45 vs 48 Pilot - Question


22 replies to this topic
  • Kmorris

Posted August 24, 2006 - 10:55 AM

#1

Greetings,

With a WR450 F - I live about at about 600 feet above sea level. I have all the free mods including a YZ muffler.

I'm running a 170 main jet. A JD Jetting Blue needle at number 3.

I had noticed that my air screw (Zip-TY) was best adjusted to almost 4 turns open for highest idle - and the cleanest 1/4 turn of the throttle.

This seemed like the classic symptom of too small a pilot jet. I also noticed that just about everyone with a 2005 WR450 at my temp and alt are running a 48 pilot.

After installing a new 48 pilot I now notice that I can turn my air screw in all the way and I still have a nice idle and smooth running motor.

Unless I'm missing something that 48 is just to large. Do others run 46's or 47's? I've not seen this.

Thanks

  • tenyart

Posted August 24, 2006 - 12:35 PM

#2

Sounds like you may need to return back to the 45 PJ. I don't completely understand the correlation between pilot jets and idle circuit, but if you can completely turn it in and the engine doesn't stall or run rough, then you are idling through the needle and jet. I have an 06 WR450 with a 48 PJ and have it cranked out pretty far, farther than others have remarked. Enjoy your ride!
Terry

  • clark4131

Posted August 24, 2006 - 02:02 PM

#3

When you set your screw, the bike needs to be completely warmed up which requires you to ride it about 20 minutes, sitting on the stand doesn't count. Once it's warmed up, use the idle screw to set the high idle (1900+), then tune the screw. Pilots go 42, 45, 48, 50 that I've seen. SudCo may have something in between.

Lastly, you may want to put in the Red needle with a 48 for the warmer weather. I switch over somewhere around 60 degrees...SC

  • Kmorris

Posted August 24, 2006 - 02:47 PM

#4

I did warm up the bike a bit. But only a bit not a ride. So I agree to get 'ur warm and try again.

I have a great internal debate going on about red vs. blue. I do want to change only one thing at a time. So I'm going to work on the pilot circuit tonight. Thanks for the heads up on the high throttle. With a garage full of tools I do not have an induction tach. but I'm pretty comfortable with knowing what 1900 sounds like and will adjust my fuel screw after I KNOW I've a warm engine. I have seen the difference between a cold and warm engine when tuning.

I am also experience a high end bog. I'm running a 170 main and was going to try a 168 after I got my pilot circuit correct. We are heading into colder weather here in the Seattle area so I was thinking about leaving the 170 alone and working on the needle - like red number 5 first.

Since Red is a little leaner I'm thinking the Red might help with leaning out the mid to upper a bit to reduce that small bog. Does this make sense?

Thanks all!

  • tony1970

Posted August 24, 2006 - 03:24 PM

#5

You and I are running about the same elevation and I found that in the winter my bike tunes better at idle with the 48PJ, and this summer the 45PJ worked the best. Also in the winter I could not even run the blue needle without some type of studder from a rich condition. I ended up running the red needle all winter and lowering it one notch for the summer and it is running great. I also run the 168 main all year, but I could go back down to the 165 on the hot days. A 170 may be too rich for you. Each bike is different, so check out the jetting sticky if you have not already to see if someone in your general area has put down what jetting works for them. Good luck.

  • Kmorris

Posted August 24, 2006 - 04:53 PM

#6

Thanks Tony,

I went out tonight and the 48 pilot is too big. Fully warmed up there is not much difference between closed and 1/2 open. So the 45 goes back tomorrow night.

Then I'm going to try the red needle. I've got a stumble at 1/4 throttle and a little stumble at full - like hitting the rev limiter too soon.

After the red needle I'll be looking at a 168 main.

I don't mind experimenting and I'll hit on it soon. I believe you're right about bikes being different.

  • tony1970

Posted August 24, 2006 - 05:09 PM

#7

The red needle at 4 or 5 should get rid of the stumble.

  • OneToGo

Posted August 25, 2006 - 06:12 PM

#8

Agree - try the RED at #5 /4 for the stumble.
My Advice,
1. Do the MJ first and test - like others I suggest 168 (the MJ does affect some fuel flow at lower throttle settings).
2. Then I would set the pilot - I feel you should be OK with a #48 provided you have a freer exhaust and open airbox (free mods). Going down to 168 on the main will afect the selection of pilot to a small degree. Fuel screww should be around 1.5 out. See jettting sticky or search for Indy/clark4131 data.
3. THEN, set the needle, this also takes more time than the MJ/Pilot so can be done last and in isolation.
4. You may want to look at ACV mods to clean up the lower end - it worked for me, see: www.thumperfaq.com
Fine tune and write down or print out the data.
IMHO the blue needle is too rich above around 20C/68F - unless you have a race bike..
:thumbsup:

  • spuddy36

Posted August 26, 2006 - 04:59 AM

#9

when your bike is fully warmed up if you do the test and you have to turn the air screw more than 2.5 turns from cloesed to get the best running then you need to drop down a size on the jet same as if you only need to turn screw out 1 turn then you need a bigger pilot jet

  • bg10459

Posted August 26, 2006 - 05:59 AM

#10

when your bike is fully warmed up if you do the test and you have to turn the air screw more than 2.5 turns from cloesed to get the best running then you need to drop down a size on the jet same as if you only need to turn screw out 1 turn then you need a bigger pilot jet

This is 100% incorrect for a 4 stroke. These bikes have a fuel screw, not an air screw like a 2 stroke. It meters fuel, not air. Turning it in leans the pilot circuit while turning it out richens it; opposite a 2 stroke air screw. If you're less than one turn you need a smaller pilot and more than 2.5 indicates a richer pilot is needed.

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  • toyota_mdt_tech

Posted August 26, 2006 - 11:14 AM

#11

... I have an 06 WR450 with a 48 PJ and have it cranked out pretty far, farther than others have remarked. Enjoy your ride!
Terry

Careful with it being out too far, you might find it has left the carb one day and ended up in the middle of a trail somewhere. If its out more than 2 turns or so, you could be in trouble or risk of it falling out. I suppose you can stretch the spring a bit.

  • Kmorris

Posted August 26, 2006 - 01:36 PM

#12

I would like to thank everyone who responded to my post.

Here is what I ended up doing (2005 WR450).
0-1000
75-80 degrees

168 main from 170
45 pilot from 48
Red - notch #5 from Blue notch #3

Idles nice - clean 1/4 throttle, quick to rev all the way up top. I lost my mid range stumble and studder at the top. I do believe that I may have hit on a good combination for the present conditions. I'm pretty sure I'm going all the way to the rev limiter because before the top end stumble was between 3/4 and full and now I can reach full throttle and then I think I'm hitting the limiter.

  • tony1970

Posted August 26, 2006 - 03:13 PM

#13

Good to hear it worked out. Post your settings on the jetting sticky and update as needed. :thumbsup:

  • toyota_mdt_tech

Posted August 26, 2006 - 06:31 PM

#14

Thanks Tony,

I went out tonight and the 48 pilot is too big. Fully warmed up there is not much difference between closed and 1/2 open. So the 45 goes back tomorrow night.

Then I'm going to try the red needle. I've got a stumble at 1/4 throttle and a little stumble at full - like hitting the rev limiter too soon.

After the red needle I'll be looking at a 168 main.

I don't mind experimenting and I'll hit on it soon. I believe you're right about bikes being different.


Keith, I live close to your area and started out with the 170, blue needle, #3. (this was the JD recommened start area for my altitude/air) Had no flat spots, but consuming way too much fuel (range was shortened quite a bit, but it didnt belch black smoke...) and installed the 168 main, and now running the 165. Still using blue needle. But I would like to try the red one. It still runs great, no hiccups and the fuel screw leans out at around 1.5 turns out. Not sure which pilot I have, but it appears to be perfect. Let me know what you end up. I'm looking for good performance at about moderate temps. If it gets super hot or super cold, I can usually just "ride" around it. Not racing anyway and dont want to fine tune everytime my temps changes. Just looking for a good setting overall in the range I naormally ride in.
:thumbsup:

  • Kmorris

Posted August 27, 2006 - 09:56 AM

#15

I noticed when I started with the JD recommendation my gas mileage also went way down. When I called JD they were pretty insistent that the 45 pilot (JD's just across the water from where I live) was what I needed.

If I hadn't experienced such a stumble or studder at mid/high ranges I would have left the carb alone. Maybe the richer recommendation is best and safest but it was obvious that I needed to lean out parts of carb to get the bike to run right.

Anyways my hope now is that I've arrived at a good summer combination. And as you know we'll be getting colder soon. My guess is I'll keep and eye on the main jet and raise the needle if need be.

My racing and thus weekly jetting exercises are a thing of the past for me and I'd love a set it and forget it scenario too!

  • 06WR450FSM

Posted August 29, 2006 - 11:03 AM

#16

I would like to thank everyone who responded to my post.

Here is what I ended up doing (2005 WR450).
0-1000
75-80 degrees

168 main from 170
45 pilot from 48
Red - notch #5 from Blue notch #3


How many turns out is your fuel screw now? (Since that is what initiated this thread) If it is now less than 4 turns, what helped? The final changes from your first post to now are the 168 from 170 and the R#5 from B#3. Since both of these changes are leaner, wouldn't that make the fuel screw have to be even farther out, or am I missing something? :thumbsup:

I am at 5500 feet and have the same fuel screw issue (many turns out) with the stock jetting 165 main, 45 pilot, stock needle (will install GYTR needle when I know what the clip position should be and if I should change other jets). I was planning on switching to the 48 pilot, but now see that 45 works better for many people at lower altitudes than me. My throttle response seems excellent throughout the rpm range. I have all free mods, AIS removed, ACV disabled, PMB insert.

Before installing the fuel screw, the bike was rough at low rpm and would easily stall with the stock screw at 1.5 turns. Vastly better with MSR at 3.5+ turns. Are there any longterm problems with running the screw several turns out? (safety wired so it doesn't fall out)

  • Kmorris

Posted August 29, 2006 - 01:15 PM

#17

Greetings,

I've learned the pilot circuit controls idle and just off idle - in relation to throttle opening. So here's a bit of my experiences with the work. All the circuits overlap a bit but my first condition was with the fuel screw - with a 45 pilot jet I had the fuel screw out about 4 turns.

I then installed a 48 pilot and discovered that even with the fuel screw completely turned in the bike idled and ran fine. No difference between closed and 1 1/2 turns.

Since I have been experiencing a mid AND top end sputter or bog I decided to start over with a new base line.

Main Jet - 168 from 170 - to combat the top end sputter - done
Pilot Jet - 45 from 48 - to lean the pilot circuit so the fuel screw would be in range to affect change - done

Needle - Blue #3 to Red #5 - to attempt to address mid range stumble - done.

Magically the COMBINATION, in my opinion, changed the dynamics to the point where the 45 pilot seems to allow for proper fuel screw adjustably.

I really haven't played too much with the fuel screw yet after these last changes but I'm currently at 1 1/2 and the bike idles great and is very crisp off idle. I'll report back final fuel screw settings if anyone's interested.

My next step is a new plug and a high speed plug test - to make sure I'm not too lean. I expect this winter to go up to a 170 main, or at least that's what I'm thinking today.

And of course these comments are the result of actual experiments in my climate in my case. I'm a little surprised the 170 main, 48 pilot, and blue #3 ran as bad as it did for the numbers seem right and are commonly recommended. But actually changing the jets and needle proved to be more valuable than theory.

  • 06WR450FSM

Posted August 29, 2006 - 03:55 PM

#18

Thanks for taking the time to explain Keith :thumbsup:

Jetting is an art...

  • 06WR450FSM

Posted August 29, 2006 - 06:06 PM

#19

Thanks for taking the time to explain Keith :thumbsup:

Jetting is an art...

A confusing art. I am still tryibg to figure this out.

Keith's bike was too lean with a 45 pilot since the fuel screw needed to be several turns out. The mid and top end were to rich with the 170 main and the needle setting. When the pilot was increased to a 48, that was too rich also.

But when the main and needle were both leaned, and the pilot was returned to the previously too-lean 45, all is now good with the fuel screw. Huh?? :applause:

  • Kmorris

Posted August 30, 2006 - 06:25 AM

#20

One very good question. Maybe an expert will chime in but I stopped scratching my head when I remembered (from my past) how little things affect little carburetors. Maybe I had a bad air box to carb or cart to manifold seal (?). Maybe I had a piece of dirt in a jet somewhere. Or those 5 beers before I started (only kidding)!

That's why I made the comment about experimenting vs theory. There may have been something wrong with my first experiments.

:thumbsup:




 
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