• Husqvarna Motorcycles Made In Sweden - About 1988 and older

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    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

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Piston Shimming

Wildebeest90210

Wildebeest90210

Husqvarna
AA Class
First time I've done this. A/C 430 motor.
I have pressed the pin in the crank at 58mm flush with the cheeks which gives me about 1mm (40 thou) side to side play on the big end. I'm told the piston is shimmed to centre the rod and I need a clearance of about 0.25/0.3mm(10 thou) side to side on the little end.
So I need to make up some shims. Its a Wossner 430wr piston and it looks like the shims will be approx 2mmthick.
A. Is this all correct?
and
B. Is it ok to make the shims from st/st or is an ally or phosphor bronze better?
 
Wildebeest90210 said:
First time I've done this. A/C 430 motor.
I have pressed the pin in the crank at 58mm flush with the cheeks which gives me about 1mm (40 thou) side to side play on the big end. I'm told the piston is shimmed to centre the rod and I need a clearance of about 0.25/0.3mm(10 thou) side to side on the little end.
So I need to make up some shims. Its a Wossner 430wr piston and it looks like the shims will be approx 2mmthick.
A. Is this all correct?
and
B. Is it ok to make the shims from st/st or is an ally or phosphor bronze better?
Click to expand...

I have not seen any shimming on any 430 piston install. Please check Halls parts PDFs
 
There are brand x fitments with woosner pistons where the space between the casting (or forging whatever it is) at the wristpin is greater than the stock and the needle bearing can creep off to the side. The cure is to buy from them (I blieve them, and isn't noted in any way this is necessary, past tense might have changed by now) a needle bearing which has the same needles but longer cage. I guess this is the function of shims which perhaps is the 250 never seen shims in a 430 or in the parts sheet for one. That is some of the reason I made sure I could returm my woosner piston if I didn't like it. The space in the middle seems within the error of measurment the same as the mahle one. Isn't this what you have in your parts?

Fran
 
My understanding is that if you don't measure the big end play and use thrust washers on the bottom end then you just press to the pin length and then shim on the little end to stop the rod floating causing wear. I know this was done early 80's on big singles so assumed this is what happens in a husky motor. I'm far more used to measuring the big end play but I'm sure you have to tweak one end or the other?
I'm getting the clearance from A Graham Bells two stroke bible and my crank man.
 
The 240 parts list shows a washer on each side of the c/rod at the little end and they are case hardened and ground steel.
The 400 parts list shows NO washers.
Putting washers in the 400/430 may upset the balance making the bike vibrate [ if they were not fitted originally ]
 
dukkman said:
Putting washers in the 400/430 may upset the balance making the bike vibrate [ if they were not fitted originally ]
Click to expand...

In theory this would seem to be sensible however if you look at the parts sheets the crank for the 400 and the 430 is the same and the piston is most certianly not the same weight. Additionally none of the replacement oversize pistons seem to keep the wall thickness and the weight the same, the outer diameter and wall thickness and hence weight increase. There are some extremely large oversize pistons for the 500 and I am kind of curious how thick the walls on them are. I believe the modern husky 250/300 has the same thing with it being impossible for ideal balance on both. Look elsewhere on this site and see they seem to be over boring 125 bikes and not re balancing unless I am missing something.
 
Looks like the 'Crank end float' thread has reached the same point but for a '78 390. I don't like the idea of not shimming and having the conrod float about so I will make some up. At least if there is vibration I will know where to look first. I will though try to contact the Wossner agent in the UK, don't hold out a lot of hope for that though.
The barrel and piston came from another bike so I've no idea how it was set up.
 
I put a Wossner 8033D-100 in my 79 390CR. The spacing rings would not fit like the original Mahle piston.
Found a wider wrist-pin bearing. Can't remember specific's except I has .040" clearance on either side with the Wossner piston and no spacer rings. Seemed reasonable to me.
 
Hey Ron, was that .040" from the needle roller cage to the piston and did you get good hours from the motor?
I'm just worried about the big end straying on to the crank cheeks without a thrust washer.
 
Yes, needle cage to piston .040" on each side. Same as the Mahle with spacer rings, but to much with the standard wrist pin bearing. Stock bearing is .830" and the one I used is .890". Got it on Ebay from the
Bike Buzzard, see item #170622904067
Unfortunately, we only got about 4 hours on the bike before the piston siezed at the Elsinore Gran Prix last November. Sucked a bunch of water into and siezed about a 1/4 mile later.

Husky wrist pin bearing 002.jpg
 
Will get back to technical stuff but you've no idea how jealous I am about where you live and being able to race Elsinore. England is sooo small sometimes...!
 
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