Motorcycle Top End Rebuild on Yamaha Four Stroke (Part 1 of 2)

July 30, 2019 posted by

Today we’re going to be rebuilding a top
and on a WR250F. the motor in steps shown in this video
are pretty much the same as the YZ 250 F and the YZ 450 F but
always you for your service manual this is part 1 of our two-part video we’re
gonna need a few standard tools and then our service manual for this job
it’s very important that you start with a clean bike that we were doing this rebuild Notre or
any other particles fall into the market so the first part of this rebuild has been is just get everything out of
the way so we can work on the motor we’re going to remove the seat, the tank, and we’re also going to remove the side
panel so we can move our muffler what’s
outside on the way we’re gonna go ahead blow everything off
it once more just make sure we don’t get any dirt
dust into the motor as we open it up an ex parte is we’re just remove the top
motor mount there’s five bolts that hold these are to in the back and three in the front
once we get those out of the way we can just take both sides out one so they’re
out of the way next steps remover spark plug cap man
ross can remove the cylinder head bent house for that other way and then the next thing we’re going to
do is just remove the valve cover so those two bolts that hold out on can
just remove those and then we can a lot of make sure you’re not but many
things uptown in the motor on south side on the way the next step
is we’re just gonna work on removing the
carburetor so we’re going to loosen the rear clap on the carburetor and they were gonna
loose and the two lower subframe bolts and then we can remove the top subframe
ball and with that bull removed we can just let the subframe job
back another the way that of a boo of the year the carburetor
what’s up a tough carburetor we can loosen the front carburetor cleaner and work on removing the carburetor slow
start from claps lease we’re gonna need do remove the hot star
cable and our other startle cables and then we also need disconnect the TPS
sensor and we compile that covered her down and how the way the next step is we just had a dream and
a freeze out at the motor so we’re gonna pull that bottom plug and
we also need listening cap on the radiator together to change what’s all that and a
freeze out we’re going to put the ball back and tighten it down now and the next step is to remove the
header and one such holder gonna move to the
other side the bike work on removing the cam chain tensioner
on these Yamaha once there’s a ball in the end we’re gonna listener and then remove
both bolts holding the tensioner in we can just pull the attention now it’s
never going to get a piece of wire we’re gonna wrapped around the camp chain and then how could a friend had a bar we
do this so they can change is a fall in the department but such cared for going to work on
removing the bolts from the camps have caps you wanna loose knees in a criss-cross
pattern in order to avoid damaging the camshaft at the
camshaft or the cylinder head surface once we have all those bolts out we can
go and pop the camshaft ap of watch for the dow pence is usually two
in each calf and then you want to make sure that you
get the locating cliff as well make sure that doesn’t fault and
in the cylinder head we’re gonna do the same thing with the
intake side pop by cam cap of much for your dow pens
and then also there’s a clip their everyone make sure we got now I can just
remove the camshaft take the intake at first notice you made
the exhaust that tension adjusting their so they’ll
reveal the buckets and then also gives access to the two
other cell under head bolts and the next thing you do is just remove
that radiator hose their insists on your head
analyst Mike Laffin just pull the hose off know when entering the ground wire
that’s run into the cylinder head as well scream about ball and then there’s two
nights when the head to the cylinder the new to come off well just remove
those one soldier offer gonna switch the other side motor in the mood there oil supply lines there’s three banjo
bolts to hold this in place so we can remove the top on cuz is
connected to the sender head to get that banjo bolt now don’t forget
that there’s a couple crush washer the sits on both sides that fitting cue
track those as well and now we can start listening or four
cylinder head bolts you wanna loose knees in the criss-cross
pattern as well I could do just that camshaft caps and once we have all for those least we
can just remove those each of these bolts he’s a crush washer
on bottom to seal and a lot of times two washers on the
head bolts inside the cylinder head will stay sitting in there so you wanna
make sure you get those out make sure they don’t drop into the
bottom into the motor we used a magnet to do this and once those are our going to double
check everything that was attached the Sun go ahead make sure there’s nothing
else can hold it up go ahead and remove the cylinder head be cautious when you moving if we don’t
wanna scratching at the surface is in Reno on Japanese thing to the
parliament now I can see air piston the next thing
we need to do is remove the cylinder so we’re gonna remove that one bowl that’s
willing so no doubt on sets out we remove our front cam
chain guide after that so the way we’re just gonna
work this under up of the piston be careful not to scratch anything gonna
drop that can change down through notice one other dow pins came off at
the cylinder wanna make sure you’re keeping track in the so nothing it’s
lost you’re gonna just quickly stuffer rack
underneath the piston we don’t want anything dropping down
into the motor as removing the piston so then using our task circlip pliers
would remove one of the circlips that will allow us to push the recipient
through the piston and then you move that respondent what’s
at risk and other way we can just pull that piston rod of connecting rod many as you can see whatever dow Penn
State in the crankcase we’re just remove that too so it does
jump into the bottom in the motor and also so we can clean that gasket
surface easier now’s a great time inspector connecting
rod organ inspect the wrist pin hole for any sign of wear scratches then we also want to check the
connecting rod for play little side to side plays okay that you
don’t want any up-and-down play disconnecting out looks great so we’re
just gonna clean up the sewing surface with the low contact cleaner wanna make sure we get any better
ask that of other what’s up sealing surfaces clean we’re
gonna work on the bottom of the cylinder we’ve still got a doubt and in there so
we’re gonna remove that so that the other one for just gonna pull the old gasket of
and then using a little contact cleaner and a razor blade you wanna be careful
not to scratch the surface you just wanna skate that all gasket of so be cautious fergie is a drag as well attack on tackling does a pretty good
job in rebuilding the whole casket on Sat stone gonna move to the farm in a
cylinder head in the same thing just for contacting a
razor blade as you can see we’ve got a clean selling
surface for the next thing we’re going to focus
on is the cylinder as you can see the cylinder looks good there’s no scratches or other regular
where but we are going to hold it is your solder flux own to remove any
old carbon buildup or glazing that has occurred you can
refer to our cylinder home video for further instructions a few passes I’ll takes ever get to go honey gives you that consistent cross
such as you see here and that’s going to help our new ring
see and help with oil retention as well rocked many TV MC carries a wide
variety a piston kits to choose from we also carry a variety a big bore kits
and that’s what we’re gonna be installing on this bike today the cylinder works big bore kit comes
complete with topping gasket kit your new piston kit and a new cell under
it’s an easy bolt-on upgrade to any machine regardless of
whether using your old cylinder or installing new cylinder like in our
case you always want to wash the cylinder out with hot soapy water after
its been home sundar works is already on our niece
owner so we’re just washing it off and then after it’s been all dried off
you want to file I could’ve oil for lubricating to prevent talk station and the next step is to check covering
in gap the way you do this is take one if your piston rings and slide it down into the cylinder
we’re going to use that person to push it down a little more but you wanted at least ten millimeters
down into the cylinder it’s critical that the ring is sitting
level in the Sun as well this will help us get an accurate
reading with feeler gauge do this without compression ring and
then both side rails for the oil ring you want to refer to your service manual
for recommended get specifications but it looks like our rings are inspect
so we’re gonna go ahead and install them onto our piston against other oil ring
first which is a three-part ring in the middle space a ring is going on
first make sure the two ends this ring tonight overlap in the group next is the two
side rails and these things are both the same which
they did but one on top and one on bottom in that space a ring
we just stop once get those on it should look like
this: with your side rails on top and bottom in the space a ring in
middle now ready to install the compression
ring these rings are almost always have marks on one side either wetherbee a number four-letter for both
as you see on this rainy it’s critical that those marks are
facing up when installing the rain so gotta rings in style and this is how
it should look last thing we need to do for the reins
is position the ring caps for this for can refer to our service
manual it’ll show you where to position the gap on featuring it’s now rings are ready the last thing
we’re going to do to get this piss me ready is install one other person circlips into one side
of the piston so we just drove to the clip up in the
place you don’t wanna bend the circlip at all and that does it for part one of this
top end rebuild please refer to the park to video for assembly instructions rockman eighty BMC carries a wide
variety of engine parts everything you need to rebuild the top
end come check out our web site rockman a2 p.m. C dot com and thanks for


86 Replies to “Motorcycle Top End Rebuild on Yamaha Four Stroke (Part 1 of 2)”

  1. rangerclass7s says:

    Thank you for this video RM , you guys are number 1

  2. jorgequiroz19 says:

    Hey my right crank case from my 01 yamaha yz 250f crack can you mane a video of how to replace it

  3. Rocky Mountain ATV MC says:

    With a service manual and referring to our Bottom End Rebuild Videos you should be able to get through it.

  4. Ashraf Ahmed says:

    Thank you for this video

  5. J Mags says:

    Great video! You mentioned that you have a valve replacement video as well. Can you provide a link?

  6. Rocky Mountain ATV MC says:

    Yeah it's on it's way, should be uploaded within a week or so

  7. RColca says:

    Do a video with a fuel injected bike

  8. Rocky Mountain ATV MC says:

    We most likely will in the near future but really the only difference between a fuel injected bike and a bike using a carburetor is the you would remove and install a throttle body instead of a carburetor and then you also have a fuel pump so you would have those wires to disconnect as well. Other than that the steps would be the same as this video.

  9. Ashton Lanier says:

    would carb cleaner work the same?

  10. Rocky Mountain ATV MC says:

    Yes you could use carb cleaner to clean up the sealing surfaces

  11. Антон Анатольевичь says:

    Спасибо за видео, а с русскими субтитрами слабо?:)

  12. ClappedNation says:

    what radiators are on that wr250f?

  13. masseyfendt37 says:

    Could you please do video on a top end rebuild for a kawasaki klx 300 thanks

  14. Rocky Mountain ATV MC says:

    We might in the future but there just isn't a whole lot of demand for that video. If you have your service manual and follow along with this video keeping in mind a few things will be different you'll be able to complete the rebuild.

  15. Erlend_Motocross says:

    i guess i would not have to check the clearance to the rings since the cylinder wall was replaced 60 hours of riding before ? i bought a high comp piston to my 09 yz 250f

  16. Rocky Mountain ATV MC says:

    Those radiators are samples of the Tusk Radiators we are working on. We hope to have them into production soon!

  17. destroyall24 says:

    best toturial ive seen for this type of work

  18. Rocky Mountain ATV MC says:

    Thank you!

  19. ola bakken says:

    hi, i have questions about my top. im rebuilding a yz250f motor since i blew my last one. after pouring gasoline on the valve seats, i found that some of my valves are leaking, and upon inspection i found damage inside most all the valve seals. is it sufficient to replace my valve seals or will i need to have my valve seats recut aswell?

  20. Toto Tojo says:

    Hey I removed my cam chain tensioner before losening the end bolt and it's tight. How should I go about getting it off?

  21. Dylan Castle says:

    This the reason why I want to replace my wr with a 2 stroke

  22. Mike Hernandez says:

    how many hours for shop top end rebuild yzf426?

  23. kevin begouin says:

    pour qu'en des sous-titre en français??

  24. Dp908 says:

    I never had to go through that much shit to rebuild my 2 strokes… hell my harley was easier than this. My oh my do I miss the 2 strokes…

  25. robert maul says:

    could you go over how to take the clutch out please

  26. Josh Blockeed says:

    Hey rocky mountain I really need your help.. Just did a lot of head work on my CRF450R new intake valves, intake springs, seals, head gasket, had my seats recut, new piston rings, and reinstalled everything at TDC and the bike will not start.. Checked my spark plug gap, rechecked timing several times and valve lashes are perfectly within spec. The carb is functioning properly and sending fuel into the engine what else am I missing? The bike shows no signs of starting when kicking it over I had my machine shop check to valves to see if there were any bends or scarring to my cylinder walls and they said they were fine. Have also put two new spark plugs in it and even tried pouring gasoline directly on the sparkplug and then trying to kick it and still nothing. What could possibly be holding my bike back from starting when it has everything it needs?

  27. DoughboyD16 says:

    like if your watching this in 2000 B.C

  28. Rob Cromwell says:

    its called a gudgen pin !!!!!!!!

  29. Rob Cromwell says:

    and con rod!

  30. marxxs says:

    Best video I have seen yet!

  31. Peter D says:

    Could you make a video on how to use a motion pro degree wheel for timing a 4 stroke

  32. James LaRue says:

    Hey can anyone tell me if I can put a bottom end out of a 2003 yz250f into my 2001 yz250f??

  33. kyle leon says:

    Awesome video was able to do a top end no problem relying on this video!!!! Thanks 🙂

  34. William Kirsopp says:

    How many hours does it take to do a rebuild roughly ?

  35. rerejinglefish says:

    should have said to set it to tdc before starting

  36. themanwiththekx says:

    You forgot to mention that you have to put the engine at top dead center before disassembly! If anybody follows your video they are basically going to destroy their camshaft or head.

  37. racequad9 says:

    Should you also replace the valves and stuff? how would you when you need new valves?

  38. Roman SK says:

    Hello guys, i am from Slovakia, and i need rebuild on kawasaki kxf 250 year 2010, when we have video please send me, Thanks:)

  39. Capy KOVA M says:

    could yous possible do a removing carburetor and how to reinstall because ion wanna mess up my throttle cable

  40. B Murf says:

    Great video, but you should fire the guy that did the subtitles

  41. Soapy Bee says:

    Should the cam lobe or lifting rods spin freely under the cam blocks

  42. steffen førnes says:

    Hello !
    I have a 2008 YZ250F with around 80 hours on it, and planning to replace the piston in the end of the season… What else is recomended to replace ?
    When replacing the piston, do I have to hone it, or can I skip it ?
    Thanks 🙂

  43. Christian Santos says:

    awsome great video

  44. Toshbar says:

    Am I correct in seeing that there is no piston wrist bearing?


    good video. can you please do one on a yamaha srx 3vn 400. will be much appreciated

  46. Tyrell says:

    awesome videos

  47. michaelovitch says:

    Few questions :
    -why you don't measure the piston to eventually re use it with new rings ?
    -why you don't measure the cylinder bore and piston to see if you have the correct clearance ?
    As i know you have to ,to be sure the new piston have the correct dimensions for your cylinder.
    How does work the cooling system on those bikes ?
    no thermostat,no cooling fan ?
    the engine is running constantly cold so ?

  48. Ezequiel De jesus says:

    Tengo una duda que e desarmado un yamada wr250f y la bambú la del medio del eje leva de anmicion abre cuando aprieto

  49. Yasin Abdul says:

    I have a 05 Yamaha YZ450F that will not turn over. It started with a bog/hesitation & pop sounds than shuts off completely. Values checked 100% and are good. Air filter checked and good. Fresh gas & oil, new spark plug, added a new fuel screw, cleaned carb 100%. Far as the top/bottom end is concerned in my opinion I believe they're all good because I don't ride it everyday or every week. I have a rebuild carb kit coming this week which I will install it just in case. Do you all think I'm over looking something that needs attention? Maybe the float is stuck or something like that!

  50. george unwin says:

    You didn't show setting the timing of the motor before removing the cams

  51. Spike Spikus says:

    Another reason why I'm probably gonna get a two stroke

  52. Mitchell HürenKamp says:

    Isn't the cylinder nikasil plated? so it can only be honed with a diamond? i thougt you could throw the cylinder away if you use a hone like that.

  53. toms gaming says:

    What do u torque the cylinder head bolts to ?

  54. DRAKE FORCE says:

    I am leaving this comment hoping that someone will reply and help me with my problem I own a 2006 YFZ 450 racing quad and it has several modifications done to the engine it has a Wiseco top end the upgraded oil pump and it has an aggressive cam in it so my problem is the quad wont idle you always have to give it a little bit of gas to keep it running or turn the idle up on the carburetor so we had taken it to a mechanic because I was too busy to work on it myself and he did a valve adjustment and he did work on the carburetor and he called me up and told me that the quad wont idle because it has an aggressive cam in it is this true if there's anyone out there with extensive knowledge can you please help me thank you

  55. Tide Pods says:

    Would this also go for a 2006 yz250f that seized up from no antifreeze

  56. MrFstasfk says:

    Is this the same top end rebuild as a 2015 wr450f

  57. FoursquareT says:

    My locating clip fell down to the bottom what do I do

  58. Dillon Kidder says:

    ok so I was riding my bike and all of a sudden I heard a click/ snap and then the bike died. I have no idea what happened, I fired it up let it warm up for a minute or so and then shifted into 2nd and took off. within 30 secs I heard the click/snap and now my kick lever is locked in position. any possible info would be helpful i haven't taken it to a shop and am considering selling the bike. ive only had it for one summer and am also considering rebuilding it myself or having a shop do it. any info on what yall might think happened would be appreciated and or price range on what a shop would charge….

  59. Wazzup says:

    How long do you say this would take? And once you do it do you get more familiar with doing this thanks! Great video👍🏻

  60. Michael Lance says:

    You guys are life savers. I can't express how appreciative I am for these videos. They have saved me countless thousands in repair expenses. I'm not the best mechanic, and I need detailed, step-by-step instructions. No other how-to videos come close. So THANK YOU!
    Not to mention you guys have the best deals, anywhere, for pretty much any part I need. Just ordered a carburetor repair kit and some odds and ends, free shipping, and it arrived the very next day! Awesome.
    Keep up the good work.

  61. The Sideline says:

    Any vids on installing a auto decompression cam on a 2001 YZ250F.

  62. Jakub Gruszczyk says:

    How long do you ride with this piston?

  63. Isaac Bueno says:

    My uncle has a 2002 Yamaha raptor 660r and one day we went riding and it started shooting oil out the air box, I've read some forums and heard that was caused by too much blow by or a bad piston ring, would a rebuild fix that? Please respond, thanks.

  64. Galafilms The_Canadiankid_ says:

    That banjo bolt.. would that be on my 05 yfz 450 as well and do you have to unscrew it?????

  65. Ashton Lanier says:

    will carburetor cleaner work fine for cleaning it?

  66. BlackCoffee says:

    If you've never disassembled an engine before, would take the engine off the bike make it easier? or is that too much?

  67. Scott Ohler says:

    I have a Kawasaki mojave 250 it's kick start and sometimes you can kick start it and sometimes you can't and sometimes it will go down half way and act like it's locked up and if I turn it over with a wrench it only goes so far then it acts like it's locked up to. it's as if its turning over then it suddenly stops can anybody help me out???

  68. BlackCoffee says:

    Contact cleaner…like WD40 or Carb cleaner?

  69. My_Name_Is_ Chef says:

    I want to like your guys company. But 50% of the time I've ordered from you guys I have had a problem getting my order in a decent time. Even an order I placed today. All of the items were in stock. I went to checkout. Selected next day air. all of the sudden, There's a problem with my order. It says. Some of these items are on back order. The order will ship when the items are in stock.

  70. Isaac Missi says:

    Hones cylinder then replaces it with new cylinder

  71. Panagiotis Pratikakis says:

    Hi i have a wr400f and the motor broke down, i want to ask if all the parts except cylinder and piston is the same in the wr450f ? because i want to do an upgrade in the motor and go to buy the parts of the wr450f !!

  72. Chris Lewis says:

    It doesn't have to be at TDC for disassembly.

  73. Dimitrios says:

    Awesome video ,very professional work …well done

  74. LizardMane says:

    Do you have to empty the oil and water before doing this or just the coolant

  75. bomark 2002 says:

    Guys how do I disconnect the motor from the frame of the yz450f? Do I have to remove the whole rear end from the frame of the bike?
    I went to my local Yamaha dealer service center and to get the engine off the bike the whole rear rack assembly and wheel has to be removed

  76. Craig Krage says:

    Great step by step video.
    Thank You for this information

  77. TheSeason says:

    Tearing apart my rmz 250 I'm not looking forward to the engine rebuild. Check it out on my channel

  78. Johnny is a Sinner says:

    old piston looked fine other than carbon build up

  79. Arvis Pavilons says:

    correct order:
    1. remove accelerator cables
    2. remove clutch cable
    3. remove carburatore
    4. remove full exhaust
    5. remove radiator
    6. remove engine put it on table

    1-6 points will take you 30 -120 min . depending on your skill and experience

  80. Andrew says:

    At 4:38 you can see two holes in the cylinder head. One, to the lower-right, is drain hole for spark plug well. What's the other one?

  81. Rj Rc Nunn says:

    I am in the process of fully rebuilding the top end on a 2004 RMZ250 with all new parts including Cylinder Head, all valve components as well as wiseco cams etc. Beings I am starting with all new parts where is a good place to start on valve shim size???? Not sure where to start as the old ones are going to be WAY TO THICK?? I am going in the morning to get the proper feeler gauge set

  82. bubba.watercraft J says:

    Great video.
    Do you do boat or waverunner engines also? Thanks.

  83. HightyRoss Supermoto Vlog says:

    do mechanic with dirty motocross…………Ok

  84. Gregrey Rosenthal says:

    How tight should the cam chain be?

  85. Trey Swingo says:

    Can I

  86. 2J_MacRae_Z says:

    Would this basically be the same for a 98 WR400f?

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