1Tuff500XC;120827 said:
So then, what is the purpose of the crank revision that was done on the '87 500's???? Was it to slightly lighten, for slightly quicker revs or throttle response? Or simply aimed at tameing vibs????
Just guessing that they went for the more I beam shaped rod from the more popsickle rod and added the scalloping at the wristpin end (250,430,500 and perhaps others) and the omission of the lube hole and the new crank cut was cost cutting thing. At least they should have made the slice in the bottom of the big end bearing for lubrication like most other pre mix cranks seem to have.
1Tuff500XC;120827 said:
Since that was along the lines of my interest in the auto crank, it leaves me wondering just what could be done to the 85/86 reciprocating assemblies, for any gains? Be they performance, reliability, or simply less vibration.
It would be nice if someone who has taken courses or runs a crank repair and modification shop would answer in here. Perhaps you would have better luck with a new thread and new title or perhaps it is not the type of advice you get for free on an internet discussion forum.
My comments to this as I have examined the situation. The only crank I have actually had re ballanced was for a 1975 Norton which is sort of similar just has two pistons raising and falling together not one, is bolted together not pressed. I went from the rubber mounted set up which has a ballance factor of somewhere in the 70's I have been lead to believe and rigidly mouned it which I think the thing came back with a factor of 50 or so.
So the first thing you need to do is find the piston you intend on using, I have stalled here as the husky piston at least the nice new oldstock Mahle one I got is really heavy, excessively heavy if you look at some of the light new stuff for the modern cycles. A modest plug for Halls here as they have told me If I buy a piston from them and don't like it I can return it though that was for the 430 at that time.
Second I would look at that picture with both cranks and pistons above and figure out why the top of the crank was made lighter when the piston was made lighter. It sure seems to me if the same balance factor was to be maintained the crank modification when the wrong way. How involved do you want to get, I have seen reference to adding another motor mount under the engine, I would investigate that and factor that addition into what balance factor is eventually chosen. I call that 85-88 two stroke frame the pedistal frame, It continued in the fouir stroke line for at least another 10 years and Vor used it as well, (just to stay in the strickly dirt bikes I am aware of) What balance factor let's say a 1999 or so 410, 510 or 577(aka 610) used?
One can fill in and cap the holes and notches but don't ruin the lube hole and then add weight to the other side commonly drilling out steel and replacing with tungsten from tig weding sources. It seems much easier to use depleted uranium from 50 caliber bullets but I have no source for that. I really don't see a big need to cap the end of those voids which is only a few thousands from the case.
The thing has it's limitations such as those long studs running through the cylinder and up to the head restricting port design so no matter what you do you never will be able to run with a bike where the cylinder bolts to the case with the bolts farther out and the head bolts to the cylinder.
Fran
