Dong Fang DF 250 RTB Bobber Information

can anyone tell me what size main jet the 2012 bikes come with?
barone, so what size jets are you up to so far?


Ive always noticed studdering at my very top end and suspected that the main jet could be sized up, but when i tried slightly closing up the choke, it immediately got worse, indicating perhaps it could use more air...

plug reads fine so I think for the most part its a good mix, just not at those rare long straight or downhill top end moments...

so it would be nice to know what size we are starting with here

how many of you have had to replace the stock horn , and how many times. My issue Is not that the horn fails to work, it is that the bracket it is attached to keeps breaking. I have had to replace it twice now. seems that it rattles so bad that it eventually just breaks. I am in the market for replacements and was thinking of going with a louder style horn set.

By the way.. I am up to 9907 miles as of last nights ride. Gonna do the Chinese fire drill when it hits 10,000. Plus take pictures.

Quote:

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Originally Posted by bowtiewagon

how many of you have had to replace the stock horn , and how many times. My issue Is not that the horn fails to work, it is that the bracket it is attached to keeps breaking. I have had to replace it twice now. seems that it rattles so bad that it eventually just breaks. I am in the market for replacements and was thinking of going with a louder style horn set.

By the way.. I am up to 9907 miles as of last nights ride. Gonna do the Chinese fire drill when it hits 10,000. Plus take pictures.

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so what about just bolting a thicker bracket. or a rubberized bracket...
but if you want a new style horn then do that, i like the sound of my high/low over the button. But if you get a cheap pair as i did, don't expect a huge difference. Theres a differacne, but its just not huge as i thought it would be.

Quote:

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Originally Posted by axa

can anyone tell me what size main jet the 2012 bikes come with?
barone, so what size jets are you up to so far?


Ive always noticed studdering at my very top end and suspected that the main jet could be sized up, but when i tried slightly closing up the choke, it immediately got worse, indicating perhaps it could use more air...

plug reads fine so I think for the most part its a good mix, just not at those rare long straight or downhill top end moments...

so it would be nice to know what size we are starting with here

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My 2012 came with a 105 main and unmarked low speed. Tried a 108 and think it was still lean. Just put in a 120 main and 42 low speed but haven't tried yet because it is raining here.

I drilled out the catalytic converter (kinda loud now) and that helped the top end performance somewhat so maybe the 120 will be good.
I'm over 300 miles so I can run her out now.

She pulls pretty good up to about 6000 RPM then I start getting that hesitation (stuttering) at wide open too so maybe a bigger main will help. 6000 RPM equals about 60 MPH indicated with my gearing.

Quote:

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Originally Posted by barnone

My 2012 came with a 105 main and unmarked low speed. Tried a 108 and think it was still lean. Just put in a 120 main and 42 low speed but haven't tried yet because it is raining here.

I drilled out the catalytic converter (kinda loud now) and that helped the top end performance somewhat so maybe the 120 will be good.
I'm over 300 miles so I can run her out now.

She pulls pretty good up to about 6000 RPM then I start getting that hesitation (stuttering) at wide open too so maybe a bigger main will help. 6000 RPM equals about 60 MPH indicated with my gearing.

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I have the same symptoms.
With my new tachometer, I also see it top out just about 6k and 60mph indicated.

Be sure to post about your 120 jet.
Are there model numbers for these main jets i can look for?

it could simply be valve float and not hesitation , and I slapped on a CAR HORN I got off the shelf in Orilies autoparts

6k rpms is 68 indicated at the top of 4th gear for my sprocket/ratio set up

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Originally Posted by DanDaMan

it could simply be valve float and not hesitation , and I slapped on a CAR HORN I got off the shelf in Orilies autoparts

6k rpms is 68 indicated at the top of 4th gear for my sprocket/ratio set up

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I'd like to know what RPM you are turning when you are running 80 MPH. And have you checked the speed with a GPS?

Max Horsepower: 17@8000rpm :lol8:

Max Horsepower: 17@8000rpm

that's INDICATED , and at 70 indicated , im actually goin 63 , 10% off

and as I said be4 , believe its about 6k rpms then it valve floats

gearing for 85 like I did , might be pushing it because 5th has no umph when its HOT out , ill shift to 5th at 65 or so and cruise at 70-75 indicated

its funny with everyone saying its not made for it/don't try it , but I got this bike PURELY for use as a highway bike

Quote:

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Originally Posted by axa

I have the same symptoms.
With my new tachometer, I also see it top out just about 6k and 60mph indicated.

Be sure to post about your 120 jet.
Are there model numbers for these main jets i can look for?

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Main Jets
http://www.jetsrus.com/a_jets_by_car...4-36_main.html
Slow Jets
http://www.jetsrus.com/a_jets_by_car...low_26-xxx.htm

my 2010 manual states 14 @6500 rpms as standard power and 11 @ 6500 rpm max power , but max torq of 16.5 @ 5500 rpm

I stretched my gears so long I cruise at 73 ish indicated at about 5000 rpm's

aim for 4500-5500 as your powerband , if you try to use the 6k listed you will be floating valves and never possibly drag more speed from it

if I wer U , I would stretch gears so I shift from 4th to 5th at 55-60 (mines set for 68) , even if you never see the top of 5th it gives you much more relaxed rpm's when cruising nearer to highway speeds

Quote:

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Originally Posted by axa

so what about just bolting a thicker bracket. or a rubberized bracket...
but if you want a new style horn then do that, i like the sound of my high/low over the button. But if you get a cheap pair as i did, don't expect a huge difference. Theres a differacne, but its just not huge as i thought it would be.

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Problem is that the horn is incorporated into the bracket , and cannot be removed, I have looked over it like 50 times and even took the last one apart and it basically is worthless now. I guess the best thing to do is just get a new horn set. and maybe mount in onto a better bracket before I stick it on the bike.

Quote:

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Originally Posted by DanDaMan

my 2010 manual states 14 @6500 rpms as standard power and 11 @ 6500 rpm max power , but max torq of 16.5 @ 5500 rpm

I stretched my gears so long I cruise at 73 ish indicated at about 5000 rpm's

aim for 4500-5500 as your powerband , if you try to use the 6k listed you will be floating valves and never possibly drag more speed from it

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So what is being stated here is that a ratio lower than 2 and a third is required if ever hoping to do over 60 indicated...
becuase with 2.3333 as just about all of us have a standard front and 35 tooth back, no one (that im aware) is able to hold anything over 60mph indicated due to the rpm limitation.

dan, can you HOLD say at least 50 indicated on even the slightest incline?
if you can im going to suggest that something is seriously differnt about ur set up...
cuz i wont argue that down hill or even on a flat, your lower ratio will allow better speed at the 6k we can all achieve, but that decreased ratio wont help on an incline cuz the the power is what it is.
So if you can hold 50 or better on any incline its just got to be something else, maybe the forced air...

Anyway, think you can get your hands on a GPS and get a certain speed reading?

Even down hill I still seem to be capped around 6 or 6.5k, I had no understanding that the engine output would be limited in this way.
Of course there would be a ceiling but i had no idea it was so close to normal operating rpm.
Otherwise i would have went with a lower ratio myself
hopefully either forced air or jets will help increase power and there by increasing rpms

I HOLD 70 in 5th up a slight incline into the wind , but to much an incline or to much wind ill have to downshift to 4th and scream along at max rpms at 68 or so

pushrod motors are famous for producing the most power at valve float terminus , pay attention to max torq rating and set your optimul cruising speed for that rpm , then there still something left and retaines enough umph to run your cruising speed

90-95% of my 6000 miles are all highway miles in texas on 65-70 mph roadways , and its rare I feel im to slow

my wife tailgunned me in her mustang , running into the wind up a slight grade , I couldn't get bike over 70 indicated , but she told me I was going 63 according to her speedo


bowtie - local auto parts store , the doit yourself section , $8 horn - fixed it after stock bracket broke , never a problem since

Quote:

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Originally Posted by barnone

My 2012 came with a 105 main and unmarked low speed. Tried a 108 and think it was still lean. Just put in a 120 main and 42 low speed but haven't tried yet because it is raining here.

I drilled out the catalytic converter (kinda loud now) and that helped the top end performance somewhat so maybe the 120 will be good.
I'm over 300 miles so I can run her out now.

She pulls pretty good up to about 6000 RPM then I start getting that hesitation (stuttering) at wide open too so maybe a bigger main will help. 6000 RPM equals about 60 MPH indicated with my gearing.

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How does drilling out the at help? does it restrict airflow?
are you litterally just removing the catalyst inside?

votage regulator and turn signal relay from http://www.scooterparts4less.com/


Found replacement rear sprocket studs.

http://www.mychinamoto.com/forums/at...6&d=1341715023

Honda Part number 90128-382-670 made in Japan.
Source - Ebay

bent your shift rod ? http://www.gravesport.com/Graves-Mot...Shift-Rod.html

horn bracket as well as a reflector bracket broke for seemingly no reason (rewelded reflector , replaced horn with 1 from Oreilies autoparts (car horn))

sprocket - http://www.oldbikebarn.com/Motorcycl...?search=JTR279 - 520 chain - most seem to go for 36 tooth 38 if your heavy or riding in really hilly conditions , myself (175 lbs) I use a 428 chain 17/36 (17 front wont fit with 520 chain) (15/30 16/33 520 equivalant) (80+ mph indicated perfect conditions) but you MUST HAVE jetting and air ram and keep valve adjustments very close and keep flapping clothing (drag) to a minimum or you will never see the top of 5th
- and remember max horsepower (between 10-15) is produced @ 2/3rds max RPM's unlike overhead cam motors and then it drops off SHARPLY , gear accordingly , you need not reach max rpm's in 5th if you can hold your desired cruise speed at 1/2-2/3 rpm's , which also increases fuel economy and manages heat better

air injector delete

dimming headlight problem, really easy to unplug the blue and white wire from the dark green wire and plug it into the other blue and white wire like it should have been been in the first place. now my light switch works and my lights don't dim

upjet http://www.mychinamoto.com/forums/sh...ll=1#post41593

magnetic drain plug - http://www.oldbikebarn.com/BikeMaste...AG-12MM-ALU-BM

LED tail light ( buy and install new socket/bulb )

I went to auto parts store and bought a radiator hose (used the air filter for sizing) with a 180 degree bend in it cut it to only have the U shape bolted it to the carb the other end to the air filter , now I have a forward facing air intake out in the air stream - aka poormans air ram ( no real effect untill past 50 indicated )

new battery (have to chop into steel battery box to get new 1 to fit) from autozone

HAVE A HUGE PROBLEM!!!!!!
Filled up the tank and started. Holy s--t full RPM, couldn't get to the kill switch fast enough.
pulled the needle seat didnt ya :P
wide open throttle is caused by re-inserting the carb tube (with needle in it) so dont seat fully . I did that myself
look at it the cutout has to be facing the rear wheel , and it will let it seat deeper , stopping that WOT on start

valve adjust - https://docs.google.com/viewer?a=v&p...wZDM3&hl=en_US = compression stroke = both valves fully raised

chain roller - http://www.ebay.com/itm/ATV-CHAIN-RO...009836&vxp=mtr

55/65 watt sealed beam headlight that fits - its a , Sylvania H5006 , and the Wiring harness to go with it , fit inside the existing headlamp shell

all right I believe thats everything fairly relivant to the DF's for the most part (just thought I would mash all upgrade repairs together into 1 compact area) - most are from what others have found im just jamming em into 1 post

Quote:

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Originally Posted by barnone

Main Jets
http://www.jetsrus.com/a_jets_by_car...4-36_main.html
Slow Jets
http://www.jetsrus.com/a_jets_by_car...low_26-xxx.htm

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yikes i didn't realize these little bits of brass were so expensive...
I buy 1/4 in brass rod stock at 1$ a foot
ok, when i get ambitious i turn out a few out on the lathe...

Quote:

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Originally Posted by DanDaMan

my 2010 manual states 14 @6500 rpms as standard power and 11 @ 6500 rpm max power , but max torq of 16.5 @ 5500 rpm

I stretched my gears so long I cruise at 73 ish indicated at about 5000 rpm's

aim for 4500-5500 as your powerband , if you try to use the 6k listed you will be floating valves and never possibly drag more speed from it

if I wer U , I would stretch gears so I shift from 4th to 5th at 55-60 (mines set for 68) , even if you never see the top of 5th it gives you much more relaxed rpm's when cruising nearer to highway speeds

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Dan,
Your hp and torque numbers sound about right .

I was thinking the same thing about the gearing earlier today and ordered a 30 rear sprocket to try in place of my current 35 tooth one. I can pull my steep gravel driveway in second gear with the 35 so I should have plenty of first gear still and will just have to downshift more often here in the mountains.

Seems like I could run 68 MPH GPS on my 2010 with a 35 tooth but I could be dreaming.:lol8:

Quote:

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Originally Posted by axa

How does drilling out the at help? does it restrict airflow?
are you litterally just removing the catalyst inside?

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Take a flashlight and get down on your knees and look up the muffler. The catalytic converter is in the front of the muffler. Yes, you are removing the catalytic guts. I used a one inch bimetal hole saw with a 12 inch extension and did a slow cut. I was lucky this time and all the guts blew out when I started her up. When I did it on my long gone 2010 I has to take the muffler off and run a snake from the front of the pipe to get all the pieces out.

Warning:The exhaust note is going to be a lot louder. Nothing like a Harley loud but...

Doing this gets rid of that real hot spot in the front of the muffler. That cat puts out some heat.

Dan,
I bought a 1157 led and replaced my taillight and didn't have to change the socket. Got rid of the dimming when I put on the brakes on my 2012. I didn't feel the need to fool with any of the wiring.

Thanks for bringing up the common issues post.

Hey guys. I got my air injection off today and capped the port. Bike sounds a lot better. When adjusting the valves, how can I tell when the engine is in the compression stroke? In the past ive just put my finger over the spark plug hole or listened for the air sound. is there a visual way or easier way to do this on this motor? I know both valves should be closed for the compression stroke.



Most say that these bikes run lean. I still think my bike is running rich and not lean. It seems to run better when the motor is cold.. and as it warms up I lose performance. My plug has some black around the base. barnone said he thought my plug looked lean.. but I dont see any white on it, just black.

Hey guys I was just wondering what the make and model is for this bike? I talked to my insurance guy today and he needed this info! I apologize if this is a dumb question! I'm new to motorcycles and definitely new to the DF250! Thanks for your help!

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Originally Posted by jeperezjr1371

Hey guys I was just wondering what the make and model is for this bike? I talked to my insurance guy today and he needed this info! I apologize if this is a dumb question! I'm new to motorcycles and definitely new to the DF250! Thanks for your help!

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my Allstate guy said it was a bit odd to find and it came up as an engine and not a bike entirely
I just gave home what was ever on the title, which I believe was
make: DONG FANG
model: 250RTB_B
Like I said he just ended up finding the engine DF250RTB or something.

I bet ur insurance is going to be like 10 cents where u live

Quote:

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Originally Posted by barnone

Dan,
I bought a 1157 led and replaced my taillight and didn't have to change the socket. Got rid of the dimming when I put on the brakes on my 2012. I didn't feel the need to fool with any of the wiring.

Thanks for bringing up the common issues post.

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your referring to the headlight right?

what were the specs, did it have a rated wattage? led count? were the diodes SMD or discrete component?

how was the output, of the low beam vs high?
and if you recommend it, how about the link?
thanks

Quote:

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Originally Posted by barnone

Take a flashlight and get down on your knees and look up the muffler. The catalytic converter is in the front of the muffler. Yes, you are removing the catalytic guts. I used a one inch bimetal hole saw with a 12 inch extension and did a slow cut. I was lucky this time and all the guts blew out when I started her up. When I did it on my long gone 2010 I has to take the muffler off and run a snake from the front of the pipe to get all the pieces out.

Warning:The exhaust note is going to be a lot louder. Nothing like a Harley loud but...

Doing this gets rid of that real hot spot in the front of the muffler. That cat puts out some heat.

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so exactly what your doing is removing an impedance to air flow, thus allowing the engine side to run more cool. makes sense.

reckon it helps our top end at all? Sometimes lack of back pressure isn't a good thing...

Quote:

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Originally Posted by Bobthebobber

Most say that these bikes run lean. I still think my bike is running rich and not lean. It seems to run better when the motor is cold.. and as it warms up I lose performance. My plug has some black around the base. barnone said he thought my plug looked lean.. but I dont see any white on it, just black.

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its the porcelen color not the color of the threads your looking for

stock sprocket a 43 ? and it floats at 55 , so dropping it to 35 tooth adds (3 teeth =10%) = 26% more top end = 14 mph increase , = 69 mph when reach valve float rpm's

I hope sprocket fits , my rear rim cant fit smaller n a 35 without chain contacting rear hub (different bike different rim)

this is a 125 bored n stroked to a 250 (look at specs engine is almaost perfectly squared XD with the throat of the 125 it came from ANY airflow disruption = loss of power

crelow plug em together as reserve

Quote:

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Originally Posted by axa

your referring to the headlight right?

what were the specs, did it have a rated wattage? led count? were the diodes SMD or discrete component?

how was the output, of the low beam vs high?
and if you recommend it, how about the link?
thanks

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1157 is the taillight. I had it in my junk box so not sure about the wattage, probably less than 2 watts?

Attachment 13001
maybe 12 leds
Attachment 13002
Ebay

Quote:

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Originally Posted by DanDaMan

its the porcelen color not the color of the threads your looking for

stock sprocket a 43 ? and it floats at 55 , so dropping it to 35 tooth adds (3 teeth =10%) = 26% more top end = 14 mph increase , = 69 mph when reach valve float rpm's

I hope sprocket fits , my rear rim cant fit smaller n a 35 without chain contacting rear hub (different bike different rim)

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Stock is 45, I'm currently running a 35 with 6k RPM approximately 60 MPH.
35/30 x 60 MPH approximately = 70 MPH if she will pull it and I will be happy.

Attachment 13003
My 35 currently installed. Should not be a fit problem with the 30.
Went ahead and ordered the Honda bolts ( 90128-382-670).

Quote:

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Originally Posted by axa

so exactly what your doing is removing an impedance to air flow, thus allowing the engine side to run more cool. makes sense.

reckon it helps our top end at all? Sometimes lack of back pressure isn't a good thing...

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Reduced back pressure in the exhaust should allow more air/fuel flow through the engine which should equal more power.
Muffler is still intact so there should be some back pressure. I can always add a baffle at the end of the muffler to add some back pressure and quite it down a bit if needed.

Hi guys, still working out some kinks on my DF. I don't remember reading this one before (I'm up to page 272). My front turn signal flashers are swapped left and right. when I signal left, the right one comes on, and vice versa.

My question is, where to the front turn signal wires tie in to the wiring harness? Is it under the gas tank, or back in the electrical box?

Thanks again.