Dong Fang DF 250 RTB Bobber Information

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Originally Posted by axa

If you need to ask I think your question is answered, leave it be.
But some of us get this bike because they enjoy not only riding , but working on it.
I bout this bike expecting to work on it, which i do more than ride it...

I for one like finding things that are broken or unoptimal, and then the challenge to fix it correctly.

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Yeah I dont mind working on it either. Like I said, my bike is a work in progress and like my Jeep bikes are easy to customize to your liking. My issue is not the work, it's the money. I dont have much of it. It's the main reason I bought this bike in the first place, it was cheap and the only one I could afford at the time.

On the flip side I would prefer to ride my bike than work on it. She is my first. And Im of the "if it aint broke dont fix it crowd". But even if it were perfect I would still add my own personal taste too it either way.

CAT is in downpipe , at front of engine though not in the front of the muffler ..........................................

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Originally Posted by DanDaMan

CAT is in downpipe , at front of engine though not in the front of the muffler ..........................................

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drillilling out the muffler , is drilling out the muffler :p


im tellin ya , and everyone sub 200o lb's to grab that 33 to 30 tooth rear

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Originally Posted by barnone

axa,
Are you saying that I did not remove catalytic converters from my DFs with my hole saw?

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what Im saying is that you did not remove your cat with a hole saw like mine.
I found it not readily possible to remove the cat with a hole saw with a very shallow depth.
Looking at yours, being that you provided a pic, I estimate depth was likely 2 or 2.5x its diameter, were mine wasn't even 1.

What ended up happening was i'd cut a nice neat looking perimeter, and the piece wouldn't break away from the longer mass. That was my original concern as i didnt know how rigid or deep the element would be.

that said, thanks for the info, thats one mod that ive always passed on my bikes as i didnt want to be the first...

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Originally Posted by Bobthebobber

How does she sound and ride now ?

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Without the cat sound seems very similar to me, I have a hard time determining any differences just yet.
The first thing i have noticed is the lost the back fire. Which doesn't make sense to me on its face value.
So I should note i had just added the reverse air ram 2 days earlier, so perhaps that is was killed the backfire, but i was too busy paying attention to the eliminated top end sputter.

The next thing i noticed now with the combination of no cat and reverse air ram is while all out cruising, closing the choke a quarter or even a third perhaps bit has little to no noticeable effect on the engine at top RPM.
So this must be direct evidence that airflow has notably increased.

This makes me personally believe top end sputter is caused from an air shortage, which again was eliminated just with the rev air ram. But i didn't try this test before removing the cat.

But I have to admit, ive been pretty fortunate, Ive never had any problems except that sputter and the ride is pretty much the same as always.

Next step is to open my jets and see if i can get some more power.
Mine are still all stock.

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Originally Posted by DanDaMan

CAT is in downpipe , at front of engine though not in the front of the muffler ..........................................

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It was on the 2010 DF but not on the 2012 DF. It is in the front of the muffler as I stated in a previous post. That is why it is important to mention what year DF you have and to remember that DanDaMan has a different bike but the same engine.

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Originally Posted by barnone

I did mention that I removed the catalytic converter which reduces the back pressure in the exhaust and that should allow more air/fuel to flow through the system therefore needing the larger jets.

Anyway, whatever works for you is good.

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I have to second that, I think our 2012 bikes are bordering on a rich condition to begin with.

As ive said now a bunch and dont mean to repeat, but just adding the air ram eliminated the sputter and allowed me to REV as high as 7k resulting in a slightly higher top end (slightly downhill be it)
Before that I tried applied a bit of choke to test a lean condition, and had immediate engine trouble.

Doing this now has little effect, so thats my first piece of rich evidence.
Second is even with both air modifications, -cat and +ram, it seems to have a very limited amount effect when closing the fuel/air mix screw. that i believe would close off the slow pilot jet, so reducing the fuel at idle (as little as one turn from seated) and it will still idle smooth. That said it also seems to idle well all the way to 4 turns... (so im still probably doing something wrong here. I do adjust a half turn at a time and wait about 15 seconds for a response...)

I'm going to ride around for a while with choke full open, and as soon as i remember pull the plug, i expect to see a slight to moderate lean condition... but if i dont, then that will be the third peice of evidence for me to judge these bikes come at least a bit rich.

While even though dan may protest, rich afaik is a safer condition. A bike might seem to run well a bit lean, but i haven't yet found evidence that it adds power, the added heat i don't imagine helps anything. but we'll see

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Originally Posted by GonzoX

Yeah I dont mind working on it either. Like I said, my bike is a work in progress and like my Jeep bikes are easy to customize to your liking. My issue is not the work, it's the money. I dont have much of it. It's the main reason I bought this bike in the first place, it was cheap and the only one I could afford at the time.

On the flip side I would prefer to ride my bike than work on it. She is my first. And Im of the "if it aint broke dont fix it crowd". But even if it were perfect I would still add my own personal taste too it either way.

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I hear ya, i too bought into this cuz the low buy in cost.
but its all a personal preference and how you prioritize your time and money.
that said, you can always work on the looks if dont feel confident to work on the performance.
its not like all these tune ups will buy you much at all...
The sprocket change is like 90%, all the rest is quite marginal.

how about this for a signature
only, i get the feeling people will get tired of seeing it

your right rich is safer , and even though having it start to lean out near max speed because of air ram does "slightly" increase power , its almost pointless because it only has 9-11 horsepower to begin with :p so another .2 hp isn't much , with the added danger of added heat

but doing a chop plug check at 50 I'm dark brown , chop plug check at 73 its light brown