Pinch What??

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Old 02-27-2011, 11:45 AM
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Default Pinch What??

I was just curious to see how many people use the pinch test to fine tune the low end.
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Old 02-27-2011, 11:55 AM
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I never do it to my own motors as I never get them that far out of whack. I do sometimes do it when trying to figure out what is wrong with someone else whack out, head scratching, tuning nightmare
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Old 02-27-2011, 01:03 PM
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If you're not used to tuning an engine, the pinch
test can help you get a ballpark setting on the low-
speed needle. Then you should fine tune from there.
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Old 02-27-2011, 02:06 PM
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always
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Old 02-27-2011, 02:24 PM
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I haven't done the pinch test to tune the low end. Just over heard some local racers. So I was just curious. I got a B5, and I'm doing the works method.
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Old 02-27-2011, 05:44 PM
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whats the pinch test?
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Old 02-27-2011, 09:56 PM
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Originally Posted by dburt86 View Post
whats the pinch test?
the pinch test is where you pinch the fuel line near the carb an if ur engine cuts off around 4 seconds or so the ur low speed needle is set just bout right. If ur motor cuts off in longer or shorter than 4 seconds then u still have a little tuning to do with LSN
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Old 02-27-2011, 10:00 PM
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I always do it. I think this is a good step for newbie tuners like my self. Gets you in your range so you have decent starting point.
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Old 02-28-2011, 03:22 AM
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wow, im gonna give it a shot
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Old 02-28-2011, 05:50 AM
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When you pinch the line, you should count around 5 seconds. The motor should die cleanly without the revs rising much.

If the motor carries on longer and raises revs alot before dying, then the motor is too rich and you need to lean the LSN.

If the motor dies before 4-5 seconds then it is too lean and you need to richen the LSN.

Don't forget though that any changes to the HSN will ultimately effect the LSN, so it is important to use the pinch test t ensure that the LSN is still in.

Another way I have found to get to a ball park is to check the idle. If you rev the engine quickly and then let it settle to tick over it should do it fairly cleanly. If you hold high revs before it dies, this is usually a sign that your tick over is set too high and your LSN is too rich (the revs die as the rich LSN fuel loads up the crank).

A combination of the 2 techniques helps me alot with tuning.
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