The cylinder head
When removing the cylinder head one must first remove the camshafts. When I removed the camshafts I descovered this.
A damaged bearing for the intake camshaft. Notice that the valves are already removed. The picture was taken later.
The camshaft had survived better.
Ceeping parts organized.
Despite this i lost one of the valve collets.
The tool
The cylinder head without valves
With the valves removed i could see two things. The valve stem seals were in good shape. And the exhaust valve stem guides were in a terrible shape.
Now it was a searious top end job, not just replacing a faultly intaled stem seals.
The easiest way out of this is a now cylinder head or engine. I have done a cylinder hed renovation once, and it's not that much fun.
A search on internet resulted in a TDM 900 -03 that had been crashed and should be sold in parts. It had done 21000 km. And this was prety much the only option. The other was an option of buying a used cylinder with damaged camshaft bearing. :/
The 900 bike was crashed and the crankcase was damaged. Se buying the whole engine was only slightly more expensive than buying only cylinder head and cylinders.
The obvios question was, will the 900 engin parts fit on the 850 engine?
I searched for anyone whos made a 900 conversion, but it was hard to find anything. I missed the thread that was presented here earlier.
I found this:
https://picasaweb.go...ProjektinKuvat#Puting a 900 motor in a XTZ supertenere. There is a forum thread somwhere about the build.
I also read quite much about the history of the engine. It seems that the early XTZ engine is the beginning to the 850 and 900 engines.
I only needed the cylinder head, but I didn't know if the 900 head fits on the 850 cylinders. I didn't know if the 900 cylinders could be used on the 850 crankcase.
In the end I ended up comparing the spareparts catalogs for both engines.
I found that bottom end conrod bearings were the same for both engines, knowing that the stroke is the same for both ebgines one could asume that the cylinder would fit. I also found that camchain and one of the tensioners are the same. Camshaft sprockets are the same. Oil pump is the same. Starter motor is the same. And some other parts. I could also see that many parts were the same as the XTZ engines.
I had also learned thet the 900 model had fuel injection instead of carbs, an aluminium frame and some other goods. The 900 engine had 6 gears, some more power, and that the oil consumpsion was reduced. One should use the 900 cylinder barrels with the cylinder head to reduce the oil consuption.
Knowing this I was confident enough to buy the used 900 engine. I also bought turn indicators, but they turned out not to fit.
The primary plan is to instal the whole engine. Use the carbs and som much parts as possible from the 850. But I didn't know how damaged the crankcase would be, and if any mounting points be the same. The 900 model had a new frame, and I knew from looking at pictures that the front brackets were different.
The secundary plan is to use the cylinder head and cylinders only.
One thing that is bothering me now is the ignition system. How different are they. The 900 model has fuel injection, but does ut affect the ignition?
He sad that the bike was smoking quite bad, and thats why he did't use it. Whe were'nt able to start the bike when I bougt it because the battery was flat and it had been standing for a year and a half. 
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