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royaloilfield
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Intake Valve Seals? What are these things?!?
#767504 03/08/19 2:39 am
Joined: Jan 2019
Posts: 1
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Hello everyone,

I found these rubber "boots" on the intake valve seats when I took the head apart. I am working on a 1976 Bonneville 750. Does anybody know what these things are? Why are they only on the intake?

A couple quick searches I did mentioned that they are valve seals. Are they harmless to leave inside? I'm not sure if those are from the factory or from some dude wrenching on it in the past.

Thanks for your help. Appreciate it smile

[img]https://lh3.googleusercontent.com/b...Xgm4YYgz12LOJDmhXe5ebn5oA=w1198-h1596-no[/img]

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Re: Intake Valve Seals? What are these things?!?
prmatzinger #767517 03/08/19 8:06 am
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Can’t see the picture, but valve stem seals go on the top of the valve guide.

People say they don’t do any harm.


Amateur Loctite enthusiast.
Re: Intake Valve Seals? What are these things?!?
prmatzinger #767521 03/08/19 9:47 am
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Fitted as std to Commando's to reduce oil consumption, only need to be fitted on inlets as the inlet sucks, not needed for exhaust as it blows.

Picture url is not right hence its a no show.

Re: Intake Valve Seals? What are these things?!?
prmatzinger #767524 03/08/19 11:45 am
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They’ve been known to crumble from heat, on the exhaust side of old bikes.


Amateur Loctite enthusiast.
Re: Intake Valve Seals? What are these things?!?
prmatzinger #767539 03/08/19 2:41 pm
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Certainly not a factory fitment.
Fitted on inlets only for reasons as per Kommando.
Some people swear by them--others swear at them.
Sometimes fitted in an attempt to "cure" oil leakage down the valve guide giving rise to exhaust smoking.
HTH

Re: Intake Valve Seals? What are these things?!?
prmatzinger #767551 03/08/19 4:43 pm
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It's a pretty popular mod for the triples, never heard doing to a twin though.


When given the choice between two evils I picked the one I haven't tried before
Re: Intake Valve Seals? What are these things?!?
prmatzinger #767554 03/08/19 5:05 pm
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Amazed me when I tore apart a Triumph for the first time-no seals! Modern 4 strokes have them on intake and exhaust valves


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