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Re: Dong Fang DF 250 RTB Bobber Information
I should be topped out at about 65 MPH with the 35 tooth rear sprocket with a cruise at 55 to 60 MPH which is fine for me here in the mountains.
45 divided by 35 equals 1.3 times 50 equals 65
My bike feels like it might need jet changes at the higher rpm like the 2010 did. I'll have to take a look at the jets.
Reading through the post I found that the 2012 still has the 105 main and 40 pilot.
So I gonna go with the 108 and 42 to richen her up a bit.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
culcune
A few people have started DF 250 threads; I have suggested to post on the 'original' thread simply because that is what brings people to mychinamoto from Google (those with DF). But I see the point of going over 3000 pages being difficult-I am sure there will be double posts, if not triple, or more by now, so if someone new brings up a question that had been discussed a couple years ago, I bet there are others who would also like an answer. Thanks for sticking around, 4950cycle!
Agreed. Most questions have been answered several times in this thread. Considering it's size I would do a search in this thread before posting. I always try to do that first. Either way, this forum is newb friendly thank God as I am defenitely a noob. Only been riding for one year now.
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Re: Dong Fang DF 250 RTB Bobber Information
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3 Attachment(s)
Re: Dong Fang DF 250 RTB Bobber Information
Raining here big time so I changed out the rear sprocket to a 35 tooth one. I removed about three link in the chain.
Attachment 12558
Checked the wheel for balance and true and it was just about perfect.
https://picasaweb.google.com/1091387...71657308021714
Attachment 12559
Hope I didn't go too small on the sprocket.
Attachment 12560
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Re: Dong Fang DF 250 RTB Bobber Information
I wouldn't think you have gone to small. If I remember right they come with a 12 or 13 on the front. That being said, I have a 15 on the front and a 38 out back. You are only 3 teeth less than I have for rear. And 2 to 3 teeth less in the front. If I remember the old rough formula was 1 tooth up front is equivalent to 4 in the rear. Skip all that mumbo jumbo, Bottom line, I still have taller gearing than you do even with your 35 and mine is spot on for my 250 lbs., 6"3 butt. My guess is you'll want to go with a 14 tooth up front to go even taller once you test it out. Unless you like it quick instead of higher top end.
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Re: Dong Fang DF 250 RTB Bobber Information
I'm brand new to the forum, but it looked like some good info on here. I'm really considering getting one of these df bobbers, and suggestions on who to order from? Any direction would be greatly appreciated.
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Re: Dong Fang DF 250 RTB Bobber Information
Don't pay any attention to these jokers. It is a good bike. It runs..
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
Gearhead45
I'm brand new to the forum, but it looked like some good info on here. I'm really considering getting one of these df bobbers, and suggestions on who to order from? Any direction would be greatly appreciated.
Gearhead45,
I have ordered two DFs from Chad at http://www.extremescooters.biz/gas-p...-choppers.aspx with good service from him.
BUT be sure and check that you can register the DF in Colorado.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
ghost1133
Don't pay any attention to these jokers. It is a good bike. It runs..
What? Which jokers?:lol8:
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Re: Dong Fang DF 250 RTB Bobber Information
I appreciate the help. Still talking to the wife, you know how that's goes. Haha. Probably going to order one in the next week. I know these china bikes have some issues, I've been a mechanic for a few years though so no worries. Any heads up on issues with these?
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
Gearhead45
I appreciate the help. Still talking to the wife, you know how that's goes. Haha. Probably going to order one in the next week. I know these china bikes have some issues, I've been a mechanic for a few years though so no worries. Any heads up on issues with these?
Gear,
I've only had my 2012 DF for a week or so I have limited experience with it. Had the previous model back in 2010 and sold it.
Issues so far are minor.
Lack of clearance between rear tire and tail light wiring under fender. Some don't seem to have this problem.
Valves adjustment and oil change were necessary before starting bike.
Click on my photos at https://picasaweb.google.com/1091387...FangDF250RTBA#
for changes to my DF.
Probably will up the jet sizes, add some saddle bags, etc.
Very easy bike to modify and maintain but you do need some DIY skills which you appear to have.
I'd go back 20 pages or so in this thread and read forward. So sense in going back to day one.:lol8:
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
ghost1133
Don't pay any attention to these jokers. It is a good bike. It runs..
yeah just ride it.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
chruk bashre
yeah just ride it.
If it ant' broke, don't fix it,
Living the life I am living.
Hell yea !
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Re: Dong Fang DF 250 RTB Bobber Information
This should be a good motorcycle for someone to learn about working on them too. For instance, on the CCW Tha Heist Facebook page, there are several owners trying to adjust the valves and having problems. There is nothing easier to get your feet wet than on a pushrod single like these two motorcycles. One guy was obviously trying to do the valve adjust while on the wrong stroke. He kept backing off the adjuster at the rocker arm and couldn't get any clearance. Good thing he stopped and asked. On the Royal Enfield 500 Bullet (2007) I used to have, they never even gave valve clearance measurements. You got it at TDC on the firing stroke so both valves were closed, grabbed the pushrods and tried to turn them (spin them round). If they turned pretty easily, and had no up and down play, then you were good.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
birdmove
This should be a good motorcycle for someone to learn about working on them too. For instance, on the CCW Tha Heist Facebook page, there are several owners trying to adjust the valves and having problems. There is nothing easier to get your feet wet than on a pushrod single like these two motorcycles. One guy was obviously trying to do the valve adjust while on the wrong stroke. He kept backing off the adjuster at the rocker arm and couldn't get any clearance. Good thing he stopped and asked. On the Royal Enfield 500 Bullet (2007) I used to have, they never even gave valve clearance measurements. You got it at TDC on the firing stroke so both valves were closed, grabbed the pushrods and tried to turn them (spin them round). If they turned pretty easily, and had no up and down play, then you were good.
Is that RE technique with a cold or a hot engine?
I'd like to try that on my DF with a hot engine and then measure the clearances when cold.
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Re: Dong Fang DF 250 RTB Bobber Information
Cold. Though some owners said they did it hot, and said it worked too. The point being, on the Enfield, once you got the feel of the proper valve adjustment, it was something you would remember. I bet that would work just fine on these bikes too. I tried to get across to the Heist owner, that, if he goes to TDC, then checks both valves for looseness and finds one tight. DON't adjust it. Rotate the engine once around, and recheck for looseness. He would have then found that, after rotating once, he was now at TDC on the firing stroke, the correct position to make the valve adjustments. There are two top dead center's. But only one TDC with both valves closed (the firing stroke). He didn't do any harm, because he didn't try to start it. He would have spit a pushrod out and possibly caused damage, if it would have even started. With as much excessive valve clearance as he had, the valve may not even come open.
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Re: Dong Fang DF 250 RTB Bobber Information
Since it is still raining here I'm gonna try the RE method hot and then check the cold clearance.
Makes sense that you want almost zero clearance (able to spin the push rods) when hot, right?
EDIT: No room to spin the push rods for my fingers and didn't want to use needle nose pliers.
Installed the mini tachometer and it works. Took off the tank to get some slack for the ignition switch and then mounted it right side up.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
birdmove
Cold. Though some owners said they did it hot, and said it worked too. The point being, on the Enfield, once you got the feel of the proper valve adjustment, it was something you would remember. I bet that would work just fine on these bikes too. I tried to get across to the Heist owner, that, if he goes to TDC, then checks both valves for looseness and finds one tight. DON't adjust it. Rotate the engine once around, and recheck for looseness. He would have then found that, after rotating once, he was now at TDC on the firing stroke, the correct position to make the valve adjustments. There are two top dead center's. But only one TDC with both valves closed (the firing stroke). He didn't do any harm, because he didn't try to start it. He would have spit a pushrod out and possibly caused damage, if it would have even started. With as much excessive valve clearance as he had, the valve may not even come open.
Birdmove. you are right on.
Always worked for me and that's with 36 years of road underneath my feet. But at the same time, I would of been lost without you guys. Go figure.
Thanks.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
4950cycle
I wouldn't think you have gone to small. If I remember right they come with a 12 or 13 on the front. That being said, I have a 15 on the front and a 38 out back. You are only 3 teeth less than I have for rear. And 2 to 3 teeth less in the front. If I remember the old rough formula was 1 tooth up front is equivalent to 4 in the rear. Skip all that mumbo jumbo, Bottom line, I still have taller gearing than you do even with your 35 and mine is spot on for my 250 lbs., 6"3 butt. My guess is you'll want to go with a 14 tooth up front to go even taller once you test it out. Unless you like it quick instead of higher top end.
Mumbo jumbo alright
How can you arbitrarily equate x amount of teeth on one gear to x amount on its coupled gear?
As the number of teeth in the system change, the number of teeth on one gear that relate to the coupled gear changes in kind.
In the end its all the ratio.
so as an example, 36 on the back 12 on the front, while exactly the same as 45 on the back 15 on the front, both 3:1,
if you do as you say take 1 tooth from the front and 4 from the back on both of these systems.
You end up with 32 to 11 a ratio of 2.9090, where 41 and 14 now results in a slightly differnt ratio of 2.92...
increase these numbers and grater the difference will be.
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Re: Dong Fang DF 250 RTB Bobber Information
You can sound as smart as you would like axa. And yes, I know all about ratio math and numbers. I've built home made multi ratio power transmissions from scratch with belts and pulleys successfully ( I could send you pictures of my two speed belt driven motored bicycle that works like a charm). But the number of teeth on any said sprocket directly correlate to the circumference of same sprocket hence dictating what final ratio you end up with. All I was saying is, We noticed and was told by our local motorcycle mechanic when we were kids " you can add one tooth to your front (drive) sprocket or lose 4 on your rear to get the same (or very close to) end final ratio result. That's how we did it and it worked is all I can tell you. Now when you build a transmission from scratch , you have a lot more variables than what sprocket to use. Try having to figure out how much distance your drive tire OD covers per revolution and the list goes on. And I never said take 4 from the back "AND" add one to the front. I said do either or ! Not both !
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2 Attachment(s)
Re: Dong Fang DF 250 RTB Bobber Information
I used my Harmonizer to adjust the idle air/fuel screw on the bottom of the carb and also verified the tachometer reading. It's a neat tach but is slow to respond so you see a little difference.
The stock (blue marks which were off a little before adjusting) setting on the screw seemed to be just right after I set it.
Attachment 12576
Attachment 12577
Yesterday I removed the tank and got some slack n the wire going to the ignition switch so I could mount it right side up in the place where the air pump was mounted.
Got a ride in between rain showers with the 35 tooth rear sprocket and she went up my steep gravel drive just fine in first gear. I'm gonna break her in slow so no top speed runs yet but first gear is now useful.
Also made a plate to block the hole where the air injection tube was.
She seems nice and solid with very little vibration.
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Re: Dong Fang DF 250 RTB Bobber Information
I've read about owners moving the ignition switch, but somehow never read where it is originally mounted at?. Where is it mointed on a stock Dong Fang bobber?
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1 Attachment(s)
Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
birdmove
I've read about owners moving the ignition switch, but somehow never read where it is originally mounted at?. Where is it mointed on a stock Dong Fang bobber?
Attachment 12597
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1 Attachment(s)
Re: Dong Fang DF 250 RTB Bobber Information
to clean up the SAIS removal because the big ugly bracket stays, you would put the ignition in its place. unless you cut the bracket off. then it looks like this.
Attachment 12598
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
4950cycle
You can sound as smart as you would like axa. And yes, I know all about ratio math and numbers. I've built home made multi ratio power transmissions from scratch with belts and pulleys successfully ( I could send you pictures of my two speed belt driven motored bicycle that works like a charm). But the number of teeth on any said sprocket directly correlate to the circumference of same sprocket hence dictating what final ratio you end up with. All I was saying is, We noticed and was told by our local motorcycle mechanic when we were kids " you can add one tooth to your front (drive) sprocket or lose 4 on your rear to get the same (or very close to) end final ratio result. That's how we did it and it worked is all I can tell you. Now when you build a transmission from scratch , you have a lot more variables than what sprocket to use. Try having to figure out how much distance your drive tire OD covers per revolution and the list goes on. And I never said take 4 from the back "AND" add one to the front. I said do either or ! Not both !
Ya, send me some pics you downloaded off the internet, mr potty mouth.
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
barnone
I used my Harmonizer to adjust the idle air/fuel screw on the bottom of the carb and also verified the tachometer reading. It's a neat tach but is slow to respond so you see a little difference.
The stock (blue marks which were off a little before adjusting) setting on the screw seemed to be just right after I set it.
Attachment 12576
Attachment 12577
Yesterday I removed the tank and got some slack n the wire going to the ignition switch so I could mount it right side up in the place where the air pump was mounted.
Got a ride in between rain showers with the 35 tooth rear sprocket and she went up my steep gravel drive just fine in first gear. I'm gonna break her in slow so no top speed runs yet but first gear is now useful.
Also made a plate to block the hole where the air injection tube was.
She seems nice and solid with very little vibration.
Im not sure why i want to, but i think I want to move my ignition as well...
That or put in some High Low snail horns, with the engine going I can hardly hear the the stock button horn, so how can i expect some old lady that cuts me off to hear it...
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
axa
And you don't have any trouble when doing valves?
Im not sure why i want to, but i think I may move my ignition as well...
No trouble doing valve adjustment.
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Re: Dong Fang DF 250 RTB Bobber Information
I think you can adjust the valves without removing the gas tank. Is this correct?
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Re: Dong Fang DF 250 RTB Bobber Information
Quote:
Originally Posted by
birdmove
I think you can adjust the valves without removing the gas tank. Is this correct?
Yes.Correct.
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Re: Dong Fang DF 250 RTB Bobber Information
I guess you could get the head off also without removing the tank, No ? I would like to do some head work and get an extra couple ponies in the near future. One less thing I have to deal with leaving the tank alone.