Jetting the YFZ

[Pappy]

anyone wanna explain the steps needed to jet this puppy and possibly fill us in on what jetting has been working the best?

[trueblue450]

whats a jet????

[Maxx_Action]

Well...

I will say this, this thing likes to EAT! I find that if you try to read the plug, it will starve. I was always taught as a young motorhead that the plug should be a nice greyish brown color. If you run the YFZ like that, IMO, you are losing HP. I also think that the hyperactivity of the accelerator pump on the FCR carb can throw off the plug reading a little bit cause that thing really dumps when you punch it. Mine runs best right now with a 178 main (cause it's cold) I am running the NVCQ needle on the 4th clip, a 48 pilot at about 2 and 1/2 turns. When it gets warmer again I will prbably be back to a 172, 45 pilot, 3 turns, or somewhere close. I also run the Ron Wood intake which flows MUCH better than the stock boot. A hundred and fity bucks well spent on that mod.

Most people Jet it up til it's too rich (it will kinda blubber and fizzle on top before it hit's the limiter) then jet it back down 2 steps and that is a good guideline. Good luck...

Maxx

[Cron]

Maxx Action what mods do you have done? All I have done is a pipe and my main jet is a 165 now and it hits the top end quick. It makes me think I am too lean if you are running a 178! Should I try a 168? I thought the 165 was perfect but now it seems too low. I hit the top end fast, it does backfire on the decel sometimes though. You are from IL right?

[Cron]

O yea i forgot to add I have a 45p, GYT-R Needle 3rd clip and my fuel screw is about 2 1/2 maybe 2 3/4

[Maxx_Action]

Originally posted by Cron
Maxx Action what mods do you have done? All I have done is a pipe and my main jet is a 165 now and it hits the top end quick. It makes me think I am too lean if you are running a 178! Should I try a 168? I thought the 165 was perfect but now it seems too low. I hit the top end fast, it does backfire on the decel sometimes though. You are from IL right?

Check the Sig...

for mods. The jetting thing, if it gets above 30 degrees, I gotta go back down or she gets a little lazy. Remember, I am runnin the Wood intake which is a 42 mm straight tube from the filter to the carb so it flows like mad, plus the K&N which increases flow as well. I think you may be able to go up on size, maybe two and you would see some more balls on top...

Maxx

[Maxx_Action]

P.S.

The cam mod also makes her want to eat a little more, and as soon as it warms up you should be fine wehre you are plus one clip position on the needle. When I first got this quad, I had the GYTR pipe, no lid, 42 pilot, GYTR needle 4th clip, and a 165 main. When I went to the K&N I went to a 170 and it ran great, when I added the Cam mod, 172, then with the Wood intake, I am guessing a 175-172 depending on temp. I haven't had a chance to really run it that much since I got the Intake for Christmas, I guess I would know if it would EVER GET FRIGGIN WARM!!!!


Maxx

[Bad Habit]

This past fall at Sand Fest in OK, I talked quite a bit with the guy camped next to me. He had the Ron Woods intake and the exhaust (still in developement, wasn't even coated yet) and he told me alot of things about jetting a four stroke. He was somewhat of an "old timer" and had some very simplistic approaches to jetting. One thing that stuck out to me was that he stated that if you crack the throttle wide open while setting still, it should puff out some black smoke. If it doesn't, it's too lean. He also said that it was really hard to read a plug on a four stroke when compared to a two stroke. In fact, he said that he would put just a tad of 2 stroke oil in the gas tank of a four stroke when trying to get the jetting ironed out. He said that it made the plug color easier to read. I was inclined to believe him cause noone could touch his YFZ that whole weekend on the drags. And he had a DS650 that was one of the fastest bikes there, two or four stroke.
Has anyone else heard of these rules of thumb or was this guy just full of it?

[RiPPiNiTuP7]

lots of good info:

http://www.eskimo.com/~daddog/index.htm

[xcyfz450]

i have a yfz 450 with just a hmf slip on and no lid and i was told to run a 180 main jet is that right? plus mine also backfires on decel can anyone steer me in the right direction if this is correct or what i need to do thanks