rok2k12
CB750 Member
I am building a cafe out of my '75 CB750F and will be changing the sprockets and chain. Suggestions? Low end vs top end?
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It's kind of up to you. I'd ride it like it is and go from there. I tend to keep things stock or gear them down just a big for more low end. Stock is 18 on the front and 48 on the rear. Some people put a 17 on the front.
rok2k12
CB750 Member
Thanks Travis. 17/48 seems to be the consensus from the 750'rs in my neck of the woods. I'll get the goods and let you know what I think after a few miles.
That should work out fine... unless you like to cruise at 100mph. 
You can gear a little higher if you build the motor bigger to keep the revs down as the extra hp will pull it. My hardtail is running 18/45 with a CBR rear wheel and tire. Which brings up another point....different circumference rear tire makes a large difference in what gearing you will need.
rok2k12
CB750 Member
Oh yes, that geometry thing. It has a 19 front/18 rear now and I am planning on running 18/18. Pirelli makes the closest matching set I've found so far. I'm looking at 110/90 - 18 for the front and 140/70 - 18 on the rear. But I am open to suggestions. I have a big cruiser that I ride also so I am leaning more towards low end performance, however, I would still like it to do the ton!
PharmD750
CB750 Member
I have stock sprockets (18/48) on my bike and riding at 55 in 5th is revving quite high. Just wondering what rpm you guys like to cruise around at? I was thinking of going to 17/41. This would take me from 2.67 to 2.41 on the ratio. I also read somewhere that using prime numbers for sprockets reduces the chance of having harmonic vibrations and controls wear better on the teeth and chain. Not sure if that is true but it makes sense.
amc49
CB750 Guru
The OEM ratio on the F hotrod bike is 18/46, I went to 42 on mine and close to where you are at, or 70-72 mph at 5500. You worry too much, the engine is made to spin (the cams come into the powerband at around 5500 rpm) and not a car one that dogs around at lower rpm, you can actually damage one doing that. The 18/42 would top out at 125+ if I wanted to go that fast. The rational person has nowhere to utilize that on the higher end making it somewhat worthless. I used 42 because it is the 1100F ratio.
The 750 actually uses something of an overdrive 5th gear, the drop from 4 is too far. Racers use the 900 5th gear to get a better rpm drop for racing, it is closer though and would make your perceived issue worse.
The 750 actually uses something of an overdrive 5th gear, the drop from 4 is too far. Racers use the 900 5th gear to get a better rpm drop for racing, it is closer though and would make your perceived issue worse.
