[SomeGuyFromCali]

So I have a 2006 YFZ450 and was hoping one of you oh wise and knowledgable YFZ450 experts out there might be able to give me some jetting tips.

She will start right up for me and idles great. Tons of power and seems fine if I accelerate relatively fast and keep the RPMs up but if I really romp the gas it will either stall and backfire or stall, sputter, and then die completely. :disgust

I have been scouring through hundreds of these jetting threads trying to find someone with my same basic setup but not sure I have found one so here is a list of the relatively minor mods I am using

Currently installed:

- Removed stock airbox lid
- Removed stock screen/plug out of my stock exhaust
- Installed zip tie on throttle assemble
- Installed Phoenix screen type spark arrestor
- Installed 168 main jet
- Installed 45 pilot
- Installed Tusk fuel mixture screw and set at 2 turns out
- Stock leak jet (unsure of size)
- Stock needle (non-adjustable type)

On order (and arriving tomorrow):
+ Keihin FCR Jet Kit (comes with NCVQ needle, 45 48 50 52 pilots, and 160 162 165 168 170 172 175 mains)
+ #35 Leak Jet (4TJ-1494F-01-00)

Any suggestion on which way to go with the pilot, main, and which notch to put the new needle on? Any other suggestions in general?

My current plan is to install the 35 leak jet and go with the 3rd notch from the top on the needle, upsize to a 48 pilot jet, and stay with the 165 main jet for now.

My reasoning for this is that I feel like it is not getting enough gas on the low to mid end and once it catches up does fine in the upper end when the RPMs are high. I understand this to be a problem with the needle and/or pilot jet as opposed to the main.

On the other hand, I wonder if it could also be from too much gas causing a flooding situation when I romp on the gas too hard?

Thanks for reading - your time is appreciated. :clap:

 

[SeniorTaco]

Alrigh. I would for sure first off do the cam mod if not done... Keep box lid off, try the 45 pilot, ncvq on second clip from the top, or flat fat side. A 160 main should be more than enough with that needle and your mods. Just given the above and your current setings you are for sure fat up top. Meaning your main is atleast two sizes to big. Even more so if your way above sealevel.

 

[mixxer]

for the love gawd.... get rid of the stock exhaust with the bafflle pulled....

that adds zero power...lots of noise....and screws up your jetting.....

buy a hmf slip on for the stock headpipe and you will be so happy with the change , you wont sleep for a week

 

[SomeGuyFromCali]

Alrigh. I would for sure first off do the cam mod if not done... Keep box lid off, try the 45 pilot, ncvq on second clip from the top, or flat fat side. A 160 main should be more than enough with that needle and your mods. Just given the above and your current setings you are for sure fat up top. Meaning your main is atleast two sizes to big. Even more so if your way above sealevel.

I appreciate the tip SeniorTaco, I will read about the cam mod and go with your jetting suggestions to start.

 

[SomeGuyFromCali]

for the love gawd.... get rid of the stock exhaust with the bafflle pulled....

that adds zero power...lots of noise....and screws up your jetting.....

buy a hmf slip on for the stock headpipe and you will be so happy with the change , you wont sleep for a week

The new slip-on sounds good, believe me I want to. Maybe next paycheck...
I looked at the HMFs and they do look mighty tempting... I have always used the FMF (Powercore) pipes in the past for upgrading.

I figured running the little Phoenix sparky for now with the stock muffler was better than using the pea-shooter they ship them with from Yamaha until I could afford a real slip-on. I can't believe the way they cork these things up from the factory.

 

[SeniorTaco]

Yes they do cork them up hard from the factory. You should be very close with the jetting That I recommended.

 

[ccole3]

I agree with seniortaco. How far above sea level are you?

 

[SomeGuyFromCali]

Sorry I left that part out. :lol

My garage where I work on my quad is in the valley at about 750 ft elevation but I often ride 3000 ft or higher as most of the trails around here are hill climbs that lead up into the mountains. I will occasionally ride up to around 4000-5000 ft but mainly my riding is done at about 1000-3000 ft.

I would like to try and target it to run perfectly at about 1000 ft and be able to just fine tune the mix with the screw but based on Mr Taco's suggestion right now it is far too rich for the screw to even help with that 168 main and the minor mods I am using right now.

New parts are all here now and I got the swamp cooler all setup in the shop (it is 106 here today).

Let's do this! 8)

 

[SomeGuyFromCali]

So in digging through the boxes i had on my bench in my shop to try and clear off a spot to work on this project I came across a white paper from Phoenix Performance (the guys who make the aftermarket spark arrestor I am using with the stock exhaust). I must have missed it when I was unpacking the sparky to install it because I was so excited. :clap

Phoenix Performance's recommendation is stock need clip at 4 from top (GYTR needle at 3), a 165 main, 45 pilot and 2-3 turns out on the screw.

Is the NCVQ needle that comes with XCBob's FCR jet kit considered the stock needle, a GYTR needle or something completely different?

Not that I doubt SeniorTaco's wise and knowledgeable advice, but I am going to start with the 165 and if it still seems rich work my way down to the 160 since I'd rather error on the rich side than the lean side. I also have a 162 I can try out. I do appreciate the advice, this at least narrows it down to a range I can work with.

I have never read about the cam mod everyone seems to love but I will check that out. Is the primary reason for a horsepower gain or does it make the bike more reliable or both? I'm trying to keep this bike relatively tame compared to some of the race quads I have seen on here since I mainly just ride the trails with my buddies and it already has more than enough power to keep me grinning ear to ear. :lol

 

[SomeGuyFromCali]

Something doesn't look right here. I am no mechanic but what the &%$* is all that black chunky stuff? I'm guessing that little bit of carb cleaner I used destroyed the rubber diaphram under the bowl?

 

[SeniorTaco]

Bro your accelerator pump diaphram is shot... Time to replace

 

[SomeGuyFromCali]

Bro your accelerator pump diaphram is shot... Time to replace

Looking at the parts diagram for my carb I saw there was another rubber diaphram up near the idle adjustment area and luckily it looks okay. :|

Just checked online and Yamaha wants at least a 20 dollar bill for half an inch of rubber.

Mr. Repairo from Amazon wants $22.71 but holy cow $11.50 to ship?

Gonna go check XCBob's parts and see if he has one he can sell me.

For anyone else reading this in the same situation my 2006 accelerator pump diaphram is Yamaha part # 5JG-14940-17-00

 

[SomeGuyFromCali]

Local dealer wants $28.50 and would take them two days to get it.

XCBob's price is $24.04 before the 10% discount and he wants $9 for shipping but even though he ships really fast he is over on the East coast and I am in California so I would be looking at 2-3 days anyhow.

YamahaSportsplaza in Oregon only wants $19.80 but $12.94 to ship via UPS and estimated arrival would be over a week from now.

 

[SomeGuyFromCali]

Well with shipping the local Yamaha shop ended up being the cheapest plus they offered me 10% off since I bought the quad from them so I had them order me up an accelerator pump diaphram but it won't be here until 8/15 so check back then for the conclusion to this story ladies and gentlemen. :blah

I guess this gives me plenty of time to go through all the jets and orifices and look for pieces of my old diaphram. :bawl

 

[SomeGuyFromCali]

New diaphram came today. The local Yamaha dealer came through as promised but I didn't get to go pick it up until today.

Everything is still taken apart so all I have to do tonight is insert the new diaphram, adjustable needle, and new jets then button her up and see how she runs. Stay tuned! :blah

 

[SomeGuyFromCali]

Here is a picture of the replacement accelerator pump diaphragm in all it's glory. Cost me $26.69 out the door.

 

[SomeGuyFromCali]

Houston, we have liftoff

Whooo hooo :clap

I replaced the messed up accelerator pump diaphragm, installed a 165 main jet, kept my 45 pilot jet, installed the new 35 leak jet, installed and set the NCVQ needle on the fourth notch from the top, and set the Tusk fuel mix screw set to about 2 and a half. I also double checked that my zip tie mod was still in place.

Fired right up and man did it ever feel better when I romped on the gas.
It was just past 10pm here and I didn't want to piss off the neighbors too much so I only let it run for a few minutes but MAN did it feel better. There is ZERO hesitation when you romp on it.

So to recap the answer to my problem was:

Replace shredded accelerator pump diaphragm located under bowl.

• 165 main jet
• 45 pilot jet
• 35 leak jet
• 4th clip down on NCVQ needle
• 2.5 turns out on a Tusk fuel screw
• zip-tie mode in place

NO BOG!!! Whooo hoooo!

:clap :clap :clap :clap :clap

 

[SomeGuyFromCali]

Total cost to fix my bog

Replacement Yamaha Rubber Accelerator Pump Diaphragm = $26.69 shipped via local Yamaha dealer

Phoenix Spark Arrestor Insert for Stock YFZ450 Exhaust = $37.98 shipped via Amazon

XCBob Jet kit with Main Jets, Pilot Jets, and NCVQ Needle = $55.64 shipped via eBay

35 Leak Jet = $18.12 shipped via Amazon

Tusk air/fuel mixture screw = $11.99 picked up at local Cycle Gear

Zip-tie = $0.02 found in garage

Grand total to fix my bog = $150.44

 

[CookieMonster]

Jetting for my setup... ?

Bro your accelerator pump diaphram is shot... Time to replace

I realize this thread is years old, but thought I'd ask Mr Taco is my jetting sounds correct for my mods...
ESR intake
Dasa full exhaust
Cam mod
Zip tie mod
TPS mod
170 main
48 pilot
Plugged off leak jet
NCQV on 3rd clip
A/F screw 2 1/4 turns out
Currently at sea level
Ride trails at 1000-1500ft and dunes at sea level

Definitely appreciate ur input

 

[pmsracer]

07
full hmf exh
pro flo filter
wiesco piston from duncan
52 pilot
40 leak
180 main
bad hesitation , bog and or die all together when chopped
runs great on top