2007 CRF450R JD jetting installation

So this is a bike I bought used but in mostly stock condition. It is in good shape and I ride in NC VA moderate temperatures(except for now) and low elevations. I use the bike just for play riding, not to serious trails and tracks. The stock jetting was very good and I was very reluctant to change anything, but I like JD jetting on my Yamahas and I was getting a little bit of decel popping and my recent FI bikes (KTM and KAW) have spoiled me with super strong bottom and mid power. So with my JD kit, my new oversized GPR radiators, and my no toil screenless air filter kit, I quickly got all parts on. The radiators look great, no problem with new air filter, but as usual JD install is tough deciding which needle and main jet. Went with recommended 190 mj even though it would seem rich based on stock 178 mj, went with blue needle for standard temps/low altitude even though most seem to use the red needle from what I read on internet, went with middle 4 cp position even though 5 cp seemed to match stock needle lenght. Set fuel screw 2ts. Got it fired, right off bat knew I was lean at idle, popping, stalling, runs on choke better. Turned fuel screw out to 3ts, idling improved, popping lessened, rode it a little, top and mid seemed right and seemed stronger typical JD results. But stock pilot jet 42 is either lean with needle in clip 4 or I need to go to clip 5. As with my Yamahas a richer pj always seemed to work well with JD kit, so I now have a 48 and 45 ordered, will try 48 and report results if weather allows, Recommendations?

The needle position isn't going to affect the off throttle fueling at all. Zero. So if it popped less on decel, it was either warmer, or the carb is clearing up a little. It's more than likely the pilot is slightly plugged, or the pilot circuit is plugged than anything else. The fuel screw will probably fall out unless youve got one of those remote fuel screw knob things, at three turns out. The screw becomes less and less effective after 2 full turns. At 2.5, it's doing almost nothing. Ive never seen a CRF NEED more than a 45 unless the temps were in the low 40s. If youre trying to adjust the fuel screw in 45-50 degree weather, hopefully the bike has been running for 20+ minutes, otherwise, You'll never get there.

The difference in the main jet sizes with the JD kit is tied to the completely different needle and the theory behind the. Take a caliper to the end of the stocker and one to a JD needle. The JD needle is HUGE in comparison. So it's way leaner than you think.

The needle position isn't going to affect the off throttle fueling at all. Zero. So if it popped less on decel, it was either warmer, or the carb is clearing up a little. It's more than likely the pilot is slightly plugged, or the pilot circuit is plugged than anything else. The fuel screw will probably fall out unless youve got one of those remote fuel screw knob things, at three turns out. The screw becomes less and less effective after 2 full turns. At 2.5, it's doing almost nothing. Ive never seen a CRF NEED more than a 45 unless the temps were in the low 40s. If youre trying to adjust the fuel screw in 45-50 degree weather, hopefully the bike has been running for 20+ minutes, otherwise, You'll never get there. The difference in the main jet sizes with the JD kit is tied to the completely different needle and the theory behind the. Take a caliper to the end of the stocker and one to a JD needle. The JD needle is HUGE in comparison. So it's way leaner than you think.

 

I always love an inexperienced reply, so fun to pick on, but to the point the 48 was dead on at about 2 turns out. But to your finer points about tuning, bullsh***, after 50 yrs of dirtbikes and doing all my own maintenance that entire time, my jetting skills are much better than most. Just a couple of suggestions from a senior rider, most all motorcycles I have ever had benefit from one or two sizes richer pilots, most benefit from one or two sizes larger mains with a little unplugging airboxes/airfilters/exhaust. Changing the main or needle will effect pilot or at least the fuel screw setting almost every time, plus the pilot is the main factor in bottom end power on both two and four strokes, many bikes can be made to run acceptably on a pretty wide range of different jetting, but they will not start as well or wont pull as well if pilot is stock or lean, main jet is similar on bikes with good open air boxes, they will run with stock jetting but not as well as richer mains when ridden hard. Also, most fuel and air screws effective range is 1.5 turns to 3.5 turns out, and thats based on experience but never lost a screw yet, but I am careful to keep up with oring/spring/washer due to how critical they are to ability to adjust, but should be around 2 turns out when jet size is dead on.

Just as a disclaimer my native ridding areas are low altitude and moderate temps.

47 minutes ago, Babywolf said:

I always love an inexperienced reply, so fun to pick on, but to the point the 48 was dead on at about 2 turns out. But to your finer points about tuning, bullsh***, after 50 yrs of dirtbikes and doing all my own maintenance that entire time, my jetting skills are much better than most. Just a couple of suggestions from a senior rider, most all motorcycles I have ever had benefit from one or two sizes richer pilots, most benefit from one or two sizes larger mains with a little unplugging airboxes/airfilters/exhaust. Changing the main or needle will effect pilot or at least the fuel screw setting almost every time, plus the pilot is the main factor in bottom end power on both two and four strokes, many bikes can be made to run acceptably on a pretty wide range of different jetting, but they will not start as well or wont pull as well if pilot is stock or lean, main jet is similar on bikes with good open air boxes, they will run with stock jetting but not as well as richer mains when ridden hard. Also, most fuel and air screws effective range is 1.5 turns to 3.5 turns out, and thats based on experience but never lost a screw yet, but I am careful to keep up with oring/spring/washer due to how critical they are to ability to adjust, but should be around 2 turns out when jet size is dead on.

Just as a disclaimer my native ridding areas are low altitude and moderate temps.

Well, it's plainly obvious to me that you have absolutely no idea of what you're talking about within this specific tuning situation, or even comprehend English very well. "Off throttle fueling" is closed throttle. The needle is buried. You can pull the main jet clear out and it wont matter (almost).  I, too, have been tuning and riding dirt bikes for 50+ years, CRFs specifically since 2003. I have extensive experience with the JD Kit and dont follow the dimwitted "put a biger jet in thar cuz more gas is better" mind set. I do crazy things like measure exhaust temps, check O2 levels, read the plug and compare ride-ability in relation to changes. You can say most, and usually and bigger air box holes and all that all you like, but, had you bothered to read the &%$#@!ing original post, none of those conditions were noted in the question.

The only reason you haven't lost a fuel screw at 3.5 turns out is dumb luck. I've had more customers come to me with "jetting issues" that had followed some moronic suggestion to keep turning the screw out because it popped on decel, while the engine was still ice cold,....that had no damn screw in it at all. Keep your ill conceived advice. And dont come back at me again. You are painfully out gunned here.

I prefer to ignore the above post, because I just got through riding my 2007 CRF450R with JD jetting kit using blue needle, and a 48 pilot jet and WOW what an improvement. My stock jetting was good, starting, idling, WFO, but just seemed weak compared to my 2011 KX450F and 2013 KTM 500 XCW. Now I am happy, starts are better, less cold natured, power is similar to my newer FI bikes, in your face, straight from the bottom with no let up or hitches in the power band, Im very happy and can recommend to anyone still riding an older carbed Honda 450, you will not be disappointed.

 

Just updating on my 2007 CRF450R, got the 13oz flywheel weight on and very pleased. Also, added a Lexx spark arrestor/muffler combo, mainly to make woods legal on state parks. Was super surprised at a nice increase in bottom end and midrange, just touch throttle for lifting front end, very nice powerband for all types of off roading. Only jetting change was half turn in on fuel screw. Also, played with rear sag a little getting rear to set a little higher helped handling and suspension plushness a lot. With all mods completed the combination is feeling like a brand new bike, very sweet. Mods: magura clutch, 2t larger rear sprocket, 13 oz FWW, oring chain, kickstand, 30” handlebars, barkbusters, JD jetting, 48 pilot, sparkarrestor muffler, softened stock suspension, dunlop mx3s front, AT81 rear, skid plate.

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