yz250 problems after tune up

[J.Quest]

Hi there,

Just picked up a 99 yz250 and ran great from test ride.

Gave it a minor tune up before my sunday ride and it crapped out on me.

All I changed was the trans oil and spark plug. After the tune up, I gave it a test ride and it ran great for about 20 seconds it started bogging and died.

Tried starting again and same thing. Major loss of power and just will not pick up speed. If I release throttle, it will just die.

I assume its probably bad gas/mixture since its been sitting with original owner, so I drained the tank and didnt fill up until the next morning (ride day)

Next morning, filled the tank with 40:1 mixture tried giving a start, same shit. What's happening here? I ran great before I touched it. Something I did wrong?

Any information will be helpful, Thanks!

 

 

[Brad04]

If your at different elevation from where you test rode it the jetting could be way off depending what elevation your at causing it to run like crap. Say you test rode at sea level and you live at 3000ft for example

[YZDOC]

Bad plug can happen. Buy a handful and try another. Also, the 3K in elevation should not make a drastic change. Bikes are tuned for 0-5500, 4-7500, etc. So, check your air screw measurement to be sure it's not closed. Next up, and this is after thought... NEVER run old fuel through the bike, could have a plugged circuit now from dirty fuel. Might need to pull carb, fully clean, adjust the float, and put it all back together. 

The only thing you did wrong was the crappy fuel, and maybe a bad/dead plug. 

Pull fuel tank and rinse it out, check the little screen filter on the petcock. 

Also, was it jetted for 40:1?

[Brad04]

5 minutes ago, P84ONE said:

Bad plug can happen. Buy a handful and try another. Also, the 3K in elevation should not make a drastic change. Bikes are tuned for 0-5500, 4-7500, etc. So, check your air screw measurement to be sure it's not closed. Next up, and this is after thought... NEVER run old fuel through the bike, could have a plugged circuit now from dirty fuel. Might need to pull carb, fully clean, adjust the float, and put it all back together. 

The only thing you did wrong was the crappy fuel, and maybe a bad/dead plug. 

Pull fuel tank and rinse it out, check the little screen filter on the petcock. 

Also, was it jetted for 40:1?

My RM250 ran great at sea level then when I took it home to 1200 ft it ran like crap and wouldnt even start and had to lean it from 165 main and 45 pilot to 155 main and 40 pilot with 1st clip on needle from 3rd clip to run and hit powerband. 

[YZDOC]

9 minutes ago, Brad04 said:

My RM250 ran great at sea level then when I took it home to 1200 ft it ran like crap and wouldnt even start and had to lean it from 165 main and 45 pilot to 155 main and 40 pilot with 1st clip on needle from 3rd clip to run and hit powerband. 

That sucks!

I can run my YZ250 here at home 1500-2500, take it down to Ocotilla Wells sea level, and up to Big Bear 3000-5800, and only need to turn the air screw for fine tuning. 

[Brad04]

8 minutes ago, P84ONE said:

That sucks!

I can run my YZ250 here at home 1500-2500, take it down to Ocotilla Wells sea level, and up to Big Bear 3000-5800, and only need to turn the air screw for fine tuning. 

There is a reason I keep saying Yamaha makes better 2 strokes. 

[J.Quest]

2 minutes ago, P84ONE said:

Bad plug can happen. Buy a handful and try another. Also, the 3K in elevation should not make a drastic change. Bikes are tuned for 0-5500, 4-7500, etc. So, check your air screw measurement to be sure it's not closed. Next up, and this is after thought... NEVER run old fuel through the bike, could have a plugged circuit now from dirty fuel. Might need to pull carb, fully clean, adjust the float, and put it all back together. 

The only thing you did wrong was the crappy fuel, and maybe a bad/dead plug. 

Pull fuel tank and rinse it out, check the little screen filter on the petcock. 

Also, was it jetted for 40:1?

Hi Thanks for the input. Im not mechanically inclined but will quickly understand if taught.

• What is the recommended spark plug? The new one I bought seems a little bit dark and is kind of wet with yellow/orange coloring, as I remembered. The bike was running with slight to severe hesitation when I give the bike some throttle. It's stalling, especially when I give the throttle a good twist and uneven idling (tends to zoom up, or down, or sputters)
• How do I check the air screw measurement and where is it located? Forgot to mention I did remove the air filter boot to get into the suspension to lower my bike.
• When you mean jetting, are you referring to my gas/oil mixture which is 40:1? If so yes.

Another thing I want to mention is the bike overall looks pretty beat up. It just ran really great. The spark arrestor silencer is missing the "spark arrestor" itself causing it to rattle in the area. The header pipe was shaking and shifting a lot because it didnt have a hanger bracket. It was so bad that during idle, the connector where the springs are located was popping out of place.

 

 

 

 

 

[YZDOC]

5 minutes ago, J.Quest said:

Hi Thanks for the input. Im not mechanically inclined but will quickly understand if taught.

• What is the recommended spark plug? BR8- EG,ES,EIX.
• The new one I bought seems a little bit dark and is kind of wet with yellow/orange coloring, as I remembered. The bike was running with slight to severe hesitation when I give the bike some throttle. It's stalling, especially when I give the throttle a good twist and uneven idling (tends to zoom up, or down, or sputters)
• How do I check the air screw measurement and where is it located? Back of carb intake, just above bowl, right next to rubber air filter boot.
• Forgot to mention I did remove the air filter boot to get into the suspension to lower my bike.
• When you mean jetting, are you referring to my gas/oil mixture which is 40:1? If so yes. So the bike "IS" jetted for 40:1, and the altitude change from bikes original owner was "NOT" grater than 5K?

Another thing I want to mention is the bike overall looks pretty beat up. It just ran really great. The spark arrestor silencer is missing the "spark arrestor" itself causing it to rattle in the area. The header pipe was shaking and shifting a lot because it didnt have a hanger bracket. It was so bad that during idle, the connector where the springs are located was popping out of place.

Get all that fixed.

 

 

 

 

Manual is going to be your first and best tool. Look in the manuals library on-line for the YZ250L for 1999. All parts can be found on-line but look at the top of the list as it is called competition YZ250L in title. 

[J.Quest]

1 minute ago, P84ONE said:

Manual is going to be your first and best tool. Look in the manuals library on-line for the YZ250L for 1999. All parts can be found on-line but look at the top of the list as it is called competition YZ250L in title. 

Noted, Will keep you posted. Thanks for all your help!

[EEE299]

55 minutes ago, J.Quest said:

Forgot to mention I did remove the air filter boot to get into the suspension to lower my bike.

 

 

 

 

If you removed the air boot make sure it was re-installed correctly. (I don't know which part exactly you removed) Any leaks after the air filter could cause a lean condition. As in air/fuel ratio... not oil/gas ratio.

[J.Quest]

2 hours ago, EEE299 said:

If you removed the air boot make sure it was re-installed correctly. (I don't know which part exactly you removed) Any leaks after the air filter could cause a lean condition. As in air/fuel ratio... not oil/gas ratio.

Now that you mentioned, I did notice the air box was loose and indeed I forgot to tighten it.

After tightening, nothing changed. You think that must've fouled the spark plug?

[J.Quest]

Tried replacing new spark plug and it started first kick. However still giving me the same exact problem as mentioned previously (bogging and dies). Gave another attempt and won't start at all. Took out the spark plug and it's black again. Messed around with the air screw still nothing. Also notice the air filter did not have a cage therefore it wasn't sealed tight. Just ordered and hope it can solve the issue. Any other suggestions will be helpful. Thanks! 

 

For your reference 

 

[Brad04]

Are you sure your getting spark?  And my bike doesn't have a cage like yours.  I use grease to seal the filter. No toil makes it specifically for the air filter

[EEE299]

You need a cage, if you want a good seal.

Interesting it sounds very rich from your description now.

[Brad04]

2 hours ago, EEE299 said:

You need a cage, if you want a good seal.

Interesting it sounds very rich from your description now.

I was tired with my original post. Mine has a cage; I was used to seeing the ones with the screens in them and thought the black part was the cage m. 

[YZDOC]

1 hour ago, Brad04 said:

I was tired with my original post. Mine has a cage; I was used to seeing the ones with the screens in them and thought the black part was the cage m. 

Only 4 strokes.

9 hours ago, J.Quest said:

Tried replacing new spark plug and it started first kick. However still giving me the same exact problem as mentioned previously (bogging and dies). Gave another attempt and won't start at all. Took out the spark plug and it's black again. Messed around with the air screw still nothing. Also notice the air filter did not have a cage therefore it wasn't sealed tight. Just ordered and hope it can solve the issue. Any other suggestions will be helpful. Thanks! 

 

For your reference 

 

DUDE! Get the entire air box off and clean it real good. Get a new filter, and KEEEP IT CLEAN!, Pull the carb off and take it apart, and CLEAN IT! Make sure all the jets are free and clear. Pull the tank petcock and rinse the tank out. Check all resistance on the electrical as discribed in the manual. 

I am surprised it ran at all!

[J.Quest]

9 hours ago, Brad04 said:

Are you sure your getting spark?  And my bike doesn't have a cage like yours.  I use grease to seal the filter. No toil makes it specifically for the air filter

It was getting spark with fresh plug and only on first kick. After that, nada. The plug just gets all burnt. 

[EmpireofDerp]

DUDE! Get the entire air box off and clean it real good. Get a new filter, and KEEEP IT CLEAN!, Pull the carb off and take it apart, and CLEAN IT! Make sure all the jets are free and clear. Pull the tank petcock and rinse the tank out. Check all resistance on the electrical as discribed in the manual. 
I am surprised it ran at all!

Hahaha, another priceless 1 picture worth a thousand words moment.

Sent from my SM-G935V using ThumperTalk mobile app

[2strokeYardSale]

You bought a neglected 18 year old motorcycle. You shouldn't ride it until you thoroughly disassemble, clean, lubricate, and replace worn and missing parts.

Or you can ride it without doing these things and it will almost certainly suffer catastrophic engine damage, seized wheel bearings, etc.

 

[Smoking 2's]

Get a manual and get to work! ?