lambretta 290 rotax

Anything related to Lambretta or Vespa Scooters fitted with LC, Motorcycle and/or Auto engines! Ask technical questions, post helpful information, pictures, or just read and learn.
holty
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Re: lambretta 290 rotax

Postby holty » Fri May 05, 2017 11:00 pm

hi daz, simple way to think of is a one way valve, its self governing, in other words when the engine crankcase creates a vacumn the valve opens allowing fuel and air mixture in, when a positive crankcase pressure is created the valve closes so ingested mixture cannot escape,its then sent to the transfer ports and then combusted above the piston, allows inlet timing to be much longer duration than that of a normal piston port engine, a more modern inlet system introduced in motorcycles mainly during the 1970s/80s and is standard fitment on most modern 2 strokes these days, helps to reduce fuel spitback out of the carb as well.
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dazblakey
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Re: lambretta 290 rotax

Postby dazblakey » Sat May 06, 2017 7:35 am

Cheers Holty
Read all this thread tonight really interesting great explanations keep it up mate and the others guys

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holty
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Joined: Wed Jul 15, 2015 11:52 pm
ebay user ID: amholt123
Main scooter: lambretta gp
Location: east yorkshire
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Re: lambretta 290 rotax

Postby holty » Sat May 13, 2017 9:47 pm

ive done an all day session in the garage working on my case, heres a few pics, first is the crankcase opened up big engough for the crank webs, next shows the circlip to retain the drive side main bearing, and you can see the trench ive cut to give the big end some clearance, and then a view looking into the inlet, some more shaping here and there, but happy with the progress.
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