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This was posted over on dotheton by BigSherm. This is great info for anyone looking to upgrade the front end of their bike. All credit to Sherm.
EDIT: Looks like allballs site has changed. However the ohiocafe pdf is very usefull.
EDIT: Looks like allballs site has changed. However the ohiocafe pdf is very usefull.
Dudes,
Check it. Go to the all balls bearings website, (goallballs.com) and find steering head bearings for your frame. I input my 1978 CB750K and got this page - http://www.goallballs.com/Product_Lookup_results.asp
Now, click on "Click to buy online" on the left of the screen (it doesn't make you buy them), and get to this page - http://www.goallballs.com/Product_lookup_results_shop.asp?zipcode=37042
Now, click on "Details" under "Steering brg - seal kit" and it takes you to this page - http://www.goallballs.com/SHOP/shopexd.asp?pagefrom=Ret&id=582
Here's the good part - it lists every bike that those bearings fit!
So by using this tool, I can tell at a glance that a front end (forks, triples, everything) from a CB400F, GB500, Ascot, etc. will bolt on to my bike using the stock CB750 steering head bearings!
Now, for my next trick, (listen up streetfighters) check this for way more options - Use this chart, http://www.ohiocaferacers.com/OCRStemSizes.pdf and find your steering stem size. For example, my 78 CB750 uses bearings of this size - Upper: 26 x 48.5 x 15.2, Lower: 30 x 50 x 14.4
The info from this to remember is the first measurement of upper and lower. In my case, 26mm upper and 30mm lower stem sizing.
Now, you know the measurements of your stem, there may be another section in the same chart (http://www.ohiocaferacers.com/OCRStemSizes.pdf) that has those 26 and 30mm stem sizes. for example, I found "Upper: 26 x 47 x 15, Lower: 30 x 55 x 17"
Disregard the - "47 x 15" Upper and "55 x 17" Lower because you only want to know other bikes with the same stem size, not the size of the area where the bearing sits in the frame of that bike.
Ok - here's the money shot. Go back to goallballs.com and input any bike from that other section with the same stem sizes, and when you follow it to the "Details" page, it will list every other bike with your same stem size! For streetfighters, this covers even new bikes that aren't listed on the Ohio cafe racers site.
Using this, I found that virtually every CBR600, 900, 954, 929, VFR, CB1100F, and even newer CBR1000rr front end has the same stem size as my bike, making them virtually a bolt-in swap!
Ahh, but you say "what about the length of the two stems? If the CBR stem is shorter, you're screwed because it won't reach through your steering head."
That's when you use your stock CB750 stem in the CBR triples, because they have the same diameters where it counts. You also use your frame's stock size steering head bearings because the stems are the same size.
HAHA! Now all I have to do is source an eBay CBR1000rr front end, complete with the latest radial brake and fully adjustale suspension technology and hook my bike up!
Of course, you could use this data to create a custom bearing set to fit your frame with a stem that is not the same size as yours, but if the new stem is too short, you've just increased your cost substantially because you'll need to get a longer stem custom made. Typically, modern sport bike front ends complete with brakes, triples, forks, and axle (not the wheel) go for about 500-800 bucks on eBay. That's CHEAP for the height of suspension and brake technology.
