Athena works kit....wow!

[snosurfer05]

After searching through 120 threads about the athena kit I'm still scatching my head.

I have a 2001 yz125, everything is stock except the works 125 kit from athena that comes with the cylinder, power valves, flat top piston and high comp head.

everything is installed and the bike runs. the topend power rips my arms off. By far one of the fastest 125s I've ever been on.

The issue I'm having is the bottom end power is not there. Now I know you're saying "it's a 125 there is no bottom". It is borderline 4stroke boggin on me which leads me to believe it's a jetting issue. I'm running 110 race gas from the race track down the road at 32:1. The kit instructions suggested 104 oct but I could only find 110 near me.

I'm in FL at sea level, and weather is in the 70-80s. It has the stock 460 main jet in it and like i said it rips high speed. It had a stock 25 pilot jet which I replaced with a 22.5 pilot with no success. I've moved the clip down and up with again no success. I've played with the air mixture screw with no help there either.

the plug is golden brown and looks perfect. This bike is going to be mainly used in the woods for hare scramble racing so a little bottom end would be nice.

[qwert321]

Bogging on the bottom end on a two stroke is usually lean. Even when they are a quite rich on the pilot the wont bog.

[06yz]

After searching through 120 threads about the athena kit I'm still scatching my head.

I have a 2001 yz125, everything is stock except the works 125 kit from athena that comes with the cylinder, power valves, flat top piston and high comp head.

everything is installed and the bike runs. the topend power rips my arms off. By far one of the fastest 125s I've ever been on.

The issue I'm having is the bottom end power is not there. Now I know you're saying "it's a 125 there is no bottom". It is borderline 4stroke boggin on me which leads me to believe it's a jetting issue. I'm running 110 race gas from the race track down the road at 32:1. The kit instructions suggested 104 oct but I could only find 110 near me.

I'm in FL at sea level, and weather is in the 70-80s. It has the stock 460 main jet in it and like i said it rips high speed. It had a stock 25 pilot jet which I replaced with a 22.5 pilot with no success. I've moved the clip down and up with again no success. I've played with the air mixture screw with no help there either.

the plug is golden brown and looks perfect. This bike is going to be mainly used in the woods for hare scramble racing so a little bottom end would be nice.

If the plug is looks perfect, the jetting is good, right.?.? Check your powervalves, make sure they are not sticking.

MAX!!!

[USED YZ426F]

I know nothing about the Athena kit, but smaller bikes usually have very little bottom end to begin with. If they engineered the Athena kit for more topend, it probably was at the expense of the bottem end.

Have you contacted Athena to see if they have any information or recommendations?

[bad72ss]

Run the air screw almost all the way in if it starts to get betters then up the pilot jet . If it gets better the more you turn it out then go smaller on the pilot.

[snosurfer05]

Bogging on the bottom end on a two stroke is usually lean. Even when they are a quite rich on the pilot the wont bog.

In my experiance lean makes it ping..? unless it's REALLY lean?

If the plug is looks perfect, the jetting is good, right.?.? Check your powervalves, make sure they are not sticking.

Checked the powervalves, they are moving freely and no abnormal slug build up.

I know nothing about the Athena kit, but smaller bikes usually have very little bottom end to begin with. If they engineered the Athena kit for more topend, it probably was at the expense of the bottem end.

Have you contacted Athena to see if they have any information or recommendations?

No luck there, Contacted motosport also with no reply yet.

Run the air screw almost all the way in if it starts to get betters then up the pilot jet . If it gets better the more you turn it out then go smaller on the pilot.

Thanks Bad72ss, I know how the air screw works and I've done both screwing in and out with no improvements.

thanks for the replies, I guess I was just hoping someone else had this issue and knew of a trick. I checkdd my plug gap, did a compression and leak down test all of which checked out great. Ordered bigger pilot jets. stock is 25 and I have tried 22.5 and 20. I also have tried one bigger 27.5 with no luck. I ordered two sizes bigger so hopefully that will help.

[snosurfer05]

a bit more research, I called the speedway that I got the race fuel from and found out some specs. it's sunoco standard race fuel which is 110 octane and 0% oxygen. I thought maybe the fuel might be oxygenized causing a lean state but that's not the case.

I'm going to put the 27.5 pilot jet back in it and screw the air mixture screw all the way in and see if that helps at all.

here is something else I thought of. If I start it up. warm it up and then keep it at low rpms around idle..1 would it build up on oil and foul the plug at 32:1? and 2 after doing that if I pulled the plug at a lean state it should be "sooty" white almost burnt, correct?

thanks again for your help guys...

[BRM]

If the plug is looks perfect, the jetting is good, right.?.? Check your powervalves, make sure they are not sticking.

MAX!!!

Plug chops are done at high RPM = mainjet

[MrBlahh]

and plug chops are unreliable with all the strange fuel additives now

the pilot jet is the easiest to dial in imo

[USED YZ426F]

here is something else I thought of. If I start it up. warm it up and then keep it at low rpms around idle..1 would it build up on oil and foul the plug at 32:1?

If properly jetted and as long as there are no other issues, you should not not build up excess oil or oil foul the plug.

and 2 after doing that if I pulled the plug at a lean state it should be "sooty" white almost burnt, correct?

A bike jetted lean will have a very light color on the plug electrode. A bike jetted rich will be dark brown to black. There may or may not be "oily" deposits depending on the premix and fuel. There are so many additives in fuels today, that I don't get too hung up on plug deposits as long as my bikes are running crisp.