750 SF2 Stem Seal Advice

Allthingsiti

Allthingsiti

New member
Location
Preston
Hi guys, advise if you can please.
1973 SF2 - Should valve stem seals be fitted or not?
I bought a valve / spring and associated bits from Wolfgang and according to my engineer the seals supplied don't fit the original guides.
According to drawings on the Paradies website, stem seals are shown, but in my original Parts and maintenance booklet doesn't show any seals at all.?
Thanks in advance ☺️
 
I would reach out to Wolfgang, as he supplied the parts, and ask him if the seals are suitable for your guides or not.

Gerald
 
Early twins ran just fine (and for a very long time) without seals, their guides were not machined to accept them.

If the bike is destined to be ridden about 2000km/decade (as most are these days :rolleyes:) , I wouldn't worry too much running it without...

Valve stem seals were introduced around '72(?), as was the trend at the time. But actually, a healthy 750 will not burn oil without seals, making them redundant until mileage creeps to 100000, where guide wear slowly sets in. Oil consumption is far more often down to worn rings and bores, as well as widened top ring grooves, all of which occur far earlier!

piet
 
sfcpiet said:
Early twins ran just fine (and for a very long time) without seals, their guides were not machined to accept them.

If the bike is destined to be ridden about 2000km/decade (as most are these days :rolleyes:) , I wouldn't worry too much running it without...

Valve stem seals were introduced around '72(?), as was the trend at the time. But actually, a healthy 750 will not burn oil without seals, making them redundant until mileage creeps to 100000, where guide wear slowly sets in. Oil consumption is far more often down to worn rings and bores, as well as widened top ring grooves, all of which occur far earlier!

piet
Click to expand...
Hi Piet,

thanks for the prompt reply. My trusted engineer tells me the guides are perfect and I believe the mileage is wayyy under 100k. Bores are clean/honed and new rings to be fitted so hopefully all will be well. I'll go without 😉
 
My 1973 SF1 (13768) came without guide seals and guides were still perfect when I removed them to go to 7mm SFC valves and other goodies after well over 160,000 km. I still have the guides and would happily put them into another head with confidence. The cast iron guides are an excellent material - Dukes would be ripping bronze guides to shreds and my trusty SF just kept on keeping on - ditto with big ends.

When I pulled the top end off my motor at 100,000km (after running without air filters for 2 years over some of the dustiest roads in outback Oz) the top rings were in pieces, there was a deep ridge at the top of the boresand the oil ring gaps were about 3mm. It still ran fine and those guides were still perfect. I had to go straight to 2nd OS bores, but once rebuilt I discovered it had been about 50% down on power. Amaxing what you get used to.

Bloody good motors!
 
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