Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: Smithdad on May 07, 2013, 02:29:20 AM
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Ok. I brought home a very nice 06 YZ250 tonight. Did a quick service. Cleaned all of the old gas out of the tank and carb. Changed the oil and filter etc..... Bike was hard to crank but it had not been ridden in a while. Got it running OK. Kickstart seemed stiff and choppy feeling. Not smooth like our other YZ250. Rode it around very easy for a while and then picked it up a bit. About 2 minutes in it just died. Will not crank. I am getting a little bit of a backfire now. Haven't had time to diagnose anything yet just put it up for tonight and will tackle it tomorrow but just thought I would ask you guys for some opinions. Any suggestions? Thanks
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It wont crank as in nothing moves when you try to kick it over? If that's the case then it sounds like its seized up. What do you mean by backfire? Does it start/run?
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It is not seized. If anything it is kicking smoother than it was. It will not crank. About every third or fourth kick you get a little backfire type sound thru the pipe but it doesn't crank.
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Ohhhh gotcha. Maybe the plug just fouled out
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You know I thought of that as I was typing the first post and I hope it is that simple.
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Keep us posted. Odds are it is, easy fix to getcha back out riding quick
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Simple fix. Replace every jet that is in the bowl. The ethanol ruined them. Can't clean them like the old days. A few bucks and it will run like new.
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My RMX did a similar thing - was getting spark, but would not fire and every third or fourth kick would backfire.
Turns out it broke the woodruff key that locates the flywheel on the crank so the timing was massively off.
So, just something else to check beyond carby stuff potentially trashed by ethanol/fouled plug.
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Ok. I brought home a very nice 06 YZ250 tonight. Did a quick service. Cleaned all of the old gas out of the tank and carb. Changed the oil and filter etc..... Bike was hard to crank but it had not been ridden in a while. Got it running OK. Kickstart seemed stiff and choppy feeling. Not smooth like our other YZ250. Rode it around very easy for a while and then picked it up a bit. About 2 minutes in it just died. Will not crank. I am getting a little bit of a backfire now. Haven't had time to diagnose anything yet just put it up for tonight and will tackle it tomorrow but just thought I would ask you guys for some opinions. Any suggestions? Thanks
Scrap it, buy a CRF250 instead preferably one that's been raced and abused for the last few years, that should be much more reliable and a heck of a lot cheaper to run.
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OK new question. Found out that the rings had seized on the piston. Got everything I need for a new top end build. There is some minor scouring in the cylinder however. Not bad but you can feel it with your finger. Can I hone it with good results?
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If your cylinder is nikasil plated than you can't hone out grooves. You'll need to replate it. I've heard you can use a very fine ball hone on nikasil with good results, but I've never tried.
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How can you tell for sure that is nikasil plated? Is it just too hard to be honed. I was told today about using a 1:1 ratio of water and muratic acid with a scotch brite pad.
Would it hurt to try honing to see if it works?
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Well the thing with honing the plating is it might look like it'll work really nice, but you take away the cross hatch that all freshly plated cylinders need for proper lubrication. Also, even you manage to keep a good coating on it, it might start to peel around the port areas and cost you another rebuild. Honestly it sucks, I just ran into the same issue with my RM. But I'd rather spend the money on a replate and not worry about it. If you do try, and it works, please let me know. The muriatic acid trick only works to remove aluminum build up on the bore, like if parts of the piston heat seized to the cylinder walls.
But, I also ran into the same problem to see for sure whether or not it was plated. I heard of a magnet trick, if it was resleeved with a steel sleeve than a fridge magnet will stick to it nicely. My issue was the magnet slightly stuck, but not as strong as it stuck to the fridge. Conclusion: most likely plated.
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Ok turns out that it was just Alum build up and I was able to clean it with the Muratic Acid and water. Polished up nice. New top end fixed the problem and he rode it tonight. Thanks for all the help.