CrimsonPrince
Member
Hi all, I bought a CNC sprocket from Amazon that JUST DOESN"T FIT my 415 chains! Should I try to work with it (shave down the teeth) or just get a new one?
My CNC rear sprocket DOESNT FIT. ARGGHHH
- Thread starter CrimsonPrince
- Start date
CrimsonPrince
Member
54 teeth!
JerryAssburger
Active Member
I had a similar situation with a sprocket whos teeth were darned-near square, viewed edge-on. Once I tapered them, it helped quite a bit.
CrimsonPrince
Member
How did you file them down? What kind of tool would you recommend? Honestly though, I'm thinking of just getting rid of my sprocket from Amazon and going with a T8F size sprocket with 54 teeth...
I’d advise you to return the 54t sprocket.
I miscalculated your gearing needs.
Since you’re running 20” wheels, then a 14.4:1 ratio is equivalent to 18.75:1 on a bike with 26” wheels.
A 40t sprocket with your 25t BMX, along with 54t/9t engine-jack shaft sprockets will yield 14.4:1.
Being a smaller sprocket than the 54t, the 40t should clear the frame stays easier.
I miscalculated your gearing needs.
Since you’re running 20” wheels, then a 14.4:1 ratio is equivalent to 18.75:1 on a bike with 26” wheels.
A 40t sprocket with your 25t BMX, along with 54t/9t engine-jack shaft sprockets will yield 14.4:1.
Being a smaller sprocket than the 54t, the 40t should clear the frame stays easier.
CrimsonPrince
Member
Thanks! May I ask what the basis of the calculation is?
I remember discussing the gearing ratios earlier, but I never thought it involved the wheel sizes!
Just out of curiosity, what happens if I have a very low gearing ratio like 24:1? How do you predict that it will affect the bike? What about a high gearing ratio like 4:1?
Just asking questions to get an idea, lol. Sorry for all the pestering inquiries! Thanks again for your time!
MEASURE TWICE
Well-Known Member
I know of my experience with first trying with 8:1 ratio and 26" wheel on a 3hp 4stroke Briggs. I weigh 135lb and the bike weight maybe 70lbs as lots of extra metal welded on for off roading on trails. This 8:1 ratio was not enough to even get the bike going well at all on flat ground.
I eventually have been using it at 20:1 and also 12:1 ratios. 20:1 better for steeper hills on trails, but 12:1 can work just not as good. Trade off top speed.
Not having made motor bikes with 2 stroke engines, I'm not sure if you can use this as a guide. I never saw mention of the type displacement and horsepower output. I did see that the size physically inside the frame on the 20 wheel bike leaves it to be where I would think 18:1 could be good.
Anyway why I am posting is since I found initially the difference between unusable at all with too high a ratio, and what works in my situation.
What does seem odd is the terminology higher ratio is a lower number with relation to the number 1. But that's OK.
I eventually have been using it at 20:1 and also 12:1 ratios. 20:1 better for steeper hills on trails, but 12:1 can work just not as good. Trade off top speed.
Not having made motor bikes with 2 stroke engines, I'm not sure if you can use this as a guide. I never saw mention of the type displacement and horsepower output. I did see that the size physically inside the frame on the 20 wheel bike leaves it to be where I would think 18:1 could be good.
Anyway why I am posting is since I found initially the difference between unusable at all with too high a ratio, and what works in my situation.
What does seem odd is the terminology higher ratio is a lower number with relation to the number 1. But that's OK.
A 24:1 ratio would have lots of low end power.
With 18.75:1, good all around power, even low end.
The 14.4:1 ratio should give you good power, along with using your pedals.
With 4:1 ratio, it’ll be like trying to pull away from a stop, in 4th gear with a truck.
Your clutch would self-destruct.
That’s a good reason to keep your pedals.
JerryAssburger
Active Member
It wasn't the most scientific method- I took n angle-grinder and tapered the sides of the teeth, both sides. But in light of the fact that you need a different sprocket, don't touch it.
Rusty_Nail
Active Member
I had the same problem with a 44t cnc sprocket I bought. Teeth seemed squared and my chain kept trying to jump off it or the chain would bind and not want to turn freely.