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Convert combustion deposits on intake valves

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bigbikerrick:
Hi Folks, when I removed the intake manifolds on my Convert last night, I noticed quite a bit of black carbon deposits all on the underside of the intake valves. It reminds me of how the bottom of a well used, old cast iron frying pan looks. Poking it with a screwdriver does not remove it. Its pretty hard stuff! The exhaust valves show some light soft carbon coating on the same area, but nothing like the hard burnt on deposits on the intake valves. Is this normal on an engine with 14 K miles ? I dont recall seeing this on the intake valves on other Guzzis I have owned, with more miles.  The bike runs very well, and the plugs look a nice tan color as they should.
Opinions?
Thanks
Rick D.

Shiny Hat:
Blast with walnut shells. Thereís a kit to do this or you can make one.

moto-uno:
  Spend much time with the choke on ?
  Are the actual valve seats (and valve faces) still shiny ? Peter

bigbikerrick:

--- Quote from: moto-uno on November 21, 2023, 07:28:26 PM ---  Spend much time with the choke on ?
  Are the actual valve seats (and valve faces) still shiny ? Peter

--- End quote ---

I dont know about previous owners, but in all the time I have owned the bike, I never have needed the "choke" for cold starts. It fires right up after a couple of twists of the throttle. I cant see the condition of the seats, but compression is good. I had no idea walnut shells can be used to clean this up in situ. but as easy as it is to remove Guzzi heads, it may be better in the long run to take apart and clean up properly as well as lapping the valves. It just surprised me to see so much carbon on an intake valve. Where in the world does it come from?  I would think that fuel air mixture flowing past the valves underside,would keep it clean. Could it be caused by oil from worn valve guides?
Thanks
Rick.

Shiny Hat:
Could be worn seals, guides, does it smoke when starting after sitting then clear?
Hot crankcase vapors come in contact with the valve (which are cooled by the entering fuel) condense and turn to baked on deposits.
You see a lot of posts in threads about cleaning throttle bodies, the cause is oil vapors being vented to the air box. Some remove the hose, add a filter and vent to atmosphere.
Then again I have no idea what a convert is (something was changed from original?) 14k seems low for a lot of buildup but this is a Moto Guzzi and Iím finding they arenít the best designed machines, intriguing none the less.

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