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Author Topic: i dropped a valve seat  (Read 242 times)

marcbeez

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i dropped a valve seat
« on: September 17, 2017, 08:52:45 pm »
after nearly 4000km my favorite bike died on me, severe loss of compression.
 back home i took the engine apart, the inletvalve wouldn't close and there was lots of play,2mm, between rocker and valve.
removed the valves (are those valvesprings strong!) and saw that the valveseat had lifted and it was sitting at an angle;
the valveguide on the exhaust was loose, one tap with my hammer and the guide was out.I measured the bore and piston, as good as new.
I would like to doubleplug the head and put 8mm valves and guides in;
What is the best adress to repair the head or find the right parts ( oversize 8mm valveguides)
I removed the right side cover and noticed that the end of the crankshaft was badly grooved, the plan was to use oilseals instead of the alu bush in the oilfeed to the crankshaft.
The bike has only done 23000km?
please HELP
marc

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huub

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Re: i dropped a valve seat
« Reply #1 on: September 19, 2017, 04:59:39 pm »
i cant help you with a good adress for the 8 mm valve conversion , i tend to do the machining myself.
you are quite lucky the valve didnt snap
you found out about the valve springs  :-) those should be changed too...
having this happen after 23.000 km sucks.

banquo

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Re: i dropped a valve seat
« Reply #2 on: September 20, 2017, 12:18:42 am »
My valve seats didn't drop out, but my head's gone off to Germany to have new guides and smaller stem valves (one 8mm and one 9mm).
The engineering shop is here:
http://www.mon.de/ufr/Fischer.356688
Language and payment may be an issue; I have a friend who's kindly arranging it for me locally.
I'm told there's no advantage in twin-plugging unless the bore is taken out to maximum, so I'm not having that done.
Mine needs a rebore (rust) a new oil feed for the inlet rocker, cam followers (badly pitted) and had badly worn valve guides.
21,000 km....

marcbeez

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Re: i dropped a valve seat
« Reply #3 on: September 20, 2017, 10:48:49 am »
Huub, hoe kan met jou in contact komen , ik woon in  antwerpen , tel. 0474/566037
bedank in ieder geval voor de snelle reactie;
groetjes
marc

huub

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Re: i dropped a valve seat
« Reply #4 on: September 20, 2017, 11:12:57 am »
Huub, hoe kan met jou in contact komen , ik woon in  antwerpen , tel. 0474/566037
bedank in ieder geval voor de snelle reactie;
groetjes
marc

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Nitram

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Re: i dropped a valve seat
« Reply #5 on: September 21, 2017, 09:04:40 pm »
Bad luck about your head Marc, but I'm with Huub, you're lucky the valve didn't break. :-\
But in re the right hand end of the crank, I replaced the aluminium bush with a rubber lipped seal about 10,000km ago and it's been fine. I don't remember the size seal, but it was a very straightforward swap with no machining required other than to tidy up the grooves in the end of the crank.
Good luck with the rebuild.   
Cheers,
Nitram

banquo

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Re: i dropped a valve seat
« Reply #6 on: September 22, 2017, 10:24:46 pm »

But in re the right hand end of the crank, I replaced the aluminium bush with a rubber lipped seal about 10,000km ago and it's been fine. I don't remember the size seal, but it was a very straightforward swap with no machining required other than to tidy up the grooves in the end of the crank.

Interesting Nitram; just to be clear, there's no bush in there now, and you just have an oil seal?