Jump to content
Sign in to follow this  

athena 290 bigbore kit jetting

Recommended Posts

hey guys my bud has an 08 with the 290 kit,and stock jetting,stock exhaust.he lives in western new york.any help in the jetting dept.?he says its quicker more power down low,but runs out quicker on top,powerband feels shorter,less broad than stock.he wants to try jetting to get the most out of it,without pipe,cams etc(budget).let me know what you east coast guys are running,thanks.

Share this post


Link to post
Share on other sites

Ya he better re-jet it, he's going to burn up his motor running that lean! he's going to have change the main and pilot jets and the needle and go richer with everything, stock is a 162 main 42 pilot and NCLT needle the fuel screw 2 1/4 turns out. Check out websites that sell athena bore kits, they should have a chart.

Edited by RMZed250

Share this post


Link to post
Share on other sites
Ya he better re-jet it, he's going to burn up his motor running that lean! he's going to have change the main and pilot jets and the needle and go richer with everything, stock is a 162 main 42 pilot and NCLT needle the fuel screw 2 1/4 turns out. Check out websites that sell athena bore kits, they should have a chart.

Thats incorrect.

Athena should have info provided for this. Normally with a big bore kit you either leave the jetting or run leaner jets. People wrongly think bigger capacity requires bigger jets. Don't forget how a carburetor works - venturi effect. The bigger the pressure difference (suck) the more fuel it will pull through the jet. The bigger the capacity the more "suck" it will have, thats why you normally jet down an overbore.

Share this post


Link to post
Share on other sites

kev250,sounds like you know about the mod.do you have the kit?my friend acts like he didnt receive carb info.do you have any carb info for the 290 kit?thanks.

Share this post


Link to post
Share on other sites

Well, I never thought about the vacuum pulling more fuel, I knew it would pull more air, thats why I assumed you would need larger jets. I guess if you simply increased the air flow (air filter, slides, larger carb) then you'd increase jet size, you could probably pull some more power by doing that though.

Share this post


Link to post
Share on other sites
kev250,sounds like you know about the mod.do you have the kit?my friend acts like he didn't receive carb info.do you have any carb info for the 290 kit?thanks.

We run the Athena 290 in our 08 and 10 RMZ's and kev250 is right. If he has stock jetting it's too fat. He'll need to lean it out. I have no clue how much being I'm in Texas but we went from a 164 to a 160 main and down to a 34/36 pilot. Also... one reason he fells it runs out of top end is because he get there faster. After getting the jetting set-up he will want stage 2 cams

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×