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Not back-pressure persee. It does make a more dense A/F mixture available @ the carburetor inlet. Kind of like increasing atmospheric pressure ever so slightly. The biggest advantage is not allowing fuel to be sprayed to the atmosphere were it is wasted.
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I think that's what the rotary valve in my Rotax does - shuts the inlet from the carby before the crankcase pressure spews some of the A/F goodness back into the atmosphere. But that's 2-stroke tech. Prolly not applicable here...
BJ
BJ
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
YS F 120
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Richard, you're talking about a set up like this, my MAICO 125 had a fiber disc that served as a rotary valve, fed by a 26mm Bing carb. Note air intake tube going up to air cleaner chamber. You are correct about the YS, the rotary valve traps two intake charges in the crankcase to create the super charge effect, it's only about 35% efficient.
The MAICO had two stingers inside the muffler cap, one long and one short, that gave it a power band that went from 4,000 rpm to 8,200 rpm, whereas the Japanese competitors of the time had a spike at about 10,000 rpm. as the joke went at the time, you had to row your way around the MotoX track on the Japanese bikes using the gear shift lever. They got that right after while though.
The MAICO had two stingers inside the muffler cap, one long and one short, that gave it a power band that went from 4,000 rpm to 8,200 rpm, whereas the Japanese competitors of the time had a spike at about 10,000 rpm. as the joke went at the time, you had to row your way around the MotoX track on the Japanese bikes using the gear shift lever. They got that right after while though.
Last edited by Hobbsy; 02-24-2015 at 06:33 AM.
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Except those with reed valves, rear intake two strokes also have a rotary disc valve driven by a pin on the crank for intake control. My OS .80 has this. That engine could be reversed by relocating the crank pin to an alternate hole in the disc. My Yamaha MC from the 70's also had a rotary intake valve. I think YS engines have a rotary valve intake that enables the "supercharging" effect?
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
YS F 120
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
YS F 120
For whomever it was that was looking for Saito flex pipes, try this site: http://www.freelandacres.com/saito-180.html I found it looking for 180 parts, but they may have other size parts. Good luck
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
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Yah - the rotary valve controls the intake timing... but.. when the boys open it out too much, she'll blow back through the carby. Same thing happens if you open the inlet port timing on conventional 2 strokes (old Villiers/Amyl did that).
The Rotax 256 (inline twin) is way peaky - nothing under about 10,000rpm, and all done by 12,500 or thereabouts. Plenty of gear-slamin
BJ
The Rotax 256 (inline twin) is way peaky - nothing under about 10,000rpm, and all done by 12,500 or thereabouts. Plenty of gear-slamin
BJ
Bj i own up as well.Had a 93 gear driven cam version of the 750.The first 800"s were gear cam driven as well,sweet sound.These new lifestyle harley riders can make you wonder.It's either a plain black open face helmet and at every stop you spend ten minutes picking the bugs out of your face or,a plain black open face helmet with a strap on bottom half which can be a skull(favoured by many)or something like a gorilla mask.It rminds me of the old 'punch and judy' puppet shows.
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Still, good to hear Horizon had some and you got one.
Yah - the rotary valve controls the intake timing... but.. when the boys open it out too much, she'll blow back through the carby. Same thing happens if you open the inlet port timing on conventional 2 strokes (old Villiers/Amyl did that).
The Rotax 256 (inline twin) is way peaky - nothing under about 10,000rpm, and all done by 12,500 or thereabouts. Plenty of gear-slamin
BJ
The Rotax 256 (inline twin) is way peaky - nothing under about 10,000rpm, and all done by 12,500 or thereabouts. Plenty of gear-slamin
BJ
Sincerely, Richard
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
I've been looking for a saito thread. I'll have to read more of this a little later. I have a 180 that needs a good cleaning after being benched for two years. Can't wait to get it in one of my top flite war birds.
Richard i bought a second hand bsa 350 single that the previous owner had fitted and tuned back in 69,and my mate who dinked me there to pick up my new 350 would follow me back on his 500 matchy to my place.In short i had a big carby fire when i backed off on the way home so i was a bit late.
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Pete, I went back to using Corrosion X to preserve and to rescue gummed up engines.
This was the very first motorcycle that owned myself, a 1952 Indian Brave that was possibly a re-badged Royal Enfield. It was a 250cc flat head, three speed
This was the very first motorcycle that owned myself, a 1952 Indian Brave that was possibly a re-badged Royal Enfield. It was a 250cc flat head, three speed
Last edited by Hobbsy; 03-01-2015 at 04:45 AM.
Sincerely, Richard
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