1988 XC250 revival 2016

I measured the head gasket and it was the same. Used a cometic base from the kit which visually looks identical, though I haven't checked it with my calipers yet.

I've seen those vertical lines before to, I'm not sure what it exactly means tho. One thing about taking it in and having them inspect the cyl . and them actually explaining it to you is that you get the knowledge of what this or that means. Straight from a pro not a key board surfer. It's kinda like some one telling you how to do your job that you do every day and they have only ever seen it done...
Keep us posted on what you find, this replacement piston is a perfect example situation that you have made for the 87-88 husky man. Take your time and post your findings this will be a great reference from now on into the future.

Wouldn't a keyboard be a bit small for surfing?

Boogie board.

Can't imagine the salt water being very good for it either!

if that bike truly has that low of compression, i dont think id disregard that. just keep riding it? down 70 psi?
probably has a bad gauge, but if not the motor isnt right.

vertical lines are almost always dirt ingestion. the 87-88 filter is tricky to get to seal right, as the filter wants to slide down to the bottom of the housing. also, very few people grease the filters edge so it seals against the box. i started cutting a piece of foam to lay in the bottom so the filter cant slide down.

Salty water ? eeewww...

I was wondering about how the filter was supposed to seal! I'll slather mine up with some grease before I fire it next. But I think I may have figured out what's going on. Silly me mr no leak down test.

I pull the stator cover off to notice some oily residue. I think to myself hey that's not right at all.

I pull the flywheel and other electrics out to discover the bottom side of my seal retaining plate thing wet with the same oily fuel smelling stuff. Upon further inspection I realize that my retainer plate isn't fully seated at all. So I splash some soapy water on the whole thing and slowly stroke it over and see a gyser of bubbles on pretty much all sides of the plate!

After much fiddling I've concluded that I must have installed the bearing just slightly too flush in the case on that side for the lip of the retaining plate to fit down into the bearing bore far enough to get the gasket to do jack shit really.

I will never be able to move that bearing with both races press fit that's for sure. So I plan to take the retainer into work and have it milled down the nessecary amount to make the gasket mating surfaces, well, mate.

Now whether this is where my 70 psi is going or not is another question. Something tells me that a small loss down low would have a stacking like effect. Example loss of three psi down low equals six up in the chamber. Maybe compressing air doesn't work like that, I am no scientist.

nice work, thats why you dont ignore things! you are learning alot, too bad some good learning is from screw ups.

Crank seal ????

sounds like that crank seal is bad though, maybe damaged from installation?

Not sure as of yet. It didn't spew any bubbles really, though it was hard to tell from the bubble bath the paper gasket area was making. Once I get that sealed off I'll do a proper leak down test to check the seal. My crank seems to have a slight wear area on it where the seal sits, presumably from dirt getting in there. The old seal was caked in filth.

Got the freeze plugs for plugging the ports off, just need to get an inline gauge/regulator which I should be able to source from NAPA tomorrow.

Good job finding that. I get what you are thinking as far as milling the retaining plate, but I'm not sure all will be well if you do. Hopefully the added (radial?) force/leverage from being outset farther from stock will not have ill effect on the rotating mass. I'm not sure how the bottom end pressure ratios out with the combustion chamber compression.

Thanks.

I'm not sure the plate does much other than retain a seal. In all reality the amount the bearing and plate are off by I'd say maybe .010-.020, which to me is a lot. I'll get a precise measurement before I have it just cut down. Load wise I don't think the plate supports the bearing much at all, with how snug fit the bearings are in the bores it doesn't really need the lateral support, in my opinion.

i dont think the plate does anything but function as a seal retainer. the bearings are held by their press fit

I agree completely.

Sounds like Kyle has a good grasp of the principles, if the seal retainer is leaking, a lack of compression will be evident.

Back to what i said lol lack of air to compress hey or eh in Canadian

So I finally got a pressure test done.

Got the seal retainer to seal finally but my brand new reed cage gaskets are leaking like crazy. Gonna use some fuel resistant rtv on it and see what comes of it. The good news is the actual crank seal showed no signs of leaking.

Still think my gauge could be way off though, still reading about the same compression. I'll ask my coworker if I can borrow his Monday and see what it says.

Let's talk about the PTO side for a second. I've noticed when I run the engine the oil gets what appears to be milky. However when you let it sit it looks like regular oil. I figure it's actually aeration, either caused by the constantly rotating clutch assembly or a leaking pto side crank seal. When I was looking for leaks I actually plugged off the case vent for awhile and then just lightly cracked the oil fill cap open and shot it with some soapy water and absolutely nothing happened so to me that sounds like it's more likely aerated from the clutch and not a seal leak. I should also point out that the oil level looks like it hasn't moved a bit, hopefully further confirming my suspicions.

how much air are you pressurizing the engine with?
the oil shouldnt get milky, maybe post a pic of that.