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YFZ450 Jetting


Randog
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For now i wouldnt worry about the popping on decel.If going up on the main doesnt fix this cutting out you really need to think about the stator.I wasted alot of time messing with my carb and the stator fixed it.To me a 175 seems good enough for your mods.You can try the 178 but to me it sounds like something else.Hopefully it still has the stock flywheel.Like I said before if it has a Trailtech -4oz or -6oz that will cause the same thing.Ive personally never had my YFZ cutout like you describe because of a slightly lean main jet.Not saying it cant happen but just my experiences.

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ok when jetting always remember this:

idle to1/4 throttle = pilot jet

1/4 to 3/4 = needle

3/4 to full throttle = main jet

so cutting out on top end (if full throttle) go up on the main

and popping on decel up the pilot jet 1 or 2

what's your idle screw set at?

Great info on the jetting. :lol:

I got the idle screw out 3 turns.

For now i wouldnt worry about the popping on decel.If going up on the main doesnt fix this cutting out you really need to think about the stator.I wasted alot of time messing with my carb and the stator fixed it.To me a 175 seems good enough for your mods.You can try the 178 but to me it sounds like something else.Hopefully it still has the stock flywheel.Like I said before if it has a Trailtech -4oz or -6oz that will cause the same thing.Ive personally never had my YFZ cutout like you describe because of a slightly lean main jet.Not saying it cant happen but just my experiences.

Also Great info. as usual. :lol:

I defiantly owe you guys some beers. :headbang1:

I'll step up the main to 178 and give it a run. maybe through the 48 pilot back in while I'm there.

But you really got me thinkin' about the stator, cuz it started cutting out like this before I did any of the changes. also that was at mid and full throttle I think.

That's why I started changing things in the first place.

I don't know about the stator or the flywheel. I imagine their stock. We may find out soon though.

Thanks again, I'm lookin' forward to this season more and more every day. :black:

R-

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Well the flywheel if stock is like a goldish color.If its a trailtech it will be all silver with a bunch of holes in the back and you can actually see the magnet strip on the inside.On the stocker its all covered on the inside with a metal strip.If it is the stator they are very very easy to switch out.You will just pull off the cover on the left side and its inside that cover.

here is a link for one on ebay

http://cgi.ebay.com/ebaymotors/Yamaha-YFZ4...mZ370077675433h

Ive had this exact problem twice.The first time it was my Trailtech Flywheel,the second time it was my stator.Good Luck!!Another thing to think about is when you are making changes with the jetting to fix an issue and you get the exact same response as you had prior its usually time to go to plan B.I messed with my carb forever before I finally thought it might be something else.

Edited by Sand_YFZ
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  • 1 month later...

its at 165 main 45 pilot 2.5 turns on mixture screw and 4th clip it bogs and yes full exhaust

where does it bog at? That will tell you what you need to adjust. Check a couple posts up;

idle to 1/4 = pilot jet

1/4 to 3/4 = needle

3/4 to full = main jet

You could also go to www.yfzcentral.com and do a search for jetting your quad. Tons of information there, you just have to pick the good information out from all the bad :whoop:

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