YZ250 Top End

Rebuilding the top end on a YZ250 2 stroke!
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[@mcanderson0]

Yes viewers, we should DEFINITELY use a torque wrench as often as possible to avoid warpage, excessive wear, cracking, and other destructive occurrences that are ever-present and always possible, ESPECIALLY with magnesium and aluminum frames/blocks/brackets that make our modern toys so lightweight and awesome. "Crow Foot Wrenches" that mount to your torque wrench's square drive shank are awesome for those hard to reach areas and are super cheap at Harbor Freight or Princess Auto or whichever chinesium discount tool warehouse you have in your local hood. Good vid man, thanks for taking the time to whip up a how-to.

[@tyleradams6002]

Just did my first ever top end job on my 21 yz250, this is the first 2 stroke iv ever had and after a year of learning to deal with that crazy torque and power like a light switch. I see why everyone loves 2 strokes...made me learn to ride more flowy and use my clutch at all times..no lazy riding like I did with my previous crf250r's that iv had. Also added a apex head with the sx dome. Was able to drop a jet size and damn it's a different animal

[@highlandcycles]

Awesome! YZ’s are the best

[@peteregger7928]

Noticed the Scottish flag in the background! I was born and raised here in the U.S. but my Mother is from Glasgow, Scotland. With her heavy Scottish accent I would always have to act as a translator when my buddies came over to the house. Lol! The Romans built Hadrian's Wall to try and protect themselves from the Scottish Highlanders. The Romans made some inroads initially but weren't able to keep the territory or conquer the Highlanders! The Highlanders were one of the few groups of people the Romans were afraid of!

[@highlandcycles]

YES! Both my mom and dads families have very Scottish roots.

[@Ward1228]

I just did a top end on a new to me 01 cr250 after discovering the piston had a crack while changing the reeds. After watching basically every video you have put out I decided hell I can do this. I didn’t have a ball hone so I just used a little scotch brite to knock off that glaze and the cross hatch was still present. Needless to say a 2 stroke is WAY more easy then my old kx450f. I learned real quick why 2 strokes are better after rebuilding that thing. Keep up the great vids and sound effects 😂

[@highlandcycles]

Thanks so much. Glad you tackled that job.

[@michaelwebster2416]

another good video , i learn somthing every time , great stuff!

[@highlandcycles]

Awesome! Thanks so much for watching

[@ericraherimanjato9688]

Excellent video!

[@highlandcycles]

Thanks a ton.

[@11MrRichi]

Super cool love ❤️ this keep it up 👍🏼 love it

[@highlandcycles]

Thanks. Will do

[@11MrRichi]

I’m in to the desert with my kids and did a rebuild on some kx 65s with out knowing nothing and u make it seem so simple ur fan for sure 💯 %

[@Meekerextreme]

The more I watch you with this YZ the more I'm thinking of getting one, much easier to work on then the GasGas. So only question I have what headlight can you run with the 80 watt stator you got with this bike. Lights are very important.

[@highlandcycles]

You can run the biggest one that baja designs makes I think. XL Pro

[@BikerBenny]

20:15 ive come acrossed alot of videos talking about different base gaskets thicknesses used for compression but dont known whats behind it all?

[@highlandcycles]

The thinner the base gasket, the higher the compression

[@jzsquad6866]

Hey man great video when you said 7th that’s the measurements you like for the ring in the cylinder

[@highlandcycles]

7 thousandths

[@jzsquad6866]

@@highlandcycles thank you I’m doing a rebuild soon on a yz250 I got on a trade and your video was a huge help I’m confident enough to do it now thanks to you since you did it with no fancy tools.

[@Shooter_Mcgavin93]

Lmfao that Henson sticker I did the same shit for jokes before it burned off 😂

[@highlandcycles]

Hahah

[@colton_vesik9973]

Did you do the power valve mod as in taking out 1 spacer on the governor so it opens sooner

[@highlandcycles]

No. I like how it works. This is a YZ, not an X

[@tomcross2956]

Should I take apart the power valve before honing? Also stock bore size ok using a weisco piston 66.4?

[@highlandcycles]

Yes on power valve and I use the vertex b piston

[@GravyReactions]

Hey! I have a question. Is it ok to be able to use steel washers on the top end? Or do I need the copper ones.

[@highlandcycles]

You should use the copper ones if you can. But in a pinch you can use steel ones.

[@thefourwheelerdoctor7808]

Hello what brand of homing ball do you use? As shown in the video. Thanks in advance

[@highlandcycles]

I don’t know the brand but I got it from Snapon

[@user-ww7fv1nw4x]

A quick question piston at BDC do you think the ports should be fully exposed be nice to see a pic of that when you did the top end. I noticed mine are not and the squish clearance is over 1.5mm so it seems to me the cylinder needs to be raised and the head brought down to a 1mm squish what are your thoughts thanks.

[@highlandcycles]

It sounds like it would be optimal to do that but I can say that the bike will probably have better low end the way it is and better over rev if you were to raise the cylinder.

[@vince5946]

I am looking for a winter project and thinking of doing a YZ250 woods bike build. Any recommendation for a model year? Looking at parts availability it seems that the 2006 year would be the best to start with?

[@highlandcycles]

Anything 2006 and up

[@RideWithTheWolf]

My yz250 makes a low end growl and knocking noise at low idle. I've read that it can be a normal noise for these bikes? I've watched a lot of YT videos and the yzs all have that kinda tapping noise, for the most part. If it was a bearing wouldn't I know it? Bike runs good.

[@highlandcycles]

They are noisy motors. I wouldn't worry unless it gets worse

[@trentonrobinson2745]

What kind of hone did you use aluminum oxide of silicon carbide and what grit

[@highlandcycles]

I don’t know the grit. They are from Snapon many years ago. They just deglaze and put a crosshatch back in. They will also expose anything that is coming apart too. I have had a few where after I run the hone, I find some part of the plating coming off or an imperfection. That way I catch it before I put it back together.

[@benjaminsanabria5212]

What did you use to clean the head thanks greatly appreciate

[@highlandcycles]

Brake cleaner

[@mushmanist]

I’m looking for a power valves for a cr125 02 to 03

[@highlandcycles]

Dang. I don’t have that

[@tomcross2956]

How did you clean cylinder after honing it?

[@highlandcycles]

Brake cleaner

[@hoangsolo3314]

What’s size of the piston 66.35mm? I want to order for my 2004 yz 250 too.

[@highlandcycles]

I don’t remember what size. I normally use the equivalent of a B piston.

[@benjaminsanabria5212]

So go with a B piston is the bes bet for a stock yz250?

[@highlandcycles]

Yes

[@grantallen5274]

I have a serious run away issue after a top end bike was running fine any quick tips please mate

[@highlandcycles]

Sounds like an air leak or carb slide stuck

[@benjaminsanabria5212]

How often should I replace a top end on a brand new yz 250 how many hours thanks

[@highlandcycles]

Depends on how you ride. If lots of top end wide open then 50-60hrs. If more low to mid, I’d do 70-80

[@benjaminsanabria5212]

What size hone do you use for a yo 250 stock cylinder

[@highlandcycles]

I don’t know the actual size. I’ll try to remember to measure it tomorrow

[@marioguzman9290]

Hey bro! Did you measure the cilinder diameter? Also what state do you live in? Greetings from Las Vegas Nevada!!!

[@highlandcycles]

We are in CO.

[@justinpeterson8754]

I just put a new top end on my YZ250. I also replaced the head with an RKTech high compression head. I checked the crank bearing according to the manual. Everything checks out. It sounds like there’s a rattle coming from the bottom end. Is it possible that the crank bearings in the cases are bad? Is there a way to tell without disassembling the engine? I also have video I could send to you. Thanks for the help?

[@highlandcycles]

That sucks. You can take the side covers off and try to move the ends of the crank up and down.

[@justinpeterson8754]

@@highlandcycles thanks for the advice. Do those bearings commonly fail?

[@highlandcycles]

@@justinpeterson8754 Not super common but it happens.

[@michaelhahn1278]

how much would it be if you did a top end on my xr400r?

[@highlandcycles]

Depending on what needs to be done to the cylinder, between 600-800

[@simtak6620]

Hi great video men like always , I have my 2019 yz250x 2 stroke and my question is , Do you run jd jetting on your yz ? , beacause I will try jd and run motorex 50:1 for trail riding. What your opinion on that ? Thanks

[@highlandcycles]

Thanks. My YZ actually has a Lectron but I do recommend JD specs in the stock carb. And 50:1 is grear

[@simtak6620]

@@highlandcycles yeahh thanks men !

[@user-dd4ng6uv9w]

What topend kit do i get for a 1994 yz250

[@highlandcycles]

I like Vertex

[@user-dd4ng6uv9w]

U where saying there wasn't really a difference in the vertex piston size, u said A.B.C are slightly bigger what should I go with for the 94?

[@TheYAMAMAHA]

Link to the hone you used please?

[@highlandcycles]

SnapOn

[@TheYAMAMAHA]

@Highland Cycles okay, was curious because I just mine with a flex hone and used the brands honing oil. Did it for about 5-7 seconds at 500-600 rpm and turned out beautiful.

[@highlandcycles]

@@TheYAMAMAHA perfect

[@crx187]

No rk-tec head?

[@highlandcycles]

Not on this one. This is an old video

[@GL-zo3vz]

30 seconds honing?

[@highlandcycles]

It is just to deglaze the cylinder and put a crosshatch back in it.

[@GL-zo3vz]

@@highlandcycles nice.

[@travisk5589]

Wait? So is it a Yamaha crank or hot rods? You just explained that yamaha makes there cranks super tight and need to heat them up but then say its a hot rods.

[@highlandcycles]

Yeah, sorry that wasn’t clear. Yamaha oem does that and hot rods does it on yamaha cranks. It’s actually on most cranks really. It seems that KTM ones aren’t normally blue like that.

[@travisk5589]

@@highlandcycles Thanks for the reply. I am getting ready to rebuild a 2008 yz250. It's still on the original piston, rings, and crank. Is never been spilt. I am wanting to throw in a 250x 4th and 5th and figure i better rebuild the motor while i am at. Do you like hotrods, wiseco, vertex, etc better than OEM? I would like to get another 12 years out of the motor.

[@highlandcycles]

@@travisk5589 I like hot rods cranks and vertex pistons. You can get that set up in the Wrench Rabbit kit