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Best balance factor? Tonti framed 850 and 950

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ReggieV View Drop Down
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    Posted: 27 Dec 2017 at 18:44
I wonder if anybody can tell me the best balance factor for the Tonti framed 850 and 950's, when using the max revs not infrequently.
 
I have tried to find information on the internet, and the few references to 90* V twins that I have found suggest a 50% balance factor, but not specifically for a Moto Guzzi. Also on the V11 Le Mans forum, one person has written that 52% is  the ideal balance factor, as this leaves the engine with the same vibration level at low revs but becomes silky smooth at high revs, but does this also apply to the Tonti engines?
 
Previously I have used Basset Down for this, and they did a great job on my 950, but I believe that they changed hands a few years ago, and have read mixed reviews since including a T140 crank that I had done by them which vibrates badly above 5,000 rpm.........maybe that's as good as a T140 gets? LOL
 
I then rang another company near to Derby and they asked what factor I wanted it doing to, and when I wasn't sure suggested that I found out some information myself before instructing them???ConfusedConfusedConfused
 
I've looked on Gregory Benders web sight and although he discusses the importance of crank balancing and reasons why it is important, there aren't any recommendations of what balance factor to use......at least where I looked.
 
So enough waffle from me, does anybody have any known, used balance factors that they have used and even any Moto Guzzi knowledgeable / sympathetic crank balancers?
 
 
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IanB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanB Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2017 at 12:39
Dave Richardson says that cranks were balanced to 50% up to around 1993, but the factor was revised to 52% around then (Guzziology section 5-43). He says: "Any pre-'93 engine can benefit from rebalancing, especially those that have had a component changed."

Looks like 52% is best bet.

Clean out the sludge trap first...

HTH
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ReggieV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReggieV Quote  Post ReplyReply Direct Link To This Post Posted: 29 Dec 2017 at 12:24
Hello Ian, thanks for your information. It looks like it'll be 52% then.
 
Interestingly you mention "clean out the sludge trap first," well when I sent my 950 crank off (mentioned above) for balancing I did forget to do this. I realised that I'd forgotten to do this when it was returned to me, and unfortunately it had a substantial amount of crud in it, so I had to return it for re-balancing and £££+++ Censored. I wont forget again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanB Quote  Post ReplyReply Direct Link To This Post Posted: 29 Dec 2017 at 14:44
Yup - I found out the hard way too... Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil Quote  Post ReplyReply Direct Link To This Post Posted: 29 Dec 2017 at 22:32
This is not an exact science as there are many variables and assumptions. Things like conrod length to stroke ratio have an effect. Assumptions are made regarding ring drag and the weight of the oil on the piston. For road engines the tolerance will be more than a few grams, I cant see why you would re-balance to account for the weight of the sludge removed from the trap.. did they take into account the mass of oil that would be in the trap cavity ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 15:54
Pretty sure it only means clean it out while you got the crankshaft out and so can get access to it.




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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 16:14
Apparently, there are 27 grams of oil in the crank pin when the engine is running and must be taken into account when balancing the crank.Gleaned from Greg Benders' site.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 16:17
One would assume that any swarf would be heavier than oil.
 
But does the "weight" of the oil make a difference? WinkLOL
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Phil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 18:03
You have real problems if you have swarf in there as it will have passed the strainer and oil filter and gone through the pump. The trap centrifuges minute solids from from the oil that haven't been caught by the filter.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 21:40
Exactly, that's why it's there and those solids, sometimes called swarf, will be heavier than the oil.
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ReggieV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReggieV Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 22:13
Phil wrote; I cant see why you would re-balance to account for the weight of the sludge removed from the trap.. did they take into account the mass of oil that would be in the trap cavity ?
 
I had the crank balanced again because the first time that it was balanced it had this "heavier than oil" sludge in the trap, and the trap was nearly full. I did weigh the sludge at the time but can't remember what it weighed, but I can only liken it to a big lump of (black) plasticine . As the sludge trap doesn't spin along the axis of the crank, the sludge must have had an effect, possibly very small (as it spins not a huge distance from the axis), when removed. Therefore as I wanted the balance to be as good as possible, I sent the crank back for re-balancing. Whether the oil weight that would normally be in the trap cavity (27 grams apparently) was ever taken into account, I don't know because I am not a crank balance expert, and left factors like this up to the balancer.


Edited by ReggieV - 30 Dec 2017 at 22:16
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Phil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 22:19
I have never heard anyone call the sludge removed from a crank swarf. swarf is metal shavings, sludge is the oxidisation and contamination of the oil, usually caused by leaving it in too long.
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ReggieV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReggieV Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 22:31
I never said that the sludge was "swarf," just that it will be heavier than oil, being semi solid.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2017 at 22:42
There is no " correct " balance factor.. i have heard numbers between 50 and 60 percent.. so the difference in density between oil and sludge will make a tiny difference to overall result unless you specify the exact factor you want and what tolerance is acceptable .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote red leader one Quote  Post ReplyReply Direct Link To This Post Posted: 31 Dec 2017 at 10:38
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