I am totally fed up with this

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#1
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:
 
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#2
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.
 
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#3
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
 
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#4
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.
 
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#5
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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#7
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#8
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.
 
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#9
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.
 
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#10
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.
 
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#11
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
 
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#12
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

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#13
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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#14
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.
 
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#15
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?
 
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