Stihl 084 build

[jacktheripper]

To keep things moving along some work on the sub-assembly's was in order.

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What was the purpose of going through the process to have these pistons made by Wiseco? Sure, you have a stronger piston, better flow into the lowers, wider skirt, and better weight, but if effectively it doesn’t even fit, who cares? It’s an expensive chunk of s***.

 

[Stump Shot]

What was the purpose of going through the process to have these pistons made by Wiseco? Sure, you have a stronger piston, better flow into the lowers, wider skirt, and better weight, but if effectively it doesn’t even fit, who cares? It’s an expensive chunk of s***.

Building custom stuff for racing, some work is to be expected. Expensive? Yeah, maybe. Chunk of chit? Not at all.

 

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Figured after double checking the triple check of the pistons being the same dimensionally, might as well get some squish and timing numbers to start out with. Before I put the cylinder on, I like to use a coffee filter with a touch of WD-40 on it. This ensures the cylinder is clean, even though it was washed without leaving any lint particles and such behind. This is a trick that automotive racing engine builders do and I figured if it's good enough for them it ought to be good enough for me as well. What I like about it is it leaves a light film of lube that isn't messy and allows the piston friction free movement while you work.
Setting up a digital timing "wheel" is a simple process that can be set up from within 0 to 1/10th every time the first time. With the piston at top dead center place the unit on the crankshaft as upright as possible and turn on. install a piston stop, swing up to the stop each way and take note of the number being displayed. For conversations sake, let's say it reads 30 to the right and 40 to the left. Take 40 minus 30 which equals 10. Divide 10 by 2 which equals 5. Remove the piston stop and swinging to the larger side, which was 40 to the left, and go until the unit reads exactly 5, push zero. rotate the unit and replace the piston stop to check your work. it should read the same each way left and right now. If not, repeat the process and correct your mistake. Remove the stop and you're ready to go.

 

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Got the goat a head to use the old pulley in the starter which was still a good used part. The spring pack had other ideas, starter is back to waiting again...

 

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There's parts of building saw's that's downright boring, yes I said it, not everything is exciting. And here's that part, making a new base plate and mandrel for turning the cylinder on the lathe.

 

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Now with our fixtures all made I can move ahead and do some machining on the cylinder.
One note I would make at this point is, prior to taking this step, I happen to be talking with @tree monkey one evening and thought it best to confer with him on the porting specs of this, which I do not usually do, but figured this was kind of a special case and just wanted to know my plans weren't going off the rails, he was gracious enough to respond in kind to me, and this was greatly appreciated.
I still went through my process of coming up with my own specs and while not 100% exact, very, very close to what Scott had given me. So, I forged ahead and started the whittling down process on the South Bend.

But before I can, I needed to get some longer bolts for this cylinder to do the squish band.

 

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Finished squish band.

 

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After rechecking the squish clearance, the base can then be cut.

 

[hacskaroly]

Man, that's a process, but still neat to see! Way more than I will ever get into!

 

[singinwoodwackr]

Wow

 

[jacktheripper]

Tell us about your setup for checking runout for cutting squish. What kind of indicator is that?

 

[Stump Shot]

Tell us about your setup for checking runout for cutting squish. What kind of indicator is that?

I believe it's called a coaxial indicator.

 

[DillonBuck]

Does that Klein angle finder remember zero.

The finder I have doesn’t. So if I step away for a few minutes, it forgets.

But it seems to kinda recall!

It’ll be close enough that you wont necessarily see the error, but if you check its off a couple degrees. ( Its not because I moved the saw and it’s sitting different.)

 

[EFSM]

Now with our fixtures all made I can move ahead and do some machining on the cylinder.
One note I would make at this point is, prior to taking this step, I happen to be talking with @tree monkey one evening and thought it best to confer with him on the porting specs of this, which I do not usually do, but figured this was kind of a special case and just wanted to know my plans weren't going off the rails, he was gracious enough to respond in kind to me, and this was greatly appreciated.
I still went through my process of coming up with my own specs and while not 100% exact, very, very close to what Scott had given me. So, I forged ahead and started the whittling down process on the South Bend.

But before I can, I needed to get some longer bolts for this cylinder to do the squish band.View attachment 489772View attachment 489773View attachment 489774View attachment 489775

What are you checking with the level?