I personally don't think the gain(if any) if worth the dollars for a header. I did the dg o series, K@N, rejet and dual snorkle lid along with a 13 tooth front sprocket. Its night and day compared to stock power levels.

 

I've seen claims that using a KLX300 header makes a difference on the 250, but it only necks up in size the last few inches, so I don't see the point. I thought about having the stock pipe abrasive extruded which polishes the interior for better flow but that would cost more than a good quality aftermarket header (FMF, FSW,or similar). Port matching the exhaust port to the header makes a huge difference too, but that involves the potential for metal shavings in the block unless you tear it down - not going there. I'll make the call on exhaust after I try tuning with new jets, etc. on the stock exhaust with my hillbilly modification.

What jet are you running with the DG? And what altitude are you generally riding?

I have the hi-flow snorkel coming along with all the other stuff, but of course I'm leaving for Asia Tuesday so I won't get to install it until I get back! 13T sprocket is on my list too - better gearing makes sense if you have more horsies. And one day I hope to actually get to ride instead of tinkering with the bloody bike.

 

I ended up with a 122 MJ and 2 shims, but i am going to try a 124 soon. it runs like a raped ape but i think i can get a bit more out of it. 127 was too much and it would surge at WOT. You will be doing more than one rejet, so be prepared....ALso the kouba t screw is a must.

 

122 and 2 shims at what altitude (generally)? I ride from sea level to over 6000 so I need a jet with some latitude for altitude. I can dial the mixture to compensate for big changes - putting on an EZ-Just mixture screw instead of the Kouba. I'll mark that up so I have good reference points.

I'm thinking to start with a 125 main and whatever DJ recommends for needle specs. I'll go from there...and I'll bring my tool kit when I go ride the mountains.

 

I live at 1600 and go up to 7k usually every time i ride.

 

Thanks, that's good to know as I collect data to compare. I did the rejet and new needle last night. Also dumped the smog gear. Decided to try a 128 and DJ needle set 4 slots down with two spacers, and also cut the spring down by 1". That EZ-Just screw is awesome too! I test drove it with the snorkel off and 2 turns out on the screw, then tested it at 2.5 turns out, which was better. Hell of a lot harder to try different mixture settings with the stock mixture screw, that's for sure. I'll make the final call when I get my new filter and KDX snorkel. Pretty sure I see an aftermarket muffler in my future though.

 

'Port matching the exhaust port to the header makes a huge difference too, but that involves the potential for metal shavings in the block unless you tear it down'

?????

The cylinder head exhaust port is larger in diameter than the header opening. There is no need to do any grinding to the cylinder head.

I ground out the weld bead in the headers (oem and pwrbmb) and matched the exhaust port I.d. by grinding till it matched the exhaust gasket I.d. Further welding on the outside of the header flange to prevent failure.

 

Hey, thanks for that info. I did not know the port was larger than the header (obviously). I've always seen it the other way around...granted, that's on chainsaws, so I guess there are bound to be differences. On saws you usually have to grind and polish the port into the head - PITA. I suppose I would have learned this once I took the header off but I had no reason to do it yet.

Did you just lay a bead of extra material around the flange to strengthen it after grinding out the interior? I could put a small MIG bead there so there's a bit of extra material but I'd be concerned about flange and bolt clearance. Thanks for the photo.

 

I have an extra oem header that I modified if anyone can use it....

 

Update: Dumped the modded stock muffler and put on a DG-O Series - sounds awesome and runs great with better throttle response and pull through the range, although I'm still not sure how that 128 jet will operate at higher altitudes. I'm being told that 132 MJ with lid off is the only way to go for a rich enough AFR. Seems like that is a mighty rich combo for higher altitude riding. I'd like to keep the lid and snorkel on, so maybe the smaller jet makes that a good combo.

BTW, anyone considering the DG: it sounds awesome and seems to be really nicely made. Fit pretty well as far as mount points and clearing the rear peg, but it was actually a bit too short to reach the stock header on the 2006 (250H6F) despite DG's claims that it was the right one. I made a custom coupler which seems to work fine for now. I wonder if the "H" designation was somehow different from the "S". I thought it just meant it was Aussie market or something - everything in metric, etc.