• 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 The previous version was outdated and no longer supported.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!

1971 250 MX - Rebuilt Engine - Piston Rings seized

Vinskord said:
BTW - what is the cylinder squish - with the head off, where does the top of the piston sit at TDC?
Click to expand...
This comment by Vinskord could be a clue. I admit to not having any experience with the 250's from this era but a used base gasket that has been smashed to paper thin may cause the piston to strike the head, but then I would think the result would be apparent as in damage to the head and the top of the piston.

Just check out the piston pic and it looks okay.
 
DFA brings up a good observation regarding chamfering. Not to inundate you with too much info - but take a look at a video on chamfering two-stroke ports (many on YouTube). Here is a link to an older video that covers the topic very well:

View: https://www.youtube.com/watch?v=UJbtzxtPpSs


Your challenge may end up being a combination of a number of factors. As you can see, there are many very knowledgeable members here willing to provide advice. I am sure they all wish they could come over and help in person.
 
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DeathFromAbove said:
you ran the second piston for 30sec
why did you stop running it what happened
Click to expand...

I just pressed the kill switch. It was running fine, and it was always the plan to run it for a short time and kill it to check it over. The video on this thread is that first run. I came back to it a week later when I was expecting to take it out for a short ride around the yard. Checked compression, re-torqued head etc. It ran for 5 seconds and died on it's own. Then low compression.....and that's where we are.
 
Vinskord said:
DFA brings up a good observation regarding chamfering. Not to inundate you with too much info - but take a look at a video on chamfering two-stroke ports (many on YouTube). Here is a link to an older video that covers the topic very well:

View: https://www.youtube.com/watch?v=UJbtzxtPpSs


Your challenge may end up being a combination of a number of factors. As you can see, there are many very knowledgeable members here willing to provide advice. I am sure they all wish they could come over and help in person.
Click to expand...
That video is gold. I fully appreciate the help I'm getting here. Alot of forums ( I have a few old bikes ) are not this active, or supportive. I'm am an absolute noob on these Husqvarnas but have always loved how they look, based on old Steve McQueen / Malcolm Smith footage. I've never ridden one, but if I get it sorted out it will go into the limted classic MX and hare and hounds events here in the UK.

The biggest challenge is there are not common in the UK and there's not the hands on experience you all have over there. This one was imported straight from Sweden to California and came back to the UK in a container as a non runner. It's had some racing time in deserts over there.
 
Crashaholic said:
This is a really good point.
Click to expand...
I'm going to take much better photos over the weekend, and have a proper prod around. The main takeaway so far is that it doesn't look like I've done anything significantly dumb, but I need to look closer.

Vintco also responded now and are up for a phone call to talk it through. They said I have 'a lot of things going on' so maybe they spotted something :) I'll report back.
 
Crashaholic said:
Oh, okay. This makes sense.


This doesn't make sense.
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I've checked a few times. The docs and parts diagram for the 1971 are clear. No gasket. It came with no gasket. It was rebuilt with no gasket and the service manual talks to lapping the surfaces to make sure they mate correctly with no leaks, which is not a job when you have a gasket.

Join between cases and cylinder ? Gasket
Join between cylinder and head ? No gasket. It has an overlapping 'spigot' that mates the two surfaces.
 
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NMc said:
I fully appreciate the help I'm getting here. Alot of forums ( I have a few old bikes ) are not this active, or supportive. I'm am an absolute noob on these Husqvarnas but have always loved how they look, based on old Steve McQueen / Malcolm Smith footage. I've never ridden one, but if I get it sorted out it will go into the limted classic MX and hare and hounds events here in the UK.

The biggest challenge is there are not common in the UK and there's not the hands on experience you all have over there. This one was imported straight from Sweden to California and came back to the UK in a container as a non runner. It's had some racing time in deserts over there.
Click to expand...
Crashaholic said:
This comment by Vinskord could be a clue. I admit to not having any experience with the 250's from this era but a used base gasket that has been smashed to paper thin may cause the piston to strike the head, but then I would think the result would be apparent as in damage to the head and the top of the piston.

Just check out the piston pic and it looks okay.
Click to expand...
I'll take better photos but both look to be OK. I'd recognise impact damage there as I've seen it before on other bikes.
 
Join between cases and cylinder ? Gasket
Join between cylinder and head ? No gasket. It has an overlapping 'spigot' that mates the two surfaces.

correct
 
OK. Lower edges of every port are razor sharp. I actually cut my finger on one. There’s no obvious debris in any of the ports. I’ll check in the bottom end today
 
There is a fine metal grit all over the bottom of the cylinder. What I’m not sure of is that the cause, or the effect of something else being out ? Either way i can imagine this fine grit getting dragged up and Down is why there is damage to the cylinder and piston skirt. Could those port edges really be the cause?
 
Who Knows? Sharp enough ports to cut you can trim the piston.
But she has to come apart hope the crank bearings are not damaged.
Sounds like a Mess.
Moving forward Great Luck.
 
Had a good long look now. Some more photos here. I can definitely see 'crumbling' at the edges of the ports.

Bottom of the port here.
https://drive.google.com/file/d/1GXJl6zUscgLFg3__xLHsNpiC6Nwlrliq/view?usp=drive_link

You can see here that there is marking immediately above the port.
https://drive.google.com/file/d/1N3iFGDv0As65Jg3WvuBRStEKlDeWL2CY/view?usp=drive_link

Bad photo, but there is fine grit everywhere.
https://drive.google.com/file/d/1Fpvqven4FtkP38QXKhHr7iYfPfjTJLeS/view?usp=drive_link

I've got a honing stone so I'm going to see if that brings out the scoring, as I think the cylinder it already at max oversize. Then the bottom end will come apart and I'll see about what needs to be done there,.
 
A couple more things to consider while working on the motor.

Running the engine with no 2T oil for five mins may have ruined the right crank seal. It depends on that oil to lube it. It should be replaced or at least keep it in mind when attempting to start the motor next time. You'll know its damaged by the lean condition and can add to difficulty in starting.

The smoke you said was coming out of the exhaust may be from the seal on the left side of the crank. These seals are notorious for allowing gearbox oil into the crank case whether its from a damaged seal or a damaged stub shaft. Over the years I've had to replace damaged stub shafts or install a Speedi-Sleeve during a rebuild in order insure theres no excessive smoking and carbon accumulation in the combustion chamber. Even a new rebuilt motor will smoke when this seal is new but the shaft is damaged from wear or moisture trapped in the crank case for an extended amount of time.
 
Thanks everyone for your help and advice here. Could I ask one more favour. The only way forward is through, and I'll so it myself this time so I know the thing I own better. Does anyone have a good photo of two of what 'good' looks like ? I'm trying to find reference photos of that cylinder and particularly the ports. The video in this thread talks around chamfered edges, and I want to see how far our my own is. The rebore that was done should only have taken it out by 0.05 so that would not turn a 0.5mm chamfed edge into a razor :)
 
DeathFromAbove said:
I think you'll need a new cylinder. What are the measurements? Who did this work?
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Ewww. I'm going to rehone to see what it looks like at the end of that, and then have a look at doing the chamferring on the ports. If I get that wrong, then I'll need a new cyclinder anyway.

It has the 1.5 oversize piston in currently. Last time I looked that was the biggest. I'm guessing I can't have this one re-sleeved ?

It was a local machine shop. Admittedly they work on much larger engines usually, and they don't know these bikes at all. The ask was to take the cylinder out to fit the new oversize piston which should not have seen them make a significant difference to the cylinder ports, I'd have thought.
 
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