Damn, now I have TOO MUCH power!

[GuzzTim]

but it's not delivering Tuono or RSVR front lifting power

 

ah, so that's what my Tuono's for !!! I haven't got it up on the rear wheel yet... I'm feeling like Bob Dole..

 

 

Cheers!

Tim

[pete roper]

You can't just toss lighter pistons into a bike and expect vibrations to decrease.  They have to be balanced against the crankshaft counterweights. 

 

So, has anyone weighed the fbf slugs?

 

J

40701[/snapback]

 

Jason, just some archive experience here . When i built the first itteration of my hot-rod I spent a LOT of time and money lightening and ballancing things. OK, so it was an old roundfin donk and I'd short stroked it which intrinsically made it less vibratory and the rod/stroke ratio was better too BUT.... After I'd torched the big ends for the third time and been given a 'Walking Licence' for three months by the local wallopers I decided that it was time to stick all the go-gear into a race bike and de-tune the hot rod. I didn't want to sacrifice too much though as the hot-rod is fun and I wanted to keep the short stroke format simply because I love the way they perform. SO! I ended up building a squarefin motor to hog it out a bit, 90mm is about as big as you can go, safely, with a roundfin with the squarefin I was able to get a suitable 92mm kit from RAM designed for a 78mm crank throw SPIII with mid-valve heads. With a bit of farting about I found that this gave me very nice compression with smallvalve heads and a 70mm crank plus a couple of other unexpected benefits. Thing is that as well as weighing considerably more than the super-marvey Wiseco slugs I was using before I changed flywheels and never bothered ballancing anything, just ensured that the reciprocating components weighed the same as each other.

 

Result? Barely any detectable difference in vibration Yes, I'm sure if I'd gone to the trouble and expense of doing the 'Full Monty' to it all over again I might of got it a smidge smoother and probably would of gained a poofteenth more power but really the difference between the motor that had all the careful ballancing and the one that hasn't is negligible.

 

I'm aware that this goes against all engineering convention and good sense, yes, we do get the race bike engine components ballanced dynamically to 52% but really I'm beginning to doubt whether that is really worth it at this stage of development. I'm not saying that people shouldn't ballance things, simply that a change of piston, and therefore reciprocating weight, of 25-30 grams seems to make very, very little difference to the way the motor feels or performs so I simply wouldn't die in a ditch about it, I'd consider it to be way down the list of 'Important Things To Worry About', that's all.

 

Pete

[jrt]

Interesting Pete. I had 1L pistons in my Eldo for a year (stock "1L") and it vibrated like a sonofagun. I replaced them with an 850 kit and the whole thing is now much more smooth. Unfortunately, I didn't weigh the stock 850 pistons/pins, so I can't compare against the bigger set.

I'll weigh the 1000 pistons and see if perhaps they don't match up well.

On the other side, a couple years ago I rode a V7 sport that had been gone through by Manfred Hecht- all or most of the plain bearings replaced with rollers, balanced, ported, yadda yadda. Verrrry smooth to the point where it didn't 'feel' like a Guzzi.

But now I'm confused- I thought the SPIII had the big-valve heads...