Balance Factor of Eldo Crank

[stuck amals]

I sent my loop frame Eldo crank to be balanced as I have gone to oversized pistons and jugs. From what I have read online as well as on Greg Bender's sight, The balance factor should be 50 - 52%

The balance shop says the race balance is 52% and the street balance is between 65 and 70%

One person confirmed that 52% is the number to use and suggested I get the crank back and try using lighter wrist pins.

Any suggestions?

[Antietam Classic Cycle]

You might want to tell "the rest of the story": 88 mm big bore kits.

On my customer's Eldo, which I am nearly finished, I used these "big bore" kits:
https://www.mgcycle.com/index.php?main_page=product_info&cPath=68_129&products_id=5307
I bought Wiseco wrist pins that were 2.5" long and had them shortened to 60 mm. The resulting weight loss from the piston assembly was 20 grams. I just got back from a 40 mile break-in ride on the Eldo and it's every bit as smooth as a stock Eldo. 









 

[lucky phil]

I sent my loop frame Eldo crank to be balanced as I have gone to oversized pistons and jugs. From what I have read online as well as on Greg Bender's sight, The balance factor should be 50 - 52%

The balance shop says the race balance is 52% and the street balance is between 65 and 70%

One person confirmed that 52% is the number to use and suggested I get the crank back and try using lighter wrist pins.

Any suggestions?

Sorry but I can't believe this figure. A 90 deg V twin is either 50% or very close to it no matter whether it's a race or road engine. Guzzi went to 52% I'm told on later engines which is within reason and there will be slight variation to a Ducati due to the installation orientation. Every road and race Ducati 90 deg V twin I've ever done or seen was balance to 50%. Interestingly I don't know how many balancers calculate the weight of the oil carried in the crank pin when they do their calculations, some dont and that makes a difference.
I've also had friends install big bore kits in Ducati's without balancing and they've had not issues.

Ciao

[LesP]

Gilardoni 88's with 1993 GT rods and Eldorado 850 crankshaft = 177 grams of Mallory metal (1/2" and 5/8" for dynamic) to get the correct balance factor without trying to remove weight.

[stuck amals]

You might want to tell "the rest of the story": 88 mm big bore kits."

I thought "oversized pistons" was enough

[LesP]

I have a 50% BF @ 948 cc, it runs so smooth it is almost disappointing.

Weigh an old piston (83 mm ? ), pin, rings, circlips.
Do the same with the replacement parts to get the weight difference.
Report back at your leisure.

[Antietam Classic Cycle]

I have a 50% BF @ 948 cc, it runs so smooth it is almost disappointing.

Weigh an old piston (83 mm ? ), pin, rings, circlips.
Do the same with the replacement parts to get the weight difference.
Report back at your leisure.

On my customer's bike the difference was 50 grams - 490 for the 83s and 540 for the 88s.

[LesP]

On my customer's bike the difference was 50 grams - 490 for the 83s and 540 for the 88s.

I had around 60 grams (30 grams heavy for each piston assembly iirc) and as above nearly three times that weight in added Mallory metal to get back to 50 % BF. (Not that I know what it actually was previously with stock components)

The lighter wrist pins are probably a much easier route and should have done more homework at the time. (Done now as long as the pad welds on the counterweights stay put)

 

[jacksonracingcomau]

I never had original 80mm pistons for my V700, fitted used 83mm from Ambo, only thing I balanced was (lightened) flywheel. Thing is smooth as silk, idles at 700rpm almost silently (tiny hole Ambo mufflers)
0f course it doesn’t rev high, rarely touch 6k, cruise at 3– 3500 again nearly silent, proper stealth bike.
You have to try hard to build a shaker from a Guzzi twin in my experience, 90 deg V forgives a lot

[moto-uno]

  ^ +1 , Peter