Wildguzzi.com
General Category => General Discussion => Topic started by: amamet on October 29, 2023, 02:58:26 PM
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I have an eldorado engine torn down for rebuild. Bike had been rear ended at some point, frame twisted to the side and output shaft pushed forward. Decided to tear down the whole bike. Discovered iron lined 88 venolia pistons. Head gasket was wrong as push rod holes were incorrect (probably 1000 gaskets used) ordered customs ones from cometic gaskets. Do i “need” to rebalance or should i just rebuild away. Don’t know much about the art of balancing so id have to find someone in the nyc metro area
Thx
Allen
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Weigh the piston assemblies (piston, rings and pin) to see how much more they are than the originals (490-495 grams). I'd want the Venolia piston assemblies to be as close as possible to the originals.
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ill check my old notes, think they weighed @ 515 grams. piston, rings, pins and clips
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When I rebuilt the engine on my 73 eldorado, I used Gillardoni cyl/pistons, and those pistons are forged , where the oem were cast. The forged ones weighed a few more grams. I was able to remove material from the insides of the pistons to make the weight equal. I weighed the pistons,rings,wrist pins and circlips all together. It did smooth out the engine a bit, I think. It has 22K miles under its belt, since rebuild, and running great! :grin:
Rick.
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My 2¢ worth. When I did my engine, I took the pistons into work where we had a very expensive digital scale and as I recall very little material had to be removed. I don't recall if I did the rods too. I'm thinking an automotive machine shop could do the work if you are unable and don't think it would be expensive.
Also, I took the crank to a machine shop to have the oil holes chamferrred and radius the rod journal area...both per Guzziology. Oh, and clean sludge trap and whatever else I could find at Greg Bender's This Old Tractor( https://www.thisoldtractor.com/moto_guzzi.html ) regarding the subject.
Good luck!
Art
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What if I don’t have this original pistons to compare the weight of the venolia ones too? Bike came with the 88mm setup
Thx
Allen
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Necessary? No. People replace cast iron pistons on very old v-twins with modern aluminum pistons and then run them cross country without issue other than vibration. May as well make an effort to balance it while you have the opportunity though.
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What if I don’t have this original pistons to compare the weight of the venolia ones too? Bike came with the 88mm setup
Thx
Allen
As I posted above... Eldo piston assemblies average 490-495 grams.
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Thx Charlie, is there a preferred area to dremel? Or equidistant areas?
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Thx Charlie, is there a preferred area to dremel? Or equidistant areas?
When I installed a Gilardoni 88 mm kit onto a customer's Eldo, I found that the piston assemblies were nearly 50 grams heavier than the original 83 mm piston assemblies. My machine shop was of the opinion that there was not nearly enough piston material that could be safely removed. Instead I chose to have lighter wrist pins made (starting with Wiseco tapered-bore pins, cut to length), which were 30 grams lighter than the originals. I could have had even lighter ones made (of titanium), but the cost would have been nearly $100 each.
While that Eldo wasn't as smooth as a stock 844 cc one, the vibration was really not bad at all - sort of like the carb balance was slightly off.
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When I worked in the aircraft one of my duties was to weigh the pistons, rings, wrist pins and wrist pin buttons, used instead of wire rings, less chance of failure. I had a fixture to weigh the reciprocating portion of the rod. This information was sent with the crank to be balanced. Usually but not always the cranks came back with Mallory Metal added. A lot of the engines, radials, were built during WWll so I wondered if they took the time to balance them but get them into service as fast as possible. We always joked that WWll was a myth because there was no way that so many of these could have been built in such a short period of time. I learned an interesting bit of information a few months ago. Chrysler built more Wright radials during the war than Wright did. They also made several improvements to the engines in the process. One was an improved oil pump. Mopar Blue showing through again. :wink:
kk
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For a smooth engine it is...and also if you want to be able to use your rear view mirrors