questions from every new person coming to the site but we ain't there quite yet. Almost every one of you folks have learned some GOOD stuff that I wish I knew. I don't even know what I don't know and if you took the time to put it down, I could look through it and learn something new. That is the MAIN reason I am here... to learn something new...

And TWT! Do you have an explanation for what the ratios are? If you are right about the 2240:60 and 2:1 both working, then the numbers can't be direct ratios and I really and truly don't understand how these ratios work. There are only a couple guys I know of who I could ask... If ANYONE knows what these ratios represent, it sure would be interesting to hear. Why didn't the 2240:60 get reduced to say 1120:30 or 560:15? The numbers must not be ratio... must mean something else...

it can be reduced all the way down to 36:1 i dont know what they mean. i have heard it explained from people who say they know, but not a one of them has the same answer. i think it belongs to the black arts or somethng like that.

as far as me jumping on him. sorry. i get a little worn when i see the same question by the same guy on other forums.