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valve replacment

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zman
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valve replacment

#1 PostAuthor: zman » Sun Mar 04, 2012 10:11 am

If you,ve seen my other bike help posts im sure i need 3 new valves :(
Can i put in a used one and just seat it with past?how would i go about this?
when i replaced the head gaskett i did not remove the valves so am suprised that all shims are wrong.Is this to br exsected?
keep thoses wheels turning

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ade woollams
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#2 PostAuthor: ade woollams » Sun Mar 04, 2012 10:51 am

if they where ok before you stripped it ,it should be ok now .the shims may have lifted alittle so it may just need running a touch to re seat the shims down .or just turn the motor a few times.
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CAT3
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#3 PostAuthor: CAT3 » Sun Mar 04, 2012 11:11 am

If you're going to use old valves you'd at least want to measure the valve stems to make sure they are still within the manufacturer's limits & the valve guide bore sizes, again to ensure they are still within limits.
Depending upon the condition of the valve seats they may need re-cutting prior to lapping with paste. Someone like SEP at Kegworth could advise if they are close to you, or a similar company nearer to you.
Only the valves that you replace/change should require the shims adjusting.
To lap the valves you need to remove the valve from the head & spead a little lapping paste on the sealing face of the valve. Three little spots spead around the valve should suffice. Then with a lapping tool, a short wooden stick with a sucker on the end, spin it between your hands clockwise & anti-clockwise until you get an even ring around the valve & valve seat. The paste is normally supplied in a double ended tin with corse paste at one end & fine paste at the other end. Depending upon how marked the faces are depends upon whether you'd need to start with the course paste or go straight to the fine paste.
Personally, depending upon your budget, with the head removed it would be advisiable to check the other valves/seats/guides & replace the valve stem oil seals while the head is off, unless this has been done recently.
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zman
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Posts: 340
Joined: 11th Jun 2011
Location: northampton[upper heyford]

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#4 PostAuthor: zman » Sun Mar 04, 2012 12:14 pm

The head had been recently done.thats why im a bit suprised.But im not over confident about the workmanship.

have spun engine by hand a few times.but still to tight.May be not done correct in the first place.
keep thoses wheels turning

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chrisu
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#5 PostAuthor: chrisu » Sun Mar 04, 2012 1:26 pm

i might have some spare valves.

inlet or exhaust - how many of each.

what collet type ? - round or square ?


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