My testing indicates the stock header (with a DGR or a FMF PC4) "runs outta steam" at 9 to 9.2k on a stock bore.. At that point, TRQ and, therefore, HP fall off..( The larger DIA. headers (MegaBomb, PowerBomb) with a PC4 or QC4, allows power production to redline..)

 

Always depends on how throttle happy I am, and I'm roosting out of every dirt corner now with the 351!!! Tons more fun to slide around. Probably lost around 20 miles (32kms) until reserve. Used to get about 100 miles (160kms) until reserve, now about 80 (130) but the smile factor has gone way up! Well worth the extra fuel, and, if I wasn't so throttle happy now, would probably be much closer to stock mileage.

 

Still on the 142.5 with airbox removed. (just not had a chance to pull the carb yet) and i when i pulled into my garage tonight i was at over 72miles on a full tank, and still not gone to reserve.

Plus i spent the first 50, being very throttle happy. Like at every opportunity giving it full.

I think my initial 100mile break in the constant opening and closing of the throttle even despite it only being half way, to keep the break in at different rpm, severely reduced my gas mileage.

Will pull the carb this weekend and go for a couple of long runs so will have some better stats to share.

Really enjoying the KLX351 at the moment.. Having lots of fun with it. Am able to lift the front in 1st and 2nd providing i snap the throttle open at the right rpm. So happy about that ! Still a little fine tuning to do though.

Next on the hit list is new tires. Then finally a new header. As i'm still only on the stock header. But that can wait for a while.

 

I guess you want to lean out the bike so that you can put the airbox lid back on..?

Aftermarket headers will "offer" increased power levels above 6.5k - I say "offer" because to get it all, you have to leave the lid off and use a huge main jet to properly fuel the "new" top end... Probably a 142.5 !!

 

So changed to a 140, and put the lid back on, with stock snorkel and it was bogging down around 8k, full throttle. (after adjusting the fuel screw, to maybe 2turns out) So pulled the snorkel off while keeping the lid on, and it seems perfect.

Guess i have a choice here. Leave it as is, or pull the carb again, and throw a 137.5 main in.

Truth be told, i'm not in the mood right now to do anything other than ride the socks off the thing. Its working, its working good. Maybe i'll buy a KDX200 snorkel and install it, maybe i'll just duct tape some kind of gauze over the hole to stop any crap getting sucked into the airbox.

Not sure yet. But the thus far, the perfect setup for me on a 351 with TM33/34, at sea level is about 2turns out on the fuel screw, and a 140main with no snorkel.

I'll pull the plug in 50 and see where's she's at in terms of rich or not... Maybe she's even lean, probably not tho, if she's running rich with the snorkel...

Don't know what the jet needle is set to in terms of clips, i'll just take Bill's word that its at the best place it could be, and don't mess with it.