2014 Berg TE250 (and KTM, Husky) jetting thread

[malcolmzilla]

Yay, another jetting thread!

As opposed to trial and (mostly) error, I am looking for insight on jetting for local conditions, new to the pinger scene...

Set the bike up for 1st ride at Moab by the book. 3- 5K elev, 16-24 degrees.

N8?? factory needle on 4th clip, 165 MJ, 40PJ, 2 turns on screw, ran OK, but a terrible bog (or loadup?) right before the powervalve (factory spring and preload) came in, made it hard to ride right in the middle... always shifting to avoid it.

Did a bit of reading on jetting, and dropped the needle to 3rd. Way better, bog almost gone, growls along nicely into a manageable hit. Way less shifting. 50:1, and some spooge...

So I am going to drop to a 162MJ as the book recommends for local 5-7K elev and 16-24 degrees (or is that too warm?). Or what is everyone running that works well here, response, spooge minimizing, and economy wise?

From a search: I see most at 162MJ, factory needle at clip 2, 38-40 PJ and mess with the airscrew every day...

Friend recommends an NECJ (RM250) needle (more progressive taper), anyone using this locally on a 13/14 250, and what MJ, PJ, clip, etc?

[malcolmzilla]

Safeway 91 gas at 50:1

Maclean May 29
Ambient about 12-9, 25 km mixed.

Maclean June 1
Ambient about 10~15, 46km mostly ST.

162MJ, factory needle at clip 3, 40 PJ, airscrew 1/2 to 3/4 turns off idle speed picking up.

Ran well, growly below powerband, 2" of fresh spooge on the tip, but not too bad?
Didn't check fuel economy. Not on the pipe that much , so the needle and PJ are where I'm working at.

Ordered an NECJ needle.

Head shave maybe, coming off a 4 stroke I miss the linear torque and the bottom grunt on the loose rooty ledgy climbs.
1st too pipey, 2nd seems too tall, boggy unless on the powervalve, but might be the wide ratio trans?

(Ride faster my buddies tell me )

[Dobi]

the head shaving may not help make jetting any easier. I put the SX head on my 300 and am really struggling now to clean up the bottom end. It does have way more low end grunt, but almost feels too 4 stroke like.

I am experimenting with needles too.....

[350scott]

the head shaving may not help make jetting any easier. I put the SX head on my 300 and am really struggling now to clean up the bottom end. It does have way more low end grunt, but almost feels too 4 stroke like.

I am experimenting with needles too.....

Ride faster, your buddies say!

[sthomps]

Safeway 91 gas at 50:1

Maclean May 29
Ambient about 12-9, 25 km mixed.

Maclean June 1
Ambient about 10~15, 46km mostly ST.

162MJ, factory needle at clip 3, 40 PJ, airscrew 1/2 to 3/4 turns off idle speed picking up.

Ran well, growly below powerband, 2" of fresh spooge on the tip, but not too bad?
Didn't check fuel economy. Not on the pipe that much , so the needle and PJ are where I'm working at.

Ordered an NECJ needle.

Head shave maybe, coming off a 4 stroke I miss the linear torque and the bottom grunt on the loose rooty ledgy climbs.
1st too pipey, 2nd seems too tall, boggy unless on the powervalve, but might be the wide ratio trans?

(Ride faster my buddies tell me )

I too am not totally satisfied with my jetting. I feel its good but could be better. I am running:

165MJ, stock needle 3rd Clip, 38PJ, forget my airscrew. 40:1 Amsoil interceptor with any gas 91 or higher.

Rarely spooge unless its a rainy day. Thinking of trying a JD kit, they done wonders in the past.

[malcolmzilla]

Maclean June 5

South Fisher and up Barwell way, so a bit more elevation? Dunno as an errant branch destroyed my GPS, again!
Temps were 7C dropping to 1-2 as the ran turned into snow... high humidity, wet, cold.

Same 162MJ, factory needle at clip 3, 40 PJ, airscrew 1/2 to 3/4 turns off idle speed picking up.

Ran ok, no idea on spooge as it was a mudfest... Noticed idle a bit high with the low ambient so turned the air screw out a half and the idle dropped back.. which is contrary to the results from web 2 stroke tuning articles? Unless my PJ is too rich and the cooler air let to a better pilot mixture...

Maybe I have no idea what I'm doing... I better try this setup again and then count airscrew turns... hmm.

NECJ needle not arrived yet.

One way to set the air screw on a 2-stroke is have the throttle set to where its idling a bit high; use a piece of tape on the grip and another on the housing. Open the throttle a bit to get the higher idle. Mark a line on the two pieces of tape (so you can hold the throttle in the same place else it's hard to set the air screw). Clamping it is even better.

This will allow you to hold the throttle
open at a steady rpm.

You want to hold the throttle open and steady so that the engine is running
at about 1,200 rpms, and sounds like, "tat, tat, tat, tat."

With the throttle being held steady so that the rpm's don't change, adjust the
air screw on the carburetor slowly in and out, at 1/4 turn each adjustment, until
you find the highest running rpm spot. The engine should noticeably slow when you
go in too far. When you back out the screw the rpm's will increase up to a point and then will not change when you keep backing out the screw. Find the point
where the rpm's are at the highest point and stop backing the screw out right there.

When you are satisfied That you've found the correct adjustment, shut the engine
off and see how far the air adjustment screw is backed out. You check this by
slowly screwing in the air screw in 1/4 turn increments, counting as you go, to see how many turns the air screw is out from the carburetor.

If your air screw is more than 1-3/4 turns out, this means you need the next
size smaller pilot jet. If the air screw is less than 1 turn out, this means you
need the next size larger pilot jet. After you have changed the pilot jet in the carburetor, you need to repeat the tuning process above and find the optimum
rpm point by adjusting the air screw.

[trailguy]

Maclean June 5

South Fisher and up Barwell way, so a bit more elevation? Dunno as an errant branch destroyed my GPS, again!
Temps were 7C dropping to 1-2 as the ran turned into snow... high humidity, wet, cold.

Same 162MJ, factory needle at clip 3, 40 PJ, airscrew 1/2 to 3/4 turns off idle speed picking up.

Ran ok, no idea on spooge as it was a mudfest... Noticed idle a bit high with the low ambient so turned the air screw out a half and the idle dropped back.. which is contrary to the results from web 2 stroke tuning articles? Unless my PJ is too rich and the cooler air let to a better pilot mixture...

Maybe I have no idea what I'm doing... I better try this setup again and then count airscrew turns... hmm.

NECJ needle not arrived yet.

One way to set the air screw on a 2-stroke is have the throttle set to where its idling a bit high; use a piece of tape on the grip and another on the housing. Open the throttle a bit to get the higher idle. Mark a line on the two pieces of tape (so you can hold the throttle in the same place else it's hard to set the air screw). Clamping it is even better.

This will allow you to hold the throttle
open at a steady rpm.

You want to hold the throttle open and steady so that the engine is running
at about 1,200 rpms, and sounds like, "tat, tat, tat, tat."

With the throttle being held steady so that the rpm's don't change, adjust the
air screw on the carburetor slowly in and out, at 1/4 turn each adjustment, until
you find the highest running rpm spot. The engine should noticeably slow when you
go in too far. When you back out the screw the rpm's will increase up to a point and then will not change when you keep backing out the screw. Find the point
where the rpm's are at the highest point and stop backing the screw out right there.

When you are satisfied That you've found the correct adjustment, shut the engine
off and see how far the air adjustment screw is backed out. You check this by
slowly screwing in the air screw in 1/4 turn increments, counting as you go, to see how many turns the air screw is out from the carburetor.

If your air screw is more than 1-3/4 turns out, this means you need the next
size smaller pilot jet. If the air screw is less than 1 turn out, this means you
need the next size larger pilot jet. After you have changed the pilot jet in the carburetor, you need to repeat the tuning process above and find the optimum
rpm point by adjusting the air screw.

Like you mentioned Malcom thats not making any sense. With temps that cold the bike runs leaner - which would cause the idle to pick up and the bike to "run on", turning the air screw in (richer) should be the solution. I have to do this with my 200 when temps get that cold.

[malcolmzilla]

Problem solved, I have been messing with the wrong screw LOL.

OK, will "retune" after its washed up tonight.

[malcolmzilla]

Ok warmed it up, did idle test, air screw is about 1-3/4 turns out where it bogs faster idle. So I guess I am right on the margin of the pilot, in town...

Should I drop to a 38? Thanks.

[malcolmzilla]

Long time pinger buddy rode it, in anticipation of tomorrow's ride, we decided to drop the needle to #2. Airscrew 1.5 turns out, dropped idle speed a bit. Alley test it growls along decent, perhaps more torquey.

[malcolmzilla]

June 9, south ghost, 10-15 ambient, not sure on elevation but likely 5000'+...

40/1.5/n8rj/#2/162

Much improved bottom to mid.

[gstout]

All my KTM's have the JD Jetting kits and problems solved every time. You can jack around all season or spend the $85 bucks and be done with it. They have done the dyno work and ground the custom needles for you. Friend with TE 250 Husaberg put one in and it is perfect.

[malcolmzilla]

Oh I've done the JD kits on my thumpers, for sure a set it and forget it option. If not a bit rich (literally and figuratively).

For this bike, I understand rejetting is required season to season and for elevation, and the mags said the factory jetting guide was quite close, so this is more of a learning exercise than an end goal.

Cheers

Next up a 38 pilot, see what that does to bottom and economy. Then maybe a 165 main, as it does run out on top a bit early IMO.

[dirtyboy]

I ran KTM 250XC for a number of years (6) and once I tried a 38 pj but left the 35 pj in once I learned about the needles. The letter on the needle is the size of the straight section so that is how you adjust the idle circuit on these bikes.

How does the MJ feel when you hold it wide open when the bike is in neutral? It should really sound like power and no blubbering or rpm miss.

I usually ran the 160 or 162.

Actually, I found that the jetting chart was pretty good. Just go one square leaner on it and that was very close.

Usually that meant the 2nd clip position.

Don't forget to set your float position first as it can affect the jetting.

Rambling over.

[malcolmzilla]

Thanks for the tips Dave, I will give them a try.

On my 4 strokes access to the carb in the bike was always so limited that I removed them,and thus checked float level.
This bike rejetting is done in the frame so I assumed the factory had set the level...