Need Optimal Jetting #'s

[shane.ballard.nf]

I have YZ490J and i need to get it jetted right
i live in newfoundland canada

the carb has bigger needle/seat then stock, bike runs way to rich not gettin half the power it should running poorly due to jetting i think.

 

[trial_07]

you might want to check out the sticky at the top of this forum. i can't help you not knowing anything about the terain, your riding style, etc...

 

[shane.ballard.nf]

well terain = crushed stone, gravel trackbeds (no trains here anymore) thats mainly it!

Riding style, well this bike is my first 2stroke and i know with 2strokes u goto wang on em hard cause there made for it
i will be driving the bike on nice days not in muddy conditions

I'm wondering should i go below stock jetting with the pilot needle/seat and bigger slide or if i can get away with stock

I read the stuff in the jetting sticky i understand it but i need to start off with the right carb parts before i can begin the process

 

[trial_07]

I'm running in the same problem as you are. I'm sending mine to be done by Kawasaki mechanics. I guess I'm too lazy for trial and error stuff!

 

[shane.ballard.nf]

heh, ya my bike runs but it's not revving you know, these bikes rev realll high but mine is just movin along with minimal revs and just isn't gettin that wangy power
im sure its just jetting bike got hella good compression goto tow it to start it, most hills wont even bumpstart the bike

 

[mat24c]

dude who did ur top end last?
well if the power valve is either not correctly put back together or is gumed up this could happend its just not openin up

 

[Chili]

I could be wrong but I don't believe the early 80's YZ490's have a powervalve.

As far as jetting no one can really give you the numbers as there are too many variables. If you have the manual I'd reset it to stock and go from there. If I recall correctly the 490's like to burn holes in the pistons so I would leave it a little rich.

 

[2strokerfun]

Just get it in the ballpark and live with it, or have the head reworked by a pro. Otherwise, you cannot jet a 490 properly. Once warmed up, they will either ping or run too rich. I prefer changing a spark plug now and then instead of changing a piston and honing a cylinder. So, I agree with running it a bit rich.

 

[shane.ballard.nf]

Yes, i agree
but the thing is it's running a lil to rich now and runs like ****, i want to lean it out just enuff to run good without any damages to the engine.

I now have all the parts i need to get the bike jetted close to stock, everything in the carb is stock except the needle the seat is stock #440 but you can't get the needle new anymore i might try to find one sometime but i don't think it's a big deal to have the stock needle.

i got brand new uni air filter to go in the bike and new reed gasket and stuff

 

[Rcannon]

Yes, i agree
but the thing is it's running a lil to rich now and runs like ****, i want to lean it out just enuff to run good without any damages to the engine.

I now have all the parts i need to get the bike jetted close to stock, everything in the carb is stock except the needle the seat is stock #440 but you can't get the needle new anymore i might try to find one sometime but i don't think it's a big deal to have the stock needle.

i got brand new uni air filter to go in the bike and new reed gasket and stuff

Shane, that is all any of us wanted with the yz 490. Just to make it run without running like crap or pinging. Its not achieveable without head mods.