Author Topic: Dresda CB500 with CR gearbox info  (Read 622 times)

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Offline Dresda500

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Dresda CB500 with CR gearbox info
« on: December 04, 2023, 04:47:20 AM »
Good day! I finally had time to pull the motor to get it ready to build and was happy to find the previous owner was correct that it had a close ratio trans. Its a '73 CB500 block, so early style clutch.  So my question is if anyone might know the possibilities of the origin of the trans. It basically has tightened up ratios in 2nd and 3rd, which match the Yosh 5spd ratios. It still has the deep 1st gear and 0.90 5th gear. With these tighter ratios, this gives a large jump from first to 2nd, so would like to get a higher first gear if possible, like from the CB500T, if it will fit. Did anyone every try these gears ? Below are the ratios.  The tracks I race on in Scandinavia I think will be great for this trans as I would use 1st for start only and the slowest chicanes are 2nd gear . It has basically a 13% drop in all top gears change.
Does anyone know if one could buy just gearsets from Yosh or had to get the whole kit? Did they use stock shafts?
This was a previous road race bike in the UK back in the 70s-80s but unfortunately don't have lots of history on it.



                              
   1st Gir      2nd Gir      3rd Gir      4th Gir      5th Gir   
   CB500   Dresda CR   CB500   Dresda CR   CB500   Dresda CR   CB500   Dresda CR   CB500   Dresda CR
Main Shaft T   17   17   22   24   26   26   28   28   30   30
Counter Shaft T   40   40   36   33   33   31   29   29   27   27
                              
Ratio   2,353   2,353   1,636   1,375   1,269   1,192   1,036   1,036   0,900   0,900
                              
                              
   CB500    % Drop   Dresda CR   % Drop                  
1st   2,353      2,353                     
2nd   1,636   30,5   1,375   41,6                  
3rd   1,269   22,4   1,192   13,3                  
4th   1,036   18,4   1,036   13,1                  
5th   0,900   13,1   0,900   13,1                  
                              
                              
CB500 Clutch Drum   64t                           
Drive Gir   23t                           
Instagram: hansrodncycle
Roadracing CB250K, Dresda CB500 and Martin KZ1000
Special intrest in hand made frames/bikes, porting/flowbench and Dyno tuning of vintage bikes

Offline Dresda500

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Re: Dresda CB500 with CR gearbox info
« Reply #1 on: December 04, 2023, 04:51:22 AM »
and if anyone can give some tips on running this clutch I'd appreciate it. I've never built or used one before, but read the updated 550 is much better....but since I have the CR box, I'm going to run this clutch obviously. The clutch fibers were of a metallic embeded type and had stuck to the steels, so will need new fibers and can prep the steels to use again.
Instagram: hansrodncycle
Roadracing CB250K, Dresda CB500 and Martin KZ1000
Special intrest in hand made frames/bikes, porting/flowbench and Dyno tuning of vintage bikes

Offline HondaMan

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Re: Dresda CB500 with CR gearbox info
« Reply #2 on: December 06, 2023, 07:02:29 PM »
I don't have any info on the gears, but a possible recommendation for the clutch lifter: make sure the small screw ramps are in good shape. This trans shifts so effortlessly in street use that the clutches often got pulled in less than full stroke, which puts a small 'notch' at the end of that turn of the screw, making it hard to pull the clutch in all the way.

Just a thing to check. ;)
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Offline Dresda500

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Re: Dresda CB500 with CR gearbox info
« Reply #3 on: December 07, 2023, 09:43:54 PM »
I don't have any info on the gears, but a possible recommendation for the clutch lifter: make sure the small screw ramps are in good shape. This trans shifts so effortlessly in street use that the clutches often got pulled in less than full stroke, which puts a small 'notch' at the end of that turn of the screw, making it hard to pull the clutch in all the way.

Just a thing to check. ;)

Thanks Hondaman! yeah, I race a CB250 K at the moment and uses the same system and has been working fine and gets serviced every winter, but some guys like to use a lever style like this one and say it gives better feel. Only thing I don't like about it is it's pretty vulnerable if you lay  it down.
Or go hydraulic as I've seen done, but then this gets even more complicated and more special spares for levers etc
« Last Edit: December 08, 2023, 02:17:35 AM by Dresda500 »
Instagram: hansrodncycle
Roadracing CB250K, Dresda CB500 and Martin KZ1000
Special intrest in hand made frames/bikes, porting/flowbench and Dyno tuning of vintage bikes