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2 stroke revving to the moon after rebuild. Lean?

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So I recently did a topend to this cr250 (wiseco), and started it for the first time today. Sounds a little off. After a bit, it revved to the moon and I couldnt stop it with the kill switch, unplugging the spark plug, or turning off the gas!!! Does this mean its lean? I noticed it wasn't spewing much smoke. 

A detail which would affect it, is that theres a crack a ways under the exhaust port on the case. Would this cause it to lean out? Its had the crack for a long time and ran fine before the top end was done. 

Jetting is the recommended by FMF, and it ran rich before, although it was run for a long time before this top end. Could it be a leak somewhere between the carb and intake port?

Recording of firt startup and run away: 

 

 

Edited by Albert Hernandez

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It's a runaway caused by something glowing in the combustion chamber.  That's why pulling the spark plug boot and the kill switch didn't work.  Sounds like it was already running out of fuel. Check your carb. They say you can open the throttle and it will shut off but I have never tried it.  I have always dropped it into gear and choked it down.

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4 hours ago, Motox367 said:

Check throttle cable definitely not the throttle cable. I can hear the needle/slider moving freely. 

3 minutes ago, YHGEORGE said:

One thing for sure is that the chain is way too tight.

Yes it is lol. 

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3 hours ago, Pygmy Warrior said:

It's a runaway caused by something glowing in the combustion chamber.  That's why pulling the spark plug boot and the kill switch didn't work.  Sounds like it was already running out of fuel. Check your carb. They say you can open the throttle and it will shut off but I have never tried it.  I have always dropped it into gear and choked it down.

Kind of hard to tell, but I turned off the fuel. I'll try another spark plug and I'm reassembling the carb. Seemed like it was running super lean, and I've read that could be a vacuum leak somewhere.

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Just watched the video.  Definitely a running out of fuel runaway condition.   Why didn't you just put it in gear, hold the brakes and choke it down?

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5 minutes ago, Albert Hernandez said:

Kind of hard to tell, but I turned off the fuel. I'll try another spark plug and I'm reassembling the carb. Seemed like it was running super lean, and I've read that could be a vacuum leak somewhere.

Did you turn off the fuel before it ran away or after?

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1 minute ago, Pygmy Warrior said:

Did you turn off the fuel before it ran away or after?

After. I'll be home in 3 hours. I'll run it on the field in gear so I can slam the rear breaks if it runs away, after I make sure I put everything together tightly

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3 minutes ago, Albert Hernandez said:

After. I'll be home in 3 hours. I'll run it on the field in gear so I can slam the rear breaks if it runs away, after I make sure I put everything together tightly

Get video of that please :ride: and like I said check throttle cable isn't out or anything at carb top

Edited by Motox367

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Alright guys, I think the carb hadn't seated correctly to the rubber intake manifold. It runs rich as hell now, so I need to adjust the carb. Here's a video. Hear some stuff clinking, but I'm sure that's due to nothing being tighted yet, such as the tank etc. 

 

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12 minutes ago, Motox367 said:

New top end,old bottom end, old bike. Be lucky if it last 2 hours but never know :ride: rich may last longer

I put about 15 hours on it prior to the rebuild, and still ran good. It was running on 3/4ths of a piston lol. Crank has no play, everything seemed smooth. I think 2 hours is far too conservative ?. It's a trooper.

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Just now, Albert Hernandez said:

I put about 15 hours on it prior to the rebuild, and still ran good. It was running on 3/4ths of a piston lol. Crank has no play, everything seemed smooth. I think 2 hours is far too conservative ?. It's a trooper.

Yes is a good old Honda I agree there :thumbsup:

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Clean and grease the steering head, linkage/swingarm.  I'll bet three nickels and a Benjamin it needs it. I still prefer the steel frame models. :thumbsup:

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6 minutes ago, YHGEORGE said:

Clean and grease the steering head, linkage/swingarm.  I'll bet three nickels and a Benjamin it needs it. I still prefer the steel frame models. :thumbsup:

Yes I agree . Got this 96 last summer off CL. 400$ in a box broken cases but thing was in very good shape.  One of best 250s ever 

0929161235.jpg

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