Dong Fang DF 250 RTB Bobber Information

**Crelow** · 03-08-2013, 06:17 PM

Thanks Chruk,

Ill keep it in mind. All job welded this morning but not sure if I fully got into the areas it needed most. Ill check it in a few hours. While working on the bike I took the carb apart to see what kind of jets I had. It's the 40/105. And looked at the needle to see there is only one groove for the clip. So my question is do I still need the washer? Or was the adjustment was based on the old carbs with smaller jets. I just wonder if with the new needle needs the extra hair of space

Here a pic of the needle. image.jpg

**Goodbar** · 03-09-2013, 09:01 AM

Crelow, If you have the 105 jets in your carb I believe the needle was already raised so you should be good to go as I remember. You may want to clean your jets to be sure they are gum free. Remove and shine a bright LED flashlight thru the hole. Or just clean them with a jet kit to be sure they are open. The shim under the needle won’t really make it run better but gives it quicker throttle response. I would also focus on fine adjustments to carb or major ones on your air fuel mix screw and your idle screw/ and get a good NGK spark plug and gap it per specs. Below are just some random tips and general ones.

If your carb backfiring is a “intermittent” problem then maybe a jet is partially clogged.

NOTE: A rich problem gets worse as the engine heats up.

. NOTE: A lean problem gets better as the engine heats up.

Just a quick revealing test to get a better understanding...
If the bike seems to be lean then partially cover the intake to the air filter housing with duct tape, if the carburetor improves it is running lean.

Excessively lean carburetor settings can contribute to backfiring thru the carb. If the mixture is too lean, it may burn very slowly and unevenly. This condition, in turn, may result in burning mixture remaining in the cylinder until the beginning of the next intake stroke when it can ignite the incoming air/fuel mixture. Partially clogged jets from our ethanol gas sitting in the carb contributes to this condition. Gum and crystals form a clog.

Screwing in is richer and out is leaner , so try 1/2 a turn at a whack or do tiny 1/8th turns ( I found that my carb screws were very sensitive once I got close to the sweet spot. Work on the High speed screw adjustment first to get rid of any carb back firing or crappy running when engine warmed. Unless you increase the idle jet to 42 44 it will always be a bit cold blooded.

Also
PROPER STARTING PROCEDURE FOR THIS BOBBER: something that is never really discussed but it is the most common mistake on ownership of small bore type carbed street or dirt bikes… is the proper warm up procedure that many people do wrong.
-Start the bike with choke up for 5-15 sec, go to half choke 10 sec then off and Let it idle and don’t do any revs until it warms up for at least 1min minimum. Then a few small slow revs are ok. If it starts to die don’t rev the bike but just go to half choke position for a few sec and the choke off until it idles on its own. Most people start there bike and then shut choke off and then start to rev a cold engine, thinking it will warm quicker and it may sputter and backfire during warm up. Just “don’t” touch the throttle until the bike is warmed. It is always the best, get your idle set just high enough where the bike will stay running without blipping the throttle when it’s cold after it’s just been fired up. People want to start these little engines and then start revving it immediately ,and that is not the way to let this little bike warm up. Messing with the throttle is not the way to go.

As the bike breaks in it will get a to a better running condition faster and run smoother. So bottom line is/ no throttle during warm up is a good rule.
I have a fuel injected big twin Harley, heck i can start it and drive off in 10 sec a totally different animal. This bike has one carb and one small cylinder so a patient warm up is the procedure and will always be one for the DF.

**Goodbar** · 03-09-2013, 09:11 AM

Originally Posted by Bob form NV

Thanks Goodbar, The more I know you the more I know. I'll get some of that stuff and rub it out. We don't have the custom decal outlet here but threre are plenty on the net. I've done a couple of custom sewing machines and the decals look great.

I've found some useful information on the net about engine break in and a repair manual for a 125cc honda that our engine is a clone to.

I'm not sure where all these adjustment screws are but the carb in the manual looks the same as ours and the brief look over I gave it is pretty detailed on adjustments.

Got to get to work.

Thanks againAttachment 10351 Attachment 10352 Attachment 10353

Bob I wouldnt get that cool looking billet one but get a clear fuel filter that you can see crystals forming and dirt or crude, rust crud etc, Plus its nice to be able to see vaccum lock and fuel flow. All auto stores have them and even chrome and glass ones. just so its 1/4" x 1/4" on both ends. "Clear is always Better"

**Goodbar** · 03-09-2013, 09:19 AM

Originally Posted by Crelow

Yesterday I must have done a hair more than finger tight on the thank. Suggestions on repair? Epoxy/ jv weld or get it welded? So far is just a drip.

Bummer on the tank man. These things are fragil for sure. JB should certainly fix the tiny leak.
Skulworkz, it will be interesting to see if preventive JB will work also. One would think the kreem would help prevent leaks also?
Finger Tight only on tanks and maybe a drop of crazy glue in threads to prevent the nuts from vibrating off then is maybe the new method for those who take off their tank. How many turns with the wrench did you give the tank nuts after finger tight Crelow?

**skullworkz** · 03-09-2013, 02:14 PM

Originally Posted by Goodbar

Bummer on the tank man. These things are fragil for sure. JB should certainly fix the tiny leak.
Skulworkz, it will be interesting to see if preventive JB will work also. One would think the kreem would help prevent leaks also?
Finger Tight only on tanks and maybe a drop of crazy glue in threads to prevent the nuts from vibrating off then is maybe the new method for those who take off their tank. How many turns with the wrench did you give the tank nuts after finger tight Crelow?

I've had my tank un-bolted twice to do the ignition mod and re-installed without any issues. I did snug up the nuts a bit but not tight as this tank kinda floats on top of the wiring harness, a little red locktite to prevent them from backing off.

**Crelow** · 03-09-2013, 02:39 PM

That was the info I was looking for on the carb and jets! Like always thanks.

Now as for the tank. The the first time when I broke the weld I just wrenched it softly. Then it leaked. I never turned the tank over as it was full of gas. But when it leaked I drained it. The side that was leaking had a hair line fracture that I couldn't even see. The other side the bracket was broke in half. So what I did was epoxy putty around every area of the welds. The hardest areas are under the brackets and epoxy the bracket together. I should have taken pictures. Before that I looked inside the can and noticed rust formed in the areas that the brackets were welded and a bigger rust spot where the leak was comming from. When reattaching to the bike one side would screw in more than another as the bracket on the left was welded a little lower. I put harbor freights version of loctite. Turned by finger then a half or quarter turn with wrench. The left nut barely made it on so I made sure it was flush with nut. And hope the cheap version of loctite will hold.

I think I had the carb tuned perfect at one point but the screw is so hard to get to during the ajustjustment that I got it close and figured that ill get back to it next time. Ill have to ask if my friend if he has a jet cleaning kit. It's so easy to pull apart.

**SR.MAILMAN** · 03-09-2013, 02:41 PM

LT4985TLCapabilityGd.pdf

Be careful which loctite you use in which place

**Crelow** · 03-09-2013, 02:53 PM

BTW, I found where the horid noise is comming from. Durring decel the gas cap vibrates.

21 miles and just put my tag on. Magnet oil plug in the mail.

Soon as I feel things are perfect ill start riding it to work. But I need to figure out a way in case I do break down how to trailer it home. I seen that in the CCW forum that their is a trailer hitch that can hold our bikes. And another that just attaches the front wheel. What do you guys think?

**Crelow** · 03-09-2013, 03:34 PM

Originally Posted by SR.MAILMAN

Be careful which loctite you use in which place

Thanks Sr.mailman. To think I was just putting the loctite on the head of the nut. No wonder it never worked. LMBO

Just kidding. This will definitely help me and others.

**Woody87** · 03-09-2013, 09:09 PM

Hello all,

I'm currently conducting the break-in on my D250RTB, and I'm having an issue I hope you all may be able to help with.

I'm having issues getting the bike to shift into neutral after coming to a stop, and during riding I am sometimes unable to shift up past 2nd gear. It sometimes won't shift down into first at a stop as well. I've also noticed that the neutral light sometimes comes on incorrectly, while the bike is still actually in gear. The whole situation is keeping me from riding it anywhere but traffic-free sideroads. The clutch cable pulls in easily, but the shift lever gets stuck and won't shift gears. Rolling the bike forward/backwards with the clutch in seems to help correct the issue. Any ideas, suggestions or similar experiences?

Thanks all for your help.