Dong Fang DF 250 RTB Bobber Information

[axa]

Seems that the general consensus so far is that the chain needs to be replaced. I am going that route at this time. The wheel is straight with the front sprocket, I checked all that,
My next question is what is the size of this chain again, I do not remember.. I remember a 512 or something like that. Thanks.

its 520

[bowtiewagon]

Thankx AXA .. 520 ..

[axa]

im itching to tear down the engine and have at it... but for me riding season aint over for at least a month...
but it rained today, so i thought i would start looking for myself what it will take to apply these 'secret' weaver mods


First the intake.
The ports matched spot on, and the casting wasn't nearly as bad as i expected. There were some casting marks as seen here on the left.
These will be removed, and the sand marks will be eased down a bit.
Not much to do, not much to gain.

intake (Large).jpg

In the back from the top you can see the valve fairing pretty sleek and in line, no point to fill or manipulate in any way.


The exhaust:
On this side its hard for anything to be very aerodynamic really, as the face of the valve gets in the way when open.
It will be polished down to a fine finish, but its short and sweet, again not much to be gained here.

carb detention 009 (Large).jpg


Now the a potential issue i found has to do with the crap stock exhaust gasket.
Basically its just one of those rolled up piece of cardboard wrapped in a thin metal sheet gaskets.
Nothing to keep it from unraveling and interfering with the flow path, and im sure this one is doing that a bit and needs to be replaced.
Had needed to reconstruct this one as it was falling apart.

carb detention 008.jpg


Now after all that i was a bit disappointed, the port and polish isn't going to do a hell of a lot. but then i saw this:
spacer (Large).jpg

this is the carb spacer, not sure if you can see but it is riddled with bumps and lumps, never mind the bend...

I supposed that spacer was inserted to allow the feedback from the SAI, as well as back it off from the engine mount, but otherwise it cant be helping.

So i decided it had to go, shouldn't hurt.

After tapping a new set of carb mounting holes, m6x1, I now have this spacer-less mounted carb.

refit (Large).jpg

Curious to see what if anything it will do for the intake flow...

[ UPDATE: now with this spacer removed i have to back off the air intake by applying 20-25% choke. Seems that removing the spacer in one way or another increases air flow (be it becuase there is less flow resistance, or that it has repositioning my reverse air ram).
I guess it is the less resistance becuase the angle of the ram is reduced into headwind.
I'm sort of surprised to the degree this increases flow. More than drilling out the cat.
I dont expect to get any better flow with the head polishing.
Anyway, this seems promising as it may allow to bump the jets up]


By the way it seems the stock head gasket are likely a good 50 mil. by recent whispers, it seems possible just honing down mating surfaces, one might be able to eliminate the gasket and thereby increase the compression ratio. I may try this first before milling down the head.

[barnone]

bow,
It is a 520 chain. Definitely needs to be replaced and looks dry as a bone also. You been oiling it?
I assume you bought sprockets for a 520 chain, right?
I'd spring for an o-ring chain then oiling is not so important but still should be done and as mention should last 30k miles.

[barnone]

axa,
For some reason I failed to get email notification of the posts here and I though it was very quite so I checked.

I agree that most of the mods that Gordo claimed were bogus except for milling the head. I seem to remember that the Heist came with a non pumper carb so all they did was use the pumper carb and the jet sizes that we on the the DF thread came up with.

I checked the ports like you did and also did not see any need for porting but failed to check the short intake manifold.
Looks like you are on to something there.

So are you gong to pull the hand and try to true up the surfaces and run without a gasket? In the old days we would use a thinner head gasket or mill the head to raise the compression ratio.

[axa]

axa,
For some reason I failed to get email notification of the posts here and I though it was very quite so I checked.

I agree that most of the mods that Gordo claimed were bogus except for milling the head. I seem to remember that the Heist came with a non pumper carb so all they did was use the pumper carb and the jet sizes that we on the the DF thread came up with.

I checked the ports like you did and also did not see any need for porting but failed to check the short intake manifold.
Looks like you are on to something there.

So are you gong to pull the hand and try to true up the surfaces and run without a gasket? In the old days we would use a thinner head gasket or mill the head to raise the compression ratio.

Ya it really bums me out when people lead others down a false path...
And he does it so fervently with such disregard, knowing full well most what he is saying is just crap. And there is no other end game than merely to convince others that he has, or has achieved, something that they have not and can not, cuz its not possible.


So for an extra grand +, the heist doesn't even give you a carb with an accelerator pump?
So here is the final piece of the 'secret' carb upgrade, and the ccw 'racing' carb... it's merely the same carb that comes stock on the DF stock.
Of course it is also magically 32mm if you listen to gardo.
X'st sake, please someone tell that Im wrong (and then back it up).


By the way did you say you got kicked off the hiest forum for having the balls to speak the truth? it wasn't this site's heist forum was it?? Or was it this post that did it?
Classic, call a spade a spade. I dont know how that guy looks himself in the mirror. No wonder that thread died, pathetic really, but i digress.


Yes, just removing that short intake manifold my tune is entirely off, im hoping this indicates flow potential. Tell me how far off was the 120 jet you previously attempted? Im maybe 20% applied choke to run after warm.


Yes, Ill inspect and if true enough first just try a .015 thin gasket.
Then mill if need be, and if i get to the point that both heads are true ill continue gasketless taking it down until ive gone too far and start seeing problems like difficulty turning over, or timing issues. Then I'd back off by inserting gaskets... or else I'll try to continue until I achieve +2 pts, but im sure ill hit a problem first.

[bowtiewagon]

bow,
It is a 520 chain. Definitely needs to be replaced and looks dry as a bone also. You been oiling it?
I assume you bought sprockets for a 520 chain, right?
I'd spring for an o-ring chain then oiling is not so important but still should be done and as mention should last 30k miles.

Yes sir, 520 sprocket. Did a how to on buying a new chain, and I am going to take every ones advice and get a O-Ring chain for sure.
As for my chain, Yes I had been oiling it up regularly, but with the Texas weather, and my lack of knowledge on motorcycles, just using a 40 weight oil was probably not all that good. So thanks every one for the assist. Will keep ya posted.

[barnone]

axa,
The Heist forum that I was kicked off was the one on the Cleveland CycleWerks web page.

The 120 jet seemed to be too much fuel but I guess the problem might have been restricted air flow.

This engine just seems to not have the same power at higher RPM as my 2010 DF had but that could be a faulty memory on my part. I did run 68 MPH GPS on my old DF and can only manage 65 MPH indicated on my 2012 DF with the about same gearing and the same jetting. That is probably only 60 MPH GPS as the speedometer appears to me to be off by 10%. The engine does seem to have good power until about 4500 RPM and then goes flat.

I hope you are on to something with the air intake. I ordered a shorter intake off Ebay and will report on it when I test it.

Also ordered a head gasket that I hope will be thinner.

Actually, I am enjoying the bike as is for now. Reasonable top speed here in the mountains is usually only 50 or so anyway.
When I hit the flat lands of FL in a month for the winter then the top speed will be insufficient. They will run over me there.

[barnone]

Continuing search for more ccs lead me to
http://www.aliexpress.com/store/prod...752848938.html
$130 shipped to USA
Asked vendor if it will fit the DF motor and what cc will it be.
Probably another wild goose chase.

The cylinder can be purchased separately and it has a 75mm od skirt so could stand some overbore if a larger piston can be found.
http://www.aliexpress.com/item/LONCI...079925191.html

Here is a 70mm piston.
http://www.aliexpress.com/item/70MM-...752380917.html

[ben2go]

There's always going with a CV carb.Could help bottom end.Doubtful top end would get any better than the pumper carbs.