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  #1  
Old 02-25-2015, 02:22 PM
wFo250's Avatar
will fall over
 
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Default 2003 YZ250F

Ok got the top end off of this thing (bloody mess!) I think I may have gotten too agreesive with the pressure washer (PO left it dirrrrty) and some beads of water were on the piston and valves. does anybod know if the head gasket is designed to be in triplicate? Doesn't make much sense to me why it would need to be that way. Also, intake valve clearance is loose by -+ .10mm and exh are tight by .2mm but the shims aren't numbered. Could the intakes be like that because of buildup on the faces/seats? Thanks




Stay tuned for a fAzillion more questions I'm sure
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Old 02-25-2015, 02:41 PM
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You will have to measure each valve shim to find the size as the markings wear off over time. Then you will have to figure what size shims you need for each valve to obtain the proper clearances on each valve.
Stock intake clearances should be... .004"-.006"
Exhaust should be .007"-.009"
In answer to your question of build up on the valves...I would say under normal usage the answer would be no.
If you valves are too tight then you are showing signs of valve seat damage and or valve stem stretch. The real way to fix is to replace the valve train and have the seats cut.

Paw Paw
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Old 02-25-2015, 02:50 PM
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With that bike being over 10 yeas old I think new valves and cut seats are in order...
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Old 02-25-2015, 05:05 PM
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I see that it has a hot rods crank rod so somebody's been in there ..
Not too worried about the expense of headwork, I'd rather have the piece of mind. Just being that the intakes allowed a larger feeler than spec means .. if under normal operation no buildup would increase the distance that either the seats aren't hammered or somebody just put in shims that are too thin. The cam lobes have slight discoloration but look to be in good shape. Guess I should mic em
sorry just thinkin out loud

Last edited by wFo250; 02-25-2015 at 05:12 PM.
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Old 03-19-2015, 08:10 AM
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will fall over
 
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----put in new wheel bearings



..filters





Never been into a four-stroke motor so here we go!

took it down and mic'd the springs, lobes and ring gaps



Cleaned up the piston



has a wiseco PN ..that coupled with the Hot Rods crank I know at least I'm not dealing with stock hours, although I've got no idea how many. Everything spec'd out in tolerance with the exception of the valve clearances. Ok check this out I had 1.65 shims on intakes @ .20 / .25 / .25 and had 1.70 shims on exh @ .15 / .15 I need .10~.15 on the intakes and .17~.22 on the exh. so I swapped the two wider gap intakes for the two tight exh shims and voila got .20 across the board! Yeah the intakes are .05 wide but I figure any recession may tighten them up. I'll check them again after a few rides and order some shims to have them on hand just in case.

Blew all the residue out the carb passages and put er back together and she runs great! Lights on 1st kick. Had an issue while setting the rekluse though it was idling and suddenly started to lean crackle and died! Looked down and found the fuel screw spring and teeny tiny washer laying on the motor. (luck) found the o-ring still seated in the passageway (luck) found the fuel screw lodged between the case and the c/s sprocket. More luck, only bad. It was really lodged. I tried to lift it out gently and it didn't want to come out. gently..gently..gently ain't working and a little tug and it came out and left a groove on both sides of the threads. string of expletives
Knowing I would probably be about to buy a new carb I used a razor and tried to clean the threads up and put it back in. Of course, it snugged up right away so I know I'm screwed (pun) ha ha no idea where "lightly seated" is now.. I just kept going in 1/4 turn at a time and kicking it over. Finally found the sweet spot (luck) I think I may have ruined the threads though well see how my luck holds up. Hopefully the brass is sacrificial. One thing is certain it won't fall out again lol
Got the rekluse set up, turns out the PO replaced the plates, basket and all and never got one ride out if it! His loss=my gain! the clutch makes a lot of noise on engagement though. Its only noticeable if I tease the throttle, if I just whack it open and take off there's no noise. Net says it's common so I'm not gonna worry about it.
So there we go I successfully lost my four-stroke virginity! Not nearly as scary as losing my actual virginity



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Old 03-19-2015, 09:42 AM
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Why didn't you just toss the fuel screw and order an aftermarket one? If you ruined the threads in the carb you're going to have one heck of a time finding the right tap to clean them back up.
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Old 03-19-2015, 10:20 AM
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Because!! Dude I was so close to the test ride.. I just couldnt help myself. I tried to razor the threads as best I could. I know I'm going to have to get into it eventually, but yeah I forced the issue. and tapping ant gonna happen!
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Old 03-19-2015, 10:44 AM
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The bike will still run without the fuel screw installed, just not perfectly. Hopefully you'll get lucky but I see damaged threads and a new carb in your future.
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