Question about 2003 Yamaha YZ 250

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93 yz250 Not on the piston. It's the bearing that cnotrols something for the exhaust on the side of the cylinder head.

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There is no exhaust bearing or any bearing that controls exhaust.
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Posted on Feb 01, 2009

  • Randy Hough
    Randy Hough Feb 01, 2009

    Are you refering to the exhaust cam timing?

  • Randy Hough
    Randy Hough Feb 01, 2009

    look at your other post and if that is the info you needed,please rate all as fixya's

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Bike was running great on saturday. Went to the races bike started right up when the gate dropped bike won't rev out all the way. Didn't have this problem yesterday. When we got home i cleaned the car


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
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3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
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7. Faulty reed valve.
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YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

May 19, 2014 | 2007 Yamaha yZ 250

1 Answer

A piece of metal scrathed the side wall of my piston sleeve and goudged the top of the inside of my crankcase,like where my spark plug scews in.it siezed up and when i opened it i noticed antifreeze on top...


There should be no play up and down. Any play is coming from a worn out needle bearing on the crank. A bit side to side is okay and normal. The crank will need to come out then it gets pressed apart and fitted with a new bearing. Price out the difference in cost of fixing the crank verses getting a new $170 crank assembly.What probably happened is a broken piston ring extended into a cylinder port and the piston against the ring is what gouged the cylinder and head. Please rate my answer.
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May 29, 2011 | kawasaki 125 Dakar Motorcycles

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How do i go about replacing the piston and rings for my 2003 honda cr 125 r


Take off seat, and tank.
Drain coolant, remove exhaust, remove coil, and ground wire from head.
Remove triangle head stays, and spark plug.
Remove right side power valve cover, and clip and spacer for the power valve arm.
Remove four cylinder nuts.
(If you remove the lower radiator hose that goes between the left and right radiator, you can get the cylinder off without removing the head.)
Use a soft blow, or dead blow hammer to free up the cylinder (Piece of wood)
Use kick starter to get piston low, and carefully remove cylinder upward.
Put a rag around connecting rod, and remove piston pin clip on one side. (So the clip doesn't fall into engine) Then push the pin out and remove the piston.
Note, you will have a mark on the left side of the cylinder of "A" or "B" for a stock piston, but Wiseco's don't use this.
Use caution when putting on the new ring, and getting the cylinder onto it as not to twist the cylinder because it will "catch" the end of the ring and do damage.

Dec 09, 2009 | 2003 Honda CR 125 R

1 Answer

I have a 2003 YZ250. The engine seized up. There


The engine will need a complete overhaul. New bearings throughout, new piston, rings, water pump and a full set of seals. A cylinder bore job or new cylinder also. You are probably looking at $2000 to $2500 for the repairs. A used engine may be a lower cost choice. Google motorcycle salvage yamaha and see what you can find.

Nov 12, 2009 | 2003 Yamaha YZ 250

1 Answer

Top end repair: After all is removed and replaced, how do I reinstall the piston into the cylinder? What are torque specs for cyl? Inch or ft. lbs?


You will want to install the piston onto the crank before you install the cylinder and head. With the head and cylinder off, the crank rod will be exposed. Put some shop towels around the crank rod before you start to avoid dropping any small parts into your lower end while you replace the piston. Your new piston kit should come with: (1) piston, (2) circlips,(1) wrist pin and (1 or 2) rings depending on the bike. Also it is suggested that you should replace the wrist pin bearing as well (usually sold seperately). If you have not removed the existing piston you will need to remove one of the circlips from the side of the piston. Do this by using a small screwdriver in the teardrop hole where the wristpin attaches the piston to the crank. Then push the wristpin through the piston from the side that still has a circlip through the side that it has been removed from. Once the wristpin is out, the piston will pull straight up off the crank and the wristpin bearing will slide out of the crank rod. Before installing your new parts you will want to have some 2-Stroke oil on hand. Lube up the wrist pin bearing with 2-stroke oil and slide it into the crank rod. Install ONE of the circlips into the piston before connecting it to the bike. Do this in a clean area because these things like to jump out when you're trying to put them in. BE SURE IT SEATS FULLY INTO ITS GROOVE. Once ONE circlip is in, slide the piston over the crank rod WITH THE ARROW ON THE TOP OF THE PISTON FACING THE EXHAUST!! so the wrist pin hole lines up with the wrist pin bearings. Lube the wrist pin and slide it into the piston from the side with out the circlip, through the wrist pin bearing until it seats against the circlip installed on the opposite side. Install the second circlip and MAKE SURE IT SEATS FULLY INTO ITS GROOVE. Install the rings onto the piston. (Some OEM rings have a flat side and a sloped side be sure to match the piston you have removed) Notice that there are tiny notches in the rings that must line up with nipples in the ring seats. This is the only way the cylinder will slide on properly. Next, put a thin coat of oil on the cylinder walls, remove the shop towels, and put on the cylinder base gasket. Now, with one hand, pinch the rings tight to the ring seats making sure the nipples in the ring seats sit in the notches of the rings. With the other hand, slide the cylinder over the piston. THIS SHOULD SLIDE DOWN EASILY! If not, remove the cylinder, verify the rings are properly seating in the ring seats and try again. Once the cylinder is on install the base nuts. If you can get a torque wrench on the cylinder base nuts tighten down to manufacture spec's (24 ft lbs) Usually you can not get a torque wrench on the base nuts because the cylinder walls are in the way so I give it a german torque "goot-n-tite" (good and tight). Next put the head gasket on and the head gasket, and tighten down finger tight. Do this in a criss cross pattern, starting off with hand tight, then 3 or 4 steps until reaching the manufacture spec (18 ft.lbs). Put the plug in and you should be ready to go. Be sure to break in properly by running 3 heat cycles through the enging. From fully cooled, start the bike and ride it using NO MORE THAN 1/2 throttle until it reaches full temp. keeping the RPM's varying. Let cool COMPLETELY. Second heat cycle, same thing except use up to 3/4 throttle. Cool COMPLETLY AGAIN. Third heat cycle ride up to full throttle. Be sure to keep the RPM's varying in all heat cycles. No long runs at the same RPM level. Here is where I got the specs for the cylinder and head torque settings so you may want to call a local shop and verify. http://www.thumpertalk.com/forum/archive/index.php/t-764174.html

Oct 11, 2009 | 2003 Suzuki RM 125

1 Answer

I had to replase the piston and fogot how to put it back togther


Put the piston in with the mark on the top of the piston facing the exhaust port of the cylinder. put one circlip in the piston in the bore seated correctly in the groove. place piston over rod facing correct direction and insert wristpin into piston and through the rod needle bearing in the top of the rod. insert other circlip and seat correctly in groove. install compression rings with letter or any markings facing up. markings usually located at end gap on either side. install oil ring with straight ring on top squiggly ring in center and straight ring on bottom all in the same groove which will be the lowest groove on the piston.stagger all the ring end gaps. do not let all the gaps line up. install base gasket on engine case. clean everything and make sure everything stays clean. slide cylinder over piston and compress rings with fingers and finesse cylinder over piston. do not force. put nuts on studs and tighten to spec in service manual. install head gasket correctly and put head on and put nuts on studs. tighten to spec. reassemble rest of motorcycle and get hurt! have fun

Jul 28, 2009 | kawasaki KX 250 Motorcycles

1 Answer

93 cr 125 has lack of power and a loud nocking


In a 2 stroke engine there are no valves and thus no adjusting required.The itself acts as a valve too.
Maybe you will have to rebore the cylinder and fit an oversize piston -kit or if the cylinder is to its tolerance thn fit in new setoof piston rings.

Jul 23, 2009 | 2005 Honda CR 125 R

1 Answer

I bought dirt bike for husband! is 2005 yamaha yz250 a 2-stroke or 4-stroke? i'm not sure if it's yz250 or yz250f now that i'm to get posted i'm not sure of year. sleeve around cable say nov 2005


Congrats on the purchase! easy way to tell look at the exhaust pipe. if it is just a thin tube that is tight to the engine and goes right to the muffler it is a 4 stroke (250f). the four strokes have a square-ish head. Deep/bass-y engine sound. If you have a large (probably black) exhaust pipe with a large bulge in it (5-6" diameter) that wraps around the front of the frame, its a 2-stroke. They have a more round cylinder head. Beautiful pingy sound and a little smokey at start up. DON'T FORGET TO MIX YOUR GAS!!! there should be a serial number sticker at the very front of the frame (behind the number plate where your triple clamp/handlebars connect) Probably on the left side. Hope it helps! rate please :)

Jun 14, 2009 | 2004 Yamaha YZ 250 F

1 Answer

Motor not turning over


bearing or more likely piston is wrong bore size

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