S1 Publishing(Oxford)© 2009

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S1 Publishing(Oxford)© 2009
Dogdragons Yamaha XS 650 Engine photo's - Page 2
 If you are about to do your own maintenance, using these pages, I take no responsibility if you get things wrong!
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Then the cap-
and the two springs
Then the valve it's self, as I pulled the valve I put a finger over the rubber boot from the other side, I got a bit of vacuum as I pulled. this showd me the rubber boots weren't split as well as checking the valve sems for streightness.
I then checked the stem, although carbonized, no sign of burning. I noticed some pitting on the valve seat, a good clean up and a re-grind is in order. 
Before re grinding the valves, I decided to clean the head. Polished it too (when all valves were removed, noting which valves came from each port
I found some pitting on the head seat too.
 I used fine gringing paste and valve grinding tool, I re-seated the valves. Then I removed all used paste before replacing  the valve. I repeated this for all four valves. (I don't like using reills for this)
by using the valve spring compresser as above but in reverse order

Barrels and pistons


The barrels seemed to be near perfect, I could hardly feel any ridge. No scores to worry about either.
 When checked with an internal guage it showed that hardly wear had occored to the bore. No need for re-bore
 Piston, one had 2mm of carbonizing on the head, same as the 2mm found in the head. The other was nearly clean. This I deduced is due to fuel getting into the combustion chamber, but not exploding. Thereby sleaning the piston. This could be due to an electrical or carb problem, we'll have to suss that when the engines back in the frame and running.
 There is the possability that the fault has already corrected, but either way, that machine has been running on one or one and a half for a while, even if it was running just before we stripped it.
 I removed the piston rings and using normal feeler guages, I checked the gap. As there was plenty of room between the ends of the rings I knew that the rings were worn.
 Worn rings let oil into the combustion chamber, which burns, smokes causing the carbonizing found the both piston and both hemi-sphere. 
 Confident I had found diagnosed the engine problem, I gave the part list to the owner.
With new rings underneath the old, the width of metal worn os obvious
The gap should look like........
Checking with the book (Haybes in this case) I selected the correct feeler guage and checked the gap in the rings. It they had been too wide, then the barrel would have been worn too much to really use these rings (might have gone for the oversive, +.5 ones, but not in this case)
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If you are about to do your own maintenance, using these pages, I take no responsibility if you get things wrong!
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