Homemade crank balancing

[velardejose]

Hi
I disassembled my engine to balance it
Vibration and a rattling sound I noticed a week ago
Before disassembling I discovered a broken mounting stud, rear mount
At the machine shop we took the broken stud out, and went to balancing
Piston+pin+rings+clips = 70 gr
Light rod end = 35 gr
Total reciprocating weight = 105 gr
I fixed a 55 gr weight to the rod journal
And checked the crank balance using two metal rods (horizontal bubble level checked) and suspending the light rod end with a string
Too heavy
I started drilling the crank added side pieces, and found it had holes in it
Was not enough
I had to drill 1/4 holes through the center crank plates
And balance was perfect
Thing is, when taking the parts to the machine shop, to the local representant to use his extractor, and to the gasket shop to make a center gasket the front gear dissapeared
Grrr
I will see my mechanic today, hope it will be assembled, maybe the gear is in my bag...
Jose
PD I am replacing all studs with automotive grade ones

[velardejose]

Hi
Crank balancing (sort of)


Piston mod, there were 2 mm skirt in the intake path with the piston in the top dead center


And cyl+head after a light pass using a 320 wet sandpaper
You can notice it is not flat exactly...


Hope it helps
Peace

[jak stoll]

hey there
that will help allot with longevity
Ive put a few together using silicone RTV no gasket with no problems at all
take care
JAK

[velardejose]

Hi
I visited my local representant looking for a front gear replacement (right crankshaft end)
He lent me a used gear to use it as a template to make another one for my engine
I got the duplicate gear today (after 5 days and 30 usd)
My engine will be assembled tomorrow
Can't wait to try it and see if the mod reduced the vibration
Peace

[Goat Herder]

Glad to see more people are noticing the piston clearance at TDC. This mod will make the little china run with lots more power. When you had the jug off hope you played with the porting. [matching exaust &intake]. Do look closely at the gasket to the bottom of the jug.[trimmed mine considerably it blocked half the ports at bottom of jug].Not all of these chinas have piston clearance issues at TDC some modols put the intake hole lower, clearing the piston skirt.

[velardejose]

Finally
I tried my mb today
Loud gear noise, just as new, because of the 'new' crankshaft gear
Easy for a couple blocks, and then I tried high revs
Smooth as silk!
Danger is there is no 'vibration rev limiter' anymore and thing goes fast
I highly recommend it
Jose

[TexasDav]

Good to hear, I bet it will make that engine last a lot longer.

[europorsche914]

do you have any specific measurements on where to drill the two holes through both crank plates? and what size holes to drill? Thanks -Justin

[craigant]

I would like to know more too

[velardejose]

Report
2 mods at the same time: crank balanced and piston skirt filed to clear the intake path
All studs upgraded to automotive grade ones
Result
I can cruise at comfortable speeds, no variation
I can accelerate to higher revs (higher speed too), and I am too scary (old?) to keep it for more than a few secs
Engine is normal at lower revs and at higher revs vibration seems to be in the pedal area, not the whole mb
Idle seems to be more stable
Mileage seems to be the same
Will make a diagram with the holes I did in the crankshaft
Peace