Dong Fang DF 250 RTB Bobber Information

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Originally Posted by booi10

barnone .... yes mine is 45 T ,,,, so how do you which one to choose if our make of bike is not listed ?? I take it the engine a such are a copy of something ?? I don't think it would be worth swapping the engine for 250 you would be better changing the bike or up to least 450cc,, thanks very much for help you sound very knowlagable and its the first time I have used a forum .... so happy days

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You should change out the rear sprocket if your first gear is used up when you cross an intersection. Maybe like the one I suggested off UK Ebay ASSUMING your rear wheel is the same as ours which it probably is.

Like axa said we think you need a JTR279.xx. xx is the number of teeth. For example JTR279.35 is a 35 tooth rear sprocket.

The DF250RTB engine is sort of a copy of the Honda CB125 engine and is called 167FMM.

I do think it would be worth swapping the engine out for a air cooled over head cam full 250cc engine that is a copy of the CB250 engine. Probably could gain about a 50% increase in HP. Should be an easy swap. Going to any thing else gets complicated.

Well I did it, hit the 12,000 mile mark. landed @ 12,006 when i parked her in the garage last night. Purrin like a kitten still.

http://img.photobucket.com/albums/v6...ps6562a744.jpg
http://img.photobucket.com/albums/v6...ps58fd9fc1.jpg
http://img.photobucket.com/albums/v6...ps4f91a87e.jpg
http://img.photobucket.com/albums/v6...ps89f4535e.jpg

Now,the tank is weird. I was going for that non paint brushed steel look.Hit it with an adhesive clear, then cleared it. But for some reason it seems that under the clear coat, it is rusting? Oxidizing? something. Not sure why. But it looks cool to me, and I have had quite a few compliments on the tank, and people asking me how I did it. Honestly I do not knwo how it happened, but I tell them it is a trade secret. makes me look smarter.. :)
Oh, and yeah she needs to be washed, but it has been raining on and off here, and i ride anyway. Thanks for looking. http://img.photobucket.com/albums/v6...ps5f967c6d.gif

Bow,
Looking real good. That tank is perfect.

I saw a DF bobber going through downtown Hendersonville,NC today.All I got was a quick glimpse of the bike and rider.Looked like a younger guy may mid 20's at the oldest.I was a few cars back waiting to turn left on hwy 64 toward Horse Shoe and Etowah.Is that any of you guys?

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Originally Posted by bowtiewagon

Now,the tank is weird. I was going for that non paint brushed steel look.Hit it with an adhesive clear, then cleared it. But for some reason it seems that under the clear coat, it is rusting? Oxidizing?

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well it's is certainly oxidizing, rustng, same thing...
so what the heck is an "adhesive clear"
I'd guesstimate whatever that was is a water based whatever and thus the oxidation.

anyway I think it's really cool, I can see a frame, tank and matching fenders done like that.

Adhesive clear is a prep coat (automotive paint) you can get at Autozone, to prep the metal o the paint will stick. It is basically a clear primer with an adhesive in it. I wanted that metal look, but was not expecting this. It does look cool, but I hope it does not make the tank bad after time. That would suck.

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Originally Posted by bowtiewagon

Adhesive clear is a prep coat (automotive paint) you can get at Autozone, to prep the metal o the paint will stick. It is basically a clear primer with an adhesive in it. I wanted that metal look, but was not expecting this. It does look cool, but I hope it does not make the tank bad after time. That would suck.

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that does seem odd. i wouldn't imagine a proper product would do that. even if they expected you to paint it over an opaque color.
i dont think surface rust, like you have now, is damaging. what you want to look out for is if the oxidation continues then starts pitting, at that point its eating into the metal and thinning the walls. so see what happens if it starts to get worse, darker, and bumpy.

odd indeed.

http://img.photobucket.com/albums/v6...ps6562a744.jpg
http://img.photobucket.com/albums/v6...ps58fd9fc1.jpg
http://img.photobucket.com/albums/v6...ps4f91a87e.jpg
http://img.photobucket.com/albums/v6...ps89f4535e.jpg

I have a question for ya. Did you tap into frame or did you weld in nuts? I have to get my tank done, I've had it a year now and has been pushed to back burner. Just bought a Tap set but not sure if it will damage the integrity of the frame.

I tapped the frame. used 1/4-20 at first then went bigger cause the 1/4-20 stripped on me. Too small. I am seeing how well these work. I may have to get nuts welded on later. so far so good,I check after every ride. I used some large bushings to fit in bewtween the tank and the frame to sit on for cushion.

i think bow used some sort of bushing to take the load off of the fastener.
id recommend it, and as large as possible. Id use a larger flange headed bolt with perhaps even a washer to support the larger bushing.
And for that top half, my bushing might be some sort of rubberized material hollowed out to hug the tank tab, and flat on top to span the washer...

And when you tap, because of the relatively thin wall, you would do well with a higher pitch count while not going too large on diameter to weaken the frame itself... a 1/4 seems a reasonable diameter, but that has a fine thread of 28 to conciser.
And the hole drilled might be on the smaller size, usually that for softer materials, in the case of a 1/4 tap, use a 3/16 tap, slowly make your threads.

That said a pair of quarter inch tapped holes are marginal mounts at best, hopefully a good set of bushings will prove good enough... id weld it if you have the choice, you can put a bolt in after anyway cuz it looks kind of cool.

so how long might i expect from this stock Chinese battery?
ive always seemed to have a bit of trouble turning it over... but now due to my higher compression ratio i tend to pay it more attention...

i kept it tendered while the bike was down... curious to know what to expect


Also, anyone change their exhaust gasket? where did you get it.
save me from needing to remove the pipe to measure...

I would not weld the tank to the frame. Bolts with rubber pads like bowtie used looks fine to me. If you are worried about tapping in the tubing holding, how about through bolting with curved washer underneath?

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Originally Posted by axa

so how long might i expect from this stock Chinese battery?
ive always seemed to have a bit of trouble turning it over... but now due to my higher compression ratio i tend to pay it more attention...

i kept it tendered while the bike was down... curious to know what to expect


Also, anyone change their exhaust gasket? where did you get it.
save me from needing to remove the pipe to measure...

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My original battery on my 2012 lasted one year. About the same on my 2010. Not good batteries.

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Originally Posted by barnone

I would not weld the tank to the frame. Bolts with rubber pads like bowtie used looks fine to me. If you are worried about tapping in the tubing holding, how about through bolting with curved washer underneath?

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Bar, i do not think he meant welding the actual tank to the frame, but perhaps welding a nut to the frame to attatche the tank. I was thinking about doing that, and I may still. I also considered going through the frame , to make sure it would be on tight enough with all the vibrations and being a hradtail it takes some abuse. with the terrible roads. I am watching the mounting choice I have made, to see if I need to tweek it any. So far, it is good.but I am still concerned about the actual lack of threads due to the thinness of the frame itself.

Maybe I can get a small steel tube, drill through the frame, add the tube through the frame then bolt through the frame.. leaing the tube to be a more reinforced replacement for the lack of metal drilled out for the bolt. work in progress.

Just wondering, has anyone had a flat tire yet? I have a small staple like thing in my rear tire.. saw it this morning.I am going to just cu the excess off the wheel and leave the remainder in it until I get home. But just wondering how thick these stock tires are. I had a pretty decent size tack stuck in the front wheel a couple weaks ago, pulled it out, but have not lost any air as of yet. I guess if I loose air I can always plug it. Any thoughts on replacement tires? I know these are tubless. Haven't look any up yet.. may do that today just for giggles.

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Originally Posted by bowtiewagon

Bar, i do not think he meant welding the actual tank to the frame, but perhaps welding a nut to the frame to attatche the tank.
Just wondering, has anyone had a flat tire yet?

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Yep, I probably misunderstood but mentioned it just in case...
Knock on wood, no flat in years on any of my vehicles. I carry a can of fix a flat in the tool roll on the DF.

no flat no deflation while the bike sat. I'm kind of pleased with the tires

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Originally Posted by barnone

My original battery on my 2012 lasted one year. About the same on my 2010. Not good batteries.

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being that all these bikes might well been slapped together around the same time, i suppose i should be happy with it lasting this long, that would be 1.5 years

what did you replace it with?

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Originally Posted by axa

being that all these bikes might well been slapped together around the same time, i suppose i should be happy with it lasting this long, that would be 1.5 years

what did you replace it with?

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This one http://www.amazon.com/Shorai-Lithium...A2-BS12+Shorai

Check out the different sizes. You can get a LOT of cranking power in a smaller than OEM physical size & weight.(also it pays to shop around).

Battery Specifications - Shorai Lithium Batteries

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Originally Posted by SR.MAILMAN

Check out the different sizes. You can get a LOT of cranking power in a smaller than OEM physical size & weight.(also it pays to shop around).

Battery Specifications - Shorai Lithium Batteries

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Though Im not sure what it benefits to purchase anything larger than what is needed.
Now Im not a physicist and dont know who is but the way i see it is this...

The only pro to buying a larger battery than needed is the possibility that the battery work a bit longer when it starts to crap out.
When it starts losing power perhaps it will be able to crank over a smaller engine another season or so...

The cons are classic, higher cost, extra weight (negligible with Lithium batteries i suppose)

I suppose a detailed study on the power characteristics of a dying Lithium Iron battery is the only way to really know this

an interesting analysis of problems these lithium iron phosphate batteries may suffer:
http://ka7oei.blogspot.com/2013/05/l...e-lifepo4.html

i see there is a port for individual battery charging... thus you need purchase the shorai charger, or know what your doing otherwise...

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Originally Posted by barnone

This one http://www.amazon.com/Shorai-Lithium...A2-BS12+Shorai

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I noticed sometime back the DF regulator at idle was over 15v.
I wondered if this was a problem, and now wonder if it contributed to the shorter stock battery life.

Shorai specifically indicates to charge at "13.6V-14.4V".
How long have you had this battery?
Any ill effects so far?
Have you ever measured your magneto output?

Maybe 6 months. No ill effects that I know of and I have not measured the charging volts at higher RPM.

Three year warranty.

ok well i jumped the gun and supposed my battery was bad... turns out im getting just 6.5v at the leads, have to test if its the stator or rectifier... im betting its the rectifier.

it never ends for me and this bike...

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Originally Posted by axa

ok well i jumped the gun and supposed my battery was bad... turns out im getting just 6.5v at the leads, have to test if its the stator or rectifier... im betting its the rectifier.

it never ends for me and this bike...

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So i dont have a bad stator nor rectifier, with these disconnected from the rest of the bike, each stator coil puts out 15VAC on idle and something way higher, like 30 to 40 VAC with a blip of the throttle. Good.
And the rectifier puts out roughly 12 V on idle, but 13-14 V with some throttle. might be on the low side of things, but that's the problem...

As soon as I hook things back to the bike, keeping the battery disconnected, I immediately see roughly half the DCV on idle, decreasing with increasing rpm.
This is a serious problem...

Just as can be seen with the head light dimming fiasco, this +V node that runs to the fuse and on to the battery, this which is responsible for charging the battery suffers from this reduced voltage.

I suppose the only saving grace is while moving even with the lower VDC, the generator is still providing some current to the circuit so the battery is slower to discharge. And at idle the battery is apparently gaining back some of the lost charge lost while running.
But i say this is not an adequate charge at just around 12 v for that short a time.

There is something seriously wrong with this bikes wiring.
With brief study the manual wiring diagram it doesnt appear to be for this bike. I may be wrong about that but i couldn't make heads or tails of it.

Right now im suspecting there is a poorly placed component, maybe that diode in the box, but im not sure.
But i surmise that this problem not only causes the headlight dim but contributes to premature death of batteries.
I'll find and fix as soon as i find the time
bummer

If the system is fine until the battery is connected,I'd say the battery has a bad plate(s) in it.Has the battery been tested?Have you cleaned the battery connections and the grounds on the engine/frame.I'm not sure where the ground wire runs to from the battery.

I agree with the bad battery diagnosis. Have the battery tested or get a new battery before you tear into the wiring. My 2010 Chinese battery went bad after a year and the new battery solved the problem.

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Originally Posted by ben2go

If the system is fine until the battery is connected,I'd say the battery has a bad plate(s) in it.Has the battery been tested?Have you cleaned the battery connections and the grounds on the engine/frame.I'm not sure where the ground wire runs to from the battery.

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What I said was the system is fine until connected to the rest of the wiring WITHOUT the battery connected. Bad circuit

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Originally Posted by axa

What I said was the system is fine until connected to the rest of the wiring WITHOUT the battery connected. Bad circuit

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Ive never tried running a bike without the battery connected.I'd say all the voltage is going away to run the CDI and lights since the battery isn't there to supply the electrical system.

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Originally Posted by barnone

I agree with the bad battery diagnosis. Have the battery tested or get a new battery before you tear into the wiring. My 2010 Chinese battery went bad after a year and the new battery solved the problem.

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I dont agree.
As mentioned, the generator is fine without the bike wiring.
The battery is fine when charged and used elsewhere.

Anyone care to disconnect their battery and with the bike running and confirm they get a dip in VDC across those terminals when rpms increase??

And even if this is confirmed, your battery might be fine for a while as i mention, it is getting somewhat of a charge at idle even though likely being somewhat drained while running.

Hopefully someone will tests VDC while running with the battery disconnected. (better off someone who didnt do the headlight mod as that may well be the culprit, really cant say at this point)

Or even pull the battery after a long ride, and see if your charge is roughly 12v rather than closer to 13 as it should be

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Originally Posted by ben2go

Ive never tried running a bike without the battery connected.I'd say all the voltage is going away to run the CDI and lights since the battery isn't there to supply the electrical system.

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Vehicles are not designed to supply current (power) from the battery to the electrical system while running.
And rather, current is supplied from the highest potential. In this example, the highest voltage source (assuming there is no other voltage dividers in the circuit)
Just like an alternator in your car, the battery's sole purpose is to start the engine and then generator takes over sourcing current to the system as it has a slightly higher voltage than the battery (the higher potential voltage mentioned above)
And as a reciprocal function if for some reason the battery has a higher voltage, it will be what sources current until it dies down to meet the alternator/generator.
At which the generator takes over and then sources current to all less potential components (including the battery)

But as im saying we have here is a fresh battery first gets reduced to the idle voltage as it has to supply current, and instead of recharging to 13/14v with higher rpms, our bike for some reason reduces voltage with higher rpm, so rather it only gets re/charged to the idle ~12volts, which is not suffice as that is not what a battery should be charged or maintained at....

This evidence leads me to believe all of you are suffering through the same thing (unless the headlight mod some how disconnects the fault and fixed the problem)

Furthermore, even my higher compression engine will start with a battery potential (charge) of just below 12v, as i experimented with yesterday.
So I don't believe anyone can assume they DON'T have this reduced voltage problem but rather your battery is still new and strong.

And I dont yet believe we can assume if you did the headlight mod it relives the problem in the battery node (or rest of bike for that matter)

Ive read charging to an inadequate 12 volts or so will degrade the battery more quickly so we should all be concerned.