Goldenoldy63
CB750 Enthusiast
Hello. Has anybody messed with sprocket size. My 1970 Honda 750 at 60 miles an hour is arriving at about 4000 RPMs. I would like to drop in a little bit. Any thoughts out there? Thanks, Rob.
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Sprocket sizes for 70 cb
- Thread starter Goldenoldy63
- Start date
madmtnmotors
CB750 Addict
Sounds perfect as is. These motors don't even "wake up" until you get between 6 and 8K on the "grin-ometer". To reduce RPMs at any given speed either add a tooth or two to the front sprocket or reduce the number of teeth on the rear. Count the teeth on your current sprockets and go from there. Trial and error will be the only way to find the combination to your liking since the current condition of your engine could respond very differently from another motor based on the mileage and/or state of tune. You could very well need a new chain depending on how far you go on the tooth count. Reducing the number of teeth on the rear could possibly be accommodated by removing one or more links from the chain. Adding one tooth to the front and reducing the rear by two teeth might not require any change to chain length. Raising the final drive ratio in this way could reduce low end performance and may require more effort when pulling away from a stop.
I am currently running a 16/52 setup and turning about 9200rpm at 100mph on my dragbike:
I am currently running a 16/52 setup and turning about 9200rpm at 100mph on my dragbike:
Goldenoldy63
CB750 Enthusiast
Sorry for the late reply. But thanks for all that information, I am revving around 4000 RPMs at 60 miles an hour which is totally fine, but I just thought a few hundred RPMs less at that speed might be nicer. I am running the stock sprockets and it works totally fine especially for around town and stuff like that thanks that’s a cool drag bike
madmtnmotors
CB750 Addict
You could try different sprockets if you were planning a long haul road trip, maybe add one tooth to the front and drop two teeth in the rear. This would give you four combinations to work with and probably not have to make any changes to the chain:
1. Current front and rear
2. Bigger front, current rear
3. Current front, smaller rear
4. Bigger front, smaller rear
The drag bike is a blast, running bracket class (Street ET) on a budget. Mild 836 flat top overbore, 1-1/2" longer swingarm, and spacers in the forks to reduce rebound effectively shortening the forks by 1-1/2".
1. Current front and rear
2. Bigger front, current rear
3. Current front, smaller rear
4. Bigger front, smaller rear
The drag bike is a blast, running bracket class (Street ET) on a budget. Mild 836 flat top overbore, 1-1/2" longer swingarm, and spacers in the forks to reduce rebound effectively shortening the forks by 1-1/2".
Goldenoldy63
CB750 Enthusiast
Thanks. And yes, I do have sitting around here a front sprocket one tooth larger than whats on now. if that would drop the RPMs even 100 or 200 RPMs, I would be happy. The stocks set up is absolutely fine and fun for driving around.
