Scooterotica

Diablo wrote:Also good way to reduce primary compression.

He said Jehovah !!! Stone him!!

Slight thread drift while we wait for an exhaust so we can see a dyno chart.
Since the interview in Scootering when C E stated that LC was the way to go there's been snippets about how far C E had gone to increase the volume of the primary compression chamber.

Is this effectively what a boost bottle does ??

yes a boost bottle does do that in a way for sure

and its maybe no coincidence that the use of boost bottles arose exactly at the same time that reed blocks (small ones incidently)were being used together with ever better expansion chambers

A boost bottle works off the inlet manifold and in short returns some of the fuel back down the inlet on the next cycle at the same ratio, without one the fuel will reach the needle and return at a richer ratio. The boost bottle won't make a difference to crank case volume (pressure) .

well of course it does ..if the volume of the boost bottle capacity is say 20/30 cc s then how can it not affect PCR ?

early type Reedvalve motors such as yamahas etc were developed from earlier piston port motors of typically HPC ..
and as they were developed using initially quite small reed blocks ,boost bottles were employed for a few years ...but were then disgarded as bigger reed blocks ,better expansion chambers etc came on ...who uses boost bottles now ..no one really cos they dont need to

Because a boost bottle works with caburation, all 2strokes send some fuel back to the carb at a certain part of the cycle, wot the bottle does is let the fuel return but with the same ratio, with out one it is returned at a richer ratio, effecting performance, this will happen anyway with or without a boost bottle, so has no effect on the crank case volume.

boost bottles worked on the principal that once the piston descended on the down stroke and so shut off the reeds ..the extra was forced into the boost bottle extra volumne ...and tempararilly stored there for the next induction cycle ...were they not ?
actually i think that we are getting to loggerheads on this due to the two different types of boost bottle systems employed ...
the type that i,m refering to is the boost bottle fixed and fed from between the reeds and piston ...whilst i assume that you mean the so called boost bottles fixed between the reed block and carb ?

The fuel that is captured in the bottle isn't a extra volume of fuel, it stores the fuel that would have reached the needle and become richer before being sent back down the inlet and instead it's sent back at the same ratio. Adding area to the crank case will increase volume.