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Old 03-30-2011, 06:26 PM
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Default New pipes and high idle?

Hoping you guys can point me in the right direction on this. I recently replaced my stock exhaust with Samson true duals on my 94 Heritage, and it seems like my idle RPM is quite a bit higher than before. The pipes are 33", baffled, no other perf mods other than air cleaner. The bike has a stock Keihin CV carb.

Are the new pipes likely the cause, and if so do I need to replace my slow jet? Or is it simply a matter of adjusting the idle? Is this better for a real wrench to tackle rather than a mechanically challenged newbie like myself? I'm pretty sure I can handle the re-jetting if necessary, but don't have any diagnostic equip or even a multimeter to check revs. Wondering also if timing becomes an issue.

Thanks for any knowledge you can pass along.
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Old 03-30-2011, 08:13 PM
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I'd adjust the idle first and see how she runs. Not every bike needs rejetted. If you believe Joe Minton, most bikes will run fine with the jets they have as long as the jet needle is replaced..
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Old 03-30-2011, 08:18 PM
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Adjust idle and for jets you won't know unless you do a roadside sparkplug check. Get the bike doing 65mph for a mile or so hit the kill switch, pull clutch while keeping throttle in same position and coast to stop , pull plugs and check the color.
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Old 03-31-2011, 10:41 AM
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From messing around with tuning EFI systems, the idle will raise if it leans out some, more fuel will load the engine and slow down.
Turning your air/fuel screw will tell you if you need a low speed jet change and should be able to get the idle back with that adjustment, if you go too close to being seated or to far out and not right, you need a low speed jet change but as members have mentioned, a stock low speed jet is versitle.

Hopefully a member can break the air/fuel screw down a little bit more because I can't remember which way is which and don't want to put out some bad info, everytime I put something new into my head, something else leaves

By the way, love the Silver/White Heritage
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Old 03-31-2011, 03:04 PM
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Thanks a lot guys. I'm tempted to swing it by a shop but I'm going to pull the carb so I can get that idle mixture plug out and see if I can play with it a bit. From what I've read, right is leaner left is richer. I'll try to do it by ear and hope I can get close to 1000 rpm.
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Old 03-31-2011, 03:21 PM
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no need to waste money at the dealer. you can do it, ive rejetted many carbs on older harleys. onece you get the hang of it its easy! do a search on "how to rejet the cv" do some reasearch and watch the color of the plugs. if it pops out the carb alot you may be running lean.
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Old 03-31-2011, 03:35 PM
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Quote:
Originally Posted by creatv1 View Post
Thanks a lot guys. I'm tempted to swing it by a shop but I'm going to pull the carb so I can get that idle mixture plug out and see if I can play with it a bit. From what I've read, right is leaner left is richer. I'll try to do it by ear and hope I can get close to 1000 rpm.
Just make small adjustments at a time and see what happens. If it was idling OK before you changed things the adjustment shouldn't need too much work.
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Old 03-31-2011, 05:47 PM
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And start with the idle speed adjustment before going into the idle mixture adjustment..
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Old 03-31-2011, 05:53 PM
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Sure, if it's just a couple of hundred rpm's high just turn the idle adjuster in 1/8 turn at a time and see if it fixes it.
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Old 03-31-2011, 08:48 PM
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I would do as said above and back off the idle adjustment till she sounds right. If you have to change jets later, most bikes can be done with the carb on the bike. I just drop the bowl off and it's an easy job. My 99 carb already had the idle mixture scew drilled out when I got it. I had a stock 42 slow jet in mine, and changed it to a 45. Main jet was already updated from a 75 to an 80. Mine had a K&N air filter, and drag pipes.
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