• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

+28 grams?

Tonerjockey

Tonerjockey

High Miler
GT Contributor
Joined
Oct 28, 2008
Messages
788
Location
San Jose
OK so I am in the throws of balancing the Eldo crank. Too much fun.
I've read to add 28 grams to the rotating weight to compensate for oil in the journal.
I've also heard that one takes 50% of that oil weight into consideration when determining the bob weight.

So... I gotta know:

do I:

Determine the rotating weight (large end of con rods, with bearings) PLUS 28 grams (oil compensation). =Rot
Multiply the rotating weight by 52%
Determine recipricating weight (con rods small end, bushings, pistons, pins, rings, pin clips).
=Rec
add the 52% plus the recipricating weight.

.52(rot+28g)+Rec=Bob Weight

or

Do I divide the oil compensation by 2 (for some reason). I have been told that the oil compensation is divided by 2...

.52(rot+(28g/2))+Rec = BW


Or have I got this all back asswards?

No one said there would be math involved... heh heh

Alex
 
52-55% is the number from memory.
 
After sleeping on this I think my subconcious has gotten a handle on the equation.

.52(Rot+28g)+REC=Bob Weight

I think.

Now I'll make a lead piece the correct weight, that will fit into the journal oil passage...

Alex
 
Egads, after reviewing Guzziology I see that it is 52% of the Recipricating weight.

so..

.52Rec+rot+28g= Bob Weight

Maybe

Alex
 
Ok final final answer (maybe)

52% of recipricating parts (pistons etc) + rotating parts + 28 grams (oil) = bob weight

That's what I am goin with... I hope

Alex
 
I think the 52% is the factory approved number that Guzzi arrived after years of study. It was I think originally 50%.

Personally I leave this sort of thing up to a shop with a dynamic balancer which is more accurate.

In England I used Bassett Down which were reasonably priced, quick and extremely professional.

In retrospect I have found that balancing to the nth degree is really not a good way to spend your money and I would only do it if I changed to different rods/pistons with dramatically different weights

On any spinning crank there is a lot more than 28 grams of oil - and it constantly changes depending on RPM and direction of G's at any given moment. I once did stroboscopic studies on a F1 engine and was amazed even with a modern F! engine how much oil stuck to the crank - basically think dough hook.

You can limit the oil coating the crank by fitting a proper windage tray with scrapers - a dry sump system that is actually able to draw a vacuum helps even more as well as stopping oil foaming,

That being said the balance factor is really about reducing vibration at the RPM where the bike tends to run - which is largely determined by cam, exhaust/intake tuning, gearing, rider preference. With a 90 degree V it is a compromise - done right it can make a bike a lot sweeter to ride long distances but don't expect any real performance gains,
 
You must log in or register to reply here.
Back
Top