Valve Clearance

[Guest scottd132]

I have a 2001 V11 sport CF with the Guzzi Ti exhaust and ECU. After spending a great deal of time at my dealer figuring out why it would not run, we found a minor mistake and the bike has run flawlessly for some time. I just had the bike in for a rear seal replacement and we decided to loosen the valves a bit, .001-.002 looser than stock. KNowing there has been a lot of discussioin that Raceco (European) valve specs will allow for at a minimum better idle. This turned out to be the case, yes I no longer get the stumble, and sometimes shut down at idle. GREAT news.

 

However, when riding home the bike did not rev as quick through the midrange AT ALL! like someone blocked off the air intake.

 

I know that tighter valves are going to open a bit more but your thoguhts on making that much difference.

 

Nothing else was done other than a output shaft seal replacement.

 

If this makes that much diff. I am going to have my heads worked on, and get a cam at a minimum.

 

Thoughts. (yes we have discussed in other links the benefits of valve clearance, but never the downside I describe)

 

Scott in Seattle

[dlaing]

It was touched on a little...

http://www.v11lemans.com/forums/index.php?...ic=96&hl=raceco

but I would like to see dyno tests of different valve settings.

I use .15/.20mm, but I bet I would get more power at .10/.15mm, especially at higher RPMs.

I wonder if John T. gets so much more power than Al's because of valve settings???

I am basing this on John's dyno results before the aftermarket cam.

Of course, once Al hooks up the twin plugs, all bets are off.

Also, I am pretty sure valve settings are important for making power commander maps work between bikes.

[Guest Jeff Kelland]

Loosening the valve clearance not only changes lift, it also changes the cam timing, it retards it. The cam will now rotate a bit further before it begins to lift the valve off it's seat and let it close a bit earlier than before. Retarding cam timing as a general rule will increase midrange power at the expense of top end power. I am currently running at .006 in. intake and .008 in. exhaust. I absolutely agree that this cured the idle stall and poor running at low rpm. I also feel, subjectively, that it made a slight improvement in the midrange power but that it slightly aggravated the torque dip in the 4k to 5k rpm range, which I would guess is an exhaust problem. I don't think it lost anything in the dip, just made it more pronounced because of the improvement in the power around it. The stock valve clearances are probably no mistake, MG was probably trying to reduce the clatter to get through noise tests.