yz 85 cuts off

[lkisktr0]

my freind just got a 2004 yz 85 that spun a rod bearing. after we fixed that the new tank of gas we put in it was 26:1 with stock jetting. after we burned that we went up 28:1. when we put the 28:1 gas in the bike it would start first kick run for about 10 seconds and then bog out. we took the spark plug out and it was soaked with gas we dried it off and then put it back in and it would do the same thing. we have repeated this about 5 times so something is wrong!! what??? ? thanks

[tekknikkx]

Have you tried adjusting the air (idle) screw?

Also, clean the air filter and put a thin layer of filter oil on it if not done already.

[lkisktr0]

i dont think it would be the idle because we are revving it when it bogs out. we just cleaned the airfilter also

[tekknikkx]

I know my bike will bog out if the air screw isn't adjusted properly (it has to be pretty far off, but it can happen none-the-less)

Just turn the air screw all the way in, then unscrew it about 2 full turns and see how that works? Let me refer you to the 2 stroke jetting guide. It can be a bit complicated, I was stumped at first with my problems (bike bogged when trying to get in powerband) and simply adjusting the air screw sovled everything. https://www.thumpertalk.com/forum/showthread.php?t=412662

If anyone else has any ideas please post them!

Also, once you get the bike running decently, go buy a new spark plug.

[lkisktr0]

the weird thing was it ran fine on the first tank but the second it is screwing up. i will try that though. the farther u screw it out does it get less air and more gas?

[husabutt]

my freind just got a 2004 yz 85 that spun a rod bearing. after we fixed that the new tank of gas we put in it was 26:1 with stock jetting. after we burned that we went up 28:1. when we put the 28:1 gas in the bike it would start first kick run for about 10 seconds and then bog out. we took the spark plug out and it was soaked with gas we dried it off and then put it back in and it would do the same thing. we have repeated this about 5 times so something is wrong!! what??? ? thanks

The correct thing to do would be to lean out the jetting, slide, needle and main or run a hotter spark plug to burn the excess fuel off the plug. Your oil/fuel mixing ratio has little to do with it.

Quick fix:

Go from the stock BR10EG plug to a BR9EG or better yet a BR8EG. This is a band aid but will help.

Better:

ER9EG Plug and a 135 or 132 main jet

Better yet:

Same as above but lower the needle jet afew clips

Getting there:

BR9EG plug

135 main

Kawasaki KX85 needle jet (NAPE)

Ultimate plan:

BR10EG plug

48 pilot jet (one larger than stock)

135 main (one smaller than stock)

3.5 carb slide AKA throttle valve (stock KX85) (stock Yamaha is a 3.0)

NAPE carb needle jet (stock KX85)

Super Ultimate plan:

Same as above but advance ignition timimg from .9mm BTDC to 1.2mm BTDC

Use 50/50 mix of race/pump fuel

[lkisktr0]

great help!

will try today

[yz rida]

I'm no expert but i think your gas mixture is off. i ride and 85 and my mix is 40:1 it probably isn't a huge contribution to the problem but it might help a little ?

[DLHamblin]

my freind just got a 2004 yz 85 that spun a rod bearing. after we fixed that the new tank of gas we put in it was 26:1 with stock jetting. after we burned that we went up 28:1. when we put the 28:1 gas in the bike it would start first kick run for about 10 seconds and then bog out. we took the spark plug out and it was soaked with gas we dried it off and then put it back in and it would do the same thing. we have repeated this about 5 times so something is wrong!! what??? ? thanks

The plug is fouled; cleaning will do no good. A new plug will fix you up.

Stock they come with a BR10EG which is way too cold. Even modified YZ85's typically run BR9EG plugs. If you trail ride a BR8EG may be needed.

We run Yamalube 2R at 32:1 in my son's YZ85 (2006) with stock jetting (airscrew turned out 1 1/2 turns) and a BR9EG.