Motor Teardown & AnalysisWe start with a pretty good looking specimen, complete and on the parts washer.
But on closer inspection there are some defects ... chipping/flaking/faded paint.
And some frame marks where I gave it a bit too much rage while pulling the motor.
More pics of the failing paint...
The heat really caused it to bubble on the fins.
Overall the lower cases look good but they have a few spots themselves that aren't so good.
Real bad flaking here.
Lower cases look pretty nice.
... but have some rash from road debris and bugs.
So lets pull it apart!Everything comes apart nice since it's only been one season since the last rebuild. ha
Nothing shocking here.
Pull off the exhaust flanges ... man they were in there good. I used loctite since the vibrations tend to loosen them and create exhaust leaks.
Parts shelf starting to fill up.
At last the cam towers are free! I tried to wipe up the pooled oil under the valves so oil wouldn't go everywhere when i pulled the head.
There was oil down in the cam tower bolt holes ... I thought it might be a source of a leak but it seems to be a blind hole. I pulled the cam tower "pucks" and some of them came out easier than I'd like to see... however there seemed to be no sign of oil that got past the seal underneath.
Oil jet o-rings really look like they flattened out big time. Seems like it's barely even above the surface...
I like to put everything partially back together exactly like it came out. Much easier to keep track of everything.
I checked the head bolt torques before I pulled the head. I tried 18lb*ft first and only one of the nuts moved just the slightest fraction before it clicked. I went to 20lb*ft and a couple of nuts tightened up a little bit before clicking but most just clicked. I pretty much ruled out "loosened" head fasteners as a cause of the leak.
Some oil trails along the edge of the head (next to #4 I think?)
Same thing on the other side.
This is the underside of the head. (Looks like I was running a bit rich but I was screwing with my idle mix just before I put the bike away for the winter so I think that's probably why it looks like that.) You can see the oil trails along the sides.
Same deal on the other side. I was originally thinking that maybe the corner dowel pins had caused the head to hang up and not fully seat down. There is also a little ridge inside the dowel pin bore that looked suspicious.
Hard to see but there is a ridge down in the bore that I thought might have been holding the dowels off the bottom and preventing a good head/cylinder clamp.
Same thing here but you can actually see that the oil probably came around the corner dowel pin and probably didn't escape from there. And on further though, the corner dowels actually aren't oil drains like the rest of them so there really is no way for them to leak!
Looks like the oil came around the corner and the was pushed back by wind force (and mad G forces from sick acceleration ...
)
The pressure delivery port o-rings looked a little wonky ...
For some reason they were a weird almost triangular shape? Didn't look like it leaked from there though.
There's that ridge i was talking about.
Got the cylinders off with a minor fight.
Fortunately, the pistons looks good and the cross-hatch from the hone is still clearly visible.
Parts pile starting to grow.
So that's where I left it for the night. Decided I would let it stew in my brain for a while and see if anything popped up.
Threw the head on top of the cylinders just too have a look .... you can see oil on the first fin of the cylinders.
But looking above that, there is really no where that oil could have come from on this side.
You can see the oil streaks down the edges but I think that's from the casting marks and wind pushing the oil up there.
By this photo, it looks more like the leak was probably coming from the 3/4 cylinder region and just flowed around to both sides on the top fin of the cylinders.
The 1/2 side has a much lighter coating so I don't think the leak was over here.
Pull the MLS gasket off to take a look. No super obvious signs of exactly where it came from but seems to be definitely coming from somewhere around the #3 I think.
Same trails around the sides from the wind carrying the oil.
I thought it might have been coming from here but there is no where above here that shows an oil trail and the exhaust flange screw hole is just a blind hole ... so nope.
Lets try and measure these sleeves... see if my initial guess of the cylinders creeping after the resleeve was correct...
Not the best way to measure it but I could repeatably show that the sleeve was down from the surface of the head (about .002").
Zero it out on the sleeve...
The other side is down about .001"
And the #3 ... on zero (almost) on the sleeve.
Oh #$%* ... this sleeve is proud of the surface by about .001"...
#2 is down about .002"
#1 is also down .001 or .002".
.... So that might explain the leak in the area of the #3/#4. If #3 is proud of the surface a thou or so and #4 is down a couple thou... I'm thinking that is enough to cause a bad seal. Thoughts?
Random aside on rings ... Do they rotate or not?!When I installed my rings/pistons I made sure to orient them all about 120 degrees apart ... even though I didn't really believe that rings won't rotate while the engine is running. Here is how they were when I pulled the cylinders...
#1 where almost together ... definitely didn't leave them like this.
#2 were also quite close to each other.
#3 where about 30 degrees apart.
And #4 where like 180 degrees apart.
Anyway, so I think I've probably found my oil leak after much deliberation. I'm guessing the MLS gasket, though good, just couldn't take the .002" - .003" difference between those two sleeves. The dowel pins in the corner may have also played into it in giving reduced clamping force due to friction in the dowel bores.
Do you need to trim your dowels pins down when you resurface a head/cylinders? Do you need to trim the alignment dowels as well as the dowels in the oil channels?
I appreciate anyone's thoughts on this.
Thanks
IW