Tighter valve springs for SFC 1000 and F1 cams

[MotoJouni]

I once tried to rev it to 9000 some years ago but get frightened when the valves started to bounce at 8800 rpm for a couple of seconds and never tried it again. I think those original springs feel very loose when assembling even they are measured to be ok, still quite small safety factor. The compressed lenght is also correct for the springs.

I was told a hint that the F1/F1A (A is for mechanical tacho) cams can breath if tighter valve springs are fitted. Which springs do you prefer and who sells them? Maybe it's still safe not to rev the engine so much, at the moment I have Ignitech rev limiter at 8000.

 

[redax5]

few years ago I bought valve springs from a number of dealers and then measured them all at installed height and open height with my Rimac Valve spring tester
was an interesting result, even though most were at recommended length or a little longer the spring rates varied quite a lot between dealers

There was one set I got out of the UK that looked like they had been made from fork springs and cut to length in a drop saw so I did not even bother testing them
threw them in the bin and never bought another single item from him again, was probably his last set anyway

in our hot rod engines we try and set the valve springs at 55-60 lbs closed and that should give you 155-165 lbs open @ 9.8mm valve lift
coil bind with the springs I use is a further 1.75mm on
we have the Ignitech on Paul's track bike set at 8,900 rpm and the engine revs clean to that point with no drop off in the power

 

[Vince]

Red have you tried the double valve spring kit made by the factory.

 

[GregT]

in our hot rod engines we try and set the valve springs at 55-60 lbs closed and that should give you 155-165 lbs open @ 9.8mm valve lift
coil bind with the springs I use is a further 1.75mm on
we have the Ignitech on Paul's track bike set at 8,900 rpm and the engine revs clean to that point with no drop off in the power

that's actually quite a low seat pressure Red. My big 2V per cylinder Suzuki's I run at 72 - 75 lb seat pressure - but I'm using cams around .460in lift...
from memory, Pete's motor for which you have the crank at present runs about .420 in lift - and about 70lb seat pressure.

aftermarket competition springs in all cases and close to 2.0mm before coil bind.

 

[redax5]

that's actually quite a low seat pressure Red.

you would be totally amazed at what a 1980 triple engine valve set measures, being the year the factory changed to shorter springs and different retainers
have seen them at less then 10 lbs closed

 

[GregT]

Ha, not that surprised - i've seen a lot of Italian motors.....

One of the guys I've done work for locally has a Bimota Vdue....original and unmodified. IE bloody useless...
he's leaving it that way as he reckons it'll soon be unique - and valuable.

 

[tom3c75]

you would be totally amazed at what a 1980 triple engine valve set measures, being the year the factory changed to shorter springs and different retainers have seen them at less then 10 lbs closed

I've often wondered what Laverda's rationale was for fitting those shorter springs to the 1980 Jotas, and whether the bigger valves on that year model in any way influenced the decision.
Any ideas?

Tom

 

[phil37]

The valve springs that I use are made with a ? turn less than standard - gives a bit more leeway before coil binding and makes the spring a tad stronger. - Regards - Phil