Dong Fang DF250RTG

[Barnone]

Found a rear sprocket for a 428 that might fit the rear wheel of our DF250RTG.
I will order a 35 tooth and will see if it will fit.

https://www.amazon.com/JT-Sprockets-...TTRC0JQCSTWQCT

Now to find my chain break tool.

[Megadan]

All the same sprockets the Hawk 250's use. If you wanted a 520 chain setup a JTF328 sprocket would take care of the engine side. Just a random tidbit of info.

I am actually quite amazed at how tall they geared those things.

I agree with Barnone. Gearing is fine where it is. If you absolutely must gear the bike up some more, I wouldn't go beyond a 36 rear sprocket.

[Geaux-T]

Originally Posted by Barnone

Pulled the rear wheel off and did some measuring and counting. I count 38 teeth on the rear sprocket. If I remember right the front is 17 and a larger one cannot be installed.

EDIT: I just found an old post of mine where I found the chain is a 428 so the JTR279 will not work.


38/17 is 2.23 stock
35/17 is 2.05
32/17 is 1.88
30/17 is 1.76

How high do you want to go?

Guess it a little too soon to tell. Still breaking the bike in. Just noticed that at 45-50 mph in 5th gear the rpms are kind of high and I haven't even gone half throttle yet. I would like to do 55 - 60 mph on the bike in the future but would like to bring the rpms down a little.

[Megadan]

Originally Posted by Geaux-T

Guess it a little too soon to tell. Still breaking the bike in. Just noticed that at 45-50 mph in 5th gear the rpms are kind of high and I haven't even gone half throttle yet. I would like to do 55 - 60 mph on the bike in the future but would like to bring the rpms down a little.

I am assuming you are going by ear and not a tachometer. If these bikes do indeed have a 17 front and 38 rear sprocket, then 60mph is going to put the motor at about 5700rpm in 5th gear. These little engines, especially the OHC motors, are just starting to get into their power curves at that engine speed, and are usually happier at 6000-7000rpm.

[franque]

What is it revving to? Honda had two separate primary drive ratios, and I'm certain they use the lower ratio for Chinese utility vehicles (4.05 vs ~3.33), perhaps they're using them in this motor?

[Megadan]

Originally Posted by franque

What is it revving to? Honda had two separate primary drive ratios, and I'm certain they use the lower ratio for Chinese utility vehicles (4.05 vs ~3.33), perhaps they're using them in this motor?

Pretty much every dual sport bike uses the same 3.33 primary ratio as does most of the "250" street bikes.

[Geaux-T]

Originally Posted by Megadan

I am assuming you are going by ear and not a tachometer. If these bikes do indeed have a 17 front and 38 rear sprocket, then 60mph is going to put the motor at about 5700rpm in 5th gear. These little engines, especially the OHC motors, are just starting to get into their power curves at that engine speed, and are usually happier at 6000-7000rpm.

Yes going by ear. Guess I'm just use to my big cruiser . Now that you say it though I've heard that before of other 250s that they are meant to ride at higher rpms. I'll see how she dose once I break her in. Thanks for the info guys.. well appreciated!!

[Barnone]

Waiting on the new sprocket from Amazon to see it it will fit. Should be here soon.

[Megadan]

Originally Posted by Barnone

Waiting on the new sprocket from Amazon to see it it will fit. Should be here soon.

Gearing up or down?

In my opinion, these bikes could gain a couple of teeth out back, but that's me lol.

[Barnone]

I am going the other way by reducing the number of teeth by three. If the sprocket fits then I will do some "high" speed runs and check the max RPM with my mini tach and the max MPH with my speedometer app on my cell phone. Then I will swap the stock sprocket back on an compare the results.


Edit: Not going to swap the 38 tooth rear back on, too much trouble. LOL

[Rangerscott]

Whats the shipping weight? Two guys should be able to lift onto a little harbor freight trailer, you think?

[JerryHawk250]

Originally Posted by Barnone

I am going the other way by reducing the number of teeth by three. If the sprocket fits then I will do some "high" speed runs and check the max RPM with my mini tach and the max MPH with my speedometer app on my cell phone. Then I will swap the stock sprocket back on an compare the results.

I think you will like the gear change. I know on both my bikes it just makes the bike feel so much better not screaming at higher speeds. Less vibration as well.

[Barnone]

Originally Posted by Rangerscott

Whats the shipping weight? Two guys should be able to lift onto a little harbor freight trailer, you think?

Sellers claims gross weight of 250 lbs in the crate so can your boys lift 125 lbs each?

Mine when I uncrated it several years ago. Angle iron crate in the background. It was covered in cardboard so if you remove the cardboard you will have better places to grip it.

[Barnone]

The 428 35T sprocket came in a day early so I installed it this afternoon. Luckily I didn't need to shorten the chain. The stock one is stamped on the back as a 428 38T so my tooth counting was right.
Took the DF out for a short ride and she can stay in first gear longer and pulls just fine. I will take her out for some higher speed run tomorrow after I check my install.
A better test will come later when I get her up in the mountains of Western NC. I weigh 200 so you lighter guys might wanna go with a 34 tooth 428 sprocket.

38/17 is 2.23 stock
35/17 is 2.06
34/17 is 2.00

[Barnone]

Originally Posted by JerryHawk250

I think you will like the gear change. I know on both my bikes it just makes the bike feel so much better not screaming at higher speeds. Less vibration as well.

I have changed the rear sprocket to a lower tooth count or the front to more teeth on almost all my bikes in the past with satisfactory results. The DF250RTG seems to like the less teeth rear sprocket just fine.