So I had a full stock exhaust on my 2006 250H, then I cut out the back end and yanked out the first length of baffle, capping it off with a chrome closet rod flange (See my earlier post for this Hillbilly Custom approach). Made the bike sound a lot better but did little to increase power, even with the other mods I had done - re-jet to DJ 128 Main, new DJ needle, EZ-Just screw(works great), cut the spring, bored crank vent, drilled slide, Uni filter, backfire screen removed, smog off, etc.

Yesterday I pulled the stock exhaust and added a DG O-Series on the stock header. The DG looks and sounds awesome. I had to fabricate a connector pipe because A) the DG pipe didn't quite reach the stock 250 header pipe and B) the DG pipe would have slipped over the back end of the header if it had reached, but it didn't. So now I have a length of pipe RTV'ed and clamped into the header and muffler-tape-wrapped into the leading edge of the DG pipe. A little hokey but seems to work and does not seem to leak. I don't know if I just plain ordered the wrong DG or if their claim that it fits the 2006 is wrong.

So it sounds better and the overall power seems a bit better but I think it is still not optimal. I dialed the mix back to 2 turns out since it should theoretically need to be [Edit: RICHER!] with the increased airflow. Bit of popping on decel now, which seems to be a normal by-product of exhaust upgrade, but I'm wondering if anyone has opinions on what to tweak for snappier throttle response - I don't quite have wheelie capability yet, which I thought I would.

BTW, I'm basically at sea level in Seattle but will be riding generally around 2000-6000 feet, so I plan to lean down a bit when I get high.

 

I don't know how to jet with a snorkel but if you pull the lid, you'll need the #132 and the needle raised one notch above standard stage ll - even then you'll still be a bit on the lean side at sea level. Doing the above should get 1st gear wheelies on engine alone. See my wheelie video on my signature line. .

BTW, Increased airflow requires more fuel, not less, to maintain a given AFR.

 

If you want that wheelie power, try a front sprocket change by dropping a tooth, You will feel more of a power change from that than any mod you have done.

 

I have standard sprockets. A 13t primary certainly would make a difference but I don't like the procedure for removing it.

 

Right on the AFR. I was just sub-2 turns and opened to 2 - keep flipping that in my head. Maybe I'll go to 2.25 or 2.5 and see how it reacts. I wondered about changing the needle position but I'm trying to avoid tearing into the carb too often - rather be riding. I'll play with the mix a bit more before I go back in to try a different jet/needle combo. From the mods sheet it looks like you (KLXster) are running stock intake (filter,backfire screen) with the DG but needed to move to the 132 jet. I wonder if being in Dallas with warmer, drier air than we have in Seattle creates that need. We're pretty damp and humid. Lots of factors to take into account.

I've thought about going to the 13t front sprocket but haven't gone there yet. Not really concerned with actually being able to wheelie, just looking for good pop and pull through the range. Digging that rippin' new exhaust though!

 

Hoots, you are correct - I am running the stock backfire screen and filter. (I had an air filter catch fire once upon a time from a back fire through the carb and so will never remove a backfire screen.)

You are also correct that more humidity has the same effect as higher elevation - less oxygen molecules available for combustion - therefore less fuel is needed to maintain a given AFR.
However, Dallas is very humid, especially in the summer. Perhaps not as much as Seattle but the difference would only serve to give you a better AFR than I have. Your temps are, no doubt, cooler than Dallas which offsets the increase in humidity. Remember that my suggested setup is still a little lean here in Dallas as per the Dyno.

You will pick up at least 1hp if you pull your lid and set up your carb like mine. I picked up 1 hp (Dyno verified) just by going to the 132 from the 128 , all with the lid off.
Try it - you'll never look back.

 

Interesting, and good to know. I would have guessed Dallas was dry. I've had a number of people tell me I should have gone with the DJ 124 and that the 128 was going to be way too rich. I opted for the 128 so I would have some rich side to play with since tweaking isn't too hard with the EZ-just screw (like the Kouba - simple twiddle without cramming a screwdriver in there - nice!). I'll see where I get with this setup and go from there.

BTW, are you running the DG with the stock rear port? I like the sound but I was thinking to fab a 1" or 1 1/4" quiet tip to keep the noise down for scouting/hunting. Don't mind the roar on the street, but would like to keep the trails a bit quieter.

 

After researching this forum prior to modding, I was very suprised to find the usual recommended jetting to be way too lean for max power. My Dyno testing has shed light on this issue and cannot be dismissed. W/O lid, it's hard to get enough fuel into a uncorked stock bore with the dynojet kit. I'm running the DG-R and also have a full FMF w megabomb n PC4.

 

Click on my login, go to statistics and pull up threads I've started for my dyno testing..

 

I love my DG 2 years of constant riding and the packing is still good!