TPA-MX

Fouling plugs or flooded?

34 posts in this topic

Hello everyone

So, I am a little stumped on the behavior of my 02 yz 125.  After a top end rebuild, new gaskets and crank seals, repacked muffler the bike still seems to run rich, based on the pic of the plug, the bike seems to still be running rich?  Here are the settings on the bike:

AS is 2.5 turns out

Pilot:  25

Main Jet:  415.

It started just fined earlier today, and I rode is for about 5 minutes, it was hauling!!  My son then came home, started on first kick, i did notice there seemed to be a constant white smoke coming from the pipe.  It started up with a high idle, but then calmed down.  He rode it around for about 10 minutes and it was riding fine.  He was riding in 2nd gear and cruising and then it started to bog out and then died.  He tried to kick start it, but nothing.  He and his friend then tried start it from pushing it then popped the clutch and it would never turn over.  This has happened before and once I replace the plug, it starts right back up.  

I thought by lowering both the main and pilot jet it would help resolve these issues.  

Anyway, any tips would be VERY helpful and appreciative.  

Thanks!

IMG_20170216_201052_01.jpg

Share this post


Link to post
Share on other sites

Hmm what premix ratio are you running? Also how's the air filter?

You possibly need to readjust the jetting for the new top end. 

 

Share this post


Link to post
Share on other sites
2 minutes ago, SpaceChainsaw273 said:

Hmm what premix ratio are you running? Also how's the air filter?

You possibly need to readjust the jetting for the new top end. 

 

I am running 32:1.  Air filter is good..just cleaned.  I did lower the main and pilot jet after the new top end.  Let me further clarify...the jets in the bike prior to the ones I mentioned, I could not read the numbers.  I am thinking they were stock?

The bike was having the same issue before the top end as well, fouling plugs and would not start.  After a new plug, it would be fine.  Very frustrating.  

Edited by TPA-MX

Share this post


Link to post
Share on other sites

I believe the clip is stock, I will have to check tomorrow....getting late here on the East coast.

Do you think I should move it up one slot so the needle sits further down in the housing?

Edited by TPA-MX

Share this post


Link to post
Share on other sites

Check the float / fuel level, too high and it will make the engine run richer.

 

Inspect the reeds for damage, if in doubt about their age, replace them.

Despite 'looking ok' they are a wear item just like a piston/ring (they loose tension)

If the current jets are un-identifiable, replace them with known good ones of the proper size.

 

You mentioned 'He was riding in 2nd gear and cruising', needless to say a 2-stroke MX race bike isn't the ideal bike for casual riding,

unless re-jetted leaner it's prone to fouling plugs at lower combustion temps.

If indeed it's used for trailriding, don't hesitate to lean out the pilot jet by at least two sizes and lower the needle one clip position,

(keeping the main jet a tad rich for those WOT moments), also avoid 'racing' type premix oils, rather choose a lower flash point one like Interceptor or Lucas.

A fine tipped 'Iridium' type plug might resist fouling a bit better in low speed situations when the jetting isn't ideal.(BR9EIX comes to mind like on my YZ)

Edited by mlatour
2 people like this

Share this post


Link to post
Share on other sites
7 hours ago, mlatour said:
Check the float / fuel level, too high and it will make the engine run richer.
 
Inspect the reeds for damage, if in doubt about their age, replace them.
Despite 'looking ok' they are a wear item just like a piston/ring (they loose tension)
If the current jets are un-identifiable, replace them with known good ones of the proper size.
 
You mentioned 'He was riding in 2nd gear and cruising', needless to say a 2-stroke MX race bike isn't the ideal bike for casual riding,
unless re-jetted leaner it's prone to fouling plugs at lower combustion temps.
If indeed it's used for trailriding, don't hesitate to lean out the pilot jet by at least two sizes and lower the needle one clip position,
(keeping the main jet a tad rich for those WOT moments), also avoid 'racing' type premix oils, rather choose a lower flash point one like Interceptor or Lucas.
A fine tipped 'Iridium' type plug might resist fouling a bit better in low speed situations when the jetting isn't ideal.(BR9EIX comes to mind like on my YZ)


Awesome insight mlatour. I will check the needle position this morning. Regarding the red valve, I don't know the age, but it is a vforce3 installed by the previous owner. Do you have to replace the entire Reed item (housing, etc) or do you just replace the reeds inside?

I am running the recommend NGK plug.  I will check the reeds this morning while I am looking the needle/clip setting.  

Regarding the cruising, he was blipping the throttle here and there, we was in the neighborhood so I did not want him to upset the neighbors.  

Edited by TPA-MX

Share this post


Link to post
Share on other sites

I've seen V force reeds leave a gap even with new Reed petals installed. Turns out the plastic cage was bad. I've typically found bad reeds will show a problem idling.

From your description of how he was riding, he was definitely on the pilot and needle. First off, verify what needle is in there.

As stated check float height. If the float needle has a spring on it, check float height at a 40 degree angle or so. If you flip the carb completely upside down it will give a false reading as the spring collapses.

Edited by zeke383
1 person likes this

Share this post


Link to post
Share on other sites

The mention of white smoke in the original post concerns me.  Is it possible that the right side crank seal is leaking?  The smoke should really clear up once the bike is warm and ridden on the pipe.  

BUT, start with the simplest thing possible.  It's perfectly fine to run a hotter plug if you are trail riding or even woods racing.  I run BR8ES plugs in my YZ125s for the woods, but I will put in a 9 for the track or deep sand.  The 8 plug will be much more resistant to fouling, and the ES version only costs about $2.50 at any autoparts store.

You don't give your location, but if you are anywhere near sea level the stock jetting should not be that far off.  The main could maybe go one step leaner, and pilot could go a couple for trail riding or inexperienced riders.  One of my YZs came with a half step needle which is useful.

Leave your premix at 32:1

 

Edited by rpt50
1 person likes this

Share this post


Link to post
Share on other sites

Hey guys, thanks for the input. I am in Florida, so that is about as sea level as you can get.

I had a new needle from a carb rebuild kit I just installed. The original needle was installed when I bought the bike and I can not figure out what number it is. None the less, I put the new needle in and clip is on #2 from the top, this should lean it out a bit, right?

As far as the reeds, I see some light coming through the side, a bit, and small amount coming from the ends, see pics. I have seen where people have reversed them to extend the life. Based on the pics, should I just order replacements?

The crank seals were just replace while I was working on the top end so that should be good to go.

The back story to this bike is that we have always had problems with it being rich and fouling plugs.

20170217_092022.jpg

20170217_092059.jpg

Edited by TPA-MX

Share this post


Link to post
Share on other sites

High idle off the initial start where it then dies down is usually a symptom of being lean (someone verify please, but I think thats correct).  The extra air seeping into those loose reeds can definitely cause that.  I've never rejetted a bike based solely on a new top end, or a season for that matter, but some folks here would probably like to smack me for that.  To me it's just not necessary.  Back to you, air leaks can make diagnosing jetting a REAL PAIN.  I'd do what I could to fix the reeds first, then go from there.

Share this post


Link to post
Share on other sites

That being said, my 09 YZ125 smokes a bit as well.  It could use leaner jetting, always has been the same though.  It doesn't bother me.  I wouldn't worry tremendously about the smoke unless it's a grotesque amount.  A lot of 2 strokes smoke, that's what they're for! Nothing that can't be cleared up with a little TLC.  Fouling on the other hand is another symptom.  I can run the same plug in my bike for YEARS, never fouls.  That indicates a bigger problem, as in air leak, or jetting that TOO far off.

1 person likes this

Share this post


Link to post
Share on other sites

Gents,

I just realized something after further looking at the bike.  The Airbox boot item that clamps down on the intake side of the carb has a rubber notch on the inside of the boot, right where it attaches to the carb.  If that is off a bit (think left or right) could that notch cover the pilot intake on the carb, making the system rich?

If this is the case, should I trim off the notch?  I am saying this because I feel like the notch might be covering the AS intake (where the small metal filter) item is on the intake.

 

20170217_095650.jpg

Share this post


Link to post
Share on other sites

Hmmm...interesting.  I can't compare to my YZ as its a newer model and doesn't have that.  Most newer bikes have a notch on the outside of the airboot that lines up with a notch on the carb to ensure that you don't misalign during install.  Is the notch you've pictured a solid piece of plastic (like immovable) or is it flimsy? 

Share this post


Link to post
Share on other sites
1 minute ago, bcssrmz250 said:

Hmmm...interesting.  I can't compare to my YZ as its a newer model and doesn't have that.  Most newer bikes have a notch on the outside of the airboot that lines up with a notch on the carb to ensure that you don't misalign during install.  Is the notch you've pictured a solid piece of plastic (like immovable) or is it flimsy? 

Its rubber, part of the boot that connects the airbox to the carb.  There are notches on the reed valve boot (exterior) that alligns with a notch on the carb...but I noticed when the airbox boot connects to the carb, it seems a little off.  It might be nothing...but I was just wondering if I should nip off the rubber notch that is inside the boot.  It looks like it is there to align up with the bolt that holds the AS metal filter in place.  I am sure for protection so that the bolt would not get sucked into the carb if it came loose.  

I am tempted to nip it off anyway, just to see if it helps.  I would think that if this is covering the AS hole, then that might be a cause to the richness as well.  

Share this post


Link to post
Share on other sites

Stock boot and stock carb?  I wouldn't mess with it, more than likely not the cause of your issue.

EDIT: I know the backside of my carb and air boot are a PITA to mate.  It takes quite a bit of finnagling on both sides of the bike, pushing and shoving to get it to seat well around the entire carb.

Like I said, if both are stock.  Probably not your issue.

Edited by bcssrmz250

Share this post


Link to post
Share on other sites

Notch is suposed to be there.

Jetting might be a little off.

See spankys thread in sticky.

Everyone here so far has hit the nail.

I am not great at jetting unless I am sitting on bike and riding. It's a feel thing and plug visual. 

1 person likes this

Share this post


Link to post
Share on other sites
37 minutes ago, bcssrmz250 said:

Stock boot and stock carb?  I wouldn't mess with it, more than likely not the cause of your issue.

EDIT: I know the backside of my carb and air boot are a PITA to mate.  It takes quite a bit of finnagling on both sides of the bike, pushing and shoving to get it to seat well around the entire carb.

Like I said, if both are stock.  Probably not your issue.

Yes, both are stock.  Just so everyone knows, I am in Florida, basically sea level.  75-80degrees.  Here is what I have done so far today with the results:

  1. Removed the carb and Reed valve.
  2. Inspected the reeds, see pic in previous post, they seem ok?  A little light coming in from the sides. Replace?
  3. Replaced the needle with one that came with a rebuild kit a while back, clip is on Slot #2 (should lean it a bit).
  4. Pilot #25 (no change)
  5. Main #415 (no Change)
  6. Reinstalled carb and reed valve system.
  7. Did my best to align the rear for the carb to the air boot so the rubber part lined up to the screw
  8. Reinstalled a plug that I had from before (Autolite plug, comparable part number to the stock NGK ).  I have more NGK plugs arriving today.
  9. Kicked over in about 3 kicks. :)

rode it around the neighborhood a bit, seemed fine.  Came back, cut her off.  Sat for about 2 min.  1st kick start.  

@Gary YZDOC:  I have read through spanky's carb tuning guide, but it mentions to start with the AS @ 1.5 turns out.  Should I go with that or the 2.5 turns that the YZ recommends?

Share this post


Link to post
Share on other sites

It's been a while since I've looked at reeds, so that small amount of light may be normal, but my initial impression is that you'd want complete sealing.  Ole YZDOC should be able to assess.  RMATV machine specs show that the stock main is 420, stock pilot is 30.

I've found this site helpful and accurate before when not having a reference or manual.

https://www.rockymountainatvmc.com/Machine-Specs

I've always worked under the impression that A/S should be between 1.5-2.5 turns out.  2.5 being the max before reevaluating the jetting.  If idling high when you first start is in fact indicative of leanness, then your A/S at 2.5 is not helping, in addition to your pilot being lean; you've got a 2x factor of leanness there at idle (if that makes sense).  The plug pic is kind of hard to read, and although it looks wet, I don't think that's truly an assessment of the jetting.  Really it's the color of the insulator tip.  In all honesty, my plug looks like that alot.  It's kinda dark, but not usually wet.  I think that's a flooding thing?  I wouldn't worry about reading the plug until you've ridden it full out 100%.  Putting around the cul-de-sac or whatever won't give you a good reading.  It's more about throttle response at that point.

It may be in spankys guide, but essentially with the bike FULLY WARMED, you want to set the idle where the bike will barely idle.  At that point turn the A/S in until it nearly (or does) cut off.  Turn the A/S out until you reach PEAK idle.  That's where you want the A/S set.  If it's >2.5 turns out, your pilot is too big (?), if it's <1, your pilot is too small.  I've worked on many bikes that in fact only needed 1 turn of the A/S, and BOOM....turned a turd into a rocket ship.

 

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

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now