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Dirt Bike Brands - Other
250F ring time, loss of power, gas in oil, cont...
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[QUOTE="nikki, post: 597501, member: 18126"] Well just a quick update... drained the oil today before tearing it down and again, it smelled like gas a little bit (oil had 1 hour on it). So got it all apart and everything appeared pretty normal. I measured the valve clearance again and all in spec although I couldn't measure the middle intake valve (might cut a feeler guage in half to measure it at a later time). First thing I noticed was that the top intake ring was angled the wrong direction with the ring gap directly under the middle intake valve right where the gas enters the cylinder. According to the manual, the ring gap should be more at 8 o'clock with 12 o'clock being facing the front of the bike (It was around 5 o'clock). This could possibly explain the gas in oil problem in itself I think? Something like the gas comes into the cylinder and as the ring forces the gas up to the combustion chamber, some gas goes right through the ring gap before combusting. Also, could be another place for unburnt gas residue to sneak through. The cylinder looked like new, as it should, with no wear marks whatsoever in the cross hatching. The top ring was slightly out of spec - limit is .12mm and it was around .13mm so more reason making me think the top ring could be a problem. There was very little carbon build-up except a little bit again around the middle intake valve. Rod has no up-down play and very little side-by-side. The crank did have two dark brown spots around the rod at TDC but didn't look to be all around the crank just TDC. The piston had no blowby spots or discolorations. I will try to snap a few pictures tomorrow. I have a new piston but think I might just do the rings right now and see if it helps the problems. I also took apart all the oil lines and cleaned out the oil strainer under the frame guard (which had tiny pieces of tree looking stuff in it). Will take a look at the carb tomorrow and clean that too. For kicks, I might take a look at the clutch too. Ol'89er - you bring up a good point about valve float as what I think happened last weekend with the power stopping earlier than normal at high RPM's did kinda respond similar to hitting the rev limiter. Also, my valves are on the low end of the clearance range. For instance, if the intake range is .10mm-.14mm, then I am right at .10mm. If the bike responds like that again, I will definately consider new valve springs and maybe shims. Another "possible" reason for the high RPM power deal might be related to gearing. I did go up one tooth on the rear sprocket back in March before the weekend that I got injured and I have rode hard just a little bit since then. But I just know it didn't feel right last weekend. I plan on riding Monday and paying close attention to how the bike reacts. Thanks everyone for your help and comments and thoughts as it is very appreciated. Wrenching on four-strokes is a whole new thing to me. And jimyz - I am 99% sure I will never ride a 125 again. This 250F is amazing (aside from a little mechanical paranoia). [/QUOTE]
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Dirt Bike Discussions By Brand
Dirt Bike Brands - Other
250F ring time, loss of power, gas in oil, cont...
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