Jetting kits

Yamaha

Hey just purchased a 05 450yfz the quad has a killer pipe system and a k&n filter with open air box.I noticed the main jet is a 42 and the pilot jet is a 142.this quad backfires like crazy.Thinking about purchasing a jet kit.Any info as to what type of kit to purchase and what size jets both pilot and main should work for the setup would be helpfull also what works for the needle where the clip should go etc.thanks again for any info you can give me

I think you have your jets backwards, the main jet is always the larger sized jet in the center of the carb. Do yourself a favor and pick up a Dynojet Jet Kit for that thing, I have installed several of those on yfz450's and man what a difference, dead on every install if you follow the directions. I would have the valve adjustment checked as well, that will also create the effect of popping and rough idle, hard to start etc,... and make you think your jetting is off. Also, I would take that K & N filter off and burn it, then run it over for good measure. Put a UNI or Moose foam filter on there unless you want your valve seats destroyed, that K & N lets in tons of dirt.

Edited by Dirt Racer

Thanks dirt racer for the reply.I will order a jet kit and a uni filter off ebay a.s.a.p.My quad starts and runs good except i had to turn fuel mixture screw out 3 1/2 turns to match the quads upgrades.sorry on the mess with the pilot and main i knew it would be one or the other.also thanks for the dynojet recommendation just cause a lot of people were telling me they sucked.But i didn't think they were that bad.Going to ebay now follow up wit y'all later ride it like you stole it :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup:

Thanks dirt racer for the reply.I will order a jet kit and a uni filter off ebay a.s.a.p.My quad starts and runs good except i had to turn fuel mixture screw out 3 1/2 turns to match the quads upgrades.sorry on the mess with the pilot and main i knew it would be one or the other.also thanks for the dynojet recommendation just cause a lot of people were telling me they sucked.But i didn't think they were that bad.Going to ebay now follow up wit y'all later ride it like you stole it :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup:

Right on, you may concider going up one size on that pilot if you have it 3.5 turns out, preferred range of adjustment out on your fuel screw should be around 1.5 to 2 turns out ideally. Let us know how it turns out when you get it dialed in. 

Right on, you may concider going up one size on that pilot if you have it 3.5 turns out, preferred range of adjustment out on your fuel screw should be around 1.5 to 2 turns out ideally. Let us know how it turns out when you get it dialed in. 

thanks dirt racer any suggestions on jet and pilot size.still about a week out from my parts being delivered so plenty of time to think.And i will bring it down on the fuel screw when i get the jet kit in and make the switches.At 2 turns out i have to give it gas for it to start then i have to keep hitting the throttle to keep it running it wont idle for nothing.But at 3 1/2 turns out it starts and idles.Also when i kill the throttle to try a donut or spin out it backtires it wants to die not completly die so i have to rap it out a couple times real quick and then she goes.But i checked out the pilot and main and they were stock i beleive.one was size 42 and the other 142.Dont understand why they would give this quad a beastly pipe system good intake but do no work to the carb to ajust for the intake and pipe system.If i have to guess i bet my bottom dollar they didnt change the needle as well.But i will keep you posted sorry for the long replys when it comes to bikes quads and machines i love this shit and could go on for hours. any who i will keep in touch happy riding.

Jet kits are a waste, buy individual jets from jets r us. I'm especially not a fan of the kit dynojet puts together

Jet kits are a waste, buy individual jets from jets r us. I'm especially not a fan of the kit dynojet puts together

That may be the best bet for you maybe having a little more experience with the whole jetting procedure then the OP but from my experience, especially with the YFZ450, the Dynojet kit works great if you follow the instructions to the T. I have put in well over a dozen of the Dynojet kits in many of my own quads and bikes and every one has been dead on with Zero issues for me. A couple of parts guys at the local Honda, Kawasaki, Suzuki and Yamaha shop are buddies of mine and actually send customers to me to have there bikes and quads jetted rather then there own service guys because they don't test and tune the bikes and get a lot of complaints, I've yet to have even one complaint. I haven't had one yet that I couldn't dial in perfectly. The DynoJet and JD jet kits are what I put in everytime and I highly recommend both.

Edited by Dirt Racer

thanks dirt racer any suggestions on jet and pilot size.still about a week out from my parts being delivered so plenty of time to think.And i will bring it down on the fuel screw when i get the jet kit in and make the switches.At 2 turns out i have to give it gas for it to start then i have to keep hitting the throttle to keep it running it wont idle for nothing.But at 3 1/2 turns out it starts and idles.Also when i kill the throttle to try a donut or spin out it backtires it wants to die not completly die so i have to rap it out a couple times real quick and then she goes.But i checked out the pilot and main and they were stock i beleive.one was size 42 and the other 142.Dont understand why they would give this quad a beastly pipe system good intake but do no work to the carb to ajust for the intake and pipe system.If i have to guess i bet my bottom dollar they didnt change the needle as well.But i will keep you posted sorry for the long replys when it comes to bikes quads and machines i love this shit and could go on for hours. any who i will keep in touch happy riding.

 

 

Is your airbox lid still on or has it been removed? When I have installed the Dynojet kit on the YFZ's I jetted them with the lid on, even with custom high flow exhaust I was able to dial in super crisp jetting with torque all over the place and a perfect idle everytime. Just for reference, the YFZ's I have jetted have been in the 05 to 09 year models, not sure if anything changed on the newer models, but yours actually came with an airbox lid, original owner could have possibly snatched it off without getting the jetting dialed in first.

Edited by Dirt Racer

Is your airbox lid still on or has it been removed? When I have installed the Dynojet kit on the YFZ's I jetted them with the lid on, even with custom high flow exhaust I was able to dial in super crisp jetting with torque all over the place and a perfect idle everytime. Just for reference, the YFZ's I have jetted have been in the 05 to 09 year models, not sure if anything changed on the newer models, but yours actually came with an airbox lid, original owner could have possibly snatched it off without getting the jetting dialed in first.

hey dirt racer my airbox lid is off i purchased it that way but if i knew you can dial it in with the airbox lid on and still get great results i much rather do it that way. just makes sense and sounds a lot safer.also mine is a 2005 model.will be fun dialing it in.I also just found out that the 2004 to 2006 yfz models have a oil system problem.it somehow doesnt get enough oil into the piston area and supposedly yamaha corrected this problem from 2007 models and on.I seen that jtatvs offers a oil upgrade kit for 200 dollars.have you had any problems with these quads in this area in the 2004-2006 models.If so what did you do to correct the problem.or am i just way to over worried.Man seriously this quad hauls ass I love it and want to be pro active in taking care of it.Plus i do not mind wrenching my quads i love it.thanks again for your time i apreciate it.

hey dirt racer my airbox lid is off i purchased it that way but if i knew you can dial it in with the airbox lid on and still get great results i much rather do it that way. just makes sense and sounds a lot safer.also mine is a 2005 model.will be fun dialing it in.I also just found out that the 2004 to 2006 yfz models have a oil system problem.it somehow doesnt get enough oil into the piston area and supposedly yamaha corrected this problem from 2007 models and on.I seen that jtatvs offers a oil upgrade kit for 200 dollars.have you had any problems with these quads in this area in the 2004-2006 models.If so what did you do to correct the problem.or am i just way to over worried.Man seriously this quad hauls ass I love it and want to be pro active in taking care of it.Plus i do not mind wrenching my quads i love it.thanks again for your time i apreciate it.

I haven't heard of any oiling problems with those bikes, I ride with a lot of guys who have YFZ's around those years, watch em drag race nearly every weekend. I ride a lot at a 3000 acre atv park so I get to see lots of quads and talk to lots of people, seems like an isolated thing, remember, only time you really mostly hear about someones quad on the internet is when there is a problem, it may have happened on one in a thousand. I always run no thicker then 10w 40 Castrol 4T oil in my atv's and dirt bikes, been using it for about 10 years now, it warms up and circulates really good. I would dial it in and have a blast on it, Yamaha makes a great motor.

I haven't heard of any oiling problems with those bikes, I ride with a lot of guys who have YFZ's around those years, watch em drag race nearly every weekend. I ride a lot at a 3000 acre atv park so I get to see lots of quads and talk to lots of people, seems like an isolated thing, remember, only time you really mostly hear about someones quad on the internet is when there is a problem, it may have happened on one in a thousand. I always run no thicker then 10w 40 Castrol 4T oil in my atv's and dirt bikes, been using it for about 10 years now, it warms up and circulates really good. I would dial it in and have a blast on it, Yamaha makes a great motor.

thanks DirtRacer man i was kind of in a panic there but i been ripping it up with it and it seems fine.Your right about yamaha making a great motor my cousins has 2 yamahas a blaster and a raptor 660 and he has had it about 8 years and he abuses it but those things still fire up and go like the day he bought it.Of course he does his maintanence but man the way he rides i thought for sure he would've busted something by now.Thanks for the tip on the 10w-40 castrol 4T i was under the impression from honda that you can only run there brand of oil wich of course cost 3 times as much.Still waiting on the jet kit,filter etc.I guess things take longer to get shipped here living in hawaii.I'll be in touch.

aloha dirt racer just got my dyno jet kit in today so i put in the size 48 pilot and worked from size 165 down to 138 on main jet i ajusted the fuel mixture from 1 turn out to 3 turns out on every size.also played with the air box lid on every one.bummer still popping and backfiring.even backfiring from time to time in the air box.sometimes shooting blue flames out the pipe as well.funny it starts good idles perfect but when i hit the throttle quick it boogs or dies out.if i hit it soft its good but when coming down from the rev it pops or shoots blue flams out the pipe.any suggestions i would greatly apreciate it :banghead:

I just bought an '04 YFZ 450 with the air box lid removed, a full LRD exhaust, and unfortunately, a K&N air filter. I'm at an altitude of around 3300'.....what jet kit should I go with and how should the carb be set?

Right now, when I let off the throttle, the exhaust makes a popping sound.

Did you change over to the Dynojet needle? The supplied Dynojet main jets will not work with the stock needle, the DJ needle is tapered specifically for the DJ main jets. It recommends using a DJ132 main jet supplied in the kit with c-clip on the forth groove from the top of the needle with airbox lid on and aftermarket exhaust. If you are going to go with no air box lid then the second set of intstructions will apply.

 

STAGE ONE INSTRUCTIONS Q421.002 (04 thru 05 YFZ450 model years)

NOTE: This kit can be installed without completely removing the carburetor. 
1. Remove the top of the carb. Remove the allen screw (Fig.A) and pull out the stock needle and spacers, noting order of assembly.                
2.  Install the Dynojet needle on groove #4 from the top. Install the small Dynojet washer above the e-clip.   
3.  Remove the stock main jet.  NOTE: The main jet can be accessed by removing the nut from the bottom of the float bowl (Fig. B).  Install the Dynojet main jet adapter (DJA001) into the emulsion tube first. Install the Dynojet main jet provided. If you are running the stock exhaust, install the DJ128 for under 3000 ft.  Install the DJ124 main jet from 3000-6000 ft. Install the DJ120 main jet if above 6000 ft.  If you are running an aftermarket exhaust or slip-on with high flowing baffle, ***use the DJ132 main jet***. Install the DJ128 main jet from 3000-6000 ft.  Install the DJ124 main jet if above 6000 ft.  Be sure that the jet you are changing is the main jet. 
4. Remove the stock pilot jet and replace with the Dynojet pilot jet provided (DPJM048).
5.  Locate the fuel mixture screw (Fig. B).  Carefully turn the mixture screw clockwise until lightly seated, then back out 1 turn.

 

*** If you are jetting with airbox lid off and Dynojet jet kit with aftermarket hi flow exhaust, then here are the stage 2 directions with aftermarket exhaust,...

 

 1. Remove the air box lid.
2. Remove the top of the carb. Remove the allen screw (Fig.A) and pull out the stock needle and spacers, noting order of assembly. (Very Important)               
3.  Install the Dynojet needle on groove #5 from the top. Install the small Dynojet washer above the e-clip.   
4.  Remove the stock main jet.  NOTE: The main jet can be accessed by removing the nut from the bottom of the float bowl (Fig. B).  Install the Dynojet main jet adapter (DJA001) into the emulsion tube first. Install the Dynojet main jet provided.  If you are running the stock exhaust, install the DJ140 for under 3000 ft.  Install the DJ136 main jet from 3000-6000 ft. Install the DJ132 main jet if above 6000 ft.  If you are running an aftermarket exhaust or slip-on with high flowing baffle,*** use the DJ144 main jet.***  Install the DJ140 main jet from 3000-6000 ft.  Install the DJ136 main jet if above 6000 ft.  Be sure that the jet you are changing is the main jet. 
5. Remove the stock pilot jet and replace with the Dynojet pilot jet provided (DPJM048).
6.  Locate the fuel mixture screw (Fig. B).  Carefully turn the mixture screw clockwise until lightly seated, then back out 1.5 turns.
 

 

aloha dirt racer just got my dyno jet kit in today so i put in the size 48 pilot and worked from size 165 down to 138 on main jet i ajusted the fuel mixture from 1 turn out to 3 turns out on every size.also played with the air box lid on every one.bummer still popping and backfiring.even backfiring from time to time in the air box.sometimes shooting blue flames out the pipe as well.funny it starts good idles perfect but when i hit the throttle quick it boogs or dies out.if i hit it soft its good but when coming down from the rev it pops or shoots blue flams out the pipe.any suggestions i would greatly apreciate it :banghead:

 

Edited by Dirt Racer

They covered the jets above. The best air system for the yfz is by far the FCI (fuel customs intake). Also check to see if your quad has the oil mod if not I suggest getting that done ASAP as it helps lube the bottom end Yamaha made this a factory mod as of 07 being that is is a much needed mod for 06-.

09 yfz450r

09 kx450f

Edited by dirtsurfer614

I just noticed that the oil mod was covered as well. My apologies!

09 yfz450r

09 kx450f

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