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Main Board => MX tech talk => Topic started by: Wait for me on August 16, 2010, 06:26:45 PM

Title: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 16, 2010, 06:26:45 PM
2005 yz 125
Sea Level (home), 2000-4000ft where i ride
Main 400
Pilot 37.5
Needle 6CHY5-80
Clip: 4th position
Air Screw: 1.75 turns

Problem: Used to run fine, but now it wont (home or at the riding area). Starts up normal, crisp, idle... Once warmed up it'll start bogging at half throttle. (which means it's running rich some where) It never did this before even after the new top end. Look at the spark plug and it's wet (again it's running rich). It doesnt even run long enough for me to take a test run. Dies while warming up.

False fix:
Took carb apart and cleaned it well. Still same thing.
Replaces the crank seal... same thing
Changed plugs (i've tried ### different types of plugs. BR9EG, BR9ES, BR8EV, BR8ES, BR8EG etc etc)

Changed
Main: 400 -> 410
Pilot: Same
Needle: same
Clip position: 4th -> 3rd position
Air Screw: 2.5


From what i can see... the jetting is not significantly off enough for the bike to die like this. Reeds are fine... Air filter is clean.

The only other thing i can see is the Tranny oil leaking into the cylinder, but the bottom end is dry and no signs of oil leakage. how else can i check? (replaced)

I reach out to you professionals and Carb gurus to please... lend me some advice! This is my 2nd two stroke (first one was nothing but headache and it NEVER run right even from the factory. I ghost rode that SOB into bushes so many times out of frustration) I've been stranded out in the desert numerous times from the bikes fouling.

Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: zman on August 16, 2010, 08:00:02 PM
I had a similar problem with a RM125
bike seemed like it just would not clean up on top and bog
after countless times of banging my head into the wall
i repacked the muffler and it was good as new after that
Packing didnt look to bad but i guess it was enough to make a difference
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: racerxx on August 17, 2010, 08:53:03 AM
Well from the limited information it sounds maybe like it's not getting any fuel. pull the petcock out of the tank and make sure it's clean also make sure your breather tube on the gas cap is not crimped or clogged. After that I would check the ignition.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: jayfox911 on August 17, 2010, 09:23:08 AM
I have no idea but have you checked the reeds? power valves? exhaust seal?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Bruce372 on August 17, 2010, 09:38:56 AM
good points, i spent weeks trying to jet out an issue from a clogged vent on the gascap

Well from the limited information it sounds maybe like it's not getting any fuel. pull the petcock out of the tank and make sure it's clean also make sure your breather tube on the gas cap is not crimped or clogged. After that I would check the ignition.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: SHOTGUN on August 17, 2010, 10:04:14 AM
good points, i spent weeks trying to jet out an issue from a clogged vent on the gascap

Well from the limited information it sounds maybe like it's not getting any fuel. pull the petcock out of the tank and make sure it's clean also make sure your breather tube on the gas cap is not crimped or clogged. After that I would check the ignition.

had the same problem...luckily it only took me two days to figure it out.  :? :lol: :lol: :lol:
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 17, 2010, 11:49:24 AM
Very symptomatic of two electrical components as well as all of the above, 1- coil [ when they begin to break down internally they often will misfire and then be fine again when cooled down.] 2- stator , [ stators can  exhibit similar misfire conditions when hot ,and seem fine when cold.] unfortunatley , both can check good [ book specs ] . you almost need to catch them in the act , test them when hot and even then , I have seen good spec. ranges on bad components .Yes , intermittent problems are the worst to trace . If you are lucky enough to know someone with the same bike you can swap components , dealerships often are able to pull parts from inventory to do this swap thing and if they burn up a good component , they can send it back on warr., but you can't. Process of elimination is your friend here.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 17, 2010, 09:39:13 PM
man i sure hope it's just a kinked hose or some packing issues....

seems as though it's a coil, stator problem...   remember blowing into the hose and it was fine. as far as re-packing the muffler... it does it on my stock and aftermarket muffler... what are the chances?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 18, 2010, 11:10:52 AM
We would be happy to look at it for you . Being a Proride Member I will only bend you over half-way .
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 18, 2010, 10:45:54 PM
wait...

why would the bike start again when i change it to a new plug? Wouldnt that rule out the Stator and ignition problem?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 19, 2010, 11:17:29 AM
It probably [ could have ] cooled down enough , during the plug change to get back to intermittant , please keep in mind this is purely speculation , but based on the process of elimination described in your post above of all the thing that were tried , I believe you still have a condition. As always , I hope the answer is the least expensive thing in the list.And if it becomes a scenario where the problem actually is just a bad ground wire , then woo hoo ! By the way , have you gone through and cleaned and checked all the grounds? Spark demands go up in ignitions with , hi - comp. pistons , extreme rpm ceiling increases , super heavy loads seen at the crank. These are just a few items that cause the spark plug to pull / demand more sprk energy. When the demand goes up , a bad ground has been known to cause this type of problem. crap - im rambling again , sorry.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 23, 2010, 09:19:41 PM
ok swapped out the ignition coil with a friends.... not the problem.

 Need to remove stator but the outer ring part seems like it needs to be pulled out with a gear puller or some sort? any other way to remove that sucker?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 24, 2010, 07:58:29 AM
No
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 24, 2010, 11:54:25 AM
$#@$#@ #@$#@$@! Time to go machine one together ... $70 for a gear puller is insane. lol

Nick:  you've been really helpful! I appreciate it.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Bruce372 on August 24, 2010, 12:03:58 PM
dude, you need a flywheel puller not a gear puller and they are cheap

http://www.rockymountainatvmc.com/vehicleSelectProd.do?prevVehicleType=2&prevMake=8&prevModel=58&keyword=FLYWHEEL&vehicleTypeId=2&make=8&model=58&applyFilter=Change+Vehicle&year=2006&navTitle=Engine&navType=type&webCatId=17&webTypeId=203&prodFamilyId=17155&stockId=&listingId=&uri=%2FproductDetail.do
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Boggn3rd on August 24, 2010, 12:07:53 PM
I am going with a vent tube clogged. Float bowl sticking will do what your saying as well. I have had similar problems with my old '89 CR. Pull your fuel line and make sure it flows good then go to carb.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Matt Fisher on August 25, 2010, 06:14:57 PM
My 92 RM250 had similar problems- the new rings had never seated properly.  New rings and it was wheelie time.  Maybe the top-end is a bit worn?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 25, 2010, 10:41:00 PM
i took a compression test and its at 120... isnt that normal?

checked reeds.. two of the reeds seep in a little bit of light.... should they be light tight?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 26, 2010, 08:14:27 AM
No - you may have found a problem . 125's should go 180 to 200 , pv-up / pv-down. Without enough compression you will not get complete burning of the fuel , hence , fouling. Pull your pipe and take a peak inside the cylinder , look at the rear wall for seizure marks , those are so simple to take apart that I'd just do a quick visual on it straight away.Drain it and pop the head off , take a little look see.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 26, 2010, 01:53:20 PM
i feel like i owe you a beer or something, nick! lol

I did the compression test all wrong! I thought it was 3 kicks WOP. I kicked until the reading stopped... *drumroll* its at 140-145 still a bit low from 180, but better than 120.

Piston seems to be ok, but when i crank the bike slowly i can see bubbles from some liquid on the sides of cylinder(i've attached video) 8 o clock and 4 o clock position. Look closely and there are some "Bubbbbleeessss".

i was thinking maybe coolant leak, but my coolant level is the same.  

http://www.facebook.com/video/video.php?v=10150255442050113  here's the video... it's still processing.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Bruce372 on August 26, 2010, 01:57:18 PM
sounds like youve sucked the base gasket.....it will run lean, which will especially cause a bog when you crack the throttle.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 27, 2010, 08:36:01 AM
Pull the cylinder , it will most likely have siezure marks , the 'flatten ' part of the ring will be on the exhaust port bridge , as Bruce indicated , you developedan air leak with made her run lean which in turn causes the bridge to bow inward and wipes out the ring face , instan blowby and lack of compression. Pull the cylinder , hone it , drop in a new piston and ring , back in business. p.s. also determine  WHY it started leaking at the base gasket , and correct otherwise its just going to be another go around. Good job everyone on this post , all you guys have some really good suggestions.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 27, 2010, 01:07:18 PM
i guess the outcome wasn't as good as I'd hoped! Off to pull the head off! hope i dont need to hone the cylinder.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 27, 2010, 01:42:30 PM
o.k. . You MUST de-glaze [ hone ] the cylinder otherwise the new rings will NOT seat correctly. If you don't have a PROPER hone / or do not know the CORRECT method of de-glazing ,just stop by here and I will do it for you NO CHARGE , only takes as long as typing one word  here. Of course if this sounds like I'm advertising [ Phil ]  if it is then maybe I can't help you , even for free ?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 27, 2010, 06:17:24 PM
nick, you're awesome. Where are you located? I can bring a 6 pack of your favorite brew (drink it after you hone my cylinder)!!!

i usually "honed" it with a scotch bright pad... not good enough?

I pulled the top off and there was "leakage"!!! one of the dowels was a bit corroded/rusted from coolant leaking i assume. 
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Boggn3rd on August 28, 2010, 06:12:42 PM
nick, you're awesome. Where are you located? I can bring a 6 pack of your favorite brew (drink it after you hone my cylinder)!!!

i usually "honed" it with a scotch bright pad... not good enough?

I pulled the top off and there was "leakage"!!! one of the dowels was a bit corroded/rusted from coolant leaking i assume. 

I thought you weren't supposed to hone plated cylinders?? Glad your getting to the cause.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Bruce372 on August 28, 2010, 06:24:10 PM
all that is needed is a quick deglaze and it will be fine.

however, its important to look at the top edge of the cylindern for pitting and corrosion- 2 strokes run really bad on modern ethanol based pump fuels and often the front of the cylinder at the top near the o-ring gets pitted from detonation causing the o-ring to fail.

the only reason i say this is from the comments below- if you take a pic of the top of the cylinder, this will be a help.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 30, 2010, 10:03:32 PM

hmmm.. so should i get it honed or no?

the cylinder looks clean as a whistle. Will get pics later this week.
I've used a weisco piston previously, should i go with the weisco or go OEM this time?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Matt Fisher on August 31, 2010, 08:55:48 AM
If you have a tendency to go a bit longer than you really should between rebuilds and are willing to thoroughly warm up the motor before really getting on the throttle, the Weisco is a better choice.  The forged design will take a bit more abuse before coming apart than a cast one will.

The oem and other cast pistons (ART, Namura, Pro-X, etc) are fine and are cheaper, but if you wait too long to swap out a piston, they'll crack and fall apart easier than the forged ones.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on August 31, 2010, 10:20:33 AM
Stop asking ,and just do it. Yes , Nikasil liners need to be honed. NOT with standard hones however. That is why I offered to do it free. And thak you for the brewski offer ,I don't drink , but maybe if i'm on this board I should .! I will also inspect it for additional problems while yo're here.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on August 31, 2010, 04:45:04 PM
Matt, thanks!!! i think i'll try the stock one this time.


nick, where are you located?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: zman on August 31, 2010, 05:50:19 PM
Matt, thanks!!! i think i'll try the stock one this time.


nick, where are you located?

Can you stop your bitching and just take it over to Nick ha ha

http://www.provalvemx.com/
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on September 01, 2010, 09:05:23 AM
I am currently sitting in my chair . The chair is located at 1281 Logan Ave. Costa Mesa Ca. 92626.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on September 01, 2010, 10:45:18 AM
Rudy... how about you go E.A.D.!!! lol

thanks nick!
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on September 03, 2010, 08:27:55 PM
Any time pal. Hope she runs fine for you.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: mxjef on September 11, 2010, 07:45:39 PM
So.........is it fixed?
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: Wait for me on September 12, 2010, 02:04:46 PM
I injured my knee the day after Nick honed my cylinder...
Been slowly piecing it back together. Top end is in. Nick mentioned my left crank seal is most likely leaking. That could very well be the problem!! Thanks again, Nick!!!
I'll keep ya'll updated! thanks for asking mxjef!!!

got the seals from a yamaha dealer in harbor city... thats a whole other story... they over charged me and are being sneaky about it.... will mention it when i go to pick it up. No parts or prices are listed under my purchase receipt and when i looked at my old receipt from 2 weeks ago the price was $7 not $9 and who knows how much more he charged for the other seal. i dont really care about the $5 difference... its the principle.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: mxjef on September 12, 2010, 08:02:17 PM
Just thought I'd mention, had a similar problem with Elmo's YZ85 years ago.
The thing would run great for a lap or so and than start cutting out and running like crap.
Tried swapping out all kinds of electrical stuff, bike ran great in the garage. Go to the track and a couple laps later it was running like crap. This went on for a couple weeks.
Ended up being the kill switch! Someone at the track suggested disconnecting it to rule it out, bike ran great after that!
Bought a new kill switch and problem was solved.
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: nickvalve on September 12, 2010, 08:16:33 PM
Good addendum Jeffro !
Title: Re: Problems on 2005 yz125 (bogging out, jetting is fine)
Post by: mxjef on September 12, 2010, 09:03:48 PM
Please don't use those big words on me, Nick.... :lol: