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Super rich running txt 250


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So I just recently got a 2014 TXT 250 Pro racing. It had a smart carb on it when I got it but didn’t run (was admitted to sitting for yr or two). I cleaned the carb and the tank but still no luck. So I ended up getting a stock carb for it. When I put it in, the bike started right up first kick but smoked like hell and was super loaded up very very rich. After taking it down the road and back, the silencer was still smoking even after the bike was off for a few minutes. I took out the 50:1 and put in 80 to 1 Amsoil dominator mix. Same issue, except this time it stalled out down the road.  I put a new plug in it and it didn’t seem to even try to start. So it seems to be way richer than 50:1 mix or a clogged carb could possibly cause.  Local bikehead suggested clutch side crank seal is bad and could be letting gear oil in that doesn’t burn, causing smoking and loaded up feel!?

So my questions are:

Is this a common problem?

Are there any things I should check before I do a crank case pressure test?

Is splitting the cases on the gas gas going to be any more involved than most 2 strokes? People seem to think these trials bikes are way different for most average guys. I split the case on my old KDX200 with a competent motorhead buddy’s help in the past, but is this gas gas trials going to be over our heads? 


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Are you losing gear oil ? Does it smell like burning gear oil ?

Talk the exhaust off and clean it out.

What was the plug like when it stopped ?

Are you getting a spark ?

Edited by b40rt
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27 minutes ago, t-shock 250 said:

you have to ask the question why it had an odd carb on it in the first place, that's a strange thing to do on a fairly recent bike, 

Some people like fiddling with bikes .........

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It could well just have been running too rich for some time resulting in a build up of oil. Take it for a much longer road run to get the silencer decently hot to allow the excess to burn off. I have known bikes that normally just puttered about to smoke for some while when switched off after a good thrash.

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thank you for your input guys!

The spark plug looked clean and still had spark. 
It only ran for maybe 8 min all together. Not sure if it lost gear oil, but I will clean the exhaust. We didn’t think to smell the smoke but plan on seeing if it smells really bad if we can get it running again.
The smart carb was a silly add-on. That’s just the way the guy was who originally had it (I know the original owner). He said smart carb didn’t make any difference and it was stupid to do in the first place. I did buy it off the second owner but he let it sit and didn’t ride it.  

I have had my cr 250 smoke for 5-10 min after thrashing but the txt was even more smoky than that.

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I would suggest you download the owners manual off the Gasgas web site, check for the stock jetting for the stock carb and use the recommended gas/oil ratio.  Running less oil in a mixture is actually richer when it comes to jetting. 


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