Arrow 7hp with 48 Tooth Sprocket 30-35mph

[FurryOnTheInside]

Thank you Furry, they're 26 inch. 26 X 1.95 Kenda K838

An approximate calculation based on 26x1.9" (accounting for some wear) and a 48t rear sprocket (10t front) gives these approximate figures:

16mph per 4100 RPM (1000rpm at the front sprocket)

7700rpm = 30mph
9000rpm = 35mph
9250rpm = 36mph



With a 40t, which is 5/6 the size of a 48t ...
7700 ÷ 6 x 5 etc....

6400rpm = 30mph
7500rpm = 35mph
7700rpm = 36mph
8000rpm = 37.4mph
9000rpm = 42mph

That's about the same as the gearing I have on my super cheapo engine that I have been working on myself (my first time), so I should think you can go smaller than 40t if it's a good strong engine and especially with a tuned pipe. I will try a smaller sprocket if I get a pipe that works too.

So if you want 49mph at 9k you need a 35t sprocket. A 36t will give you 46.666 but a 34t will give you 52.5mph at 9k ....if your engine is strong enough.

 

[Scooterduder]

I am shocked to see ppl paying over $500 a China motor, no matter how it is modded or polished. 7 HP? Ha!

There are better ways to waste money!

I agree with you Timbone. I didn't then, but I do now. I'm not going to have the knowledge and tools anytime soon so I would like to still get another race engine in the future, but not from Arrow. With my limited knowledge I do tend to agree with people that DON'T agree with the horsepower ratings assigned to Arrow engines. I never see Arrow on the forums making their case for anything. I think their reputation is based on their top engine and how people in California buy it and win races with it in California.

 

[Scooterduder]

An approximate calculation based on 26x1.9" (accounting for some wear) and a 48t rear sprocket (10t front) gives these approximate figures:

16mph per 4100 RPM (1000rpm at the front sprocket)

7700rpm = 30mph
9000rpm = 35mph
9250rpm = 36mph



With a 40t, which is 5/6 the size of a 48t ...
7700 ÷ 6 x 5 etc....

6400rpm = 30mph
7500rpm = 35mph
7700rpm = 36mph
8000rpm = 37.4mph
9000rpm = 42mph

That's about the same as the gearing I have on my super cheapo engine that I have been working on myself (my first time), so I should think you can go smaller than 40t if it's a good strong engine and especially with a tuned pipe. I will a smaller sprocket if I get a pipe that works too.

Thank you so much for that Furry. Extremely helpful!

 

[FurryOnTheInside]

No problem.


Some more very approximate figures from another calculator:

It takes 4.5hp to sustain approximately 50mph, (but more to accelerate up to the speed).

It takes 5hp to sustain approximately 52.5mph, (but more to accelerate up to the speed).

7hp is enough to sustain approximately 58mph, (but it needs more to accelerate up to speed (like you can only do 58 in real life if there's a hill start or slipstream another vehicle))

That's a huge difference in power for a small difference in speed but that's how it works.

 

[Scooterduder]

Hey, Street Ryderz, you had posted somewhere that a customer of your's had an Arrow 7hp and it wasn't as fast as one of the Fred engines I think it was? Do you recall exactly what that better engine was?

 

[Street Ryderz]

Hey, Street Ryderz, you had posted somewhere that a customer of your's had an Arrow 7hp and it wasn't as fast as one of the Fred engines I think it was? Do you recall exactly what that better engine was?

I think it was a stage 2 race engine,but Fred doesn't list that one anymore,The guy paid like 500 bucks for it and it was more impressive than the Arrow by far.

 

[Scooterduder]

I think it was a stage 2 race engine,but Fred doesn't list that one anymore,The guy paid like 500 bucks for it and it was more impressive than the Arrow by far.

Cool thanks! I'm happy with what I have for now, and I don't have a choice about it. Wish I paid less moolah.

 

[Scooterduder]

After some sleuthing, I found this picture on facebook of a guy saying his engine was an Arrow. Philip Spieler. I don't know if it's been altered at all, but the reed looks like it's mounted at a different angle. Pretty sure it's the same bike with a different paint job. A lot of pics on his page..................................... I also found that he is the same person that has a very unsavory criminal past, as a sex offender. That is now known, but irrelevant, so I ask that no one dwell on that aspect and derail what could be an informative thread to other people. Thank you.

 

[Scooterduder]

For easier comparison, this is my engine picture.

 

[Street Ryderz]

That's not an Arrow reed box on Philip's engines,looks like CDH's or Gas Bike,I'm shocked to see the stock fasteners on yours through out.He races with SMB and has had many variations of his set up.