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 The previous version was outdated and no longer supported.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

250/390/430 connecting rod question?

Joe Chod said:
Thank you Brian and Gary. I was staying quiet on this.
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Anytime you have information good or bad it's welcome. No need to sit quiet. It's ok sharing knowledge and experience is a good thing.

Ill build it now more mild than going full animal on the porting.

My 390cr had a base gasket leak it wasn't bad but she ran awesome. After the 390 was refreshed it calmed down a little. I enjoyed the wild side of it.
 
Just my luck I have the 390 and 430 cranks sitting here and the batteries are dead in my digital caliper. I need to dust off the mic's. Ok I am looking to use the 390 porkchops(counter weights) with the newer 83 case crank shafts so the 71mm stroke 390 can be installed in the 83 430 case. There is enough meat on the 420 cylinder I have to match the transfer ports. Plus the options are a internal rotor or the smaller motoplat external flywheel. With removing the larger 390 external flywheel in probably losing some bottom end torque. So she's going to zip right to the mid and upper range quicker. Rev quicker. But you guys are right the smaller external flywheel maybe the one to use.
The internal flywheel might be too much hit when it's wicked.

I'm going to need your help, advice and suggestions. Primary ratio, tranny gears in the future.

It's never been done on the newer tranny/case? I have a completely different motor that's built from parts. I'm not touching my original motors. No original bikes will be touched in this process.
 
With the 390 crank in the newer case you can build the 300 The stroke Andy used with the 250 cylinder may have been 71mm at one time early but lastI read was 72mm as he made special crank cheeks to accomplish that. Also the same stroke as the KTM 300.
 
The 390/71mm stroke crank with the 420 cylinder should workout. The 420 head is machined for the older Suzuki compression release. I have a brand new compression release. This is the larger spark plug hole threaded compression release with the cable and lever. I should be able to start it.
 
Of course it will work, the the 390/420 are the same engine, but I dont want a 420, I already have a 430, what I want is a 300ish.
 
I think I hit a glitch. I'm waiting for my new digital caliper batteries but I quick guess see looks like the 390 flywheels mic 17.50mm guesstimate. The 83 counterweights measure 20.00mm. If I install the 58mm crank pin I'm going to have some extra space in the rod area. I didn't mic the width of the lower rod journal yet. But I could possibly get the right size crank pin thrust washers. With a little thinking I guess I can be done just a few extra rivers to cross.
 
The equal bore and stroke of 72x72 or similar is suppose to be the best performing combination.

The Chevy small blocks 4" bore x 4" stroke.
 
Not a big square motor believer.....stroke gives you resistance (friction) and big bore gives you less tolerance to detonation.....just saying a compromise in middle means best is shallow argument
 
All modern 250 two strokes have adopted the under square bore and stroke of 66x72 which is very close to Maico 250s 66x70. Almost every other 250 in the 70s and 80s, just like the Husky, was the other way around with an over square setup. I think porting has more to do with it than bore/stroke layout.
 
I think it's weird but the engine seems to respond better the more or closer to being square.

The port timing plays a big factor too. Port timing is equal to the duration of how long the valves stay open on a four stroke. Duration is the amount of degrees on the camshaft. Port timing is like opening the intake or exhaust sooner on the 2t. Now it's also lengthening of the port. The exhaust gases leave the cylinder sooner if we raise the exhaust port. As it leaves the cylinder sooner it also pulls in the fresh gas from the crankcase as the piston forces it through the transfer ports. I change the port timing on the intake openings too. The ignition timing also plays a role in this too. It has to be spot on.
 
With a 71mm stroke, you would get 69.5mm=269cc, 70.5mm=277cc, 71.5mm=285cc. IF I tried to build something like this I would go 71.5mm and have the cylinder nicasil plated at that size.
 
I am sure that Andy's configuration was final at 72mm x 72mm. He had the longer sleeves made in aluminum, bored, and nikasil plated. I found only recently that 72 x 72 is the same as the current KTM 300
 
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