yz85 jetting?

[Blink-182]

i have changed the pilot jets from the 48 it had to a 42 the the 138 to a 135 following pro circuits recommendations, but im not sure if a 2 stroke is sapoused to do this.
but i know it doesnt have great roll on power either, from any gear going a decent speed if i WOT it
it bogs a bit and picks up but i know its not doing it as it should shouldent it just start picking up slowy?
until the powerband?

i have to clutch and gas it but it still seems to pick up slowy even if i do that today was my first day at the track and everytime i got to this table top i had it in at least second and gassed it but it always picked up so slow so i couldent really make it all the way over,i dont want to have to clutch everytime to take off fast it tires out your hand way too quick

 

[whenfoxforks-ruled]

It is impossible to jet a bike with issues. You have to rule out all mechanical variables. Fresh engine for starters, the proper ratio with premium gas, clean air filter, good pipe with fresh silencer packing and a new plug. There is no one who can tell you the correct jets for your bike, they are all a little different. http://www.dirtrider.net/forums3/showthread.php?t=159938

 

[Blink-182]

just did a topend about 3 hours ago, premium gas mixed 32:1, just cleaned the filter after the track, fmf fatty pipe with brand new packing mabye an hour on it, and the plug is fairly new, but isnt is sapoused to like pick up slowy or fast instead of bog hesitate and then pick speed up slowly?

 

[Blink-182]

oh and the bottem end is fairly new also it has about 20 hours on it its a hot rods crank

 

[Blink-182]

ok i found out the problem im guessing the owner before me didnt know how to install the needle they didnt put it in the little plastic thing they had it just touching bare metal so it wasnt lifting up, only problem now is that on the second notch it runs good fine and everything theres slight bogging when im not going the exact speed in that gear and i gas it, but when i tryed it in the first slot there was absoulty NO bogging but about mid throttle it sounded weird going into the band im not sure if it wasnt sapoused to do that

but since i ride in a sandy track should i go ahead and go from the 42 back to the 45?

 

[whenfoxforks-ruled]

Sand? Bigger main, usually. It would seem you did not read the link to spanky's jetting guide? Go over it again. Start with the air screw and work your way up. Check the plug frequently. If you have doubts if you are going lean or rich, jump a couple of sizes, it should be obvious, and reference the plug. Wet or dry?

 

[Blink-182]

the link doesnt work but i know somewhat about jetting i put the stock 45 pilot back in and the 135 main it comes stock with a 45 pilot and a 148 main, i dont have any problems with fouling,

i got the bike to stop bogging out and sputtering really bad when going medium speed and then just WOT, it wouldent sputter or bog it just sped up slowy until it got to the power band is this how its sapoused to go up into the band? it climbed up pretty fast
and that needle that wasnt in the plastic thing so it wouldent rise it would just sit at the bottem of the throttle assembely helped ALOT, do you think that was it ? i noticed a huge increse in power

 

[husabutt]

Things to try in order from least expensive to most expensive :

1. With stock jetting, turn in your air screw some to richen the pilot circuit.

2. With stock jetting change to one up and one down. That is:
48 pilot and 135 main (possibly a 132 if everything is stock). Air screw set for highest idle speed.

3. KX85 needle and slide, which is a NAPE needle and 3.5 slide.

4. To help restore maximum top end try going back to a 138 main when using the KX needle and slide.

Here is how Kawasaki and Yamaha differ in their approach to jetting:

Stock 2006 Yz85 jetting:
Slide 3.0
Needle NBKF
Main 138
Pilot 45

Stock 2006 KX85 jetting:
Slide 3.5
Needle NAPE
Main 140
Pilot 45

You can advance your ignition timing to 1.2mm BTDC which will add more torque. Raising the compression will give you a huge (for a 85 which has nothing to begin with) increase in torque. Also a light flywheel weight will help.

From the factory the stock YZ85 is too lean on the pilot, too rich on the slide, way too rich on the needle and too rich on the main.

Remember the "NEEDLE" controls around 1/4 to 3/4 throttle which usually is where most of your time is spent. The little YZ is jetted from the factory like a light switch, full blast or off with no in between which makes for a great pro mx bike or drag racer but not much else.