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5 hours ago, jaguar57 said:

otherwise known as a boost bottle, invented by Yamaha. read about them: http://www.dragonfly75.com/moto/YEIS.html

yes they do work on two strokes with reed valve and expansion chamber when designed properly.

An aftermarket "Roost Boost" from the mid-1980's isn't the same,

it was a electrical gizmo that plugged into the bike's electrical system

to somehow magically improve the ignition.

pics: https://www.google.ca/search?q=roost+boost&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi0hYCBh5DTAhVE22MKHW3MCnYQ_AUICCgB&biw=1416&bih=754

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Roost factory made the Roost boost bottle first, I believe answer bought them out.  I think the ignition one is a Roost Boost Plus. 

 

top20end201_zpspf0dk7qo.jpg

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3 hours ago, mlatour said:

An aftermarket "Roost Boost" from the mid-1980's isn't the same,

it was a electrical gizmo that plugged into the bike's electrical system

to somehow magically improve the ignition.

pics: https://www.google.ca/search?q=roost+boost&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi0hYCBh5DTAhVE22MKHW3MCnYQ_AUICCgB&biw=1416&bih=754

The electric one is the one I remember.  Supposed to make your spark hotter or something.  Gimmick, sort of like those Splitfire spark plugs that were hot a few years back.

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I experimented with different capacitors across the spark plug like these gimicks used and the spark system was too weak for them and so the capacitance had to be so small that it made no difference.

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8 hours ago, jaguar57 said:

otherwise known as a boost bottle, invented by Yamaha. read about them: http://www.dragonfly75.com/moto/YEIS.html

yes they do work on two strokes with reed valve and expansion chamber when designed properly.

No,  different product all together.  A "Boost" bottle is not the same as a "Roost Boost".   I stil have a new "roost boost" in the box.  We tried them when we were given a couple of them sometime around 85.  The ones we tried simply got your engine to maximum advance earlier in the rev range.  A man named CH Wheat showed us all how to do that with yamaha ignitions back in 1973 on the 500cc two stroke single,   SC500 I think it was called.  it served a purpose when that purpose was needed.   Wheat's way was a condenser and a toggle switch wired into existing wiring.   You used the toggle switch to start the rig so you weren't trying to start it advanced enough to make it run backwords or break the kickstart if it "kicked" back. 

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