2100 CD Build

[farminkarman]

So, with the shorter skirt on the 395 piston in addition to the skim off the base (.075 is more than a skim haha), the intake landed right in the ballpark. Nice!

I'll be honest, I was a little disappointed with the intake being over 80, but I can work with it.

 

[farminkarman]

The lower transfer openings need to grow quite a bit to match the windows on the 395 piston. The black marks represent the outer edges of the piston windows.

 

[srcarr52]

The lower transfer openings need to grow quite a bit to match the windows on the 395 piston. The black marks represent the outer edges of the piston windows.View attachment 431277

I used to push them all they way out but now I only do it on the ex side where the transfers have a straight shot to the ex side corner of the upper. Pushing the transfer lower towards the intake side just makes for more of a corner that everything will have to do behind the bridge.

 

[farminkarman]

I used to push them all they way out but now I only do it on the ex side where the transfers have a straight shot to the ex side corner of the upper. Pushing the transfer lower towards the intake side just makes for more of a corner that everything will have to do behind the bridge.

I follow ya. Makes sense

 

[Al Smith]

Carburetor is "trying" to say the least. .

That's an understatement .HS Tilley with a rattle ball .Could be a lot of things .The ball could be stuck dumping too much fuel .The secondary passages under the welch plugs could be fouled.Some time this week if I get in the mood I'll attact that miserable SOB again .Having said that that saw is the fastest one I own---when it decides to start .

 

[farminkarman]

One lower mostly done. Time to call it quits and go take care of a headache.

 

[Sloughfoot]

I'll be honest, I was a little disappointed with the intake being over 80, but I can work with it.

Would cutting less from the base have landed it under 80? I'm dyslexic when it comes to the ups and downs of timing numbers.

 

[farminkarman]

Would cutting less from the base have landed it under 80? I'm dyslexic when it comes to the ups and downs of timing numbers.

Yeah, that is correct. With the piston I used, I would have had to leave the squish band stock to get the 78 I would have preferred. At the end of the day, I would rather have a meaningful squish band than not. I could always add epoxy to the intake floor, but I think 81 will run pretty good.

 

[Sloughfoot]

That's an understatement .HS Tilley with a rattle ball .Could be a lot of things .The ball could be stuck dumping too much fuel .The secondary passages under the welch plugs could be fouled.Some time this week if I get in the mood I'll attact that miserable SOB again .Having said that that saw is the fastest one I own---when it decides to start .

This one ran fine for a tank or so, after a leaking warped plate was replaced. Then it didn't.

 

[Sloughfoot]

Yeah, that is correct. With the piston I used, I would have had to leave the squish band stock to get the 78 I would have preferred. At the end of the day, I would rather have a meaningful squish band than not. I could always add epoxy to the intake floor, but I think 81 will run pretty good.

I see, keeping under 80 would have made the combustion chamber a little roomy.

 

[farminkarman]

I see, keeping under 80 would have made the combustion chamber a little roomy.

The 0.020" I took out of the chamber will decrease combustion chamber size a little bit, but will also make the combustion chamber more efficient. On two strokes, the "squish" is important to provide a final mixing of the charge as it starts to burn. If you don't have an effective squish, it is hard to get the mixture to burn quickly and a lot of charge gets wasted out the exhaust. If you want a saw to make torque at a higher rpm, you need to do things to help the saw extract as much energy from the charge as possible before the exhaust port opens. As with anything, there is a point of diminishing return. The same goes for the intake. More intake duration allows the saw to pull more fuel into the crankcase up to a point. At the same time, increasing intake duration reduces the amount of charge that the piston is going to push up the transfers into the cylinder (at least on a piston ported 2-stroke).

 

[Woodwackr]

The 0.020" I took out of the chamber will decrease combustion chamber size a little bit, but will also make the combustion chamber more efficient. On two strokes, the "squish" is important to provide a final mixing of the charge as it starts to burn. If you don't have an effective squish, it is hard to get the mixture to burn quickly and a lot of charge gets wasted out the exhaust. If you want a saw to make torque at a higher rpm, you need to do things to help the saw extract as much energy from the charge as possible before the exhaust port opens. As with anything, there is a point of diminishing return. The same goes for the intake. More intake duration allows the saw to pull more fuel into the crankcase up to a point. At the same time, increasing intake duration reduces the amount of charge that the piston is going to push up the transfers into the cylinder (at least on a piston ported 2-stroke).

Will you need a kick start for this thing?

 

[farminkarman]

Will you need a kick start for this thing?

I imagine it’s going to be stout, but remember, I had to cut that much from the base because of using the shorter 395xp piston.

 

[drf256]

Great build Gregg. TY.

I like the uppers and tunnels.

I’ve got a “crate” of these. I gotta get to them, and your build is a big help.

I wonder if the jugs could be drilled for a decomp.

 

[Al Smith]

I don't see why a decomp could not be installed .In my case it's about the only option left .In that avatar picture I weighed 220 ponds and was strong as an ox but that was 15 years ago .I'm a skinny 180 pounds now and I just don't have it anymore to pull over that much compression .I've got some big old Paul Bunyan saws .Mac 125's the big 2100 Homelite, a Stihl 084 but they all have decomps and are all easy to roll over..The two Partner P-100's are the same bore and stroke as the 2100 Husky but they are at 160 PSI not the 180 of the Husky arm breaker .However those two only have about 1 hour of run time since a complete rebuild so the comp will raise as the rings seat in .

 

[srcarr52]

Great build Gregg. TY.

I like the uppers and tunnels.

I’ve got a “crate” of these. I gotta get to them, and your build is a big help.

I wonder if the jugs could be drilled for a decomp.

I have a bunch squirreled away too.

 

[farminkarman]

I have a bunch squirreled away too.

if you ever want to part with one, let me know.

 

[farminkarman]

Other lower done minus chamfering the edges of the plating

 

[farminkarman]

On the piston I just removed the casting flash from the windows and did some minor blending. Also removed the sharp ridges from the bottom of the bridge.

 

[Sawking]

ThIf you magnify and look at the piston pic that @hacskaroly posted Greg. His ring orientation is the same as yours and looks to have run awhile. Not saying it's right or wrong. Just saying

Pin location on OEM 2100 pistons as in pic is correct.Not sure on aftermarket pistons.Install piston W/O rings on and slide cylinder on, look in ex.port and pins are not visible. Also as per Husqvarna engine designers piston wrist connector is off set and will premature wear.I wondered same thing when these were introduced early 80’s.
WestCoastMuscleSaws
TheChainSawGuy
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