Need help! yz250 2stroke revvs badly.

Kevin Tõnisson
Edited Date/Time 11/22/2015 4:38am
my yz250 2stroke 97 sometimes loses power and doesn't ssound right at high revs. i have replaced the crank seals and i installed new boyesen power reeds. here's a video of it running on my instagram: https://www.instagram.com/p/-WaME_GcXh/ id appreciate it if you could help me.
|
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 11/21/2015 8:09am
11/21/2015 8:09am
Can't tell a lot from the video...
What does you spark plug look like?
Is it black, white, grey or brown on the end?
Have you set the float level in the carb?
Have you cleaned the power valves?

Paw Paw
Kevin Tõnisson 11/21/2015 8:20am
11/21/2015 8:20am
Paw Paw 271 wrote:
Can't tell a lot from the video... What does you spark plug look like? Is it black, white, grey or brown on the end? Have you...
Can't tell a lot from the video...
What does you spark plug look like?
Is it black, white, grey or brown on the end?
Have you set the float level in the carb?
Have you cleaned the power valves?

Paw Paw
it's really dark brown. and yes one of my friends set the float level. heres the thing to. i got it running for few days and then it started doing the same thing. The power valve moves freely. can it make the pike run like that if it's stuck or something?? i could do a riding vid tomorrow if it would help. Thank you for replying.
KNIGHT104
Profile picture for user KNIGHT104
Posts
149
Joined
10/15/2015
Location
Stillwater, OK, USA
KNIGHT104 11/21/2015 8:30am
11/21/2015 8:30am
did you have this issue before you changed the crank seals? what jets are you running? have you pulled the head and checked the top end?
Kevin Tõnisson 11/21/2015 8:46am
11/21/2015 8:46am
KNIGHT104 wrote:
did you have this issue before you changed the crank seals? what jets are you running? have you pulled the head and checked the top end?
yes i had. my bike run fine and then on the track it sudenly lost all of its power and didnt revv. the reds had a crack in them to. i changed them but it didnt fiks the problem. then the seal on the cluch side popped out. then i changed the seals. and the pike ran grate for 1 day. i havent cheked the topend. but the piston has like 5 h onit maybe. Should i take the topend of and chek the rings?? compression feel good. My main jet is 178. and the needle is in the middle position. i can try 176 and 170 main jets. sorry for bad EEnglish

The Shop

See All »
KNIGHT104
Profile picture for user KNIGHT104
Posts
149
Joined
10/15/2015
Location
Stillwater, OK, USA
KNIGHT104 11/21/2015 8:49am
11/21/2015 8:49am
i would start with jetting, did your new reeds seal up all the way as in there is no gap between the cage and pedals? may double check that as well before you dive in to the top end
Kevin Tõnisson 11/21/2015 8:57am
11/21/2015 8:57am
KNIGHT104 wrote:
i would start with jetting, did your new reeds seal up all the way as in there is no gap between the cage and pedals? may...
i would start with jetting, did your new reeds seal up all the way as in there is no gap between the cage and pedals? may double check that as well before you dive in to the top end
yes they did. the funny thing is that the pike sometimes runs great and then stops working again. may it be my electrical system?? it sounds like at high rpms it loses ignition.
KNIGHT104
Profile picture for user KNIGHT104
Posts
149
Joined
10/15/2015
Location
Stillwater, OK, USA
KNIGHT104 11/21/2015 9:00am
11/21/2015 9:00am
could be try removing your plug cap and cutting off just a tad of plug wire exposing fresh wires put cap back on and try that. or if you have a buddy that has a cap you can test with a known good one.
Kevin Tõnisson 11/21/2015 9:06am
11/21/2015 9:06am
KNIGHT104 wrote:
could be try removing your plug cap and cutting off just a tad of plug wire exposing fresh wires put cap back on and try that...
could be try removing your plug cap and cutting off just a tad of plug wire exposing fresh wires put cap back on and try that. or if you have a buddy that has a cap you can test with a known good one.
okay. I'll try it domorrow. thank you for your suggestion.
JZ125
Profile picture for user JZ125
Posts
48
Joined
9/14/2015
Location
Marion, IL, USA
JZ125 11/21/2015 2:20pm
11/21/2015 2:20pm Edited Date/Time 11/21/2015 2:21pm
The emulsion tube is often neglected and if it is worn (it usually is) it will allow the high needle to vibrate back and forth drawing extra fuel and cause a sputtering that will start in the pilot circuit making you think it is a rich pilot circuit. At times it will leave a witness mark on the high speed needle but not always. Both the emulsion tube and high speed needle should be replaced. I just did it just to do it.

On my bike I had a sputtering issue that would not go away. The bike was jetted spot on and I set the floats as well. Kept fouling plugs. I took the fuel enrichment plunger out and noticed it had a deep witness mark on the rubber sealer on the very bottom. I stuck a piece of duct tape on it and used a hobby knife to cut to fit and stuck it back in the orifice. Problem solved.
JZ125
Profile picture for user JZ125
Posts
48
Joined
9/14/2015
Location
Marion, IL, USA
JZ125 11/21/2015 2:25pm
11/21/2015 2:25pm
KNIGHT104 wrote:
did you have this issue before you changed the crank seals? what jets are you running? have you pulled the head and checked the top end?
Kevin Tõnisson wrote:
yes i had. my bike run fine and then on the track it sudenly lost all of its power and didnt revv. the reds had a...
yes i had. my bike run fine and then on the track it sudenly lost all of its power and didnt revv. the reds had a crack in them to. i changed them but it didnt fiks the problem. then the seal on the cluch side popped out. then i changed the seals. and the pike ran grate for 1 day. i havent cheked the topend. but the piston has like 5 h onit maybe. Should i take the topend of and chek the rings?? compression feel good. My main jet is 178. and the needle is in the middle position. i can try 176 and 170 main jets. sorry for bad EEnglish
I would just take the expansion chamber off and peer inside. Look for a lot of wear on the skirt and make sure the rings are not too loose but moving. That will be a lot easier and will let you know if you should remove the head to further investigate.
Kevin Tõnisson 11/22/2015 4:38am
11/22/2015 4:38am
okay. so i got it running for now. i did few things. 1 ting was that i noticed that my ground wire was corroded. i cleaned it. and i put new fule in it. i think i should replace my choke. it does not stay on if you pull it up and it moves sideways a lot.

Post a reply to: Need help! yz250 2stroke revvs badly.