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April 6th, 2019, 10:32 PM
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#1 |
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ninjette.org member
Name: Garry
Location: Bungendore Australia
Join Date: Jan 2019 Motorcycle(s): GPX250 1989 model and 1990 model Posts: 98
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Failed exhaust mod.
In a misguided attempt to improve exhaust gas flow I drilled four 3/8” diameter holes in the end plate of each muffler. It now sounded much, much better. Took the bike for a ride and found throttle response was noticeably worse from 4K to 7K. Took the bike back home, tapped a thread in each of the holes and blocked them all with screws. Took the bike out again and hey presto everything back to normal. Such a small change made such a noticeable difference? I learn something new everyday with this bike!
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April 7th, 2019, 06:19 AM
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#2 |
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Guy Who Enjoys Riding
Name: Jim
Location: North Carolina
Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot.
MOTM - Oct '18, Aug '17, Aug '16
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I'm glad you recovered from the mistake.
 You think it sounded better? Mine had the four rivets drilled out when I got it, and it sounded like a lawn mower engine. I did what you did and tapped the holes for screws, and it sounded like a nice quiet motorcycle engine. |
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April 7th, 2019, 11:58 AM
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#3 |
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ninjette.org certified postwhore
Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot.
MOTY - 2018, MOTM - Nov '17
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There's mid-range lean-spot on these bikes. Anything you do that increase flow-rate makes it worse and bike gets even worse in mid-range.
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1 out of 1 members found this post helpful. |
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April 7th, 2019, 02:09 PM
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#4 |
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Rev Limiter
Name: Jay
Location: WI
Join Date: Jul 2013 Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes Posts: A lot.
MOTM - Jun '18, Oct '16
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You can compensate for the increased flow, and leaner mixture, by shimming the needles and changing the mixture adjustments and/or jets.
When making carb adjustments, think in terms of the throttle position (1/8, 1/4, 1/2, etc) instead of RPMs. That way it's easier to isolate the circuit that needs adjustment. |
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