• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    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.

    When he passed, I worked with his kids to gather the necessary credentials to keep this site running. Since then (and for however long they worked with Coffee), Woodschick and Dirtdame have been maintaining the site and covering the costs. Without their hard work and financial support, CafeHusky would have been lost.

    Over the past couple of weeks, I’ve been working to migrate the site to a free cloud compute instance so that Woodschick and Dirtdame no longer have to fund it. At the same time, I’ve updated the site to a current version of XenForo (the discussion software it runs on). The previous version was outdated and no longer supported.

    Unfortunately, the new software version doesn’t support importing the old site’s styles, so for now, you’ll see the XenForo default style. This may change over time.

    Coffee didn’t document the work he did on the site, so I’ve been digging through the old setup to understand how everything was running. There may still be things I’ve missed. One known issue is that email functionality is not yet working on the new site, but I hope to resolve this over time.

    Thanks for your patience and support!

Squish Gap 1985 500xc......

Four Digit

Four Digit

Husqvarna
AA Class
Trying to get this big motor to work....anyone out there know what the squish gap should be on this monster?

Thanks
Doug Walker
 
the piston is at the top of the cylinder on these maybe a couple thousandth's below , the gasket makes the gap, they are not adjustable per se
these are high compression engines
 
There was a thread on here where picklito stated that cometic if contacted directly does have differing thickness of base gaskets. It was for the air cooled 430 but I am pretty sure that gasket is the same one. I will agree the top of the piston is darn close to even with the top of the cylinder. I would venture to say we are all equally capible of measuring a head gasket thickness. I have wondered about cutting a bevel as these are just flat and then a dome.
 
I'm trying to figure out why this motor has low compression (60-70 psi) after a fresh top end (fresh bore/hone and new Woosner piston and ring). Before the new top end I was obtaining about 60 psi.

The current deck height is .030 and the squish gap is .068. I believe this may be too big but I am not positive.. therefore my initial question.

My base gasket measures .048 and the head gasket measures .050
 
squish on my air cooled 430 measures 1.2mm, fires up fine and pulls well, never done a compression test as i have fitted a decomp valve and don't want to risk breaking the cases trying to start the bike without it.
 
so squish is 1.7mm, reeds are in good condition, bore is new, piston facing toward exhaust, ring gap in bore checks out fine, piston feels tight in bore, spark plug and gaskets all sealed, thats about all i can think of.if all that checks out and your head is unmodified you should be getting around 160 psi, does it feel hard to kick over? iam 40s and weigh 180lbs and would find starting without the decomp a real effort.
 
jo360 said:
so squish is 1.7mm, reeds are in good condition, bore is new, piston facing toward exhaust, ring gap in bore checks out fine, piston feels tight in bore, spark plug and gaskets all sealed, thats about all i can think of.if all that checks out and your head is unmodified you should be getting around 160 psi, does it feel hard to kick over? iam 40s and weigh 180lbs and would find starting without the decomp a real effort.
Click to expand...
Yes, throttle wide open, piston and bore have been checked by two machinists and both say it is fine. Piston aligned correctly. Reeds look good. I'm 70 and weight 250 lbs... the kicker moves with little resistance when kicking...I was expecting more.,
 
I measured two new head gaskets one 500 one 430 and got 0.048 at the inner metal ring. I measured a new base gasket and got 0.053 and a used one and they don't squish much if I worked at I could get an 0.051 in one spot but 0.052 or 3 was most of my measurements.


When the top of the piston goes all the way to the top of the cylinder it also goes even with the bottom of the exhaust port on the other extreme, at least any time I have paid attention.

I will throw out one more thing I have seen in yamaha rd400 and 420ae a hole from about an inch above the exhaust port to perhaps an inch or two down the exhaust passage. I don't know what is origional and what is period modification but if you have such a presumably starting aid it would sure effect the compression readings at crank revolutions per minute in the kicking range.
 
Well thanks all for the help. This is definitely a head scratcher. I pride myself on not giving up on things and so I will continue my efforts on this project. I'll post when I get this thing sorted out. Thanks again

Doug Walker
 
Four Digit said:
Well thanks all for the help. This is definitely a head scratcher. I pride myself on not giving up on things and so I will continue my efforts on this project. I'll post when I get this thing sorted out. Thanks again

Doug Walker
Click to expand...

To measure compression ratio accurately seal rings with a bit of grease bring piston up to TDC and then pour in measured amount of oil , I use a large calibrated syringe, through plug hole till oil is a couple of threads up.You now know the compressed volume, work out the swept volume then add the compressed volume to this and compare to compressed volume and you will have actual compression ratio which you can compare to your earlier results.
The squish gap you have seems far to large to me, I run my Stormers on 25-30 thou!!
 
Measure squish on torqued assy. with solder wire through plug hole. 2 pieces simultaneously on both sides of piston above gudgeon pin. Crank and extract, vernier caliper the compressed portions. 1,7mm good
1,5mm nice
1,2mm minimum safe.

Wossner piston ring exerts very little wall pressure, unlike original. It needs some rpm to seal. Also a fresh bore/hone and ring needs to to run in before ring seats well. No friction reducing lubes like silicone etc when assembling.
Run engine in with cheap mineral 2T for 2 tanks before going to the synthetic stuff.
Check compression again after run in. You have to hoof it properly with WOT.
Good luck
 
check out the thread regarding fitting a chinese coil and cdi this helps starting, i would definately go with a decomp valve as well the thread is on this forum.
good luck.
 
Four Digit said:
Well thanks all for the help. This is definitely a head scratcher. I pride myself on not giving up on things and so I will continue my efforts on this project. I'll post when I get this thing sorted out. Thanks again

Doug Walker
Click to expand...

Just wanted to drop a line to let you know that I got this 500 started. Took awhile but she fired and ran for about 30 seconds then quit. Couldn't get it to fire again but I do believe it is a carb issue this time because of the way the motor faltered and then shut down.... chug...chug...chug..stop. I'll be checking jets(again)...figure the pilot jet may be plugged.
 
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