| sammyg2 |
05-01-2012 02:12 PM |
Quote:
Originally Posted by RoadRaceJosh
(Post 6722972)
An intake tract leak on a 4-stroke will cause lean running, but a bottom end vacuum leak? That's 2-stroke territory because there is little to no vacuum in most all 4-stroke crankcases as most 4-strokes have the crankcase open to the atmosphere through the breather. Most 4-strokes use a PCV valve to prevent an excess of air flowing into the intake tract. I keep saying most because there are exceptions. Like the road draft tube on my old Studebaker.
The crankcase breather is almost always open to the atmosphere through the air box. Crankcase vapors in excess of what the PCV valve can handle flow through the breather and into the intake upstream of the throttle. There is no vacuum upstream of the throttle aside from any filter and ducting restrictions.
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Correct-a-mundo, when I first saw it I thought it was a two stroke engine, sea-do or yamahamer or such.
I didn't look close enough to see the indentations in the piston for the valves to id it as a 4 stroker.
In my OP I was referring to the bottom end leak of death on a two stroke.
A regular two stroke engine has to be sealed on the bottom end to withstand at least a 2 psig pressure test, otherwise it can suck in air on every intake stroke and lean out and sieze up.
http://forums.pelicanparts.com/uploa...1335910287.jpg
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