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Valve seal

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Al
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Re: Valve seal

#16 PostAuthor: Al » Thu Sep 27, 2018 5:51 pm

If the pistons and bore are 300 miles old then you could expect those figures to rise significantly as the rings bite in a bit more. If its the same comp ratio / pressure on all cylinders then you may well have a valve stem seal adrift assuming everything else is well.

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Re: Valve seal

#17 PostAuthor: Wrigers » Thu Sep 27, 2018 6:30 pm

Thanks AL. Its always better to get a second opinion. .

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Re: Valve seal

#18 PostAuthor: 8 Valve Mark » Thu Sep 27, 2018 7:46 pm

did you have the carbs open when doing the compression test? they should be.. it seems like a dodgy valve seal to me. i believe i have an unused viton set if you need them, but I'd advise changing all 8 if unsure of the originals' provenance (i can speak french? viola! :rock ) of the ones fitted in the rebuild. maybe fit two to the offending cylinder to eliminate the smoke problem, then fit the rest.. mark

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Re: Valve seal

#19 PostAuthor: Wrigers » Sat Sep 29, 2018 5:09 pm

Just a quicky chaps, taken the cams out this afternoon and observed this amount of oil on buckets n01, whilst buckets n04 are nearly dry. Being as though n01 pot was the problematic one, is this a clue as to what's been going on, or is just because it had been on the sidestand.
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zed1015
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Re: Valve seal

#20 PostAuthor: zed1015 » Sat Sep 29, 2018 5:16 pm

The oil is there just because it's been on the side stand.
HOWEVER! If you keep the bike on the mainstand it will allow the oil held around the cam buckets to drain away and limit the amount of oil that can seep down the guides which will then reduce the amount of smoke you get on start up...

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Re: Valve seal

#21 PostAuthor: PAULJAC47 » Sat Sep 29, 2018 5:34 pm

A lot depends on how a rebuilt engine is run in,always used cheapo oil and used the bike on the road varying load and revs within limits,seen more than one bike with glazed bores due to being run in incorrectly.
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Re: Valve seal

#22 PostAuthor: Mr Bump » Sat Sep 29, 2018 7:34 pm

Just recently I’ve had a freshly rebuilt head do something similar. It came back to me with guide seals , valves and springs fitted. Put it on the bike, did about 8 miles. Stopped to adjust the tickover and it was pluming out smoke. On strip down I could see that oil was dripping off of three inlet guides, at least one exhaust guide was wet too, lots of oil in the bores.

Valves and seals out - oil was sitting on the tops of the guides under the guide seals in all eight positions.

Compared the seals with a set of vesrah ones I had sitting about. The seals fitted are viton, slightly grey and quite soft. The inner round ridge that engages with the groove in the guide is smaller, the outside diameter is bigger and I think the diameter of the seal lip(contacts the valve stem) is bigger too.

My diagnosis is that the valve stem seals used don’t fit properly, I’m just finishing putting it all back together using the cheapo vesrah seals as I’ve never had any problems with them before.

Should hopefully get her fired up tomorrow and find out if I’ve fixed it. If I have then there are viton seals about that don’t actually fit properly. Z1000a head.

I’ll let you know. Hopefully I’m right....

Olly
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Re: Valve seal

#23 PostAuthor: Wrigers » Sat Sep 29, 2018 7:35 pm

Thanks for that.

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Re: Valve seal

#24 PostAuthor: Mr Bump » Sun Sep 30, 2018 11:58 am

Yep, fixed. Just done about 30 miles without a puff of smoke. Let’s hope it lasts.

Looks like there are viton seals in circulation that are too big. Good luck with your bike.

Olly
'In your twenties you think you are immortal, in your thirties you hope you are immortal, in your forties you just hope it doesn't hurt too much'



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Re: Valve seal

#25 PostAuthor: Wrigers » Sun Sep 30, 2018 2:40 pm

Cheers for that Olly, glad it turned out ok. Ill keep you posted on the re build,,,


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