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07 CRF450R Pilot Circuit Settings


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Hi Eddie-

07 Honda CRF450R

No modifications, stock exhaust

175 main

40 pilot

NJYR Needle 2nd Slot

1200 Feet Elevation, 90-100 Degrees in Arizona

1.5 turns out on the fuel screw

Bike starts without the choke on three or four kicks. After warming up the bike and riding it for 10 minutes, I tried to confirm the pilot circuit, I turned the fuel screw all the way in. When I did that, the idle peaked and did not die. Rode it around the block without any hesitation or missing. Would this mean that I need a smaller pilot? The manual does not call for any smaller pilot than a 40, and I guess I'm lacking confidence.

The manual suggests 175/42/1.5 turns.

What's your take?

Thanks

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That screw should be OK, at least I have not heard of any complaints other than it sometimes being hard to turn.

I'd go with the next smaller pilot jet, a 38 and give it a whirl.

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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william1-

thanks for the feedback. i appreciate your opinions on the forum.

i have a tach/hour meter. the RPM readings are delayed a few seconds, but it's good for what i need.

i've been starting the bike, riding for 10 minutes until warm, set the RPM at ~1800. i then turn the fuel screw in to try to get it to stall, but the RPMs just increase to ~2100. i also turn it out till i get 3.5 turns and the RPMs drop below 1700.

i guess dropping to a 38 pilot just kind of freaked me out, since i've never used a 38 in my CRF450R or my WR450F.

i'll try to pick up a 38 and i'll post up with the results.

also, you're right about the RD fuel screw being tough to turn. my white collar thumb and pointer finger have two big blisters on them from turning that thing so much last night and this morning.

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If your bike actually wants a 38, that would be quite surprising, since the normal range is a 42-45-48 for those bikes.

Thats why I like to use a setting that seems to work well on most bikes, and then troubleshoot why is wants such a lean jet.

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Leardriver-

you're right....it is surprising that i'm getting this type of behavior. that's why i'm posting in this section.

if the 38 works, then i'll be curious if i have an issue with the bike. i'm definitely not an intake and fuel expert. just trying to get the bike to behave in a conventional way. when the weather isn't so extreme, i use a 42 or 45 pilot. but right now, it's 90 degrees at 6 am, then climbs to 100 by 9 am - with some humidity from the monsoon storms.

anyway, i'll try it tonight and let you guys know the results when i'm done.

thanks for the replys

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unfortunately, i don't have an adjustable slow air jet. have you found it to be pretty useful? what symptoms does it help you overcome?

our temps here in AZ get pretty crazy in july and august. the humidity will spike and bikes will run a little funny. it's the price we pay for having 8 months of perfect weather.

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I might suggest turning down your idle RPM when tuning the pilot. Someone might correct me here but my understanding is that it needs to be idleing much lower to ensure you are not pulling fuel from any other circuit but the pilot. If it is too high you might be masking a lean pilot by pulling fuel through another circuit. Maybe Eddie will chime in on this.

I ride in the same heat/humidity conditions but at 5500' elevation in NM. A 42 pilot and even a 45 when it gets cold works best for my 08. I am really surprised your bike even runs with such a lean pilot. I will follow this to see what happens.

My current settings aer 160 main, stock needle 3rd from top and 42 pilot.

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unfortunately, i don't have an adjustable slow air jet. have you found it to be pretty useful? what symptoms does it help you overcome?

our temps here in AZ get pretty crazy in july and august. the humidity will spike and bikes will run a little funny. it's the price we pay for having 8 months of perfect weather.

More adjustability = better performance. You can swap slow air jets too however, adjusting or swapping can be a pain as the airboot must be off to get to it. Slow air jet works in conjunction with the pilot. The difference is as rpms rise as you come off of idle, the effect of the pilot dimishes but the effect of the slow air jet increases (unyil you get to about 1/4 throttle)
I might suggest turning down your idle RPM when tuning the pilot. Someone might correct me here but my understanding is that it needs to be idleing much lower to ensure you are not pulling fuel from any other circuit but the pilot. If it is too high you might be masking a lean pilot by pulling fuel through another circuit. Maybe Eddie will chime in on this.

I ride in the same heat/humidity conditions but at 5500' elevation in NM. A 42 pilot and even a 45 when it gets cold works best for my 08. I am really surprised your bike even runs with such a lean pilot. I will follow this to see what happens.

My current settings aer 160 main, stock needle 3rd from top and 42 pilot.

Correct. You want the idle as low as possible when setting the fuel screw. Slw the engine with idle speed screw, try to make it run faster with the fuel screw, then repeat until you have the engine idling as slow as possible with the idle speed screww while as fast as possible with the fuel screw.

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update:

just tried the 38 pilot and the sucker still ran with the fuel screw all the way in, but i set the tach at 1800 RPM. when i turned the fuel screw in all the way, the RPMs did drop about 150.

i see what you guys are saying about the RPM set too high. i'll try again tomorrow night, and set the RPM around 1500-1600 and try again.

right now i'm too hot and sweaty to do anymore. i need to go wash off in the pool. i'll update again tomorrow.

thanks for all the input.

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I would set it much lower. At least below 1000 RPM. You also need to ride it. If you just blip the throttle on the stand with no load it can act very differently than a quick turn of the throttle under a load.

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we have a resolution.

i started over. changed the pilot to a 42, set the idle down to about 1300 RPM. started the fuel screw at 1.5 turns. warmed it up for 10 minutes. turned to .5 turns, and what do you know....it starts to sputter and die. turned the screw out until the idle smoothed and peaked at about 1.75 turns out. i'm now at 175/42/175 turns.

eddie - i will check the needle jet tomorrow night. thank you for the response.

everyone else - thanks for hanging with me. i appreciate your inputs. my wr450 definitely behaved a little different than this crf450r.

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