Dong Fang DF 250 RTB Bobber Information

[ben2go]

Hey guys. adjusted the valves today. Runs beautiful.. with just a slight ticking (there was no tick at all before as the valves were RIDICULOUSLY OVER TIGHTENED). I swapped the stock filter back on and capped off the stupid port where the crank case breather was attached just so I dont suck dirt in there while I test run with it. I was able to cruise at 50 on flat ground with a lot of throttle left. I think the valves made a difference for sure. Maybe slightly more mid range power now... but hard to tell. Still 40-45 on inclines.. but it runs on the flat much better. It does run smoother and start easier... with no more back fire through the carb.

I opened it up all the way on flat ground and was able to do 55 indicated but not a hair more. When it's wide open throttle around 50-55 the engine starts to skip and cut out and do some weird stuff... I feel like if it was smooth at this speed and throttle.. that there would be a lot more speed left in her

I had some jets left over so I tried to put a 114 in (the smallest I had) and it was way too big and made the motor run terrible. I just ordered a 108 main to try.. Not sure if the problem around 55 and wide throttle is a lean issue or a valve float. Barnone is running a 108 so ill give it a try.

Dan you say you are running a 112 main. Are you able to full throttle rev in neutral without any engine break up? I was thinking that maybe it would break up in neutral.. but as you get up to speed with that ram air that it might start running leaner and counter act the large jet.. making it run just about right. If this was the case though, full throttle at low speeds would make it run like garbage.

Im going to try the 108 and keep the filter in the stock orientation. Barnone, don't go for the 120.. it is just too much for this bike. ( I tried 114, 115, 120) The 114 would ALMOST rev smooth with the air filter totally removed.. but as soon as I put in back on it ran like crap .. even after turning the fuel adjustment on the carb almost all the way in (bringing it out = more fuel , bringing it in = less fuel).

Im hoping the 108 with some proper adjustments will take care of my problem and allow me to cruise at 55 without the engine bucking.

Barnone are you running the stock idle jet or a 42 or 45.


Btw for those that have asked I can confirm the 2012 has a 105 main and a 40 idle stock.

Your issues sounds like a clogged fuel cap vent or the carb float level is set to low.It's starving for fuel.When it breaks up,reach over and unscrew the fuel cap for a few seconds and see if it gets better.I had a similar issues on my GS5.

[jeperezjr1371]

Barnone I actually love wrenching on stuff, I've just never done it on a motorcycle! I just wanted to make the purchasing and getting it legal for the road as easy as possible! I've read all the pages on this forum on the DF250 and I've read that people were having problems with getting the paperwork, that why I was asking! And I definitely like this bike WAY better than the Honda Rebel!

[ben2go]

Barnone I actually love wrenching on stuff, I've just never done it on a motorcycle! I just wanted to make the purchasing and getting it legal for the road as easy as possible! I've read all the pages on this forum on the DF250 and I've read that people were having problems with getting the paperwork, that why I was asking! And I definitely like this bike WAY better than the Honda Rebel!

There have been a few Dong Fang motorcycles reg'd in NC.There should not be a problem.If there is,take a day and go to the central office.I think it's in Charollote,NC.

[Bobthebobber]

Your issues sounds like a clogged fuel cap vent or the carb float level is set to low.It's starving for fuel.When it breaks up,reach over and unscrew the fuel cap for a few seconds and see if it gets better.I had a similar issues on my GS5.

I notice that my fuel tank leaks out under the cap after a ride with a full tank of gas. A thin line of really thinned out gas will run down the tank after I let it sit for a bit. Is this a fuel cap problem?

[barnone]

I tried the 120 and it was too much. Back to the 108 main and 42 slow and it runs fine. I'm leaving it that way until I get the 30 tooth installed. The 42 seems to help.

My DF is not leaking any fuel around the cap. Is yours leaking after sitting out in the sun?

[DanDaMan]

gas around fuel cap , COMMON , put a girls scrunchy hair tie around it to wick it away , and valve float sounds like your issue , in neutral these bike will rev to like 9-91/2 k and hold it , BUT under load depending on valve lash , the valves will "float" causeing it to sputter and miss entirely around 6-6 1/2 k rpm's , how to fix = shrink your ratio so in 5th you rarely if ever reach 6 1/2 k rpm's

17 35 428hd chain (only way make front 17 sprocket fit) , 112 main = runs great at all rpm's and is light tan at WOThrottle at 70 indicated (about 5k rpms)

the limitations u face = chain size + front and rear sprocket replacements

it is only really about 9-11 horsepower so its no racer but it will drag a 180lb man to 70 indicated into the wind up a grade and hold it if geared properly


Although if you want a snowplow 1st gear and to be able to scream up mountains at 55 (indicated) , then leave it stock :p , but the bike is capable of being stretched 50% to 70 (77 indicated) and will perform

Im also part of the K.I.S.S. army , keep it simple stupid

[Bobthebobber]

gas around fuel cap , COMMON , put a girls scrunchy hair tie around it to wick it away , and valve float sounds like your issue , in neutral these bike will rev to like 9-91/2 k and hold it , BUT under load depending on valve lash , the valves will "float" causeing it to sputter and miss entirely around 6-6 1/2 k rpm's , how to fix = shrink your ratio so in 5th you rarely if ever reach 6 1/2 k rpm's

17 35 428hd chain (only way make front 17 sprocket fit) , 112 main = runs great at all rpm's and is light tan at WOThrottle at 70 indicated (about 5k rpms)

the limitations u face = chain size + front and rear sprocket replacements

it is only really about 9-11 horsepower so its no racer but it will drag a 180lb man to 70 indicated into the wind up a grade and hold it if geared properly


Although if you want a snowplow 1st gear and to be able to scream up mountains at 55 (indicated) , then leave it stock :p , but the bike is capable of being stretched 50% to 70 (77 indicated) and will perform

Im also part of the K.I.S.S. army , keep it simple stupid

i can only scream down hill at 55 with my 35 tooth... and up hill lucky to do 40 (:

[Bobthebobber]

I tried the 120 and it was too much. Back to the 108 main and 42 slow and it runs fine. I'm leaving it that way until I get the 30 tooth installed. The 42 seems to help.

My DF is not leaking any fuel around the cap. Is yours leaking after sitting out in the sun?

Yea. Seems to do it when the temperature is very warm. I ordered a 108 main, 42 slow, and a new plug tonight. Free shipping on everything. Gotta love ebay

[barnone]

Yea. Seems to do it when the temperature is very warm. I ordered a 108 main, 42 slow, and a new plug tonight. Free shipping on everything. Gotta love ebay

Gasoline expands when heated by the sun. Try not filling up the tank so much. I think there is a flue overflow in the neck of the tank? I'll check. If so maybe stopped up or hose kinked?

[Bobthebobber]

Gasoline expands when heated by the sun. Try not filling up the tank so much. I think there is a flue overflow in the neck of the tank? I'll check. If so maybe stopped up or hose kinked?

Yea I see there is a little knob on the bottom front right of the gas tank. There is no hose attached to it though. Maybe im missing it