Sachs Red Dot or White Dot Piston?

[skipperclyde]

Does anyone know the difference between a Sachs red dot or a Sachs white dot piston for a 100cc engine?

Which on is pereferable?

thanks
phil

[gooddirt]

One or the other is for Iron barrel (White) VS the Alloy barrel A-B motors red I think.

[joe novak]

When selecting a new piston, always keep in mind the availability of rings.

[TeamSunset]

Elko manufactured the Pistons, and most likely the Cylinder/Liners too... Elko used a color coding system to match Cylinders with Pistons (for tolerance purposes) by marking the piston dome with a colored dot, and the top of it's corresponding cylinder with a color dot. I believe tolerances varied by .0004 between colors, but I could be wrong. Pistons and Cylinders did not receive individual part#s for each color code... they were simply stocked under the manufacturers part#, and you could request a certain color code when purchasing a replacement part. Color code was also marked on manufacturers packaging in most cases. Elko Pistons were used by Sachs, Kohler, Rotax and others, and they all used a similar type color coding system. Problem is after so many years, the color codes wear off of the used parts, so you can't match them anymore. How critical is this? ...people have NOT been matching color codes for years now. Here is a link to a snowmobile forum about the same subject. TG

http://www.acscc.com/forum/index.php?showtopic=3191

[gooddirt]

My main question about these Iron barrel vs alloy a-b motor pistons is ; can they be exchanged either way and run them?

[TeamSunset]

I wouldn't think so, BUT...

Here are some of the differences between the two: different Sachs part#s for both pistons & both rings, different ring coatings, different top L-ring locating pin positions on piston, different top L-ring groove locations, different bottom ring end types, and different relief grooves cut into pistons in ring areas. TG

[Ernie Phillips]

I'm pretty sure we're running an iron barrel piston in one of our alloy barrel 100's.  I recall the different ring locating pin position.   We needed an oversize piston and that is all we could find -- begger's can't be chooser's.   My logic was that as long as the ring ends didn't extend into any port openings, we'd do no serious harm.  Seems to have worked OK.  Christopher rung the guts out of that little thing for a full season + selected events ... and it still runs.

Ernie P.
Chattanooga, TN

[joe novak]

Is the wrist pin and it's location identical for both pistons designed for the cast iron cylinder and the alloy cyclinder.

[gooddirt]

Pins are the same location,  Great already race proven! The Sachs  spare parts book lists the later a-b alloy barrel pistons can run in the Iron Barrel.

[Guenther68]

Hi all,

the red dot indicates the nominal Sachs piston size

example 125 ccm standard size piston 53,93 mm
first oversize 54,43 mm and so on

The pistons with the white dot are 0,01 mm bigger.

example 125 ccm standard size piston 53,94 mm
first oversize 54,44 mm and so on.

The clearance is for all cylinders (5 and 6 speed, cast iron and alu) 0,07 mm -> 53,93 + 0,07 = 54,00 mm

The white dots have been introduced for production cost savings.
If a Sachs mechanic made the cylinder bore 0,01 mm to big, they were still good for the white dot piston. [8D]

Note that the pistons designed for the cast iron cylinder won't survive in a alu cylinder with cast iron sleeve.

quote:Originally posted by skipperclyde

Does anyone know the difference between a Sachs red dot or a Sachs white dot piston for a 100cc engine?

Which on is pereferable?

thanks
phil

Best regards
Guenther Vogt,
Hercules Club, Germany



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