another 08 Dr.D jetting issue, please help.


13 replies to this topic
  • erickdj

Posted January 10, 2008 - 10:23 PM

#1

Let me just start by saying that I DID search the forum, read the stickies, and did my homework in general about the subject. However, even after reading all of that I'm still having issues. Here's a little background info:

08 yz450f
Elevation 500-2000 ft.
temperature 50*
Dr.D full system

Just after I bought my bike I replaced the exhaust with an 06 stock silencer and a pro-circuit header. I jetted the bike with a 48 pilot, 1.5 turns on fuel screw, stock needle 3rd position(stock), and 162 main. It was running good with that combination. No backfiring, overheating, or excessively red header. It was pretty good with those settings.

Now I have a full Dr.D system, with the above mentioned settings the bike would get very hot and it would shoot some flames from the muffler. I changed the settings to 45 pilot, 1 3/4 fuel screw, needle 4th position, and same 162 main. Now the bike is overheating pretty bad and drops coolant to the floor, it also gets an excessively red header and shoots flames with more than 1/2 throttle. I've read several threads/posts from other with the same bike/pipe and my settings don't seem that far off from everyone else. Any ideas?

  • yz250o2

Posted January 10, 2008 - 10:54 PM

#2

Man Ill tell you what... I bought a White Brothers aluminum pro full system...and I still can't get that thing to jet . I resent the way it runs. Backfire and pop expecially when weather is cold. Theory says its running to lean but shit. Think the Accel pump needs to be messed with. Or the float height? New Richer needle?
Main-165
Pilot-48
Clip#5 from top
Fuel scew-who knows it doesn't seem to help. think 2 1/2

  • yamahacrazy_310

Posted January 11, 2008 - 12:38 AM

#3

I have the FMF 4.1 and I'm running a 48 pilot with a 170 main. And the bike runs great. So maybe try a 170 main. But my bike is an 06 so I don't know if that would effect anything.

  • Ga426owner

Posted January 11, 2008 - 06:04 AM

#4

Let me just start by saying that I DID search the forum, read the stickies, and did my homework in general about the subject. However, even after reading all of that I'm still having issues. Here's a little background info:

08 yz450f
Elevation 500-2000 ft.
temperature 50*
Dr.D full system

Just after I bought my bike I replaced the exhaust with an 06 stock silencer and a pro-circuit header. I jetted the bike with a 48 pilot, 1.5 turns on fuel screw, stock needle 3rd position(stock), and 162 main. It was running good with that combination. No backfiring, overheating, or excessively red header. It was pretty good with those settings.

Now I have a full Dr.D system, with the above mentioned settings the bike would get very hot and it would shoot some flames from the muffler. I changed the settings to 45 pilot, 1 3/4 fuel screw, needle 4th position, and same 162 main. Now the bike is overheating pretty bad and drops coolant to the floor, it also gets an excessively red header and shoots flames with more than 1/2 throttle. I've read several threads/posts from other with the same bike/pipe and my settings don't seem that far off from everyone else. Any ideas?


you are too lean on the mj - try 168/170 clip on 3 or 4
maybe a tad rich on the pj - try a 45
what temp?
please tell me you are not just leaving the bike still - this will cause the red pipe and overflow - it must be ridden

  • Ga426owner

Posted January 11, 2008 - 06:10 AM

#5

Man Ill tell you what... I bought a White Brothers aluminum pro full system...and I still can't get that thing to jet . I resent the way it runs. Backfire and pop expecially when weather is cold. Theory says its running to lean but shit. Think the Accel pump needs to be messed with. Or the float height? New Richer needle?
Main-165
Pilot-48
Clip#5 from top
Fuel scew-who knows it doesn't seem to help. think 2 1/2


If you resent it - rejet it :busted:
you are close to sea level correct?Richen it
1 - 500ft?
48 -52 pj
168 - 172 mj depending on temps
3 clip position
2 turns out on fuel screw - it does make a difference
do not mess with AC pump/float


Come on guys rejetting is frustrating until you find the right setting. Then write them down and use for baseline.....:banghead:

BTW it is not WB fault or anyones elses...it is the nature of carbs and maximizing air to fuel.......

  • Wes Woodin

Posted January 11, 2008 - 06:26 AM

#6

Let me just start by saying that I DID search the forum, read the stickies, and did my homework in general about the subject. However, even after reading all of that I'm still having issues. Here's a little background info:

08 yz450f
Elevation 500-2000 ft.
temperature 50*
Dr.D full system

Just after I bought my bike I replaced the exhaust with an 06 stock silencer and a pro-circuit header. I jetted the bike with a 48 pilot, 1.5 turns on fuel screw, stock needle 3rd position(stock), and 162 main. It was running good with that combination. No backfiring, overheating, or excessively red header. It was pretty good with those settings.

Now I have a full Dr.D system, with the above mentioned settings the bike would get very hot and it would shoot some flames from the muffler. I changed the settings to 45 pilot, 1 3/4 fuel screw, needle 4th position, and same 162 main. Now the bike is overheating pretty bad and drops coolant to the floor, it also gets an excessively red header and shoots flames with more than 1/2 throttle. I've read several threads/posts from other with the same bike/pipe and my settings don't seem that far off from everyone else. Any ideas?

I'm running a TI/TI Dr.D pipe. I'm at 750 ft elevation and run a 168 main, stock needle position, 52 pilot with powerbowl. Now before the powerbowl I was at a 48 pilot and it ran good for me. I would go with a 50 pilot. A powerbowl will make all the difference and eliminate the bog too. Just my opinion.

  • erickdj

Posted January 11, 2008 - 07:30 AM

#7

Thanks for all the replies guys, I wasn't expecting this many overnight. I'm supposed to go riding tomorrow and I really want to get this sorted out, maybe I'll have to mess with it at the riding area. Anyway, I'm thinking I may have some air leaking between the header and the midpipe, but since this is a slip-on there's nothing I can do to seal it, or is there something I can do? I'll bump the jetting up again to see what happens.

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  • grayracer513

Posted January 11, 2008 - 07:43 AM

#8

Let's start with your idle circuit first. Your fuel screw settings seem a little closed up to me. At low altitude and temps, you might need as much as a 48 pilot. Set the fuel screw by first warming up the bike to normal op temps, and setting the idle to a faster than normal speed. Turn the screw in until the idle drops or stumbles, then back out until it peaks out. That is, the idle speed will rise as the screw is backed out, but at some point, it should stop rising, and that is where it should be set. This should happen somewhere between 1 1/2 and 2 3/4 turns out from fully seated. If it sets at 1 1/4 or less, the pilot jet is too large. If it sets at 3 turns or more, the jet is too small.

Once you've done that, you need to get the main jet right. During this phase, set the needle in 4; no more than 3, or 5. Run the bike at full throttle in the heart of the rev range. If the the bike misses erratically and pops under a load, and there is no fault with the ignition of any kind, you can guess that it's lean. Go richer in 2 size steps until that stops, then work around that size to find one that runs the best. BTW, reading plugs only works if you make a full throttle run AND you chop the throttle and kill the engine at the end of the run, AND you're using leaded fuel. Unleaded fuel just doesn't put any color on the plug except all the way down where the insulator meets the plug shell.

Another approach is to go lean until it misses, then rich in big steps until the power drops off or it starts blubbering like the choke is on. The right jet will be roughly the size that's 1/3 of the way in between those from the leanest to the richest size in that test. The best way is a gas analyzer.

Once you have the pilot and main down, you can focus on how it runs in between. The tuning guide in your manual is actually pretty good once you get past the choppy English, and there is a lot of info there about needle selection.

There is also the Jetting Forum here on TT, and you might look at JD Jetting kits, which are available with excellent customer service. They can usually help you work through any problems you have, if you give them accurate feedback.

  • Norman

Posted January 11, 2008 - 08:49 AM

#9

I never could get mine lined out w/the Dr D full system either, I ordered a JD jet kit, it starts alot easier and seems to run cleaner on the stand, Im going riding tomorrow I will let you know my thoughts.

  • yamaha246

Posted January 11, 2008 - 02:27 PM

#10

i got the full system dr.d on my 08 and i had 1 prob and thats when i first put it on but after i rode it no pop no bog runs great just ride it

  • erickdj

Posted January 11, 2008 - 04:10 PM

#11

I just thought I'd tell you guys that I bought an NFPP needle during my lunch break from work. It's the same needle I'm using on my WR450, it eliminated some jetting issues I had with it last year. I was told by the guys at the yamaha dealer that the NFPP needle is one of the most common needles they use there to jet yz450's, and since it did help with my wr450 I think they may be on to something. The other thing is that one of their service techs there has a dyno tuning service he runs on the side, so he might have shared some info there with the rest of the techs. I'll install it tomorrow and let you guys know what happens.

  • todds924

Posted January 11, 2008 - 05:05 PM

#12

Man Ill tell you what... I bought a White Brothers aluminum pro full system...and I still can't get that thing to jet . I resent the way it runs. Backfire and pop expecially when weather is cold. Theory says its running to lean but shit. Think the Accel pump needs to be messed with. Or the float height? New Richer needle?
Main-165
Pilot-48
Clip#5 from top
Fuel scew-who knows it doesn't seem to help. think 2 1/2


I finally got my 08 dialed in with a full pro circuit TI-4. I changed the stock 45 pilot to a 42...switched to a NFLP needle 5th groove...2 turns on the mixture screw and a 160 main jet. oh yeah....and a 50 leak jet from a 55.

  • grayracer513

Posted January 11, 2008 - 05:12 PM

#13

...switched to a NFLP needle 5th groove...

So, that worked, huh?

  • Wes Woodin

Posted January 11, 2008 - 06:31 PM

#14

I finally got my 08 dialed in with a full pro circuit TI-4. I changed the stock 45 pilot to a 42...switched to a NFLP needle 5th groove...2 turns on the mixture screw and a 160 main jet. oh yeah....and a 50 leak jet from a 55.

You running at 800-1000 ft?





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