Husky 455 to 460 upgrade and porting

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Ive never cared for that style transfer cover. Sure does not look how i would shape them. Very cool that you are porting one of these. I bought my dad one of these last summer during a buddies distress sale. Super clean saw i got him for i think 80 or 100 bucks. Mot as quick as his 350 with a 346 p&c and not as much grunt as his old jonny 670. Kinda fits in with his cutting needs tho. He seems to like it and fuel economy is steller. He claims it cuts konger than he wants to on a tank. I also bought him a 511ax grinder at the same distress sale. Not that he knows how to use it he now loves it.
 
After doing some more looking inside the cylinder at the lower carb intake, I can widen that port on each side by approx. .020-.030 on each side. I won't raise or lower it, my research suggested against that. Who knows maybe I'm wrong.

I'm still trying to map this cylinder, I'm pretty unsure of when you track the number.
 
After doing some more looking inside the cylinder at the lower carb intake, I can widen that port on each side by approx. .020-.030 on each side. I won't raise or lower it, my research suggested against that. Who knows maybe I'm wrong.

I'm still trying to map this cylinder, I'm pretty unsure of when you track the number.

What are you unsure of? Easiest way is to draw it on a piece of paper. Start with a vertical line on left side of paper as TDC, then Draw a line across the bottom of the paper and use a ruler to mark and identify degrees on the bottom line (easiest to use millimeters as degrees, totaling 360, so you can hash centimeters to keep from losing count comes out to 14.173 inches). Now draw a vertical line at 180 degrees (or millimeters) as BDC, and another solid vertical line at 360 degrees as TDC again. Now just transcribe your measurements from degree wheel to the paper, start from the left of paper and mark TDC to top of intake, TDC to bottom of intake, and so forth. This gives you a solid representation of all the openings in the cylinder.

You can go one step further and use your computer to shrink your degree wheel down so it is 10mm or about 3/8” larger than the ID of the cylinder. Print it out and cut it out. Now align 0/360 degrees with the CENTER line of the intake with the shrunk degree wheel sitting on top of your cyl. The degree wheel needs to be as close to centered as possible, once it is use some tape to secure it to the cyl. Once this is done use a very sharp hobby knife or razor blade to cut along the inside diameter of the cyl. Now you have a degree wheel that will drop down into the cyl and its compliment already secured to the cyl. Put a piece of doubled over scotch tape on the bottom of your degree wheel, place your scale/ruler inside the cyl and align the 0/360 with one edge of the scale, draw a line down the inside of the cyl, then drop your degree wheel to the bottom of the cyl and ensure you align your 0/360 marks. Now you can measure the width of all the ports (top and bottom as needed), then transfer all the measurements to the paper. Connect the dots and you have a complete and accurate map of your cylinder.
 
Is Husqvarna using those damned "tri-lobe" screws to hold the transfer covers?
( The screws look vaguely triangular when looking at it from the end.)
The threads in the holes, look pretty rough in this pic.
http://i.imgur.com/qIUvTaz.jpg

They're supposed to displace the metal as they are driven in.
I've run into the tri-lobes that have a black oxide finish.
Makes them reealllly grab aluminum and just galls up the holes.
Nothing to do but tap the hole for a standard screw
Then you can toss those tri-lobes into the trash with all the Phillips (cam-out) screws
 
LDL the screws are tamper proof torx on this one. they have a very coarse thread on them for sure. I have not had an issue with them yet, knock on wood.
 
I guess I should have been more yakkity about the screws.
If anyone hasn't seen or noticed these cussed things, here are a few details about them

The threads are the problem area.
They are roughly triangle shaped with rounded "corners". [image 2555]
The first few turns into the metal displaces (tears usually) the metal of the hole and, roughly, forms the threads in the hole.

Problem is, Aluminum & and magnesium act sort of "gummy".
So the threads end up mostly tearing out of the part and as a result are weak.
The shreds of metal tend to foul in the relief areas of the screw and sort of hold it in place.
Problem with that is the shreds,(being soft metal), tend to be compacted by vibrations.
So the screws slowly get lose.
Has anyone found any lose, bottom pan screws, on clamshell saws??
Now you know -one- part of the reason why.
Weak, half torn out, threads are most of the rest of the problem.

Secondary problem is IF the screws are oxide finish.
Oxide finishes are horrible for a sliding across another part (abrasive actually).
(remember that grinding wheels are typicaly made from oxides).
The tri-lobe screw thread is designed (in theory) to have the thread slide across the metal as it displaces.
Except the oxide finish just galls and tears out most of the soft metal.

If my photos aren't too terrible, you might can see where the screw pushes the first few turns (outlined in blue) [image 2558]

Then the load sits on the three lobes up the length of the screw (outlined in red) [image 2558 again.]

As you might suspect, this is another part of why these screws work lose.
We're putting all of the load on a very, very, small region of the screw threads
and when you combine that with the ragged threads in the work piece or part,
you can see why we find lose pans, covers, etc.

This is why I wanted to know if Tri-Lobe screws were used in the transfer covers.
Combine 'em with any gasket issue and we're looking at a good chance for a leak.

A "bright finish" cadmium(?)or something else shiny would help, a little,
with the tearing of the hole.
But.... We still have the problem of all of the load being borne by the small area that the lobes present.

Here are a couple of links to vendors of them.
Their drawings show it better than I can photograph it.
http://www.abs-metal.com.tw/tapping-screws-series/tri-lobe-thread-pt-thread-screws
https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/ae1403bdc11c201c460fde20113d5446/large.JPG

But I'll still post a couple of quick snaps of a tri-lobe from my hoardings.
I might try to set better lighting and see if I can get better pics later.

Now do y'all see why I say to toss them out and re-tap the holes for a proper screw?
 

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I bought three 460's and they have served me well with in the last six years. They are only $500 including shipping each how could anyone spend much time on them and have it be worth it? I have also built 100's of 2 stroke engines to peak performance. Mostly snowmobiles and dirt bikes and they all require many hours of fine tuning in the porting. For most part it takes plenty of experience with a flow bench to get it right and then run the thing to see where it is not just right. Is it really worth it to have a hot rod saw when you are just out in nature wanting to get a tree laying down so one can cut it up to take to your yard? Not like many I for most part can not modify saws. I work with the USDA in hazardous places so if I am caught with a non stock saw it could mean many problems for me or possible jail. I often when putting rings or something in a saw will just clean up the ports and clean up jagged edges , but my saws for most part do not need it. Then my 460's are just for small work, but they can go through a 30'' log too. Thanks
 
Met that is a great answer and explanation. Then you are really missing the boat on exhaust. Any ported 2 stroker needs exhaust work big time. A larger muffler box that allows some flow instead of having to be chopped up with baffles will have a big improvement. If you went into tuned exhaust you could triple HP, but for sure with a thought out design HP will climb. Tuned exhaust is not very realistic though. Thanks
 
Te, its kind of like dodge, they put a cummins in the truck and throw 6 emissions control devices on. A 6bT should last a million miles, but they dont because they eat their own crap, breath in hot nasty air, run on bad fuel, and breath through a straw.

With this husky, its the same stuff to a degree, I am just fixing what they did not get right.

Warranty on a saw is 1 year, right, they should last 5 years pretty easy.

I have a Mac 32cc, it lived a rough life prior to me acquiring it. I did a couple mods, and that sucker runs now.
 
I am sure that you have unspeakable courage. I worked on many many 750CC triples getting the porting perfectly matched mostly. I would not have a clue what to do to 32CC engine. I would not be able to find the piston. However did work on a few 250CC triples which are pretty small. Come to think I also messed with many 80CC sewing machines. The trick was to get them to peak before 22,000 R's hit causing unspeakable damage. BTW at least for a few years did build a few KTM 550 and CR 500's which are twice as big as the 750 CC triples. As you say it can be fun as long as nothing goes wrong. Thanks
 
Very cool old home depot rental saw? It does look used but in decent shape tho. Nice score.... Did you get a good deal? Tge 6400 i ran and 7910 i ran the dame dayvran a 24 inch full comp bout neck and neck. I didnt notice enough difference at thst bar length to justify the swap. I suppose if you intent on longer then maybe 28inch the swap may be worth it. I think the oilers get stingy beyond that length anyways. Nice saw are you still going to finish modding this 455?
 

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