Dong Fang DF 250 RTB Bobber Information

**barnone** · 04-19-2015, 09:34 PM

Searched and found the bolts mentioned here
http://www.mychinamoto.com/forums/sh...olts#post60863

Honda part number for the bolts is 90128-382-670
I bought four at https://www.partzilla.com/

**axa** · 04-20-2015, 12:11 AM

Originally Posted by barnone

Searched and found the bolts mentioned here
http://www.mychinamoto.com/forums/sh...olts#post60863

Honda part number for the bolts is 90128-382-670
I bought four at https://www.partzilla.com/

thanks... at least the Tapatalk app doesn't come up with anything I search for, anyone else use it with success?
and it seems Google keyword "site:" search doesn't work from my android chrome browser either...

I had the part number for the kush bearings which are still good... I didn't want to wait so measured and machined 4 new bolts.
ended up spending near an hour as I had to thread with an old school die.
but now I see 17$ plus shipping for 4 bolts, yikes. maybe that was actually time well spent after all

**axa** · 04-20-2015, 06:50 AM

so I finally got the 30 tooth rear sprocket on and took it for a test ride...
first impression is that this bike should have come with a 30 tooth stock.
I read allot regarding this and never found anyone to recommend it, but i say there is plenty of power stock to find an appropriate spot in gears 1 to 4 on any terrain.
Perhaps not so much in 5th, but on those occasions were your on a decline and not power bottle necked, you end up quickly gear bottled necked. A 30 tooth in 5th would be quite useful and let you climb into the 60s on those declines.... then use it to cruise at a more responsible rpm.

idk, maybe I don't recall what the stock engine was like but I think I do.
now with my head work 30 is a no bringer. I can climb to 60 (indicated) in 4th, then shift to 5th and cruise at a fairly comfortable rpm on the highway. without redlining and worrying im going to blow the engine again..
(well truth be told im always worrying about this bike, especially the egine)

**barnone** · 04-20-2015, 12:01 PM

I had a 30 tooth on my DF for a while but thought it was a geared a little too high for the mountain of Western North Carolina where a cruise of 50 MPH is all I need. If axa decides to do the milling of the head like he mentioned then I might go back to the 30 and bring the DF to flat Florida where you need more speed to keep up with traffic even in town.

**axa** · 04-20-2015, 10:12 PM

Originally Posted by barnone

I had a 30 tooth on my DF for a while but thought it was a geared a little too high for the mountain of Western North Carolina where a cruise of 50 MPH is all I need. If axa decides to do the milling of the head like he mentioned then I might go back to the 30 and bring the DF to flat Florida where you need more speed to keep up with traffic even in town.

im quite willing to get into the head milling game, but as ive tried to make it known, there are actually quite a few variables that have gone into my engine... some which may not, but may well have made a difference.

So in addition to the head deck itself from 9 to 10 CR:

1. there was a new head itself, non loncin, had to rework it a bit to fit the non loncin cylinder. what are the variables here...
2. porting and mild polish the new head.
3. aluminum to steel rods (rare and hard to find)
4. back cut valves

Then does all that account for why i can run 115 jet.
And i cant discount what my P-trap mini air ram can do for my air fuel mix at high speeds..

Now no doubt i have noticeably more power, but its really hard to say the root at this point.
If i do another it may well bring some answers.

ill can deck a head to a CR of your choice, id say include the valves for a back cut and some power ringz while at it. as well as a port/polish including the carb to engine manifold.

now finding a steel set of rods is a whole other story...

**barnone** · 04-20-2015, 10:45 PM

axa,
I just thinking about it for now since I have not ridden my DF for six months. I left it in WNC and I have been in SWFL. I'll be reunited with it in several weeks and will then decide what I want to do to it if anything.
Thanks

**axa** · 04-21-2015, 02:47 AM

Originally Posted by barnone

axa,
I just thinking about it for now since I have not ridden my DF for six months. I left it in WNC and I have been in SWFL. I'll be reunited with it in several weeks and will then decide what I want to do to it if anything.
Thanks

yea I'm thinking about it as well.
I'd be interested to know how many people might be interested...
I'm sure if you go for it concur the results, some others might as well.
there was a forum member in Alabama who also blew his engine and asked me for help... but that was a while ago before I knew what was what and he was just too far away to work with...

so I'm putting the call out for anyone in the NY/NJ/CT area who might have blown their top end or wants to do the performance conversion otherwise...

I also thought about putting out a set of stainless steel rear sprocket bolts...
its something many will eventually need and I can make them cost competitive.
but unlike engine work having a set of quality bolts isn't going to do much for your ride, so really what's the interest all around anyway...

**axa** · 04-21-2015, 04:35 AM

Originally Posted by barnone

I'll be your first customer. I won't be in WNC where my DF is resting until early May.
What octane fuel is required for the increased compression ratio?
Just leave the valves in the head? Just need a new head gasket?

not sure I ever answered these questions.
with 10CR I still use 87 octane and don't see any sign of detonation problems... this leads to the conclusion the dynamic CR of this engine is way low.
and it will stay that way, forget about ever finding a more aggressive cam, let alone the work required to get at it.

no I need the valves out in order to mount the head in my jig.
having the valves out also allows the other head work mentioned.

Reuse the metal film gasket. use rtv silicone as assurance. if it leaks it's probably for some other reason.
or... as they say, if doing all this work why not start with a new gasket... depends on your philosophy and skill level...

**axa** · 04-21-2015, 05:52 AM

anyone ever try one of these...
http://pages.ebay.com/motors/link/?n...880746&alt=web

though I would argue the cylinder head spark plug gauge takes a more pertinent reading...

**barnone** · 04-21-2015, 11:25 AM

Originally Posted by axa

anyone ever try one of these...
http://pages.ebay.com/motors/link/?n...880746&alt=web

though I would argue the cylinder head spark plug gauge takes a more pertinent reading...

I have one like it on my Kawasaki W650. Oil never seems to get over 100 C.

I'll order one for my DF when I migrate to WNC in a few weeks. It comes from China so I'll won't be here in SWFL long enough for it to arrive. http://www.ebay.com/itm/321584880746
It will allow me to test the effectiveness of my oil cooler on the DF.

CHT gauge is interesting to watch. I also have one on the Ural and I see CHT of 425 F when running at 70 MPH.
It cools down when idling at stop light to 320 F.

0202141058-01.jpg
DF CHT

0813141019-01.jpg
Oil cooler probably not needed on a stock DF motor.

0405151137.jpg
2015 Ural cT

0311151023 (1).jpg
CHT gauge on right cylinder of the Ural.