Breather

[GuzziNZ]

Trying to find a reed or petal type non return to put in line down stream of the breather box on a 850T. Anyone know a valve off some vehicle I could mod ?

[wirespokes]

I think I did a search and found that a Pinto breather worked. I think it was a Pinto PCV valve - and it plumbed right in. Nothing to it. It's been working fine on my LM4.

[LesP]

The unit off Yamaha XS 650's are popular in other circles but not sure of the hose to fit sizes.

[blackcat]

The unit off Yamaha XS 650's are popular in other circles but not sure of the hose to fit sizes.

I have one of these on my Norton but a cheap generic PVC part from AutoZone,etc. did the same thing.  I only replaced the cheap one due to longevity concerns but I went with that one first to make sure the XS part was worth the extra costs.

[berniebee]

Ducati has a crankcase reed valve that might be adapted.

https://amsducati.com/ducabike-ducati-oil-breather-valve


Just curious, why a valve downstream of the breather box?

[Matt Story]

I think Guzziology recommends a ball check valve like this one sold by MGCycles.  Maybe it was standard equipment on later models than the 850T.  It drops into the feed tub to your stock breather and is trapped there.  Stock valve in box is defeated.  http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=1007

It there a different or improved function derived from a traditional PCV valve?

[Old Jock]

https://hmb-guzzi.de/Back-pressure-breather-valve

HMB do a valve but that's upstream and is for the line directly off the crankcase

I don't really know the breather set up but am struggling to understand like berniebee why you need one downstream of the breather box

The other system has is the Bunn, usually used on old Brit iron but it's expensive is an entire system and has its critics as the crankcase becomes an air pump

[GuzziNZ]

Thanks for all the suggestions.
I think I read somewhere that having the non return downstream maybe of some benefit, also I don't think you could fit anything but a ball type valve before the breather box anyway.
I like the idea of a reed type non return as it should be less restrictive passing crankcase pulses and have a better seal between them.
Could be wrong though !

[Dukedesmo]

With regards to the the Ducati breather mentioned above. If you can get hold of an old style (ally/plastic) version then they are easily modified.






I have made both inline and 'Corse' style breathers from them (though you'll need 2 to make an inline version).







I have an inline on my LM2.





The good thing is that they have a large reed valve and are very free flowing.

[GuzziNZ]

That Ducati breather looks the part and the HMB valve sounds good at a price.
Will stop off at the local Duc service shop and see what the have.