2016 YZ250 wont idle

[troycalm]

Brand new 2016 YZ250 off the showroom floor.

I've already been thru the break in period and having a couple issues the dealership cant seem to help with.

The bike takes twice as long as its125 counterpart to warm up. If fouls a plug every time i take it out,its not oil fouled,the plug just stops working.

No matter what i do or adjust it will not idle. I called the dealership,they recommended changing the stock pilot to a 47 and changing the brand of premix.

The pilot fixed the long warmup time but not the idle. I can turn the air-screw all the way in and the idle screw all the way in,no change.

I've rode 2 strokes my whole life and have never had this issue. 

[CaptainKnobby]

I would first get a good premix......like say Amsoil Dominator. I use this brand and works real well. Mix it to 32:1 which is 4ounces to a gallon. Jet the carb for this mixture.

Find out what elevation you are and the Temperature. I would say if you are at sea level to around 3k ft and temp in the upper 70's go with about a 175 MJ and needle in the 3rd clip to start out with.

Then tune the air screw

[yz250474]

Brand new 2016 YZ250 off the showroom floor.

I've already been thru the break in period and having a couple issues the dealership cant seem to help with.

The bike takes twice as long as its125 counterpart to warm up. If fouls a plug every time i take it out,its not oil fouled,the plug just stops working.

No matter what i do or adjust it will not idle. I called the dealership,they recommended changing the stock pilot to a 47 and changing the brand of premix.

The pilot fixed the long warmup time but not the idle. I can turn the air-screw all the way in and the idle screw all the way in,no change.

I've rode 2 strokes my whole life and have never had this issue. 

what kind of fuel are you using? what oil? what ratio?

 

 

you saying you can turn the idle screw all the way in with no change.... sounds like you have a serious problem.

Edited July 3, 2016 by yz250474

[moto9]

47 doesn't sound right, drop down to a 42 or 40

I run a 38 on a beta 300.

Leaner pilot should fix the idle problem.

But you need to rejet all the circuits.

If you're not good at jetting a bike get a jd jet kit, they're pretty spot on with minimal tuning.

You'll need to readjust the float level as well.

Edited July 3, 2016 by moto9

[troycalm]

Brand new 2016 YZ250 off the showroom floor.

I've already been thru the break in period and having a couple issues the dealership cant seem to help with.

The bike takes twice as long as its125 counterpart to warm up. If fouls a plug every time i take it out,its not oil fouled,the plug just stops working.

No matter what i do or adjust it will not idle. I called the dealership,they recommended changing the stock pilot to a 47 and changing the brand of premix.

The pilot fixed the long warmup time but not the idle. I can turn the air-screw all the way in and the idle screw all the way in,no change.

I've rode 2 strokes my whole life and have never had this issue. 

 

 

what kind of fuel are you using? what oil? what ratio?

 

 

you saying you can turn the idle screw all the way in with no change.... sounds like you have a serious problem.

 

Pump gas with yamalube premix per directions. adjusting the air/fuel screw or the idle screw doesn't change anything.

my sons 2016 yx125 runs great on the factory jetting which is supposed to be the same on both bikes.

Off idle the bike runs like a scalded cat.

[KPRacing]

Did you check your float level?

[YZJ]

Unless you're at elevation the stock jetting at 32:1 Yamalube should be perfect. There is a problem with the bike and the dealer needs to fix it IMO.

[moto9]

Turning in the air screw makes it run richer.

The air screw is just a fine tuner for the pilot.

The pilot first must be in the correct zone.

Ideally 1.5 turns out with the correct pilot, so you can tune rich or lean to adjust for temp, humidity and elevation.

Try a 42 pilot and check the float level while you at it.

[TMX]

Before you go throwing jets at it, changing float levels, etc...

 

If bike this truly is 'right off the showroom floor", your dealer needs to fix this issue under warranty. You start opening up the carb, etc..., the dealer may use that as a reason to consider the warranty void.

 

That said.... you say you can turn the idle speed screw all the way in with no change whatsoever? The idle speed screw makes direct mechanical contact with the carb slide, lifting it slightly in response to turning the idle speed screw clockwise. The screw doesn't engage the slide until it's screwed in a pretty good amount. Are you certain you've turned the idle speed screw in as far as it will go? Don't force it, just be sure it's reached it's actual stopping point.

 

If it is in fact turned in as far as it will go, my next question would be, can you get the bike to idle by holding the throttle slightly open?

 

-B

Edited July 3, 2016 by TMX

[neilnice]

Back when I used to rip the yz 2 strokes I always had bad luck with yamalube. Not saying that new premix will solve your idle issue but it cleared up my plug fouling. I ran both belray h1r and maxima k2. H1r goes for 30$/L here in Canada so I switch to the k2 and didn't find a difference between the oils.

[TMX]

Also, can you clarify what you mean about the plug fouling? Is it wet/dry/sooty/chalky? What color is it?

 

-B

[LSHD]

Don't mess with jetting or premix. 47, 50, any of those sizes is plenty close to get a good idle, and 32:1 is standard premix.

 

STEP 1:  Pull your subframe and observe whether or not your slide is lifting up as you screw in your idle screw. That's the only thing you need to check to start with.

[N8ster]

What does the filter look like? Did idle ok before you brought it home?

[Tony211]

I've ran Yamalube for years and never fouled a plug.

Talk to your dealer.

[numroe]

Every stock YZ250 (and YZ125 and 85) is jetted too rich on the pilot. The blubber, smoke, black spooge and fouled plugs is intriging to say the least.   I guess Yam do it on purpose in case some rare meat-head engine brakes down a steep hill for a minute in cold weather with peanut oil for premix.

 

I presume Yam would rather have the reputation for fouled plugs and black spooge than to deal with a rare minority lean seizing their motors at high RPMs with throttle near closed.  Maybe it's some company policy hanging over from decisions Yam made in the 1980s.

 

The saying that "you need to ride a 2-stroke hard on the pipe" is stonege BS.

 

The YZ250 stock needle is too lean at 3/8th throttle, so Yam also need the rich pilot jet to try compensate. But it's just a partial fix.

 

No YZ250 (of any bike Keihin PWK 38 carb) using the Yam NE3X needle uses a pilot jet anything like the small pilots in a Beta or KTM or whatever. Totally different needles.  Also different pumping pressure due to the crank case design.

 

Going down one size on the pilot can make a big difference to clean running up to 1/4 throttle, but the 3/8th throttle lean bog will be worse. For better roll-on power with the Yam needle it often works to go one size smaller on the pilot jet and one clip pos richer on the needle. But the real fix is the zook NExJ needle and the right brass for well under $50 but some tuning time. Even better is the head is corrected - for under $150.

 

In my opinion, "ready to ride off the showroom floor" aint the truth for most people with new 2006-16 YZ250s.

 

Typical stock problems:

1. Rich on the pilot.
2. Head squish clearance too wide (hyper sensitive jetting).

3. Wont idle for more than 30 secs.
4. Power delay then the mid range hit (Yam needle and the wide squish).
5. Rear suspension way too hard on high speed hits (wrong valving for the gimmicky fat 18mm shock shaft)
6. Front tire feels vague on less grippy dirt surfaces (fork reb setting and the alum frame).

 

Most stock YZ250s cannot idle for more than 30 seconds. It depends on your luck.  The problem happens because the slide is only just open at idle, and if the slide rocks or pulls left or right then the air/fuel ratio changes a lot and not in the middle where the pilot circuit is pulling. When you adjust the idle screw you are rocking the slide too, so the result is random.   The fix is to file a 2mm deep and 3mm wide notch in the middle of the bottom of the slide, then turn the idle screw out to get a steady low clean idle with air flow only through the notch  and so over the pilot circuit. I filed a small conservative 2mm wide 1mm deep notch and the improvement was huge. No negative effect found. I've no theory why Yam don't fix it in the stock bikes. Seriously easy to do it yourself.

Since I'm ranting ... To perform a lot better, your stock YZ250 does not need porting, pipe, gearing changes, V-force reeds, rear brake air scoops, flywheel weights or better stickers. Some of those things can help, but they are way down the wish list. In my opinion.

Edited July 4, 2016 by numroe

[TMX]

This thread is giving me a headache.

 

From the OP's original post:

"I can turn the air-screw all the way in and the idle screw all the way in,no change."

 

-B

[numroe]

This thread is giving me a headache.

 

From the OP's original post:

"I can turn the air-screw all the way in and the idle screw all the way in,no change."

 

-B

TT is rambling fun. ?

 

But nicely spotted.  Plug fouls with the air screw dialed in the whole way. Hmmm.  LOL!

[moto9]

Go the other direction with the air screw, turning the air screw inwards makes it richer.

[TjSteve]

I have a 16 Yz250 that was doing the same thing since day 1. Wouldn't idle, fouled plugs quickly, lots of splooge. Very frustrating.

Lower the float 1.5mm

45 Pilot

178 Main

2nd clip position

1.5 turns out

It is a different bike. Idles great, 1st kick start, great response.

Good luck!