Ducati TT1, Ducati TT2 and Ducati 750 F1 Forum :: View topic

Ducati TT1, Ducati TT2 and Ducati 750 F1 Forum http://www.ducatittandf1.com/

Valve return helper springs. http://www.ducatittandf1.com/viewtopic.php?f=10&t=11493	Page 1 of 1

Author:	618F1 [ Tue Jan 17, 2017 2:10 pm ]
Post subject:	Valve return helper springs.
Now my turn for some guidance: a while back i got some Pantah heads that had been nicely ported and, otherwise, were unmolested. (The valves are also 6mm apart, so they might have had race cams installed once) They did not have the return springs installed, and i was amazed at how little effort it took to cycle the cams! I'm thinking there might be 5 or 10 HP hidden there; yes, that could be exaggeration. I have read old articles (when i was younger) about them not being installed in bevel racers, and that compression will close things just fine with good valve adjustments. And somewhere, I think, Ed Milch wrote about removing them. So, does anyone here run a Pantah engine without them installed? Has anyone looked inside an engine and found them "missing"? It sure would be nice to not install those finger-snappers. Thanks, MikeV

Author:

Carlo [ Tue Jan 17, 2017 3:40 pm ]

Post subject:

Re: Valve return helper springs.

Ciao, the heads of my Moretti 750, I have not taken lightly, because I think I eliminate flicker that is established at the point of valve clearance, by bouncing the valve up or down. However, the original spring is too compressed, then just make a tool that serves to strain the spring up to a certain point of degrees of thrust, theoretically and practically, the closing rocker valves of my Moretti, I slip it with bare hands, without the need of strange gear.

Attachments:

immagine 017.jpg [ 62.13 KiB | Viewed 1591 times ]

Author:	flattop900 [ Tue Jan 17, 2017 4:22 pm ]
Post subject:	Re: Valve return helper springs.
Hi Mike... Funny you should mention this. Just this morning I was reading about the Sigma Performance "full monty service" and they say the valves are closed - seated by the rising pressure in the cylinder. Flattop

Author:	618F1 [ Tue Jan 17, 2017 5:40 pm ]
Post subject:	Re: Valve return helper springs.
Thanks flattop. Another confirmed. Thanks Carlo. I think you said to get Lou to bend them till they scream, and then install them in that weakened condition. I'm looking for more in this survey. MikeV

Author:	ducadini [ Tue Jan 17, 2017 6:13 pm ]
Post subject:	Re: Valve return helper springs.
Somewhere on the vvv is a discussion about the cancelling effect of valvesprings : do they actually HELP turning the camshaft (when the valve is closing) with the force of the spring (meanwhile "helping" to turn the engine) or is it all waisted effort ? How does the complete drivetrain of the camshafts act in this "help", having some backlash on some parts doesn't help much. The singles Desmo had weaker springs than the spring-valves but still needed much effort to turn them manually. I've seen heads where they were dropped and a Vtwin Imola cam was fitted (the "easy" way) without the smaller desmosprings. Now they weld the head, reshape everything from chamber, ports to valve-angle and fit springs with a specially designed cam of course. So : someone better grinds a BevelDesmocamshaft with the same timing/lift as the 860 Bevelspringvalvecam, and (everything else being equal) puts it on a dyno to get a reading . I've let the springs out of my Imolacam Bevel racer, because it was difficult to fit them (didn't have that strange tool yet) without messing around with the shims. But setting the closer rocker at 0.00 mm is difficult and shimconsuming work. On my streetbikes (where valves didn't need to be checked so often) they are in and working, eliminating the need to shim to the last few 0.0X's of a mm. Some of the rockers had a fault in the curve, and binded just a bit when opening the valve. Run them that way and rockers AND cam are trashed beyond repair. So I ALWAYS turned them by hand during and after shimming to be sure they turned freely and if needed gave the valves a bit more play. Carlo is right about springs helping eliminate the (very light) bouncing of the valve due to the clearance of the closing rocker, not so sure about they really getting rid of it. When they ask me why I wrote this : It were the little springs inside my head that made me do it ciao ducadini

Author:	flattop900 [ Tue Jan 17, 2017 6:21 pm ]
Post subject:	Re: Valve return helper springs.
Hi Mike... Just read an article on Ducatitech that says the springs help with starting, idling and eliminates a little valve chatter. Regards... Flattop

Author:	Palmer [ Wed Jan 18, 2017 6:40 pm ]
Post subject:	Re: Valve return helper springs.
Mike, I have tried with and without valve springs on the dyno and saw no difference in performance. The springs do help with the harmonics and allow for variance in the valve shimming. I agree with Carlo that softer springs are better. When building a motor I leave the springs off while setting up the heads and make sure the cams rotate freely when shimmed. With the old Vee Two cams we use to have to polish the tight spots on the cams to get them to rotate freely. Palmer

Author:	Carlo [ Wed Jan 18, 2017 6:53 pm ]
Post subject:	Re: Valve return helper springs.
The springs that are screaming !!! HAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Author:	brad black [ Mon Jan 23, 2017 5:59 am ]
Post subject:	Re: Valve return helper springs.
if it's a race bike run without them if you think it's going to help. if you want it to idle, fit them. tight closing clearances always help too. even the soft closing springs in the early 851 make them idle badly if the closing clearances open up. cylinder pressure doesn't do much at all.

Page 1 of 1	All times are UTC - 5 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/