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· Registered
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Discussion Starter · #1 ·
I found this on the Nighthawk forums posted by member Pete in PA, not sure if he's a member here. His location shows an elevation of 433' above sea level, I mention this because he gets into rejecting and I understand that altitude will affect your jetting.

I wonder what the experts think of these mods?

Pete's post:

"I've had a 2007 250 Nighthawk now for about 2 months. Here's what I've done to wake it up. Like ALL carbed bikes it's much too lean due to the EPA.

From #118 main jet (stock is #110) 1 washer under the needle. 38 pilot
Remove resistors in plug caps then open spark plug gap to .035 in. (stock is .024-.028 in.)
Remove snorkle on airbox. Several holes in air box lid.
I first adjusted the valves to .004 in. (Honda calls for .002-.004 in.) I went back in and set for .002 and got more power. (more valve lift and duration, better cylinder filling)
I left the exhaust stock. Don't know how much opening that up will help, I just don't want the noise.
Installed 15 tooth front sprocket. (stock is 14 tooth) 7% less RPM in each gear. I just felt the gears were too close, you'd be in third just crossing an intersection.
Front tire at 35 psi, rear at 40. Honda wants 29 regardless of load.
Since October 2006 a new update from Honda. Honda now recommends 10-30 motor oil. In my ST1300 also.
I'm running Rotella 10-30 synthetic in both bikes.

Keeping in mind I'm 6' 2" and 330 lbs, I can go 75 mph on level ground tucked in no windshield. Pick up from a stop and throttle response is MUCH improved. Now there actually IS a powerband.

I bought it used with 3k miles on it. With MUCH work I got the bluing removed from the header pipes. With the rejet they are not even trying to turn blue again. With the engine running cooler it will last longer.

Happy riding!"

Link to original:

· Premium Member
10,166 Posts
It sounds like you hit the sweet spot with the jets. Any further changes in either the intake or the exhaust are likely to require more fiddling with the jets. I don't think the .002 change in your valve adjustment made any difference in your performance, might have quieted the engine down a wee bit though.

Moved topic to SOHC section.

· Premium Member
23,965 Posts
All of it is pretty much valid, I'm thinking he ended up a bit too rich between the needle washer and main jet increase but he also opened up the air side so maybe it's good. Not sure on the tire pressure, he's 330#'s so that's got to be close to max GVW in which case the rear tire should be up close to the max air rating for it. Front tire probably only needs a 1-3 psi increase, depends on the tire and the tire temps.
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