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Ryan314

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Feb 4, 2007
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First of all, this is me ---> :yell:

My YZ runs absolutely fantastic. Power is there, power is smooth, never fouls plugs while riding, it's pretty much perfect. But, when it comes to starting it up after a day of riding or so, there in lyes the problem. Bike starts up first kick every time, and I don't even need to use the choke. But usually (sometimes it doesn't), the plugs fouls on start up. After letting it warm up some, when I go to take off, it makes a bogging sound, and the bikes shuts off. Fouled plug. So then I put a new plug in, and she runs perfectly normal :bang: . I always shut the gas off and my plugs look healthy after riding, brownish/tanish color. I run BR8ES plugs and Yamalube 40:1.

What could be the problem here? Is it a jetting issue, even though my plugs look good? I feel it has something to do with either:

A.) Not letting the bike warm up properly, or long enough

B.) The motor gets too much of a rich mixture on start up, causing it to foul.

I've tried adjusting the air screw, leaning it out some, but it doesn't seem to be helping.

What should I do!? I'm so tired of having to change the plug every single time. :bang: :yell:
 

FruDaddy

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Aug 21, 2005
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Just a guess here, but you might need a leaner pilot jet. If you don't get a more reliable answer, give it a try.
 

MXer666

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Jul 15, 2007
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no, when you turn the gas off the gas that is in the carb bowl dries up some and the oil is left behind. When you then turn your gas on the next ride your letting in more gas and oil but in actuallity you have twice as much oil to gas in the carb so when it strts up and fouls thats because of the excess oil.

just my .02
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
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When you let the bike idle for a long time to warm up, it loads up the engine. Then, when you try to take off, it makes no power and spews smoke. All of our 2-strokes will do this, the longer you let them idle the worse it does it. You shouldn't need to change the plug, just stay on the throttle for a minute and clear out the engine. If you run up thorough the gears at full throttle, it should clear out by 3rd gear or so. Personally, I don't idle my bike to warm it up. I start it up, run it for 30 seconds to a minute, stick it in gear and start cruising. After a minute or 2, I clear it out by running up through the gears and it's good to go. You should never really leave your bike to idle for extended periods.
 

sparkysakitas

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Aug 31, 2005
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i have 96yz used to do that
i switched to klotz at 40 to 1 with premium gas
adjusted my air fuel ratio screw and that solved my problem
 

BSWIFT

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Ryan314

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Feb 4, 2007
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76GMC1500 said:
When you let the bike idle for a long time to warm up, it loads up the engine. Then, when you try to take off, it makes no power and spews smoke. All of our 2-strokes will do this, the longer you let them idle the worse it does it. You shouldn't need to change the plug, just stay on the throttle for a minute and clear out the engine. If you run up thorough the gears at full throttle, it should clear out by 3rd gear or so. Personally, I don't idle my bike to warm it up. I start it up, run it for 30 seconds to a minute, stick it in gear and start cruising. After a minute or 2, I clear it out by running up through the gears and it's good to go. You should never really leave your bike to idle for extended periods.

Well, I've tried that exactly. But it seems to bog worse when I give it gas, or try and go through the gears upon start up. It makes that "bwauugghh" sound, not that nice crisp sound when warmed up.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
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Yeah, it does bog worse as you open the throttle more. Stay on it and it clear out. It shouldn't take much more than a few seconds, though.
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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If it is jetted properly on the idle and pilot,and does not have mechanical issues,and is not running outboard motor fuel,then it will not load up! Otherwise,yank the right crank seal out,find some gold label blenzoil,fill up the cases and run a b5es,of course I am kidding,maybe! MX666,did the devil tell you about residual oil build up?http://dirtrider.net/forums3/showthread.php?t=48348, I know,it is not the answer you were looking for! You have to learn,or find someone to do it for you.
 

kiwijohn

Member
Dec 22, 2004
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I seem to recall someone saying the bike should need a bit of choke to start ? If it doesn't need it, the pilot might be a bit rich....

Have you read the plug at the air screw, pilot, needle, main portion of the rev range?

The instructions are on here in lots of places... Spanky's guide I think it's called?

You could be good up top but way rich down low.... you need to find out for sure before you change too much else.

If it's jetted well, it should run clean and crisp all through the rev range. :cool:

Good luck mate
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
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I had a right crankcase seal fail. With a fresh plug, the bike would start and run normally for an hour or so, then die with no hope of getting it restarted. After a while, the problem got worse and after a fresh plug the bike would run for a minute, then barely at all. At the worst, the bike would start and foul the plug almost instantly. As soon as you touched the throttle, the engine would just die. Has your bike been consuming crankcase oil?
 

sick 96 250

Damn Yankees
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Jul 16, 2004
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I would say drop the pilot a size or 2, and before you fire the bike up give it a few slow kicks with the ign killed to prime the cylinder. After that give her hell on the first kick and then let her warm up then go ride. I had the same issue with my RM till I did this. To much fuel at start up was causing my plug to partially foul, then when I stabbed the throttle it killed the plug instantly

Besides that issue check your float level....
 

RM_guy

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Before you change any jetting make sure the choke circuit is alright. It should NOT start without the choke. If it is there could be dirt under the choke plunger that is keeping it from closing all the way. This will let a small amount of fuel to get past so it starts easy but the extra gas will make it run rich and foul plugs once it's warmed up.
 

Ryan314

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Feb 4, 2007
145
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Well I noticed that when I use the choke to start it, when it first fires up, it revs really really fast for about 5 seconds, then revs normally. Is this normal?
 

2strokerfun

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May 19, 2006
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Ryan314 said:
Well I noticed that when I use the choke to start it, when it first fires up, it revs really really fast for about 5 seconds, then revs normally. Is this normal?

A little fast, yes. "Really really fast," no. I usually have my choke turned off before 5 seconds goes by. The minute it starts, I reach down and turn off the choke.
 

DLHamblin

Member
May 27, 2005
268
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Ryan314 said:
First of all, this is me ---> :yell:

My YZ runs absolutely fantastic. Power is there, power is smooth, never fouls plugs while riding, it's pretty much perfect. But, when it comes to starting it up after a day of riding or so, there in lyes the problem. Bike starts up first kick every time, and I don't even need to use the choke. But usually (sometimes it doesn't), the plugs fouls on start up. After letting it warm up some, when I go to take off, it makes a bogging sound, and the bikes shuts off. Fouled plug. So then I put a new plug in, and she runs perfectly normal :bang: . I always shut the gas off and my plugs look healthy after riding, brownish/tanish color. I run BR8ES plugs and Yamalube 40:1.

What could be the problem here? Is it a jetting issue, even though my plugs look good? I feel it has something to do with either:

A.) Not letting the bike warm up properly, or long enough

B.) The motor gets too much of a rich mixture on start up, causing it to foul.

I've tried adjusting the air screw, leaning it out some, but it doesn't seem to be helping.

What should I do!? I'm so tired of having to change the plug every single time. :bang: :yell:

Well, my YZ250 or my son's YZ85 will do this if not warmed up correctly.

What we do that always seems to work is start it on the choke and don't touch the throttle for about 20-30 seconds. Then open the throttle to a fast idle and turn off the choke. Keep it at that steady high idle (not screaming, just a fast idle) for about 30 seconds or more (longer if its cool out) (don't be blipping it, the plug isn't hot yet and when you blip it you can get a cold foul). Then you can blip it a bit and rev it up to clear it out or see if its warm yet by the way it responds.

Each bike is different, but the above works for us to prevent the exact situation.

Also as mentioned; if the bike is going to sit for more than a week its best to drain the float bowl on the carb.

Also, after re-reading the original post; my bike needs the choke to start up in the mornings. I run a #48 pilot instead of the #50, but it will still occasionally cold foul if I don't follow what I posted.
 
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Ryan314

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Feb 4, 2007
145
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Could it have anything to do with the air filter? I noticed this problem started to happen after I cleaned my TwinAir filter for the first time. I re-oiled it with Suzuki foam air filter oil. Could I have possibly put too much oil on it allowing not enough air to pass through yeilding a richer mixture? Or maybe the Suzuki filter oil may be too thick?

Just trying to single out as many things as possible.
 

Ryan314

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Feb 4, 2007
145
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Well here's some good news.

I think I may have solved the problem today. When I started it up today, I let it idle with no choke and no blipping of the throttle for a good 5 minutes. When I felt the heat of the pipe/cylinder, I gave it some throttle and it sounded crisp. I gave it a whirl and it ran fine, no fouled plug.

So I hope this was the problem solver. Before I was only letting it warm up for like 1 minute, then trying to take off.
 

NM_KDX200

Member
Dec 29, 2002
441
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Ryan314 said:
Could it have anything to do with the air filter?
I was wondering the same thing. The only time my '01 KX125 fouled plugs was after I'd installed a fresh air filter (and let it sit overnight). I was using Maxima air filter oil. When I switched to NoToil, it never fouled another plug in the remaining 3 months I owned it. When I got my YZ450F, I cleaned the stock filter and re-oiled it with Maxima. Guess what? It fouled a plug. My new Twin Airs came in the next day and I used No Toil on them. It's been a year and I'm still on the same plug I installed the day it fouled. Also, I used to use Maxima on my Grizzly 660 and guess what? Yup...it would foul plugs after a couple months. Installed a new Pro Moto air filter, switched to No Toil...been almost a year, no fouled plugs.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
You don't need to sit there and blip the throttle for 5 minutes to warm up on the bike. Just hop on it and start cruising around. This will reduce how badly it loads up, it will warm it up faster, and you don't have to sit there revving yoru engine for 5 minutes (I know I don't have that kind of patience).
 

snb73

Member
Nov 30, 2003
770
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Clean your air filter, saturate with oil, then "really" squeeze the excess oil out. The filter should almost appear dry.

Clean your carburator, check float level and record your jetting.

Your bike calls for a NGK R6918B-8 plug. "Most" 125's run well on a BR9EG or BR9ES with a fuel/oil ratio of 32:1 (I don't think this is your problem)

All bikes are different, but here is a good start/warm-up routine for non-winter riding. Fuel on. Choke on. Gently kick the starter lever until you feel the compression stroke. Kick hard and firm while opening the throttle 1/4 of the way.

Once the bike starts IMMEDIATELY turn off the choke. Hold the throttle 1/4 of the way open until the radiator warms up. You should be warmed up and ready to go. This should take 30-60 seconds.

Assuming your engine is in good mechanical shape and carb/plug/fuel is correct, sounds like you need to read up on jetting.

http://www.dirtrider.net/forums3/search.php?searchid=745124
 

blanc

Member
Dec 18, 2002
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try this..dont let the bike idle onwarm up..give it gentle blips of the throttle constantly for about 1 minute. Get on and ride
 
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