DGMAX99

Member
Dec 6, 2001
98
0
Anyone have any recommendation on proper jetting for an 03 YZ85? We’re located in the northwest corner of AL, not sure of the exact elevation.

Having a problem with ours eating plugs. It seems to be waaaaay off on the stock settings. Yamaha was nice enough to include extra jets with the bike… Just wondering if any one had been thru this already.

Please include actual jet sizes, needle position, etc… if possible.

Thanks
 

karterron

~SPONSOR~
Mar 24, 2002
684
0
I've found that the only way to properly jet is to experiment with it yourself. There have been many posts in the past about the YZ jetting and they seem to be all over the spectrum. I would start going one step leaner if you are eating plugs and do it one item at a time. First go up one notch on your needle since that is free. See how it runs with that first. Then go one size down on your pilot.

For us, one step up on the needle and running better oil and gas cleaned ours up and we have not fouled a plug since doing that. I run a Amsol's synthetic premix with high grade gas. No more spooge out the exhaust and no more fouled plugs for us.

Jetting is not an exact science you can get from a message board. There are too many factors that play into it. Altitude, barometer, ambient temp, and fuel/oil mix all play a part and nobody else will be exact to yours. Thats why you see such a wide range on jetting recommendaitons.
 

DGMAX99

Member
Dec 6, 2001
98
0
Yea, I understand its not an exact science and a lot of factors play into it, what works for one may not for others. I’m actually looking for a better starting point since it seems to be way off as is.

Thanks for the info
 

oldguy

Always Broken
Dec 26, 1999
9,419
0

karterron

~SPONSOR~
Mar 24, 2002
684
0
Iwould not make drastic changes or multiple changes when jetting. If you want to drop 2 sizes at a time thats fine, but I would not do multiple changes at one time. First do the easiest change, which is raise the needle. Ride it and see how it does. Then put a new plug in and ride it with no more than 1/4 throttle and see how the plug looks.

We thought ours was way off also. Fouling plugs every ride and spooge all over the place out of the exhaust. All it took to fix the problem was higher grade gas with synthetic oil and one higher on the needle. It eliminated all problems. It may appear to be way off but it may not be as much as you think and if you change multiple things at once you won't know which direction to go.

Just a suggestion.
 

DGMAX99

Member
Dec 6, 2001
98
0
Appreciate the help guys. I moved the clip up one notch and changed the pilot while I had the carb off. Haven't had a chance to ride it tho...
 

02yz85

Member
May 1, 2002
13
0
by dropping 2 sizes on both jets, where is your clip on the needle, is the needle stock? what #'s are the pilot and main jet you have set in? i have lowered one size on p and m jets, i believe im stock on the needle, i may go up one on the clip. i bought some br9eg plugs but havent tried them yet. im not burning plugs like before, but i still have that brawwwwwwww once i put it in 1st gear.
 

gutzi

Member
Apr 20, 2000
7
0
I went with Oldguy's jetting recommendation last year in my son's 02 YZ85 & it's been great. We live in the same area so temp and altitude are the same. We now are 1 leaner on the stock pilot and stock on the main. the needle is drooped 1 notch. the air screw is variable by day. For plug we are using a BR9ES. I have found that a lot of the plug fouling has been eliminated by using 50% VP C-12 and 50% premium pump fuel. I don't think the pre-mix oil is a factor. Lately I've just been running straight race gas. I little more expensive but saves the hassle of mixing fuel all the time.
 

deadhead

Member
Mar 25, 2001
101
0
My son is a pretty good 65 rider, but he's not yet comfortable with the '03 YZ85 we just got. No problemo. However, he's fouling plugs pretty fast and there's a lot of spooge coming out the pipe. I dropped the needle one notch but didn't do anything else to the carb. Carb work usually turns into a weekend disaster for me. Now, the bike starts readily and idles fine, but you can't crack the throttle till it warms up fully without it dying. I'm here on the VA coast, basically at sea level. Haven't yet switched from pump gas, but plan to run 50/50 CAM-2 and Yamaha 2-R. The 2-R has served us well in the past, so I'd like to try and make carb changes before I change the oil.

Any suggestions would be greatly appreciated.
 

wrudy

Member
Aug 24, 2003
1
0
I to have been going nuts trying to jet my sons YZ85. Problem is not so much fouling plugs, but trying to get rid of the baaaawaaa right off idle. I have cahnged needle positions, pilot jets, air screw and nothing seems to matter. I'm beginning to think it is inherit to the YZ85 as it has no power valve. any suggestions on this would be appreciated. I'm at 900 feet above sea level in Ohio. Thinking of changing the needle jet next.
What oil/gas ratio do you guys run in your 80"s? I have always run 50:1 in my bigger 2 strokes but I'm hearing the small bores need more oil. I'm currently running 44:1
 

03YZ85Rider

Member
Aug 8, 2003
27
0
I am running 50:1 mixture with Amsoil and 91 octane non-oxygenated pump gas, runs excellent. I would say if you are using a good quality oil 40:1 to 50:1 is ok but if you are running something like Injex then I would go 32:1.
 

gnarlykaw

Sponsoring Member
May 20, 2001
986
0
We too, just bought a 04 85. it too still has the bogg in first :| . i plan on checking the float level, and drop the main and pilot one point, and switching to 94 octane, and a 40:1 ratio as soon as the tank gets lower. If it still has that bogg, phase two will be dropping the front sprocket one tooth, and installing a reed spacer block. otherwise, this bike ROCKS! :aj: This bike appears to be REALLY pipey, so, if all else fails, it's time to drop the shange for a GNARLY pipe. I'll let you all know when i do this.........
 

gnarlykaw

Sponsoring Member
May 20, 2001
986
0
ok, forget the reed spacer, wrong move. we dropped the pilot and the main one point, and it is a little better, but still too pipey. working on doing a flywheel weight instead. and no, I didn't do a pipe ........yet
 

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