Can 500 Auto crank be used in non auto 500????

I spotted a pic of a 500 auto crank, and couldn't believe how much less material the crank halves had around the rod journal/pin area. Looked like it would have to be much lighter weight. So I was curious if they can be used in a non auto engine build???? Just a thought. I'm assuming perhaps the clutch end is different from what a manual trans needs.


Apparently came from case# 2090 0358



Edit; just confirmed case number 2090 appears correct for an 84 to 85 500AE.





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And then the .......I gather 85 to 86 style water pumper 500 crank style. Which is the style both of the bottom ends I have has.

'88 crank.........

Would the 500AE crank not also allow for more case volume for air/fuel charge? I'm kinda new to getting this deep into 2 strokes, but I thought that they hold or compress intake charge in the case under the piston.

I see you found my old pictures, The width of the auto cranks is less. The pin is shorter so you have that issue right off the bat. I don't recall about the diameter of a 500 auto crank but the 430 auto is less than the 430 standard. The way I look at it is you want a crankshaft which fills the crank space as fully as possible. That way as the piston moves up and the charge moves in (and in the transfer mode) the percentage of total volume change is greatest with a filled crank. If you study the parts sheets of the new husky two strokes you will find what I think are magnesium blocks instead of holes. The 250 got this treatment before the 125 if you follow through the years. I call the less material style the pork chop ones. I have found that style in a standard 360 engine somewhere in the 1978 vintage. I think a 500 auto crank probably would be a good donor for a healthy rod cage and bearing for a 500 standard crank rebuild and only a pin need be fabricated or perhaps from a different displacement bike which died of other causes. Yes the thing which presses in the drive side is different on the auto bikes.

Fran

Yep, I made note of your pics in the other thread, previously.

Hmmm, guess I'm not following the part of 2 strokes filling the case with fuel/air charge, and if that's the case, why make more room for more charge is not a benefit. Have heard of crank stuffers or some such item, and wondered about that as well.

Very interesting stuff though, forsure. I just need to wrap my mind around it better.

What I think you are seeing is a result of the crank cheeks being thinner on the 500 auto crank hence a much more radical cut was necessary to achieve balance.

All the room for the charge you need is under the piston, Well at least the way I see it the displacement oscilation above and below a piston is the same. The more filled the crank chamber is the less of that charge escapes from transfering to above the piston as the piston comes down and the transfer portion of the stroke occurs.

Fran

Gotcha! The learning never stops.

Oh well, I was thinking, or rather wondering, if I'd just found some free power and quicker revs. Via another OE crank, simply being swapped in, but I see that would not be the case.

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????

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.

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.

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

There's also a concern in 2 strokes with crankcase volume and piston displacement in the crankcase.
If the crankcase volume is excessive, the displacement of the desending piston does not create enough pressure to force the fresh charge up through the transfer ports.
Finding the balance is the problem, since to small of an area will hurt top end performance and to large of an area will hurt the low speed performance.
All of this also effects the expansion chamber design, in the way it helps to pull in the fresh charge.
There is a whole science to it, but the calculations are way over my head.
I personally would save the headache and use the stock crank.

Some advice certainly is not for free, but use your eyes carefully and compare the material area above the holes through the crank-lobes and original Mahle pistons on your pic with two of them on it. Left is LC and right is AC. Husky knew better what they were doing than just about all others, which is why a well tuned 85 500XC will leave all behind except MAYBE the Husa 570.

What Ron said sounds in history where 87 YZ490, 83 KX500 and quite a few others had detonating and self destructing engines, and they never got the power and speed right either.

Also in my experience Mahle pistons which are way heavier than aftermarket is what makes huskies tick fast, for long.

Free advice, a good 2nd hand Mahle (know your tolerances and measuring) with new ring, sweetly honed barrel toleranced correctly will outrun and outlast any other combo.

Keep it standard, learn how to tune it well, and she will terrify you and all others for years to come. The auto and crap 88crank wont work and are inferior to the 2 on that pic.

Ps. Its the trueness and alignment of those crankpins which is where its at for the optimum vibration control. Husky says 1/10thmm. I have cranks with a bit of effort that have been done to 3/100thmm.

They will always vibrate. Does'nt bother if youre focussing best you can to stay on and handle whats coming.

Huskyhamm,
I agree with alot of what your saying. I'm working on a KX rod conversion for 500's, trying to get my machinist going..... He does alot of high end drag and circle track engines. We are going to balance the rotating assembly down to the primary drive gear and rotor. This is absolutley manditory on what we are doing in this conversion. Boring one crank cheek to accept larger OD crankpin, Cutting/clearencing both cheeks inside for the wider rod also. Piston selection is a huge factor as stated above. The factor is criticle in weight, think of throwing a baseball but not letting go!! He said all my piston work must be done before establishing a 'bob weight" for balance. This will include port work, pin, bearing, pin clips, piston ring. I'm very curious to see how it works, esp. the vibration issues. My machinist has been very busy with "paying jobs" and in no way could I pay the going rate to have this work done so I'm at his convience, which is ok.

Great input and thoughts guy's, really appreciate you all sounding in on this. After years of being into the small details on my previous strip/street musclecars, I'm kinda stuck in that frame of mind of knowing it's often all in those small details. Kind of like taking tuning a step beyond simple timing and fuel mixtures. Like gasket matching, etc. My end goal with this is to have both a very fine tuned engine, but also having any other small details covered as well.


Pipe expansion chamber design is another thing I'd like to at some point delve into much deeper as well. Have always wanted to know how the diameters and locations of them are determined, so I can analyze what has already been done, and see if I might have a different take on it. Or might recognise a design compromise in one pipe over another. Just all in the hopes of further fine tuning for the power delivery most optimized for my interests.

Regardless of what it is in, in the end, my engines always seem to have a performance edge over a seemingly identical combo, and it is all in the taking the time to pay attention to and understand what the small details are, that can help further tune power delivery one way or another (up or down in rpm, narrow and higher peak, or broader).


On a similar general train of thought, I have a second 500 water pumper cylinder on the way, and I grabbed this other one both because it was cheap, but also because it has a different intake port design/shape than the current one I already have on hand. I just wanted to see what effect the difference will also have on power output. The one I have on hand, is an 85/86 jug, and the one I have coming, is from an '87 model. Also snagged a corresponding '87 head, currently inbound. So it appears for '87, they changed the intake port shape/layout, and as well I believe I'm seeing in pics that they changed the nut design for holding the cylinder on. Looks like they shortened the counterbore for the long shouldered cylinder nuts. Hence my grabbing up specifically an '87 head. Needed the second head anyways, so we shall see once I get these parts in hand.



OK then, great info on the cranks. Didn't realize the later changes were strictly a cost cutting method. Good to know, since both 500 bottom ends I have are '86's.