Differences in 84/85 and 86/87 Spree piston and head

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Differences in 84/85 and 86/87 Spree piston and head

Post by noiseguy »

Ran into something interesting. The head design changed in '86 for the Spree. See photo: Left is '84-85 design, right is '86-87 design.

Image

Note that the later design has a raised boss for the spark plug, a wider squish zone that is evenly domed, and a much thicker material section at the back of the head.

There are also piston differences. The '84-85 pistons are dished, whereas the '86-87 pistons (and all service parts for '84-87) are domed slightly. Since they are service-interchangable, the head appears to be interchangable as well. However, if you start shaving heads this will be something to watch.

The '86-87 piston and head would appear to be the better performing combo. The head design, being evenly domed, should allow more material removal to increase compression. The earlier '84-85 design is flatter and actually has reliefs towards the circumference. These would, in my mind, negatively affect the combustion flame growth. As many members have noted, the '86 and '87 Spree are faster "out of the box," with top speeds around 35 MPH. The '84-85 models rarely seem to climb out of the 30 MPH range.

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Post by noiseguy »

More on this... some users have posted that the domed piston with the 84/85 head is the best performing combo, as it give you higher compression.

Guys with 86/87 scooters report improved performance by swapping to the earlier 84/85 head. These scooters have the domed piston stock.

Again, watch your piston to head clearance on any modification like this.
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