2 stroke issues

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7/20/2022 5:09 PM

Been a mx/sx fan my whole life but just recently started riding after a long hiatus so I’m going to need some help. I just picked up a used 2012 250sx. Went out for a ride today and stalled it while climbing a very rocky hill. Had to get off it and push it up.

When I got to the top the bike wouldn’t start. Tried kicking it 100 times. Had compression but felt like it didn’t even want to start. I bump started it going down hill and it ran fine. When I got home the exhaust smelled kind of like burning plastic. I checked to make sure no plastic pieces were touching the exhaust and I found oil that looks splattered next to the exhaust on the side panel.

My 2 questions are why wouldn’t the bike start and what’s with the oil on the side of the bike? Maybe the exhaust needs a repack? I’m running 40:1 as suggested. I’m trying to learn to fix these things on my own but it’s hard when no one you know rides and can give you advice.

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7/20/2022 5:27 PM

Take a look at the plug. Probably fouled. Don’t clean it, replace it. The carb might be jetted rich for trail riding. Remove muffler, clean mating area and apply hi temp RTV.

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7/20/2022 5:38 PM

willbilly wrote:

Take a look at the plug. Probably fouled. Don’t clean it, replace it. The carb might be jetted rich for trail riding. Remove ...more

Thanks for the advice. I have a new plug in my toolbox and will put it in tomorrow. Will Yamabond 6B work for the exhaust since I already have some of that and where is the mating area I need to put it? Thanks.

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7/20/2022 9:15 PM

What elevation are you at? Sounds like the jetting is too rich. I was normally around a 165 main on stock engine. Necj Suzuki needle on 2nd clip and I believe a 40 or 42 pilot. Elevation 1800 feet

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7/20/2022 9:16 PM

for the oil to be up there it looks to me like there would be a crack at the front of the silencer. If it is you could just get it welded up.

Usually when the plug is fouled you won't be able to bump start it as the plug won't ignite the fuel. I'm wondering if you just flooded it when you stalled it and that is why you were able to bump start it and it continued running to get you home.

By the way, I had a 2012 250sx, awesome bike

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7/20/2022 11:23 PM

GoggleFiend904 wrote:

What elevation are you at? Sounds like the jetting is too rich. I was normally around a 165 main on stock engine. Necj Suzuki ...more

Only 100-150 feet above sea level. I’m close to the ocean.

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7/20/2022 11:27 PM

chump6784 wrote:

for the oil to be up there it looks to me like there would be a crack at the front of the silencer. If it is you could just ...more

I didn’t know you could flood bikes while riding them, I thought you only flood them while twisting the throttle while the engine is off or if you start it wrong. I’ll look at the exhaust tomorrow but I don’t think there’s any cracks. Also since you owned one of these do you have any recommendations for mods/set up? So far I’ve added a power flow air filter kit and had factory connection valve the suspension. Thanks.

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7/21/2022 9:54 AM

Jetting is too rich. And it's been that way a while so the silencer packing is saturated with oil.

You need to completely disassemble the silencer, clean everything neatly, and repack with fresh packing and seal the end caps with RTV. Might as well take the pipe off and flush it a bunch of times with kerosene or something because it's probably full of oil too.

Once you have that all cleaned out, get the jetting leaned out so it doesn't spooge up again. 40:1 is fine, but you'd probably be best to switch to a lower flash point, cleaner burning synthetic oil. What oil are you running now?

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Powerband in every gear !

7/21/2022 10:18 AM

FGR01 wrote:

Jetting is too rich. And it's been that way a while so the silencer packing is saturated with oil.

You need to completely ...more

Motorex power 2t

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7/21/2022 10:34 AM

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2018 KTM 250sx 2022 KTM 350sxf
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7/21/2022 2:31 PM

chump6784 wrote:

for the oil to be up there it looks to me like there would be a crack at the front of the silencer. If it is you could just ...more

Pete The Fisherman wrote:

I didn’t know you could flood bikes while riding them, I thought you only flood them while twisting the throttle while the ...more

You said it stopped going up a hill, I just assumed that you might have chopped the throttle on a tricky uphill section and then opened it back up again causing the bike to stall and then flood. It just seemed strange that if the plug fouled then the bike would run again after you bump started it. Any time I've filled a plug the bike never started again.

As for set up, that bike really doesn't need much. I had the forks re sprung and valved and that was it. If i had have kept it longer i would have put a pro circuit silencer or full system on it too improve the over rev. Those motors go hard but then just drop off up top. Depending on the riding you do you probably don't even need that. Just set it up to be comfortable for you

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7/22/2022 12:32 PM

That little rubber connector between the silencer and header behind the kickstarter. I usually put a thin layer of rtv on the inside mating surface and then the two grooves are perfect for two heavy duty zip Ty’s. Won’t be any more oil coming out of the connection.

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