XS650 Breather Exposed!

What does this mean? If the valve is working the piston pushes out the pressure for a couple strokes and then it's done (more or less). With the regular breather it's constantly pushing against the pressure. This is most likely negligible pressure on the rotating masses as they are more interested in the combustion pressure on the other side of the piston.

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That's exactly what I meant. I was referring to an engine with no breather valve as opposed to one with a valve.

I installed one of these today just behind the oil tank in the battery area. Don't expect to visually see results, but it was cheap and if it remotely helps it is a positive.

JimC said:

What does this mean? If the valve is working the piston pushes out the pressure for a couple strokes and then it's done (more or less). With the regular breather it's constantly pushing against the pressure. This is most likely negligible pressure on the rotating masses as they are more interested in the combustion pressure on the other side of the piston.

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That's exactly what I meant. I was referring to an engine with no breather valve as opposed to one with a valve.

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Exactly, there have been loads of posts on this site re this breather mod, I have had one fitted for a few years ago on my Commando which previously leaked a little oil when hot, fitting the breather cured the leaks completely. I have had two more Commando's since then and have fitted the same breather to them, I don't use the breather used in SD's pics there are lots of inline options available in the UK for much less. It is much easier to realise the benifits if you fit the breather to an engine which has slight oil leaks, which is what I did when I had this problem and as the engine ran well apart from the leaks I did not want to strip it . If you read Peter Williams input on this he describes the other advantages from fitting the breather to the race engines.

britbike220 said:

Ya, I thought they looked similar, but the triumph ones do not have the backing plate with intake opening. I have three of them wasting away on the shelf in the garage from my daytona, but unless there is a backing plate they can't be used. I don't have a machine shop so out of luck.

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post56078.html?hilit=sai#p55897

I have been on the Mike XS website and the PCV he is offering is not the one illustrated above. His has the inlet & outlet on the same end. So, a couple of questions.
1. What is the Yamaha part number for the PCV, shown with the inlet & outlet at right angles ?

2. For what year/s was this PCV used?
3. Where can I get one?

There are numerous similar reed valves with different pipe connections. I think Mike uses whatever he can find from his various sources.

They are NOT Yamaha XS650 parts, but an innovation that Mike introduced to the XS650 crowd,

Mine are the same body and reed, but very consistent as to the configutation: inlet is through an opening in the base, outlet pipe is angled at 45 degrees vertical off one corner of the top.

Possum said:

I have been on the Mike XS website and the PCV he is offering is not the one illustrated above. His has the inlet & outlet on the same end. So, a couple of questions.
1. What is the Yamaha part number for the PCV, shown with the inlet & outlet at right angles ?

2. For what year/s was this PCV used?
3. Where can I get one?

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I got the one with in/out on same end from MikeXS and installed it a month or so ago. Now the only small leaks are out the primary and transmission! LOL

Possum said:

I have been on the Mike XS website and the PCV he is offering is not the one illustrated above. His has the inlet & outlet on the same end. So, a couple of questions.
1. What is the Yamaha part number for the PCV, shown with the inlet & outlet at right angles ?

2. For what year/s was this PCV used?
3. Where can I get one?

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You were on the right site when you were on Mike's XS.

Mine are the same body and reed, but very consistent as to the configutation: inlet is through an opening in the base, outlet pipe is angled at 45 degrees vertical off one corner of the top.

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Because you get them off new Triumphs?

swooshdave said:

Because you get them off new Triumphs?

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Yep. Always have 4-6 of them on the shelf.