250-500cc Wr250 Rebuild Questions

I finally have my 99' WR250 motor apart for the rebuild after my piston shattered last fall. I already sent out the crank to have a new rod and bearing pressed on. I just took apart the power valve so I can send out the cylinder to get re-plated.

Question #1 - how do I remove the small inner port valves with the small gear ends on the R and L side of the cylinder? I already removed the retainers but these things are stuck in there real good! In addition, this is not something for brute force as they seem quite fragile nor do I want to damage the cylinder. Hoping someone has a technique on how to get these out!

Question #2 - My engine appeared to be stock, never taken apart before. I was surprised to find 2 base gaskets on the cylinder. They are thin, but why 2? I got an Athena complete gasket kit for the rebuild and interestingly it comes with 2 base gaskets as well. However, one is thicker than the other. I would think that the gasket kit contains 2, thick and thin, for choice of setting the compression ratio. The WR250 parts listing shows several different thickness base gaskets. So how do I go about deciding which one to use?!

Question 1
I'm stuck at the same place right now. The manual calls for tool number 800090659 which is a booster valve extractor. It looks like a tiny flywheel puller. I was hoping someone would have a way of doing this without the tool since I am having trouble finding one.

I sent my cylinder to Powerseal in PA to be replated and I left the booster valves in. I called them ahead of time and they said they would get them out. I spoke to them and I believe they said they used something like a small slide hammer. The outside ends of the booster valves have threads in them. After cleaning and heating the cylinder the popped them out that way.I've seen some smaller slide hammers at Harbor Freight. I would guess using an end on one that can take a bolt that fits the booster valve would grab it that way.

Also I have another question about reassembly, maybe you know the answer. The crankcase halves on the WR have a gasket. I'm wondering if I should use any type of sealer and what type on the new gasket when reassembling. I'm use to Jap bikes that have no gasket and use 3 bond.

Another question for you all........my Athena gasket kit came with what I have measured to be a .3 and .5 base gasket. From some various reading I believe the .5 base gasket is what is supposed to be stock. My cylinder is getting replated back to stock size and I will be using a Wosner piston. I hear people going with thinner base gaskets for more low end, but I'm concerned about detonation on the crummy 93 octane that is available these days. Any thoughts on base gasket thickness? Should I just play it safe and go with the .5 MM?

You are right, a small slide hammer with a 5 (I think) mm stud on the end. The husky shop manual says "goop" on the center gasket. I just put my cases together yesterday with some Three Bond. Like DD says, so it doesn't slip.
And the stock base gasket in so it can run pump gas.

Thick or thin base gasket will effect compression and port timing but more importantly the squish area as you are raising or lowering the piston deck height or how much the cylinder is raised or lowered.
.3 will give you a slight increase in low-mid power and the port timing will be altered but not dramatically. Whilst .5 is standard (?).
Ever man and his dog will have a theory on whether to apply dry or sealant on base gaskets.... l use a very light coat of non hardening gasket cement to a) keep the gasket in place and b) insure no leaks.

xcuvator - what bike / year is that and am I correct the .5mm is stock?

ohmygewd - what kind of non-hardening gasket cement have you used on base gaskets? Most of my assortment is all hardnening to some extent so that certainly intrigues me what type you have. I have always used a thin layer of grease / oil on base gaskets to swell them and ensure easy removal, especially on the dowels. Never had a problem.

As DD said, when using a gasket on the center cases as in the case of the Husky, a sealant is not required. However, I have read that a thin film of oil can be used here to help swell the gasket. Any thoughts on the center case gaskets? This is all new to me since it is the first time I have split the cases on a Husky. All past experiences have been on Jap bikes that I have used Yamabond on. Thanks

I use Permatex Aviation Non hardening on every motor l've worked on and again, everyone will have their own theories....l'm also a fan of copper spray if you are taking the head on and off regularly.
As for the case gasket, again l use non hardening or the the gray-type gasket sealant with no silicone like yamabond..absolutely use a gasket as well. Mates racing 2 stroke gp bikes all use the same gasket sealer so if it's good enough for an RS250, then it's good enough for a mx bike!!

Again Kev, everyone has their theories but use a gasket for the case and the sealer is just added insurance for no leaks...good luck!!

I use nothing on the case gasket.

If the booster valves are stuck...the main PV will be nasty too.

Use WD40 to clean the main PV and use yamabond on the front PV cover.

The pv bearings are hard to change if needed.

Powerseal did my cylinder too and they did a great job!

Like has been mentioned, the clearances for the transmission shafts, including the shift drum and the crank depend on the gasket for their clearances.