the difference between 390 / 430 engines.

[Bigbill]

Ok I'm just thinking again about the difference between the 79/80 390 CR engine and the 82/83 430 CR engines. The 390 has the half circle balancers on the crankshaft with a monster flywheel. While the totally redesigned 80's 430 case it eliminated the monster flywheel but the crankshaft balance weights are larger and full circle. The CR flywheel is a smaller internal one. Now I see some of the later 500cc crankshafts has the flywheel counter balancers trimmed I almost triangle shape on both sides of the connecting rod pin hole. I'm confused why is the difference between these different counter balance weights.
Now excluding the 390 if we look at the three different ignition flywheel they interchange on any later 430, 500 engine from the smaller internal flywheel(CR) SEM flywheel (WR) and the heavier motoplat flywheel (XC).

Has anyone ever sent out your crankshaft, piston, flywheel assembly for precision balancing?

The Swedish design engineers are close on the balancing of the different flywheel but how close is the balancing and can it be better.

 

[fran...k.]

That is a pretty complex list of stuff.

The keyway for the ignition isn't always in the same spot for the small taper. I also to seem to recall some errors in the parts sheets perhaps for the 360 stub end. This has been discussed before I don't know all the specifics but a 420 auto crank has the key way different than a standard shift that takes the mini 6.

That triangle like crank you speak of was the very last two cycle 500. It didn't have the lube hole from the ballance voids like the two prior 500 crank designs. I bought a trashed one just for fun.

How familiar are you with ballance? What are you talking primary balance, secondary balance or third kind. You can't balance a single cylinder like these. You break it up into a balance factor some up down/some forward back. Years ago I tried to discuss the two first 500 cranks and the earlier and later piston weights and how it seemed they they went the wrong way to keep the balance factor the same. Balance factor and frame desigh are buddies so to speak.



Personally I only have had one crank pressed apart never assembled. On the bikes in this part of the internet.

 

[Bigbill]

I pressed a few crank pins in the past. I made the disassembly fixture and the assembly fixture.
I believe the rod needs to be removed then a weight consisting of the weight of the rod/piston is added to the crank pin to balance it with the ignition flywheel and gear with nut on the clutch side. Then they balance the assembly. Then they disassemble it and install the rod again. Having the bottom end balanced it will be smoother running with less vibration and rev quicker and be smoother on the response. I'm thinking of balancing one engine just to try it.

 

[fran...k.]

I pressed a few crank pins in the past. I made the disassembly fixture and the assembly fixture.
I believe the rod needs to be removed then a weight consisting of the weight of the rod/piston is added to the crank pin to balance it with the ignition flywheel and gear with nut on the clutch side. Then they balance the assembly. Then they disassemble it and install the rod again. Having the bottom end balanced it will be smoother running with less vibration and rev quicker and be smoother on the response. I'm thinking of balancing one engine just to try it.

Having the crank true is likly the most important. Put the crank in the case halves assembled so the space between the cases is a fraction more than the locating pins, spin the crank and watch for movement in the cases.

There is just no evidence on any of my husky cranks that they have been fine tuned once assembled.

You also get into the aspect of the interference fit of the pin/cheek. Often the pin is made just a bit larger on a rebuild.

One does send out the piston out with the assmbly like you state.