cb915 (you poor stupid crazy son of a bitch engine build)

yeah, it's fun when you're too stubborn or stupid to listen to people who say you can't use x tool to do y operation... I've been told by every machine shop I used to take cylinders to that it was absolutely impossible to use a bridgeport to do this kind of work... albeit, it took me a crapton load of time, but it's possible ;D

Right, impossible for them to do it, bill it, and make any money. Your time is free to you so more power to you. You wouldn't do it this way to make money, but you have the tools and are doing it and that is cool. Can't wait for the startup vid!

any recommendations on studs? the heavy duty ones aren't that all that pricey, is this thing going to leak like a sieve if I use the stockers?

also, anyone know the tolerances for taper and out of round after honing? I'm planning on leaving .0020" because I anticipate this engine is going to run hot, but how far out of round and tapered can it be without causing problems (I'm pretty new to honing and probably won't do as good a job as I'd like)

I'm pretty sure no one here has done more boring and honing than me?
You have a real hone and not 3 legged glaze buster so shouldn't have any problems
Get as close as you can to size, taper shouldn't be more than 0.0003", better to be slightly tight at top as it will get hotter so expand more but it isn't difficult to get 0.0001"
I think I've mentioned (several times : ) I used to teach 'machine shop' at MMI so know with a bit of care anyone can hone a cylinder to within one ten-thousandth of an inch round/taper, rushing and not 'feeling' what hone is doing is when you get problems
Don't have hone too tight in bore, it will cut more on initial start up which will make a round bore 'out of round'
Never get end of hone more than 3/4"~1" out of cylinder to correct taper
If you find a tight spot, put honing stones there with the guides on the loose area, that way only the 'tops' get knocked off

Do you have any old rusty cylinders to practice on?

Cool, I tried some practice boring and honing on my 378 block, I got it less than .0003 for taper, just barely, round was fine, I tried diamond filing the stones to correct taper as I saw it forming, seemed to do the trick... Maybe the next block I do I can hold .0001

turn the block around and hone from the other direction.
Once you get the stones 'square' don't let anyone touch them, they should last for quite a while, usually 100 bores or more (with 320~400 grit)
With practice you can get real good cross hatch and not bother with 'bottle brush' (beter to use hone rather than platea finish when using chrome faced rings, unless you want 5,000 mile break in )

how do you fix it going wide in the middle?

Shorter stroke so only ends of stones touch
Always set at the tightest point
Your using a variable speed drill motor?
I bought a Harbor Freight high torque max 400rpm variable speed drill specifically for honing
It is possible to use hone almost half way out of cylinder to correct tight ends but it can mess up the stones if you stay in one place too long
You'll have to remind me which hone you have, I'm really used to Sunnen and AMMCO, most 'proper' hones are base on these

it's a lisle 16000, it was free in a big lot of old tools I was given to save them from the estate auction or worse... I'll look into the drill, i'm using a regular dewalt, it's really tough to keep the speed constant

OK just looked up 16000, looks a bit like the small AMMCO I have, the 15000 is almost identical to large Sunnen
They don't like being turned much over 400 rpm, slower just takes a bit longer
As your doing the cylinders for yourself the time isn't as important as getting it right
Does your bore gauge measure in ten thousandths on in or thousandths of inch? (or metric?)
Doesn't really matter, set it to the exact size you want with micrometer then hone down to zero.
I know I've taken pictures of setting and use, just not sure if I uploaded all of them to Photobucket
You can probably have one stone 'reversed' if they get tapered so high ends are opposite each other?
Make sure you know roughly where the tight spot on cylinder is and have the stones in that position when adjusting, I've seen 'perfect' cylinders get messed up by having stones in 12/6 or 3/9 positions then adjusting too tight, when they hit the tight spot cylinder comes loose or (didn't happen in any of my classes ;D ) one guy managed to break his wrist when drill kept turning and hone stopped (Don got in real trouble over that one )
PM me and I'll send e-mail (if you don't already have it or can't find it)
Easier to send pics or video that way, online tutorial 8)

I use a foam pad to support micrometer, it's much easier to set bore gauge head on foam and rock it around to make sure setting is accurate (much easier than having micrometer in a mike stand and holding bore gauge steady)


I also find it much easier to measure the largest part of piston (usually 8~10mm from bottom of skirt) then open mic another 00015" to get clearance

When you put gauge in cylinder you'll see exactly how much too small it is, this was exact piston size

all for now,

PJ

Got the cases cleaned up, inspected stuff, threw crank bearings in to see... Looks like dome height is just about dead on for the old f pistons... This is just so right it's wrong!

Is that with or without base gasket?

without it, I think with it and the head gasket, it will come to about .040 below the combustion chamber, I doubt it will need any extra machining on the piston as long as the valves stay far enough away

Yep, you want 0.038"~0.040" squish.
I would flycut head if needed rather than thin pistons further (although above ring land isn't usually a problem as piston is real thick there)

I was always told that .040" is a minimum for squish? Many of the builds I've seen look for .020" or less when measured at the edge.

Sean, if you have the time and inclination, you can machine the combustion chambers to help. The ideal difference in angles is between 7° and 10° when measured coming away from the cylinder wall and pointing in toward the center of the chamber.

Use about 3 degrees difference on the squish band, about 8~10mm wide, the radius on piston crown will 'open' the angle further
As for the clearance, on a two stroke you can use less as there is combustion every revolution, on a four stroke combustion is every other stroke so rod has a harder life and tends to stretch further between combustion strokes (it's also why two stroke rods are lighter construction than similar capacity four stroke rods)

I'm assuming it's the exhaust stroke that is the reason on a four cycle?

Correct, gold star for you ;D

isn't the mean pressure generated in a 2 cycle less than in a 4 as well?

I gave the conrod breakage problem a though experiment and came to the conclusion that the force generated in the power stroke was many many times greater than the other forces, and that at most the tension force for the intake stroke would be 15psi*area of piston and then any acceleration and ring drag forces, so I'm assuming they break under the power stroke due to the immense pressure of combustion and the angle the rod is at through most of the stroke