• 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 The previous version was outdated and no longer supported.

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    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!

What Caused This Burned Piston?

maddog82

maddog82

Husqvarna
AA Class
86 400 Enduro.
100_3026-1.jpg


Maybe this improvised air filter caused lean condition?
100_3032.jpg
 
Does not appear lean. Maybe it is just old. And yeah, that filter is ugly****************************************
 
It was certainly heat related!
It's not easy to melt a hole in your piston :busted:

Was the pipe sealing good to the cylinder?
 
I could have been lean and had detonation then after damage was done and compression was lower limped around and colored everything black while running poorly. I think looking at the rings and ring lands on the piston will tell a lot more that the piston top.
 
PC. said:
It was certainly heat related!
It's not easy to melt a hole in your piston :busted:

Was the pipe sealing good to the cylinder?
Click to expand...

the black top and no pattern makes me think it was rich. the hole looks snapped off like a ring caught a port on the way down.

How did the bike run beforehand and in recent history?
 
^^That, doesn't look heat related to me, hasn't melted a hole a chunk of the piston's just been ripped off. When were the rings last changed?
 
Only looking at the top of the piston forces you to guess. How about a picture of the skirt and the ring lands, then it will be a lot easier to tell without guessing.
 
You are not alone. This is from a water cooled dual shock 400 I bought in dis assembled condition. The guy thought it was a crank seal. I have wonder if there isn't an inherent design defect with the head. This one has a number in it. The dome area measures about 2 5/8 inches which is less than a 430 so I bought some more heads, the ones to the left off ebay to kind of cut a squish into but never got one quite like the one with the raised numbers. The one with the gasket is a 430 head which I thought the others were just not stamped 430 however the measurement of the dome area is not real uniform between the four of them. The head to the far left has a lot more damage to it than what is on the undeside of the one under the piston, ebay good condition, nothing wrong with it.

Fran
400cc.watercooled.head.JPG
 
I don't know any history on this bike. I bought it late last fall, it was running, but not very well. I finally got around to looking at it a couple of days ago, found compression to be zero. Now I know why. Maybe it was just due to neglect and sitting for many years. Thanks for the replies.
 
The fastest way to get this results is to retard the ignition timing ( it stoped pinging but now it runs like crap ) probably adjusted by the same person that serviced the air filter
 
With an air filter looking like that, it was running lean, i've seen people make air filter fixes??? with a pair of woman's stockings :eek: How's a filter going to keep dirt out like that?

Here's another reason, i never trust what anyone tells me about what bore something is etc,when i buy a used bike. I've bought too many, it runs good bikes, only to have them blow up the next day.
Husky John
 
At one time I had some better links about mutilated pistons and the causes but I found this one lately. http://www.eric-gorr.com/pdfs/piston problem troubleshooting.pdf

If you are contemplating putting another top end on it I would think pressurizing the crank cavity and looking for leakage at the transmission breather and the electrical side would be in order.

I find it strange none of the other bike parts I have has any erosion on the piston, just this 400.

Fran
 
Thanks Frank. I'll do a leak down test before I try to start it.
I am going to put a new top end on it. The PO just happened to include a 1st over piston(hint,hint). The cylinder is at the local machine shop. What's a good source for wrist pin bearing, gaskets, AIR FILTER, etc?
 
K is for my last name Fran is a shortened version of my first name.

You might look at this thread http://www.cafehusky.com/threads/430-500-base-gaskets.6495/#post-74582 it pertains to the air cooled heads which have a champher in them not just a flat and a hemisphere like the water cooled ones. I guess the idea is to find some soft rosin core solder just a little bigger than the end result and put it on top of the piston and squish it and then measure. You will notice on the eric gorr page it looks kind of like that model might need race gas, you didn't state if you have that higher compression head with the numbers on it or not.

I generally use Halls for parts, you can call or order on line I believe the prices are the same but the shipping is computed differently They probably have that stuff, the base gasket says cometic on it, well the last one I got. Just because you can order it on line doesn't mean they have it though they send you a pdf file of your bill the next day and don't charge your card until they ship like it is supposed to be. I think there is a thread in the vintage reference section on parts sources. This link here might be of help at some time http://results.searchpowersports.com/ you put in the part number without any spaces or dashes.
 
dont even think of putting a top end on after it's been run with THAT filter, or what's left of whatever that was. get the crank checked or at least the seals and bearings replaced or you might be back in it sooner than later.

oh yeh BTW the prior owner detonated it to DEATH. all it takes is one hot spot, for a variety of reasons, then it glow-plugs after that and it exponential and catastrophic. get a/burn a hot spot on a piston and the alloy changes and it's off to the ping-ola races after that. rule of thumb- when ya hear it ping? STOP.
 
Had similar failures with 360s ,put down to high bowl level .It was a pig at putting plugs out and dinging on.
timing was spot on .the old master puts it down to uneven burn .cold sides and rear of the piston and all the heat at the exhaust side of the ring ,the combustion keeps the front leading edge under pressure all the time ,cuts through the oil and gets hotter and hotter .pop detonation holes
have similar failures with over fueling 2 strokes on methanol when there screaming
 
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