750SF2 Project Ready for Assembly

5 coils on the springs and I've been told that there's a lack of consistency concerning lift on the cams, be they 5 or 6 C. That would explain varying opinions and experiences.

Paul
 
I'm confused. I've raced and ridden loads of km with 5C cams and std SFC valve springs fitted. Never had a problem. Never suffered from valve bounce. I know for a fact bro Lee has had 6C cams in his race bike and had them in his modded road SF motor for donkeys years without problem - would haver assumed he had SFC springs not SF (Lee, please explain). I'm fitting Todd springs to the SFQ. Surprised with those that the inner springs actually contact the outer springs - inner springs larger OD than SFC springs.
 
piranha-bro2 said:
I'm confused. I've raced and ridden loads of km with 5C cams and std SFC valve springs fitted. Never had a problem. Never suffered from valve bounce. I know for a fact bro Lee has had 6C cams in his race bike and had them in his modded road SF motor for donkeys years without problem - would haver assumed he had SFC springs not SF (Lee, please explain). I'm fitting Todd springs to the SFQ. Surprised with those that the inner springs actually contact the outer springs - inner springs larger OD than SFC springs.
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Specs of springs probably vary, as apparently does lift of cams.
It's not valve bounce the matter, I imagine you'll always get some at some point if you rev the engine far enough, it's valve springs becoming coil bound, at high revs, helped by a bit of bounce, since the springs aren't binding before.

Paul
 
How can they bind at any time if they measure with clearance static? Sure you can have valve bounce but that is the valve left behind and not following the closing ramp on the cam.
 
piranha-bro2 said:
I'm confused. I've raced and ridden loads of km with 5C cams and std SFC valve springs fitted. Never had a problem. Never suffered from valve bounce. I know for a fact bro Lee has had 6C cams in his race bike and had them in his modded road SF motor for donkeys years without problem - would haver assumed he had SFC springs not SF (Lee, please explain). I'm fitting Todd springs to the SFQ. Surprised with those that the inner springs actually contact the outer springs - inner springs larger OD than SFC springs.
Click to expand...
There's no reason to be confused. 5/C cams go well with stock SF valve springs, that's my own experience and from many others, except Paul apparently.
When I bought my first 6/C cam at the factory in 1977, they told me to only mount them with the special springs with a winding less. I always respected that and so I never tried them with standard springs. Recently Augusto Brettoni confirmed same by the way.

All I stated in my last message is that when fitting new valve springs for a 5/C camshaft, those 6/C springs are the better choice for the 5/C too.

Marnix
 
piranha-bro2 said:
I'm confused. I've raced and ridden loads of km with 5C cams and std SFC valve springs fitted. Never had a problem. Never suffered from valve bounce. I know for a fact bro Lee has had 6C cams in his race bike and had them in his modded road SF motor for donkeys years without problem - would haver assumed he had SFC springs not SF (Lee, please explain). I'm fitting Todd springs to the SFQ. Surprised with those that the inner springs actually contact the outer springs - inner springs larger OD than SFC springs.
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You may have larger spring stack height due to valve seats being cut back, giving a safer working clearance.
Inner springs touching outer springs can actually help damp out reasonance, in my Jawa motor they were actually a fairly tight fit inside one another- goes against Logic I know.
 
Tippie said:
How can they bind at any time if they measure with clearance static? Sure you can have valve bounce but that is the valve left behind and not following the closing ramp on the cam.
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It's not following the closing ramp because it's inertia is keeping it going, and binding springs.

Paul
 
piranha-bro2 said:
I'm confused. I've raced and ridden loads of km with 5C cams and std SFC valve springs fitted. Never had a problem. Never suffered from valve bounce. I know for a fact bro Lee has had 6C cams in his race bike and had them in his modded road SF motor for donkeys years without problem - would haver assumed he had SFC springs not SF (Lee, please explain). I'm fitting Todd springs to the SFQ. Surprised with those that the inner springs actually contact the outer springs - inner springs larger OD than SFC springs.
Click to expand...
Q from the above and I know nothing about twins, that implies your running dual valve springs. I read years ago you could get factory dual valve springs and cups from triples but very few actually do. At one point Doug Home was inquiring at Stators to buy that kit for his triple. BTW my Todd spings are single type.
 
Vince said:
Q from the above and I know nothing about twins, that implies your running dual valve springs. I read years ago you could get factory dual valve springs and cups from triples but very few actually do. At one point Doug Home was inquiring at Stators to buy that kit for his triple. BTW my Todd spings are single type.
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If it's a triple, that's normal, if it's a 750, you're in trouble.

Paul
 
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