Dong Fang DF 250 RTB Bobber Information

[Bobthebobber]

Attachment 12948my DF will do 80 , when the air temp is 45 degree's or so , and struggles to do 70 when its over 100 degree's , so yes temperature of intake air indeed makes a difference

negligable indeed , only a 12-15% speed increase from running colder air , but its the diff from cruising a highway and having to take the access road

I shift into 5th at about 68 indicated my ratio says I should float my valves at 85 , but I cant get but a hair over 80 in perfect yet very cold conditions

bob r u running stock sprocket ? that will make u top out at about 50-55 when your valves start to float making u unable to go faster

Nope. 35 rear sprocket. My ride weight is 140 pounds. Possibly once I adjust the valves and cap off the air injection it will drive better. 4th gear full throttle flat ground maybe 46mph then i shift to 5th and keep it pegged ill hit 50 if its flat. Going down a hill i hit 55 and then my hose on the air injector exploded again

[GonzoX]

Nope. 35 rear sprocket. My ride weight is 140 pounds. Possibly once I adjust the valves and cap off the air injection it will drive better. 4th gear full throttle flat ground maybe 46mph then i shift to 5th and keep it pegged ill hit 50 if its flat. Going down a hill i hit 55 and then my hose on the air injector exploded again

Man that dont sound right to me. I weigh 100lbs more than you do and I get 55 on level ground in 5th with stock sprocket and jet. And I havent even messed with my valves yet. Maybe my speedo is off but I had my wife confirm she was doing 40 when I was doing 40 in front of her. Mind you Im not a mechanic. Maybe I just got lucky and mine got tunned better in the factory. Dunno.

[barnone]

Bobthebobber,
Aerodynamic drag (air resistance) and available engine power is what limits top speed not rider weight.
Rider weight does effect acceleration rates.

First thing you need to do is to ADJUST the valves to prevent any engine damage and maybe that will improve your engine's power.

BTW, I am still breaking in my 2012 DF but I have run it up to 60 MPH indicated on the flat. I do need to check my speedometer for accuracy but what GonzoX says about his check is good to hear.

[barnone]

Attachment 12948my DF will do 80 , when the air temp is 45 degree's or so , and struggles to do 70 when its over 100 degree's , so yes temperature of intake air indeed makes a difference

negligable indeed , only a 12-15% speed increase from running colder air , but its the diff from cruising a highway and having to take the access road

I shift into 5th at about 68 indicated my ratio says I should float my valves at 85 , but I cant get but a hair over 80 in perfect yet very cold conditions

bob r u running stock sprocket ? that will make u top out at about 50-55 when your valves start to float making u unable to go faster

DanDaMan,
Refresh my memory on your jet sizes that you are running. At what RPM are you experiencing valve float?

I'm still breaking in my 2012 so have kept the RPM under 6k. Seems I use to run the RPM up to just under 8k on my well broken in 2010 which gave me a top speed of about 68 MPH (GPS).

[DanDaMan]

im running a 112 I believe , and im still leaning out near max speed with the "ram air" , and I don't have a rpm gauge but I guess its around 6 , ive set my valves very loose if I tightened em up I may get it to 6.5krpms and a bit more speed

[barnone]

im running a 112 I believe , and im still leaning out near max speed with the "ram air" , and I don't have a rpm gauge but I guess its around 6 , ive set my valves very loose if I tightened em up I may get it to 6.5krpms and a bit more speed

You must be running a very high geared rear sprocket/tire combo to be getting 80 MPH and only turning 6k RPM. I'm running a 35 tooth rear sprocket on my 2012 and am running about 60 MPH (indicated) at 6K RPM.
IMG_2118.JPG
My Ebay tachometer. The instrument in my hand is a Harmonizer which is good for setting the air/fuel screw among other tasks.

I think Aboshi is/was running a 120 main jet which is what I am going to try next. I am still running lean with a 108.


IMG_2207.jpg
I ran the Dragon yesterday. Drew quite a crowd and gave out the info on the bike to several riders at the store there. Got 79 MPG even with the spirited riding.

[ben2go]

im running a 112 I believe , and im still leaning out near max speed with the "ram air" , and I don't have a rpm gauge but I guess its around 6 , ive set my valves very loose if I tightened em up I may get it to 6.5krpms and a bit more speed

This has been a problem that many different bikes have had.It's not limited to the DF.When you ram air down the carb at high speed,the float bowl will sometimes be slow to deliver fuel.To compensate,people have started to face the carb vent to into the wind with the airfilter.It really helps.

[axa]

its probably worth noting, not only does dan have differentback sprocket, he has a different front, different ratio, different aero dynamics, different intake, different tires, but a different bike entirely
but apparently a similar or same engine .... different

anyway, i too am not too satisfied with my top end, with all this jet, air ram talk, im ready to try and fit one of these...

http://tinyurl.com/ohlq8dr

so what do you think dan? enough ram for you or what

[Pushrod]

A few observations on my new df250rtb_b bobber. First, that lift gate delivery they advertise didn't amount to much. The driver wouldn't come into my neighborhood (twisty, hilly gravel roads), so we met out on the side of the state hwy where he put it in the back of my pick-up. Wasnt easy getting it off by myself but I wasn't about to wait for help to show up with a new motorcycle sitting there!
Bike is in good shape, only a few scuffs & scrapes. Have to get a little flat black touch up paint. The plastic canister that holds the electronics is bent off center but its the bracket inside so I'd have to remove everything to get at it. I think I'll just live with it. Another small complaint is the manual. Its title is "Dong Fang 250 cc" so I suppose its generalized for all bikes with that engine but the pics & some of the write-up seems geared towards a rebel type cruiser. And it is one of the worst English translations I have ever seen. Some of it is completely unintelligible. Ah well, who needs a stinking manual?
Anyway, put it together, made a few adjustments (all the adjusting nuts were loose) set up the battery, gassed it up & took it for a short spin down the road & back. I like it a lot! Handles real good, lots of response with that hard tail frame and springer front. The sprung seat works very well, seems about right for my 165 lbs. Have to watch for potholes though!.
Didn't have any problems with DMV. Paperwork was all in order (and arrived on time). Got more questions and took more time at the ins. agent than at the license bureau!
One thing worries me a bit is the chain tension. It is really tight. Even with the adjusters maxed in it is taut, as in no slack, none. Maybe it'll loosen up a little during a gentle break in, or if I switch to a smaller sprocket. Is this typical or do I need to worry?
Another question: did y'all change the oil right away, or run some break-in miles first? Oil seems ok to me, I was thinking putting 150 miles on it then change.
I put some pics up on my profile. Hope you can get to them. If not, let me know and Ill try to post them out here.

[Gearhead45]

Pushrod, I'm originally from missouri, moving back in a few months. Glad to hear you had no issues with getting plates.