[chuck b]

Hi all,
My sister just picked up a new CRF150R and gave it to me to go through and jet it properly. Its a left over 2008 and completely stock with about 8hrs on the engine. I own an A/F analyzer from www.innovatemotorsports.com so I welded in an O2 sensor
on the head pipe (near where the kick start lever sits), marked off the throttle in 1/4 increments then hooked up the portable A/F and went for a ride to get a baseline. I was alittle surprised how poor the accelerator circuit was working. Any quick inputs of throttle had the bike falling on its face. About the only thing close out of the box was the main jet and it was too rich.

For comparison purposes outside temps were 90F, 27% humidity and elevation at 2200ft. Once back in the shop I added a flexible fuel screw, found the accelerator nozzle was spraying a touch to early and verified float level. Here are my final settings.

Main: 135
Pilot: 40
Leak: 45
Fuel Screw: 2 1/8
Needle: 2nd clip

Idle was set at 12.8-13.0
Off idle to 1/4 throttle it would go 13.1-13.2
1/4 to 1/2 throttle it was pretty stable at 12.5-12.6
1/2 to WOT it was still a bit rich at 11.8-12.0

With fall quickly approaching I knew she'd be primarily riding in temps of low to upper 70's. As such the 135 main would be fine. If temps remained in 90's to low 80's I'd have switched to a 132 main to lean out the upper portion. I like to have 12.5 for WOT.

As far as the Accelerator pump circuit...going to the 45 eliminated most of the bog, however, if it was my bike I'd have added a stiffer spring to the pump. She's not a hard rider and doubt she'd ever twist the throttle fast enough to experience any bog as the bike is currently jetted. Ideally I'd like to see a little leaner settings from 1/4 to 1/2. I like a bike that has a crisp throttle response and having jetting at 13-13.7 really helps with fuel mileage too. Main should always be 12.5

[Asmith]

With 91 octane pump gas, maximum power is achieved at a Stoichiometric ratio of 12.5:1 - 13.3:1 or λ of 0.85 - 0.90.

Do the AP mod to the carb and it should clean up the AP circuit.

[[email protected]]

Check out James Deans web site, of JD Jetting.
He uses a Win-Peg 7 dyno with exhaust gas temerature AND content analysis to configure his kits.
Along with that a needle customized for the application is included, with AP mod instructions including the parts needed for that, even diaphram nubs when required.
We've put a couple on 150R's with spectacular results,and they are sold right here on crfsonly in the on-line store. Doug