Valve springs for 1974 750SF2

Interesting discussion. My SF0 had about 40k km on the clock and wouldn't pull above 60mph when I bought it. Investigating the problem, after going over carbs and ignition following a suggestion from Clem I measured the uncompressed valve spring lengths and some were out of spec. The theory was that over its years of standing the springs were under different degrees of compression for maybe 30 years and became permanently distorted. At that time Phil had run out and his spring man had retired, Keith only had SFC springs but Slaters had them on order. Which were duly purchased and fitted. Didn't notice any difference, but then I wasn't able to do high revs anyway. The problem turned out to be cam timing.
 
Interesting observation Robin, since been I've wondering how these springs could lose tension in only 15K miles. I've contacted my engine builder and asked how he came to his conclusion, since I left my Green Book w him and don't know if he compared them to the listed specs, or just used his best judgement. All he had to say is that the Italian valve springs are not very good, and that this engine would benefit from stiffer springs, but I don't know if he was referring to Ducati springs, since he seems to have more experience working on vintage Ducatis.

While waiting to hear from the engine builder, I've contacted Wolfgang about ordering new OEM springs since they don't appear to be very costly, and alternative springs are probably inviting problems I want to avoid.

Again, thanks to all!
 
TeddyG said:
All he had to say is that the Italian valve springs are not very good.

While waiting to hear from the engine builder, I've contacted Wolfgang about ordering new OEM springs since they don't appear to be very costly, and alternative springs are probably inviting problems I want to avoid.

Again, thanks to all!
Click to expand...
fairly certain Wolfgang buys his valve springs from the original Italian valve spring manufacturer
Sort of defeats the purpose I would have thought
 
FWIW the trick at this end of the world when rebuilding any of the old Ferrari or Maserati GP cars that finished up here was to fit OE Chevy springs.
Not necessarily greater pressures but much superior steel and way better quality control.

If you're using aftermarket springs in anything now it pays to know where they're made. I'll only use German or American origin springs - and
you've got to be sure the US branded ones aren't actually Chinese.
 
When I was investigating why my Laverda 750 valve tops had dimpled I read that on some engines this could be due to the valve springs being too weak, not controlling the the valve properly and the valve tip/ tappet got a bit chaotic a certain revs. So contrary to what you may have thought, stronger not weaker springs could prevent valve train wear. Obviously this is not the whole story and there could be material, hardness, tolerances, lash or oiling problems as well to consider. In my experience, deviating from standard fitment on anything to with valves can lead to problems, I’ve seen valve heads come off ,“special” valve cap retainers spit collets out and shims wear out.
I think it was Dave Allen that said “ your looking for a black cat in a dark cellar- difference between you and me is you’ll find it!”
 
Anything new or different can bite, I had new Stainless valves and Phosfer bronze guides fitted in the months after buying my 3c. It blew a lot of smoke before that. It seized and bent a couple of new valves soon after that expensive work from the local distributor, from what I heard they had issues with getting the correct stem clearance with the new valve material. I heard that happened a lot to others later. I also had major issues with false neutrals from the warn-out left to right side gear conversion it had. That got fixed converting the bike to a right-side gear change. Maybe I got some valve float as well with those missed changes. Anyway, I was happy to use Toddys valve springs the first chance I could.
 
I just had a lengthly conversation w Wolfgang who verified that the Laverda 750 valve springs rarely change due to the high quality of the spring. He said that slightly weaker springs would not impact a stock 750 motor that much, and he can't locate new OEM springs. Wolfgang mentioned it's important that the springs all measure the same tension. He also mentioned the Beehive springs, but Summit Racing here does not offer them for Laverda, and I'm reluctant to reinvent the wheel, and I'll just keep the existing springs.

So, I learned a good lesson from this Forum and Wolfgang!
 
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