250-500cc '08 WR250 Top End - Tips

I ordered my new piston and gaskets ect. from Halls today. It's been a decade since I've done a top end so I need some 'tips & tricks'. I'll probably do a quick YouTube search as a starting point even if it's on a different brand bike. My main concern was getting the power valve back together correctly. Can anyone comment on any tricky areas or any tips. I'll probably snap a few photos as I go so I know where the original setting were... Thanks!

i dont know

whats the point of posting on a ton of topics just saying "i dont know'?? is it to get your post count up?

if you dont like it dont read it.

i didnt say i didnt like it, but was asking a question...

its just a joke.

fredd as much as I love your current material(the joke that just keeps on giving!) I reckon its time you thought about getting some new stuff onboard.

How many hours or miles you at?

I've put about 80 hours on the bike. I bought it in 2009 and the previous owner claims he put about 25 hours on it about 9 months.

The power valve linkage is pretty straight forward. All that is needed to get the top end off is to carefully pop off the plastic rod on one side. I didn't pull my power valves out so I'm not sure what's involved there.

The cylinder nut that's inside the power valve cover is kind of tricky to get a wrench on. I couldn't find a box end that would fit so I used an open end and was extra careful to avoid stripping it. You will need a crow foot adapter for your torque wrench to torque it back on.

Good luck

i said it again, if you dont have sense of humor is not my problem, work with that.some people like it some not, i'm not a $100 dollar bill.

A two stroke top end is pretty straight forward. Here're my tips:

1. The Husky gasket kit, does not include the o-rings for the head, those are separate. Be sure to get those.
2. The powervalve plastic clip is fragile, brittle plastic. Be very careful. Even being careful it can crack. Might be worth ordering one just in case. Mine happens to be safety wired together.
3. Arrow on the piston goes to the front.
4. Rings clock to the notch on the piston. They won't squeeze in all the way if they're not right.
5. Pre-mix is good for lubing everything on top end assembly, don't be stingy with it, the extra will burn off.
6. Always have shop rags covering the bottom end. You do NOT want anything to drop down in there.
7. Drain all the coolant from the drain and with the cap off BEFORE loosening the head.
8. If you can still see the hone marks on the cylinder, it's probably good. If there is any scarring or dull spots (where the plating has rubbed through). Take it to your dealer for their opinion. Likely you'll need it plated and honed.
9. Rotate the crank to the bottom of the stroke for easier ON/OFF of the cylinder. Remove the head before attempting.
10. Check that everything moves freely as expected before putting covers back on. Rotate the crank and let the piston go up and down, should goes easily without the head or spark plug in place and with some pre-mix to lube the cylinder. Before putting the powervalve clip on manually push the actuator arm to open and close the valves (also good to clean and lubricate all of this with pre-mix).

wear safety glasses when popping the old circlips out of the piston....

both of the circlips smacked me in the forehead on the last top end I did

be careful if you need to scrape off the old base gasket from the case and/or base of the cylinder. I used a razor, I heard there's a chemical you can dab onto the gasket remants to make it easier to come off - I can't remember what it is though :\ BE CAREFUL not to gouge the metal, you can use a scotch brite pad or sandpaper to smooth out any small nicks or scratches.

When re-installing the new base gasket, use a small amount of grease so it'll be easier to remove next time you do the top end.

re-torque all the nuts after you heat-cycle the new piston

Measure ring-gap and squish so you have a baseline for the future.

whenever I scrape gaskets these days I use a shopvac, never a question if something fell into the bottom end
and on the plastic linkage using heat helps to make it pliable, if you don't have a heat gun a hair blow dryer works just takes longer

Motion Pro makes a box wrench which has a square 3/8" hole in it's center so you can attach a 3/8 drive ratchet to it. Makes cylinder nuts a breeze!

I just pulled my jug off too and had a couple questions, this is my first Husky top end. I am seeing some coolant in the cylinder. The inner head O ring looked pretty raunchy. Hopefully replacing it would be the cure. Any other thoughts? Also, some have mentioned a slot for the power valve. On my bike the bolt is all the way at the bottom of the slot. What are the pro and cons of moving it? Thanks for you help! View attachment 33748 View attachment 33748 View attachment 33749

I would recommend finding a box wrench and grinding part of the edge off because you will find most box wrenches will not fit on the front 2 cylinder nuts. Even being very careful, I stripped the front 2 nuts using an open ended wrench. Just save the time and effort and grind the wrench to fit the cylinder head area.