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Balance Factor

Rob H

Well Known and Active Forum Website User
VOC Member
Been doing some background reading on this from posts in the forum and from what I can gather that factor for the standard bike is 46% with some enigines is ducati or egli frames going up to 60%

It also seems that the type of frame used also has an impact.

I would be interested in any feedback what members have used in standard and big bore engines in the standard rolling chassis suitable for high speed cruising (approx 80 mph)
 

Vincent Brake

Well Known and Active Forum Website User
VOC Member
indeed as i did a rebuild on my rap it vibrated a lot at higher speeds at 46 % (say 150 km ish) so am building a 5 speed gear cluster in and high end ratio.
(other: Megacycle Mk I cam 1:7,5 comp ratio Mikuni 28)
now am putting a BS in for a rebuild and am going for a 54% balance factor Megacycle MKII cam and 7,5 comp ratio and see what that does, ( I might end up for a short rebuld of the rap.)

Cheers and good, safe and fast driving in 2013.....

vincent
 

Big Sid

Guest
Hello Vincent . A question . Is your vibration mostly felt in the bars or in the foot rests ? If in the bars you might try some lead shot for a distance in each bar end , not tightly packed . Must be loose enough to move about . A change in bars might do the trick by being out of phase with the internal vibes .
I did earlier mention that Videan uses 60 percent in all Vincent motors and every type of chassis . Cycle world Editor Peter Eagan described our Vincati as being " liquid smooth " , no vibration felt , after his 100 miles on it . Further said it felt like being " flung up the road by the hand of God " when he rolled on a fist full . Very impressed with it . And it is built at 60 percent .
After Matt's first time ride on it , the first , I asked him what did it feel like , was it smooth ? He answered quietly this way . " once it's up to a reasonable speed it HAS NO VIBRATION , NONE in tank or bars , a very little felt in the footrests . Feels like being inside sitting on the sofa ". I was stunned . This is a fact , everyone who tries it says words to that effect . As did Jay Leno who had it up above 90 on city streets ! His impressions were captured on tape in the pace car trying to keep up , Matt in that car listening to every word Jay radioed back to the car .
Bill Jean built this motor . I set up the carburetion and timing , and also rearranged the ignition advance curve to slow down the rise in the advance curve , runs a D Dist , so this is done playing about with the flyweights and springs . As first fired up it was a wicked beast , wanting to fly , unpleasant in town running . I also swapped its Andrews Mk2 cams for a set of original Factory Mk 2 s .
In this way I tamed it's nature to be sweeter at lower speeds , til the advance kicks in hard , then it's hang on !
We also reduced its flywheel weight by a pound and a quarter . This explains it's spinning up so fast . Sid .
 

Vincent Brake

Well Known and Active Forum Website User
VOC Member
Well what can I say Sid, its been 4 months now, but it felt horrible but especially at the bars, besides the tank and other parts coming loose, (after a fast trip of 1000KM) the footrests dont ring a bell in my mind so I will try the lead (maybe in silicone rubber) If the BS is OK I will do the same to the rap and see what 10000KM of driving wore out.
B.T.W. is an andrew cam the same as megacycle??

cheers
Vincent speet
 

riptragle1953

Well Known and Active Forum Website User
Non-VOC Member
I helped John Andrews develop and test is very first Vincent cams years and years ago. I Have not seen or heard about him for years. I was told by someone that John had sold all his grinding equipment to Megacycle and he purchase some very sophisticated computerized
milling equipment on which to build his cams. Having received this news second hand I can only believe it is true. I will have to check this out myself as I don't believe he continued making Vin cams having sold all the means for that design to Megacycle. I have no
idea of the quality of a Megacycle cam.... but Johns were the best!
 
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riptragle1953

Well Known and Active Forum Website User
Non-VOC Member
Also, I have tried to make it clear that there are many more common reasons for severe vibration than the balance factor. But it seems this is ignored and folks are stuck on balance factor only. So I have given up trying to get the methods to built a dead smooth machine
accepted as I don't like to waste my time.
 

Big Sid

Guest
Sid here . Megacycle bought out Andrews cams . If your Vincent shakes that bad its a sign that your flywheels have shifted , unless it's mismatched weights on rods and pistons . Severe detonation also makes a motor run rough .
See if the feed quill is polished and worn on opposite sides but at ether ends . This is a dead giveaway . A length of quarry inch drill rod slid in the shaft will wobble in an off center motion when the motor is spun over and this is bad news .
 

riptragle1953

Well Known and Active Forum Website User
Non-VOC Member
That is one reason a Vincent shakes another is our of round and tapered main bearings that due to the loss of the original .0025" fit in soft cases - the outer ring has expanded giving the rollers more slop than a worn out bearing....ANY bearing manufacturing manual
with their listings of correct bores for proper fittings will tell you this. Again: a bearing is no better than it's housing. period!
 
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Big Sid

Guest
While pitted and otherwise bad mains give rise to noise , moaning sounds and some roughness it's shifted flywheels that really shake . The out of balance forces ruin all fun in riding the beast , parts are flung off , fenders and braces crack as many vertical twins were known to do . The least run out , deviation , the smoother the motor . Where the Factory trued to a runout of 1 & 1/2 thou to 2 , if trued to a half or less total the motor is always much smoother . This is fact . Sid .
 
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