Dong Fang DF 250 RTB Bobber Information

[DanDaMan]

I run a ratio of 2.0588 sprocket set up (divide rear sprocket tooth count by front sprocket tooth count) and I weigh 175 , and the bike tops to 70 indicated in 4th , then I switch to 5th as an overdrive gear for good milage on the highway

but 5th has NO UMPH but its right at its max rpm/hp ratio = about 10hp around 5500-6500 rpm , as push rod motors valves start to float much past that and hp drops sharply

I think I shift to 5th about 4500 or 5000 rpms around 65-70 and have "maxed" the motor at 80 mph when my valves began to float and no more rpms could be attained , but thats rare usually holds 70 + or - 5 indicated depending on wind direction and ability to draft

if your looking for slightly more gettyup from 5th than just holding 70 indicated , go for a 2.187 or 2.333 set up

BUT with every increase in ratio , you WILL lower attainable top speed and increase rpm's at highway speeds , a 2.333 for example could prob reach 70ish but never go any faster while screaming max rpms

[chruk bashre]

hey, i think you owe the forum a pic of your dfrtb.

[Crelow]

Sorry I wasn't around lately. I've been in Mexico Shooting a wedding.

[JD630]

Sorry I wasn't around lately. I've been in Mexico Shooting a wedding.

hello gentlemen i found out that my 3 out of 4 bolts were broken in half on my sprocket thats why it was wobbling. ordered the part should be fixed soon!
my other question is where can i get a NEW throttle cable ???
i also cleaned my carb wow what a difference it made !!!
can someone tell how to adjust the jet/pilot valves right now my rpm are thru the roof (very high) and its hard to get it undercontrol ? i think something is wrong with my throttle and choke any recomendations i have #105MM needle ? wit 35t sprocket

[JD630]

hello gentlemen i found out that my 3 out of 4 bolts were broken in half on my sprocket thats why it was wobbling. ordered the part should be fixed soon!
my other question is where can i get a NEW throttle cable ???
i also cleaned my carb wow what a difference it made !!!
can someone tell how to adjust the jet/pilot valves right now my rpm are thru the roof (very high) and its hard to get it undercontrol ? i think something is wrong with my throttle and choke any recomendations i have #105MM needle ? wit 35t sprocket

ill pot up pics soon guys !!!

[DanDaMan]

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


Found replacement rear sprocket studs.



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




note JD630
him - HAVE A HUGE PROBLEM!!!!!!
Filled up the tank and started. Holy s--t full RPM, couldn't get to the kill switch fast enough.
me - 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

is that what u did ?

him - yes

that solve u problem ? if not idle screw is under moving throttle on carb (side facing out) thru the pivot the cable rides on


side note , I also need a link for the brake pads , and throttle / clutch cables , to add to this page

[GonzoX]

what are the dimenstions for df250rtb air fliter ???

Filter is a standard 42mm filter. Not sure about the length but you can measure the stock one. The stock filter can be found on ebay but I do not recommend you buy the same filter as it has no media inside at the tip. I recomend one with an endcap and many have bought the same filter. This is the filter I and many others have bought:

http://www.ebay.com/itm/400401536549...#ht_1594wt_905

I also like this one and it may be my next replacement if the above filter rusts like my stock one did:

http://www.ebay.com/itm/110505543326...#ht_2243wt_905

It has a chrome guard against rain and is a foam filter.

[GonzoX]

OK here is a new question:

Anyone here try to have a spare key made? My bike only came with one key. I would like to have a spare, just in case. Can Wallyworld or an auto shop make a spare?

Have not had any issues with my DF lately except it still hesitates when it is cold like it is starved for fuel. I noticed recently that either the fuel line or the fuel filter leaks a small bit of fuel if I leave my pitcock in the ON possition. I now turn it off when parked.

Only other issue is that if I dont ride for two weeks the battery goes dead and I have to charge it for 15-30mins before I can start it. Once I ride it, I can start it right up with no issues.

I did finally get my magnetic drain plug so I will be doing my first oil change probably in a week or two.

My next upgrade will probably be either a fuel filter or a new tool bag since my funds are limited right now.

[GonzoX]

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


Found replacement rear sprocket studs.



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




note JD630
him - HAVE A HUGE PROBLEM!!!!!!
Filled up the tank and started. Holy s--t full RPM, couldn't get to the kill switch fast enough.
me - 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

is that what u did ?

him - yes

that solve u problem ? if not idle screw is under moving throttle on carb (side facing out) thru the pivot the cable rides on


side note , I also need a link for the brake pads , and throttle / clutch cables , to add to this page

OK not sure what your looking for regarding the brake pads but I did copy this and saved it for future ref from deep in this thread:

"I have replaced these pads. Goto a certified Yamaha shop. These pads are used on the Yamaha Blasters. Most shops have them in stock and Yamaha OEM pads are $33.99. They work great also. I can send you a set if you can't find them..."

Dont remember who wrote that.

[GonzoX]

im looking for a replacement gas cap that will fit the tank properly. Does anyone know of one that will fit other then the stock one? Mine seeps gas out all down the tank when its over half full...

Freezerboy, if you find one please post it here and upload a photo if you can. I also am interested in that.