quasi888
Moto babies
Earlier this summer I bought back my old SV650 from the friend I sold it to 2 years ago, and I decided to turn it into the project bike that I had always intended it to be. Of course, suspension upgrades were first on the list, but next in line were some badly needed improvements to transform this bike from a gutless weakling to a track-ready beast.
Over the past few months I've had my friends at Hare Racing provide dynamometer testing and advise me on my upgrade path. With a fairly stock configuration (Renegade slip-on exhaust, 1 shim on the needle), I got a baseline dyno reading of 65.1 HP and 41.1 ft-lbs of torque. Mmmmehhh, lower than I had hoped, but about average for a stock SV. Air-fuel was hovering around 14:1. Definitely lean, but then, most bikes come from the factory like this.
The list of power mods for first-generation SVs is well-known, so I went with a proven combination consisting of full exhaust (M4) and the following jetting changes: main jets upgraded from 137.5 to 152.5 (Factory Pro / Mikuni numbers); pilots upgraded from 15 to 17.5; 2 shims on the needles. Airbox was desnorkled. Back on the dyno, I got 69.91 HP and 42.75 ft-lbs. However, the bigger jets proved still too small for the modded airbox and exhaust, because A/F was now around 15:1!!!
Back to work. For the next phase, Fred Garzaro at Hare recommended I go up 2 main jet sizes (to 157.5) to try and richen the A/F up a bit, but I also did the well-known "03 cam swap". This basically involves opening up the top end, removing the exhaust cams, putting the intake cams in their place, and putting in 2nd-generation (2003+) SV650 intake cams back in the intake slots. (Thanks to Mackey Stingray for helping out on this.) Of course, with the new cams, checking valve clearances is highly advisable, and sure enough 5 of 8 valve shims had to be replaced.
Back to the dyno at Hare. I was surprised (and ecstatic) to find that she topped out at 76.6 HP, 44.88 ft-lbs. A nearly 18% improvement over stock, of which nearly 7HP can be attributed to the cams (and slight increase in jetting) alone! A/F was now a bit too rich, around 12:1. Fred recommended that if I go down to a 155 mainjet, not only will I get that down to a more optimal 13:1, but I should pick up a couple HP in the process. If I can top 78HP, that will represent a 20% improvement over stock -- outstanding for a motor with no head work.
Here's what we have so far:
A/F for Stage II only:
Stage 0: 65.1 HP @ 9000 RPM, 41.1 ft-lbs, 14:1. Renegade slip-on exhaust, 15 pilot jets, 137.5 main jets, 1 shim on needle.
Stage 1: 69.9 HP @ 9300 RPM, 42.75 ft-lbs, 15:1. M4 full exhaust, 17.5 pilot jets, 152.5 main jets, 2 shims on needle, desnorkled airbox.
Stage 2: 76.6 HP @ 9700 RPM, 44.88 ft-lbs, 12:1. Cam swap, M4 full exhaust, 17.5 pilot jets, 157.5 main jets, 2 shims on needle, desnorkled airbox.
Stage 0 to Stage 1 was a moderate but appreciable improvement. But the jump from Stage 1 to Stage 2 was VERY dramatic. I felt a difference immediately even at just 50% throttle heading down the street.
This whole process has been a valuable experience in gaining more in-depth wrenching skills beyond the usual routine maintenance; and it's great to have the dyno sheets not only confirm what you feel on the ol' butt dyno, but also to provide some visual indication of your powerband and how your air-fuel mixture is doing. Thanks go out to Fred and Hare Racing for the dyno runs and the tuning advice, as well as Mackey for coming over late at night to oversee the Stage 2 operation. It was all worth it!
Over the past few months I've had my friends at Hare Racing provide dynamometer testing and advise me on my upgrade path. With a fairly stock configuration (Renegade slip-on exhaust, 1 shim on the needle), I got a baseline dyno reading of 65.1 HP and 41.1 ft-lbs of torque. Mmmmehhh, lower than I had hoped, but about average for a stock SV. Air-fuel was hovering around 14:1. Definitely lean, but then, most bikes come from the factory like this.
The list of power mods for first-generation SVs is well-known, so I went with a proven combination consisting of full exhaust (M4) and the following jetting changes: main jets upgraded from 137.5 to 152.5 (Factory Pro / Mikuni numbers); pilots upgraded from 15 to 17.5; 2 shims on the needles. Airbox was desnorkled. Back on the dyno, I got 69.91 HP and 42.75 ft-lbs. However, the bigger jets proved still too small for the modded airbox and exhaust, because A/F was now around 15:1!!!
Back to work. For the next phase, Fred Garzaro at Hare recommended I go up 2 main jet sizes (to 157.5) to try and richen the A/F up a bit, but I also did the well-known "03 cam swap". This basically involves opening up the top end, removing the exhaust cams, putting the intake cams in their place, and putting in 2nd-generation (2003+) SV650 intake cams back in the intake slots. (Thanks to Mackey Stingray for helping out on this.) Of course, with the new cams, checking valve clearances is highly advisable, and sure enough 5 of 8 valve shims had to be replaced.
Back to the dyno at Hare. I was surprised (and ecstatic) to find that she topped out at 76.6 HP, 44.88 ft-lbs. A nearly 18% improvement over stock, of which nearly 7HP can be attributed to the cams (and slight increase in jetting) alone! A/F was now a bit too rich, around 12:1. Fred recommended that if I go down to a 155 mainjet, not only will I get that down to a more optimal 13:1, but I should pick up a couple HP in the process. If I can top 78HP, that will represent a 20% improvement over stock -- outstanding for a motor with no head work.
Here's what we have so far:
A/F for Stage II only:
Stage 0: 65.1 HP @ 9000 RPM, 41.1 ft-lbs, 14:1. Renegade slip-on exhaust, 15 pilot jets, 137.5 main jets, 1 shim on needle.
Stage 1: 69.9 HP @ 9300 RPM, 42.75 ft-lbs, 15:1. M4 full exhaust, 17.5 pilot jets, 152.5 main jets, 2 shims on needle, desnorkled airbox.
Stage 2: 76.6 HP @ 9700 RPM, 44.88 ft-lbs, 12:1. Cam swap, M4 full exhaust, 17.5 pilot jets, 157.5 main jets, 2 shims on needle, desnorkled airbox.
Stage 0 to Stage 1 was a moderate but appreciable improvement. But the jump from Stage 1 to Stage 2 was VERY dramatic. I felt a difference immediately even at just 50% throttle heading down the street.
This whole process has been a valuable experience in gaining more in-depth wrenching skills beyond the usual routine maintenance; and it's great to have the dyno sheets not only confirm what you feel on the ol' butt dyno, but also to provide some visual indication of your powerband and how your air-fuel mixture is doing. Thanks go out to Fred and Hare Racing for the dyno runs and the tuning advice, as well as Mackey for coming over late at night to oversee the Stage 2 operation. It was all worth it!
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