How does this happen? Stem seals leaking a bit? Doesn't look major and bike still runs sweet but I'd like to clean them up without having to pull the heads out, vertical pot only, 16K miles testastretta,any thoughts?
You'd need to remove the heads and lap the valves to get good sealing back, clearances being correct won't alter the sealing.
Bugger. Well she’s had a tiny oil leak from that head for a while, gasket required at some point so looks like a proper winter project will be happening.
I'd want to compare with another that has done 16K miles or more. I imagine it doesn't apply even to the latest bikes, but modern emissions-compliant cars, even petrol, sometimes suffer from soot build-up on back of inlet valves, apparently due to exhaust gas recirculation and the use of direct injection into cylinders (preventing fuel mix coming in through inlet manifold from "washing" the valves). Blasting with walnut shell particles seems to be used as a clean-up method in some cases.
Further reading suggests fuel containing ethanol can cause a carbon build up on the back of hot valves. This doesn’t seem particularly unusual. Bike has suffered from an occasional misfire under 3000 rpm now and again. Engine is coming out so I might as well do them.
Compression test will tell you if it's urgent - or a nice to have shiny valves job But if you have an oil leak you want to sort it makes sense to lap the valves in - just it will now cost you 2 gaskets
What is the mark roughly along the centre line between the two valve ports (which coincides with the carbon fouling), needs further investigation otherwise valves need lapping and a compression test to validate the pressure tightness between the two heads?
Rough mark on the casting I hope but I will check when it’s all in bits. New belts here, head gaskets on way so I might as well go the whole hog and clean the valves, lap them in and get the clearances done. Should keep me out of the house after Christmas.
Looks quite normal to what I’ve e seen tbh. Just built a 1098 motor with similar build up. No issues with valve sealing or stem seals. Could be fuel deposits, could be crankcase recirc or possibly even from valve timing overlap although I’ve seen it on 11 degree motors from Diavel/MTS which is much less than the 38 degrees the SBK motors run.
The carbon deposits indeed don't appear to be close to the valve seats at all but they will be getting cleaned up anyway. The possible worry is the mark that denzil spotted, it may be a crack, maybe not. It looks like it is on the rough casting area and stops where the head has been machined above the valve seat area. Will know more when the head is off. Might be looking for recommendations of someone who can weld and machine heads.
It's a casting line, where the cores have been removed. The motor I have here is the same. The line runs down thru the inlet tract.
I wouldn’t worry about the carbon build up. That’s normal. You’ve got Fuel vapour sat on the back of a very hot valve and also crank case breather venting oil vapour back in to the inlet side of the motor all of which contribute to carbon deposits. It’s fine. Nothing to worry about. And as nelly said. The mark in the port is just a casting mark. They are mass produced after all. So next to no hand finishing in the ports.
Interesting that the inlet on the horizontal pot has been machined on that area, but there vertical hasn't. Heads are coming off for gaskets anyway, so I'm going to see my local man with a skilled grinding fingers to have a look at the rough casting area on the vertical intake.
Variation in port finish might be due to one having a poor finish or some flashing which failed inspection and was dressed back. Remember, never ever polish you inlet port or knife edge the port bridge!
Further poking about has revealed the same casting marks on the horizontal head exhaust ports. Look like cracks but are not. Which is nice.
