Three tech questions

[400exrules]

I think ive got these right but i have some doubt, i just want to make sure i understand it right.

1.)A stroker just has a longer crank rod right?

2.)When your bore a cylinder, it gets wider (bigger round), increasing volume?

3.)When you hone a cylinder, you take a thin layer off to remove any worn areas to start from a clean slate?

[ZeroLogic]

i guess i will take a stab at it

im not sure but strokers is a longer crank and boring out the sleeve to .80 and a new pistion but im probely worng with that so dont take my word for it

when you bore a cylinder it dose get wider but not taller

when you hone a cylinder you make tiny little scratches on the cylinder they hold oil so the rings has some lube when it goes up and down

[400exrules]

Originally posted by ZeroLogic

when you hone a cylinder you make tiny little scratches on the cylinder they hold oil so the rings has some lube when it goes up and down

this is not neccessary with a stock piston correct?

i might be puttin in JE piston sometime in the future and everyone recommends to get the cyclinder honed.

When your bore your cyclinder, say to a 416, do you need bigger valves, or to just raise the lift since their is more space and more mixture can fit in their?

[wilkin250r]

Originally posted by 400exrules
I think ive got these right but i have some doubt, i just want to make sure i understand it right.

1.)A stroker just has a longer crank rod right?

2.)When your bore a cylinder, it gets wider (bigger round), increasing volume?

3.)When you hone a cylinder, you take a thin layer off to remove any worn areas to start from a clean slate?

1) Wrong. Think about what determines the length of the stroke. It is the distance from the center of the crank to the rod. A stroker crank actually moves the rod further out, creating a longer stroke. It's a process that requires very precise machining. It can accompany a longer rod, or a shorter rod, depending on the needs.

2) correct

3) Honing a cylinder involves cutting little scratches and grooves into the cylinder wall. Yes, it does take off some material, but very little, it's not enough to remove worn areas or provide a clean slate. What it DOES do is provide a rough surface that the rings grind and file against. The rings and cylinder walls grind against each other, smoothing each other out and removing imperfections. This ensures the rings seat evenly and seal very well against the cylinder walls.

[400exrules]

Originally posted by wilkin250r
1) Wrong. Think about what determines the length of the stroke. It is the distance from the center of the crank to the rod. A stroker crank actually moves the rod further out, creating a longer stroke. It's a process that requires very precise machining. It can accompany a longer rod, or a shorter rod, depending on the needs.

so.....the crank rod doesnt necessarily change, its just the spinning part thats on the crank, is lengthened from the crank to the rod bearing, so the piston moves farther up and down? Wont the piston get to a point where it could hit the valves?
i probably got it all wrong, but thats how im comprehending it:confused:

this might help explain if im wrong http://auto.howstuffworks.com/engine1.htm

[bwamos]

Originally posted by 400exrules
so.....the crank rod doesnt necessarily change, its just the spinning part thats on the crank, is lengthened from the crank to the rod bearing, so the piston moves farther up and down? Wont the piston get to a point where it could hit the valves?
i probably got it all wrong, but thats how im comprehending it:confused:

this might help explain if im wrong http://auto.howstuffworks.com/engine1.htm

You are correct, and that's exactly why you change the rod length.

The rod will almost always change.

If it's stroked the piston will go further up and down. If you have a stock cylinder w/o any spacers, this requires that you use a shorter rod, unless you want the piston to hit the head. ;) You can use a spacer between the jug and the lower case to move the cylinder up so you can use a stock length rod or even a longer rod. (Note: sometimes the piston can be made to make up the stroke difference by moving the piston to rod connection further up on the piston so a rod change isnt needed, depending on the quad and stock rod connection location on the piston.)

Clear as mud? lol

[wilkin250r]

Originally posted by 400exrules
Wont the piston get to a point where it could hit the valves?
i probably got it all wrong, but thats how im comprehending it:confused:


You don't have it wrong, you understand it perfectly. This is why stroking a crank is rather complex.

Now, picture the scenario exactly as you describe. Imagine you move the rod 2mm out, which should cause the piston to go UP 2mm, right? How do you keep the piston from hitting the head?

Well, you could use a rod that is 2mm shorter, this would lower the piston back to it's original height. But remember, if the piston goes UP 2mm further, it also goes DOWN 2mm further. If the rod is TOO short, the piston could hit the crank at Bottom Dead Center.

You could put the rod 2mm deeper into the piston, decreasing the distance from pin to crown. However, some pistons don't have enough room to allow that. Also, you could run into the same scenario as #1, with the piston skirt hitting the crank at BDC. In either case, it requires a custom piston.

You could space the cylinder upwards by 2mm. However, you need to make sure the piston doesn't pull out of the sleeve at BDC, and you may not have enough slack in your cam chain, and require a longer one.

On a 2-stroke, you don't have a cam chain to worry about, but you DO have port timing, which will change with a change in stroke.

Now, the particular method used depends on the current engine design, whether or not you have room for a shorter rod, or relocating the wrist pin, or a spacer plate for a cylinder.