|
|
|
|
I am working on a custom bike project and am thinking about using some parts from a CB750. Here's the problem. According to the Honda Microfiche, the CB750 model produced in the 1990s uses a 110/80-18 tire. However, according to all 9, yes NINE, of the motorcycle specification sites I could find, the CB750 uses a 120/70-17 tire. Does anyone know which is right? I would assume that Honda's microfiche is right, but then again, how can 9 motorcycle specification sites all be wrong? I need a speedometer gear drive for a 120/70-17 wheel and tire, so I am hoping that Honda is wrong. If Honda is not wrong, I would appreciate if anyone could suggest another bike that uses a 120/70-17 front tire and a cable driven speedometer. Thanks.
|
|
|
you haven't said specifically what CB750 wheel you are talking about [front or back]. you may have misinterpreted your info, but none of them came stock with a 17" front wheel. the stock tires on CB750s are....as i recall 18 or 19 inch fronts for the 69 to 78s and the 79 to 82s were all 19" fronts. the back tires [which is what i think you have the information for] can range from 16" to 18", but most of them were 17". any honda CB750 after 82 would be a nighthawk, and had an 18" front wheel [or a 16" for the 84/85 nighthawk SC]. the early 90s nighthawk did indeed have a 19" front wheel and a 17" rear.
the first 17" Honda front wheel was on the CBR Hurricane and later CBRs. you can adapt CBR wheels to your project, with a little work. mostly with the right spacers on the axles. but your will have to go the "trial and error" route to find the right combination.
|
|
|
you need the speedo drive that is specific for the wheel you have. there is no '17" tire specific' drive. if you have a 17" wheel, like the CBR wheel, you need the drive for a CBR wheel.
http://tinyurl.com/89w28d
|
|
|
That I am aware of. However, my situation is a little more complicated than that. I am replacing the front forks, front and rear brakes, and front and rear wheels of my VF750C with those from a CBR 600F3. As such, I have a CBR 600F3 wheel that I will connect to a VF750C speedometer. The CBR 600F3 used an electronic speedometer, so there is no cable driven sending unit for it. However, rigging up any Honda speedo sending unit to any Honda wheel is a pretty simple ordeal. It really only requires adding a tab to the hub of the wheel for the sending unit to catch as it spins. The problem is that the VF750C uses a cable driven speedometer, and came stock with a 120/80-17 tire. The CBR 600F2 and CBR 600F3 use a 120/60-17 front tire, but both can accept a 120/70-17 tire. I cannot use a 120/80-17 on the CBR wheel because that size is not offered in the tire I want (Michelin Pilot Road 2). With a 120/70-17 tire, if I use the speedo sending unit from a CBR 600F2 (same size wheel and tire as the CBR 600F3) the speedometer will be off because it was set for a smaller tire, and if I use the sending unit from the VF750C, it will also be off because it is set for a larger tire. I am just looking for a bike that came stock with a 120/70-17 front tire and a cable driven speedometer sending unit. Like I said, there are several sites out there claiming the CB750 uses this size front tire. However, Honda disagrees. I am just trying to find an answer to that question. If I can't find a suitable sending unit, I'll get a Dakota Digital Speedo/Tach with the Universal Inductive Speed Sensor. That unit reads speed from the rear sprocket, and the speedo unit is programmable/adjustable. I'd prefer to keep my current gauges, but if I have no other choice, I will replace all of it.
|
|
|
so you dont have a CB750 [nighthawk], you have a VF750C[magna]. while i might have asked this question on a V4 site, i can tell you that tire size does not make a significant difference in the calibration of motorcycle speedometers. they are just not that accurate, for one thing, and honda didn't make speedos based on tire size, but wheel size.
it seems you may be making this change-out more difficult than it needs to be.
changing out the front suspension, and especially changing to 17" wheels from stock 19" wheels is a common conversion on another CB site.... www.CB1100f.net and this question of speedo calibration has come up due to this change. the general consensus is there is little change to the speedo accuracy. like i said. the speedo isn't that accurate to begin with.
|
|
|
The reason I didn't ask on the Magna sites is because no one there would have any idea what size front tire came on the CB750s. Like I said, I just started doing a little research, trying to find a bike that came with a stock tire size of 120/70-17 and used a cable driven speedometer. Sites on the web made the CB750 look promising, but Honda's microfiche did not. Since I had conflicting reports, I thought I would ask people who actually owned this bike.
The CBR 600 F2/F3 and the Magna all use 17 inch front wheels. Essentially, I have put CBR 600F3 fork lowers on the bike. The CBR and Magna both use 41mm forks, so the CBR fork lowers mated perfectly with the Magna fork tubes. This allowed me to install the CBR brake calipers on the front of the Magna, along with the CBR wheel (now I can have radial tires). On the rear, I have installed a CBR F3 wheel and sprocket, as well as the CBR rear disk brake and caliper. So, I have gone from having a single disk brake on the front, rear drum brake on the rear, and bias ply tires, to dual disk brakes on the front, a single disk brake on the rear, and radial tires. Oh yeah, I had to use a VTX front brake master cylinder because the CBR master cylinder was for 7/8" handlebars. The Magna master cylinder was too weak to run two calipers, but the VTX master cylinder has more than enough power, looks identical to the Magna master cylinder, and fits the Magna's one-inch handlebars. This process has been a PITA, but now that it is done, I finally have the bike I want: Runs fast and stops short and straight. The only thing left on the "to do" list is getting the speedometer hooked up.
It looks like the CB750 is not going to give me what I need. I will either use the Magna's speed sending unit, or I will go with a speedometer from Dakota Digital. I am not so interested in the speed being perfect, but I would like to odometer to be pretty accurate.
Thanks for the help and advice.
|
|
|
did you try the fireblades site..... http://www.fireblades.org/forums/honda-interceptor-vfr/i am sure the interceptor boys would have a little experience with trying different tire sizes. i used to have an old VF750F and saw a few conversions of this sort. in the case of the VF750F the change went from a 16" front wheel to a 17" wheel. radials really make a lot of difference in the handling, you should like the upgrade. good luck!
|
|
Locked
