Rapid (very) plug fouling

[Durks]

Hi. Just an observation from my experience (& apologies if someone has raised it already or its stating the bleedin obvious): a loose valve guide may not be apparent without taking the springs off and applying some leverage to the guide with the valve stem.

Cheers
Ade

[IanHood]

Well, it was certainly the right decision to get the head vapour blasted. Looks to me like it's been buggered about somewhat and that looks to me like a crack in the combustion chamber. Also slightly concerned with the inlet and exhaust ports...

Might be time to seek some expert advice and repair. Nigel, you did the guides on my springer head - what do you think of this mess?

Ian

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[LaceyDucati]

Ian

I think the marks you are seeing in the port look like casting marks. The exhaust seat has been replaced and in the process someone has welded up the seat recess so as to fit a smaller seat. The blending of the seat looks a bit "gung ho" and rather unnecessary! That in it's self is not really of concern, however the inlet seat is original and I would have been concerned about the seat/housing distorting during the welding. That said if it has been running for some time, maybe it's not such an issue. Did you say the guides don't have O rings? If the guide is slack that could be causing oily issues. Another observation is the second plug is in an odd position and angle, does it clear the tunnel/bango okay?

[LaceyDucati]

I would guess that the head face isn't sealing that well either, looks like it needs machining/lapping. desmo's are prone to leaks from the rocker spindles down the head bolt holes....especially after welding, fries the sealing bungs. There is a chance oil from there is finding its way across the head face into the cylinder, are any of the head bolt holes oily? More food for thought.

Nigel

[IanHood]

Nigel,

This is actually an RT head and that 'second plug hole' is where the decompressor went so I'm guessing it's in the standard position.

The guides aren't loose and the valves are a good fit in the guides. I've just put the valves in with a little grease and filled each port and the combustion chamber with petrol and there is no obvious leaks (though I guess that could change with heat).

Thanks for your suggestions on head lapping and fried sealing bungs. I didn't know about the sealing bungs but I can see one on the parts diagram. Are they only on the closing rocker and how do you get them out to check/replace?

Ian

[LaceyDucati]

Hi Ian

That doesn't look like a RT450 decompresser position, they are normally more central between the valves. Maybe it's just the way it looks in the picture. The spindle sealing bungs are only in the closing spindle holes. If you pour solvent in those holes, have a look in the bolt holes to see if it seeps through. I wouldn't disturb them unless they are obviously leaking. The spindle holes would be oily if there was an issue. As someone else said leak testing the ports is the best way to identify port/ guide issues.

Regards Nigel