ROYSTON
XS650 Enthusiast
'78 XS650, the breather plate has 2 outlets (my diagram shows one) inside the outlets are rubber plugs with small hole through the middle, is this someone's idea of a mod' ?
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C/Head breather
- Thread starter ROYSTON
- Start date
Hi Roy,
late model XS650s switched to a single vent and they were corked too.
Agreed, a mod, but the someone musta worked in the Yamaha design office because the bikes left the factory like that.
Most likely some EPA-inspired quickie fix for too much oil venting.
late model XS650s switched to a single vent and they were corked too.
Agreed, a mod, but the someone musta worked in the Yamaha design office because the bikes left the factory like that.
Most likely some EPA-inspired quickie fix for too much oil venting.
ROYSTON
XS650 Enthusiast
So Fred, keep them or give them the arse ?
Hi Roy,
well, I binned the one in my '84 mebbe 15 years ago and never noticed any difference.
But don't burn your boats yet.
Carefully save your plugs to put back in if the bike starts puking oil fumes without them.
well, I binned the one in my '84 mebbe 15 years ago and never noticed any difference.
But don't burn your boats yet.
Carefully save your plugs to put back in if the bike starts puking oil fumes without them.
ROYSTON
XS650 Enthusiast
OK, will do. Do you know why this head has the 2 outlets ?
Leave the rubber reducer plugs in place or too much oil mist will come out. Yamaha made the outlets too big and this is how they "fixed" it for a time. Eventually, they redesigned the outlet with only one tube with a very small hole in it. On earlier models, before they came up with the reducer plug idea, they actually capped one tube off completely and only used the other one. There were complaints from owners about too much oil coming out the breathers when the bikes first came out. During the production run, these were some of the steps Yamaha took to reduce it. Another was lowering the oil level in the cases by reducing the amount of oil used.
Yamaha changed that breather box near countless times trying to reduce blow by. Not a trivial task with a 360 crank twin. the corks are OEM. In 75 (the year before the EPA started screaming) Yamaha routed the CCV to a hole in the LH cover over the chain, problem solved, LOL.
Hi Roy,
most likely because the mfr was still fitting the wye-shaped breather on your model.
The later one-hole breather will bolt straight onto your bike's head.
