750 engine block breather
- Thread starter ludiluka
- Start date
Tippie
Hero member
- Location
- Dr?bak, Norway
No.
The breather on top of the head is sufficient, however SF2 and SF3 had a larger diameter breather than those before. Pretty certain the SFC had only that too, but the boffins can set you straight there. On some big bore engine racebikes that people have made they have added another breather to the cases, using the dipstick or similar.
The breather on top of the head is sufficient, however SF2 and SF3 had a larger diameter breather than those before. Pretty certain the SFC had only that too, but the boffins can set you straight there. On some big bore engine racebikes that people have made they have added another breather to the cases, using the dipstick or similar.
Additional breathers were certainly experimented with, old photos show a pipe connected to where the dipstick is fitted.
On my long-stoke GTL, I have also fitted an additional breather to the dipstick hole. Comprises of a small chamber containing a RGS-type breather baffle with a hose leading to Nirvana, works a treat. Engine definitely spins a little quicker/more freely, but have not noticed any differences on stock dimension engines.
The flat raised casting at the rear of the cases has the same shape and size as the cover for the neutral switch. Perhaps it is a left-over from the experimental/developement stage, just like the 2 unused bosses at the top of the gearbox casing. Or maybe they were retained for future use, who knows?
piet
On my long-stoke GTL, I have also fitted an additional breather to the dipstick hole. Comprises of a small chamber containing a RGS-type breather baffle with a hose leading to Nirvana, works a treat. Engine definitely spins a little quicker/more freely, but have not noticed any differences on stock dimension engines.
The flat raised casting at the rear of the cases has the same shape and size as the cover for the neutral switch. Perhaps it is a left-over from the experimental/developement stage, just like the 2 unused bosses at the top of the gearbox casing. Or maybe they were retained for future use, who knows?
piet
phil37
Hero member
- Location
- Lincolnshire
G
Grant
Guest
Is that one of them there space frames Phil??????
phil37
Hero member
- Location
- Lincolnshire
Not seen a factory breather where you say - looked at 3 engines and see the crankcases are fairly flat in the area of the two small raised circular protrusions - Regards - Phil
breganzane
Hero member
- Location
- NSW Australia
I always thought it was a boss for a (not implemented) crossover linkage? I never heard it referred to as a possible breather, it seems in a stupid position for one - not easy to get a large diameter tube either into the case or out past the frame.
But it would be interesting to know for sure what the intention was, perhaps a practical joke by the pattern maker after a liquid lunch?
But it would be interesting to know for sure what the intention was, perhaps a practical joke by the pattern maker after a liquid lunch?
MarnixSFC
Hero member
Once Laverda decided to go for the low air pression inside the crankcase by using the rubber ball construction, they needed to have the breather in a vertical position.
Until 1974, virtually all the SFC factory racers had a second breather on the dipstick hole, and they all had the rubber ball inside, so that breather needed to be in vertical position too.
I think this is why they never used the breather at the upper left rear of the crankcase.
Marnix
Until 1974, virtually all the SFC factory racers had a second breather on the dipstick hole, and they all had the rubber ball inside, so that breather needed to be in vertical position too.
I think this is why they never used the breather at the upper left rear of the crankcase.
Marnix
phil37
Hero member
- Location
- Lincolnshire
The ball type breather works well - but the ball can get contaminated and swell up to block the breather with some nasty consequences. For racing I prefer the Morini 3? type that fits in the breather hose - the later RG series used a mini version of this type too. - Regards - Phil
Attachments
GregT
Hero member
- Location
- Christchurch NZ
If you're serious about pumping the cases down to below atmospheric pressure, use a proper reed valve.
I've been putting yamaha DT/RD four petal reed valves on singles and 360deg twins for years. Even solved the Britten's oiling problems with one.It's easy enough to fabricate a box to hold the assembly, short large dia hose to the cases and tuck it away out of sight.
I've been putting yamaha DT/RD four petal reed valves on singles and 360deg twins for years. Even solved the Britten's oiling problems with one.It's easy enough to fabricate a box to hold the assembly, short large dia hose to the cases and tuck it away out of sight.