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My YZ250 problem

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So Ive been having this problem with my 2011 YZ250 that it starts bogging at the top end and then eventually stalls. The first time it happened the bike was running fine for the first hour and then it started bogging when revved and then just died. So I changed the plugs with a new one and it kicked over but then still had no top end (might not of screwed the plug in far enough?) and my mate noticed fuel coming out of the pipe.

 

After this happened I took the bike to the store and they re-jetted the bike to run a little leaner, clean the carby and repack the exhaust (I get splooge dripping from the exhaust seal onto the rear swing arm). Before this I was running 40:1 using Motul 800 oil.

 

After getting the bike back the store drained the petrol out of the tank and advised to use Silkolene KR2 oil instead with the ratio of 32:1.

 

We went riding on sunday and after around 1-2hours of riding (mostly lugging around on a enduro track) I gave the throttle 2 big blips with the clutch pull in on 2-3rd gear and it started bogging again at the top and then eventually stalled. This time I changed the plugs again for a new one but the bike wouldnt kick over at all. I took it back to the car and my mate managed to roll start the bike and he said it sounded fine.

 

The bike has plenty of compression and will normally kick over 1st go with no problems.

 

I think the bike might be flooding and it could be how I'm riding the thing. The spark plugs look fine and are not fouling.

 

Any ideas?

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1.  Disconnect the kill switch - probably not the problem but always good to rule it out

2.  Install a new spark plug - even if it has a new plug!

3.  Pull the fuel line off the carb and make sure that you are getting full flow to the carb.  A stopped up fuel cock or fuel cap vent can be a problem.

4.  Swap the CDI with one that is known to be good

5.  Swap out the ignition coil with one known to be good

6.  Lastly, the ignition stator could be going bad.  Swap it out with one known to be good.

As you can see, it really helps to have a friend with the same bike!

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Thanks for the help. We are going riding next weekend so Ill see how it goes.

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1. Disconnect the kill switch - probably not the problem but always good to rule it out

2. Install a new spark plug - even if it has a new plug!

3. Pull the fuel line off the carb and make sure that you are getting full flow to the carb. A stopped up fuel cock or fuel cap vent can be a problem.

4. Swap the CDI with one that is known to be good

5. Swap out the ignition coil with one known to be good

6. Lastly, the ignition stator could be going bad. Swap it out with one known to be good.

As you can see, it really helps to have a friend with the same bike!

I agree with all. I like #3 especially. Maybe a kinked breather hose coming from the tank. Or if the hose has the one way breather check valve, that may have some crud in it causing it not to work properly.
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Basically what everyone else has said. An ultra lean mainjet is also a possibility. Do what Kenpowel said thats good advice.

 

EDIT: An air leak that requires certain crankcase pressure to be a problem is also a possibility. check your gaskets.

Edited by Keira2142

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Had this happen. Turned out to be the fuel filter on the petcock. It was super gummed up with just gunk. Take a look at it if you haven't already

 

To get to the filter do you need to take the petcock off?

 

Pretty much a newb at working on bikes so I was thinking about putting it in to the bike shop

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To get to the filter do you need to take the petcock off?

 

Pretty much a newb at working on bikes so I was thinking about putting it in to the bike shop

 

I wouldn't. Two strokes are extremely easy to work on, even if you have to end up rebuilding the top end for this issue (just an example unlikely that will fix it but a compression check should be done as well), it can be done in about an hour if you've taken out the previous piston, wristpin and small end already. Which I always do. Very simple machines, very awesome.

 

To check the petcock, empty all the fuel out of your tank into a jerry, and unscrew the petcock on the bottom left hand side of the tank. Should be as simple as 2 philips head screws.

 

If you take it into the shop, they will just do exactly what kenpowell did but charge $70 an hour for it plus parts.

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I wouldn't. Two strokes are extremely easy to work on, even if you have to end up rebuilding the top end for this issue (just an example unlikely that will fix it but a compression check should be done as well), it can be done in about an hour if you've taken out the previous piston, wristpin and small end already. Which I always do. Very simple machines, very awesome.

 

To check the petcock, empty all the fuel out of your tank into a jerry, and unscrew the petcock on the bottom left hand side of the tank. Should be as simple as 2 philips head screws.

 

If you take it into the shop, they will just do exactly what kenpowell did but charge $70 an hour for it plus parts.

 

No worries, I will give this a go this afternoon. Its more like $100 per hour plus parts (usually double the price of US oem parts)

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No worries, I will give this a go this afternoon. Its more like $100 per hour plus parts (usually double the price of US oem parts)

 

Ahhh you're from Aus. Yes my local shop is $80 an hour. sorry I just assume everyone is from the states lol.

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So I drained the fuel tank and took the petcock off. There was a little bit of dirt around the base of the filter and dirt in the hole next to it so I cleaned it all out and put it back on.

 

Not sure if it will make much of difference. The fuel flow was good when I drained the tank.

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I had a problem with a new bike with no top end after tearing my bike down checking all electrical and changing stator and jetting it was plugged spark screen.

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I had a problem with a new bike with no top end after tearing my bike down checking all electrical and changing stator and jetting it was plugged spark screen.

 

I'm suspecting either my plug or ignition coil. My bike has a top end though, I started it up the other day and it sounds good. It just seams to start bogging after riding for an hour or 2.

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So Ive been having this problem with my 2011 YZ250 that it starts bogging at the top end and then eventually stalls. The first time it happened the bike was running fine for the first hour and then it started bogging when revved and then just died. So I changed the plugs with a new one and it kicked over but then still had no top end (might not of screwed the plug in far enough?) and my mate noticed fuel coming out of the pipe.

 

After this happened I took the bike to the store and they re-jetted the bike to run a little leaner, clean the carby and repack the exhaust (I get splooge dripping from the exhaust seal onto the rear swing arm). Before this I was running 40:1 using Motul 800 oil.

 

After getting the bike back the store drained the petrol out of the tank and advised to use Silkolene KR2 oil instead with the ratio of 32:1.

 

We went riding on sunday and after around 1-2hours of riding (mostly lugging around on a enduro track) I gave the throttle 2 big blips with the clutch pull in on 2-3rd gear and it started bogging again at the top and then eventually stalled. This time I changed the plugs again for a new one but the bike wouldnt kick over at all. I took it back to the car and my mate managed to roll start the bike and he said it sounded fine.

 

The bike has plenty of compression and will normally kick over 1st go with no problems.

 

I think the bike might be flooding and it could be how I'm riding the thing. The spark plugs look fine and are not fouling.

 

Any ideas?

My yz250 did this, it ended up being one of those shorty breather hoses that come of the gas cap, the ones with the shiny little anodized nut at the end. There is a little ball bearing sort of check valve in there that gets stuck. Loosen the gas cap, let air in and all of a sudden it works. I got rid of that thing in a hurry. No idea if your prob is that simple but what you describe is exactly what happened to me and another rider suggested I remove it. Good luck man !

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My yz250 did this, it ended up being one of those shorty breather hoses that come of the gas cap, the ones with the shiny little anodized nut at the end. There is a little ball bearing sort of check valve in there that gets stuck. Loosen the gas cap, let air in and all of a sudden it works. I got rid of that thing in a hurry. No idea if your prob is that simple but what you describe is exactly what happened to me and another rider suggested I remove it. Good luck man !

 

My breather hose is a long one that sits behind the number plate, could it be still doing the same thing?

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na probably not then. Those little shorty ones do that. The ball bearing gets stuck shut and as the fuel goes down it creates a vacuum in the tank, then the engine is starved for fuel. Maybe something else is causing a fuel starved situation, maybe float bowl level low ?  idk man sry

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Ran into similar with a buddies bike.... he rarely cleaned it (not saying you dont) his steering stem had filled with debris and it wasn't letting the breather do its job.  we found it simply by loosening the gas cap when the issue arose, I was surprised how long it ran before bogging.  simple enough test, also pull the cap and hoses and blow through them to check if theyre flowing.. they don't need to flow much 

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We went riding on the weekend and the bike was running pretty good. The track had some wide open areas so I had lots of room to clear it out.

 

Had a problem yesterday morning when I started it from cold and it fouled the plug, there was also a fair bit of spooge on the rear arm leaking from the exhaust flange (pretty much been doing this from day one).

 

I was thinking about buying the KTM sleeve to stop it from leaking. Also is it normal to blow white smoke when started from cold?, it goes away once warmed up.

Edited by Tyson29

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