Engine balancing?

[Guest IanJ]

So, I'm taking the option offered by MGNA to have my 2002 Le Mans' engine case replaced by replacing all the guts into a new case. It was suggested by a mechanic I talked to that having the engine "balanced" while it was apart would be a good idea. I wanted to ask you guys about the value of this procedure.

 

Has anyone else had this done to an engine? I gather that what they do is balance opposing parts (like piston rods) against each other, and then dynamic pieces like the crankshaft against itself.

 

I'd appreciate any comments on the procedure. It will apparently increase the shop time from about 2 weeks to about 6 weeks, during which time my bike will be subject to parts filching (parts are "borrowed" from the bike and ordered from Italy, which can obviously take a while), potentially lengthening the downtime. I don't mind losing the bike for another four weeks, but I only want to do it if the procedure is really worth it. The reason it sounds good to me is that I find the Le Mans engine to be just a bit too vibration-ful, and would be happier with the bike if the engine was just a little bit smoother.

[Baldini]

My roundhead 950 motor has balanced internals. Runs smoother, worth doing.

[al_roethlisberger]

Yep, my shop said it would be another $150 or so, and no big deal. So I plan to do it at the same time as well.

 

al

[dlaing]

I would go for it!

I would also get lighter rods like the Carrillos and possibly lighter pistons like FBF's.

I would just be concerned about too much compression with the FBF (wiseco) pistons.

[Murray]

Sorry correct me if I am wrong but I understand varrilo rods for Guzzi's are not lighter. They are infact heavier and made from billet steel instead of cast iron or whatever guzzi normally use. Thier advantage is they are significantly stronger and cope with higher compresion ratio's bigger pistions etc better. I am not familar with the Wisco pistions but I don't think thier major pourpose is to reduce rotaing wieght. Someone worked out a while ago the most cost effective way to reduce rotating mass is a carbon fibre clutch kit. As far performance goes you probally would be better off with some mild porting work for the same cost.

[Guest John T]

Been there done that.

 

Carrillo rods are much lighter and stronger than the porky rods Guzzi uses.

Also, FBF pistons are the same weight as stock. They claim straight drop in without balancing needed. (big increase in heat generated)

 

If you do go with the Carrillo rods, you have to have the crank lightened, then balanced. This adds to the cost.

I had the flywheel of my Rosso Mandello lightened and balanced and even went as far as having the alternator rotor balanced.

You want to shoot for a 51-52% balance factor.

 

There are slight tradeoffs to this.

My engine is not noticeably smoother at lower revs, about the same as stock. There is less mass in the crank and flywheel to absorb the power pulses.

 

Where it is super smooth is above 5000 rpm. It is unreal how smooth it is!! Not a vibration to be felt!

 

Also the engine is much faster to rev and feels much more snappy at all revs, banging downshifts is real sweet.

 

Do what you can while the engine is apart, if you have the money, a different cam from Mike Rich might also be nice.

[Guest dkgross]

Ian, is MI doing this for you??

 

I was just gonna take the luggage package, and repaint the engine myself in a few years if it got to ugly...

[callison]

You may want to contact Mike Rich for some candid observations and options on pistons. It gets really interesting...

[dlaing]

If you want lighter pistons from FBF, I'd confirm with them.

There website does NOT suggest that they are lighter, only that they require NO rebalancing.

However, MotoEuro Magazine's article on the FBF V11S says that each piston is 28 grams lighter, and ALSO requires NO rebalancing.

Compression is increased from 9.5 to 11.1.

This may aggravate pinging, especially if you cannot back off the ignition timing.

Probably a major benefit at high altitudes but a potential problem at sea level.

FBF may have made the piston shape better than Guzzi, so it may be no problem.

[gthyni]

If you do go with the Carrillo rods, you have to have the crank lightened, then balanced. This adds to the cost.

[...]

You want to shoot for a 51-52% balance factor.

Stupid Qs:

 

I guess lightening meaning lessen the mass of counterweight of the

crankshaft, right?

But to what do the percentage figure refer too?

[Guest John T]

Engine balancing is an art form and a very technical one at that.

I started asking questions but the guy started talking and it went way over my head.

Ill let someone who is more knowledgable answer this one!

 

Bad spellers of the world untie!!!

[Guest IanJ]

Cool. I'm not looking for any performance enhancement -- I don't care if the bike gets any stronger than it already is, it's great for me. What I really want is smoother and less vibration. It sounds like this would be a worthwhile modification, to that end. Thanks for all your input.

[Guest dkgross]

heck..I've really noticed that after only 3200 miles on my LeMans, and a VERY thorough valve adjust/throttle body sync/PCIII tweaking by Micha at M.I., my bike just runs GREAT and quite smooth, especially above 5000 rpm...

 

I'm takin' the luggage

[Guest IanJ]

Absolutely, above 5000 RPM, this is a shining example of a smooth engine. But

if I ride in that RPM range, the throttle is too sensitive, even to be riding

on country roads like I've been doing lately. Since, in order to be comfortable

with my riding, I'm keeping then engine at more like 3500-5000, smoothing out

that range seems like a reasonable investment.

 

Also, I'm pretty sure my bike (with about 4500 miles on it now) could use a quick

valve adjustment and TB balance. That doesn't alter the fact that 4000 has

never been a smooth RPM, though.

[Janusz]

Stucci X-over and Napoleon barends do miracles for 4,000 RPM vibrations.