E: Engine Crankshaft Balance Method

greg brillus

Well Known and Active Forum User
VOC Member
We always want more power........have you ever ridden a decent 600 Comet with one of Terry's top ends on it, this with the twin plug set up and a good 36 mm Mikuni or Dellorto...........They absolutely fly....... If the factory would have made them like this, they would have sold more singles than twins. This has been my thinking towards the new engine in my racer........92 mm bore x 100 mm stroke..........Should go like a "Raped Ape".......:)
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Totally agree Greg, Can't help thinking, The first time the "C" Comet was tested,
I think the "A" was a bit more Frisky ?, Ron's "A" Comet Special, The factory one ! was.
The tester should have said, " Nice Bike But !! ", Needs more Power, And maybe better gearbox ?.
I have not tried a Big One, As I have said, I got my old Comet to go well when I nicked the head and 36mm,
Dellorto of my Twin Special., But I had to give it back :) .
The engine was already Flash Spec'.
If I had another set of cases, I had thought of going Big Bore, But I think I am being Greedy ?,
And I want to see how much difference just stroking makes.
Plus I have been so long trying to build this , My last Bike ?, I have run out of Frames and Wheels etc,
And everything is so much money now.
Plus the Wife has learnt how to count :).
Have FUN, Bill.
 

vibrac

Well Known and Active Forum User
VOC Member
Sometimes Greg (especially in the UK) its wiser to select the organisation &race class before you build the bike to a capacity ;)
It would not be the first time I have put a smaller barrel back on to get more points
the BHR series is so complicated nowadays there are 50 yes 50 classes of bikes and 50 'events' .As to the actual races (length generally just 4 laps!) all get jumbled together there are no regulations regarding number plate coulors, different cc within a class get more or less points.the only time it gets separated out is at year end prize giving at the dinner which with 1st,2nd and 3rd must take days. .
We gave up when Girdraulics were banned from the girder fork class (there is a class for Vincent singles but you would run on your own!) I doubt we shall race with them any more, sad after 50 odd years.
 

LoneStar

Well Known and Active Forum User
VOC Member
Greg & Bill,

I chose the radial holes on the rim, instead of enlarging the existing axial holes, specifically because I was worried about either damaging the rod big ends or getting swarf into the bearings - the holes end right at the rods.

The holes I drilled are about 1cm deep at the edge, deeper in the middle because of cone-tipped drill bits. I wanted to get them all the same, so used a syringe to fill them with water and test how much material had been removed, during drilling. This also allows figuring how much weight has been removed. I settled on 4ml each.

With the radial holes being some distance from the big end bearing, so less of a swarf risk, I just wrapped some tape around the rod big ends at the junction with the flywheel.
 
Last edited:

greg brillus

Well Known and Active Forum User
VOC Member
I'll be running in the unlimited class, 525 cc's up to 1300 cc the bike is around 130 kg's so it should go ok i'm hoping......... Dropped that crank in at the machine shop this morning, told my friend to do his best.........It's like using a micrometer, hard at first till you get your head around it, then it all makes sense after a little head scratching.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
I know USA Gallons are different to UK,
But are UK Grams the same as Oz and USA Grams ? :) .
I make a standard small end held Horizontal 313 and a Carillo 202 ??,
I don't know if it's my cheap scales, " Salter, I thought they were good ones " ?, Or I might find a different way to hang the rods.
As Greg says, Every time you check, You get a different reading !.
 

Little Honda

Well Known and Active Forum User
Non-VOC Member
You can help yourself with cheap scales: Take a real weight, better some, and weigh them with your scale. Note
the results, repeat, list average deviation. Then do your measurements and correct by yr dev. factors.
 

greg brillus

Well Known and Active Forum User
VOC Member
Pretty much most things with a digital read out are like that, look at multi meters, they do the same thing. I'll be getting on with that crank this week I'm hoping, so it will be interesting to see how it pans out. When using the scales you just need to duplicate things as you go, so things remain mostly constant. I think it is pretty important to make sure the big end is free of any rolling friction, that is you probably should flush the big end with some clean solvent to remove the drag of the oil within.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
You put me to Shame Greg, I am only playing on the bench with the rods,
The crank won't be done till next Christmas :) .
 
Top