Aftermarket exhaust and jetting

Message

xsyamahadg · Fri Jun 23, 2006 12:03 am

I'm thinking about an aftermarket exhaust for my V-Star and a few questions come to mind. After installing the exhaust, is it best to use one of the recommended jet kits like the stage 1 kit I see in listed in the exhaust section of the catalog, or do you guys take the bike to a dealer who has a dyno and have them jet it? I'm from the old school of jetting where I take the bike out on the open road and run it at a constant speed for about 5 minutes and then read the plugs. If the plugs are white, then it is burning lean, if they are black, it is too rich. I try to find a jet combination that will show a tan color on the plug. As far as the idle circuit goes, if the engine falls back to idle properly and doesn't coast after being blipped, I don't mess with the idle jetting. However, I have never messed with a newer bike that has both side draft and down draft carbs, so I don't know if my methods apply or not. Also does the installation of a tuned aftermarket exhaust actually increase performance, or are they designed to increase noise only. I'm thinking that on bikes like the Star, increased performance may be a myth. XS

#2 Unread post by **ZooTech** » Fri Jun 23, 2006 12:43 am

There's no need to rejet just for an exhaust. If you're going to do an aftermarket intake as well, then you'll need to change the jets. You should be able to find pre-assembled jet kits that are set up for your intake/pipe combo.

xsyamahadg · Fri Jun 23, 2006 1:13 am

Not to question your answer, but as a rule of thumb, when you open up the exhaust system on an normally aspirated engine such as the V-Star, some jetting is required. I have heard that bikes with EFI may requrie some re-mapping, but not always. Understand why I am cautious, I don't want to fry a piston on a bike with only 2,800 miles on the clock. XS

#4 Unread post by **ZooTech** » Fri Jun 23, 2006 3:11 am

xsyamahadg wrote:Not to question your answer, but as a rule of thumb, when you open up the exhaust system on an normally aspirated engine such as the V-Star, some jetting is required. I have heard that bikes with EFI may requrie some re-mapping, but not always. Understand why I am cautious, I don't want to fry a piston on a bike with only 2,800 miles on the clock. XS

Of course I understand your concern about frying your bike. But if the intake remains stock (i.e. restrictive) then you're not likely to lean out your A/F ratio by changing your pipes. Your engine will still only be able to swallow the same amount of air as it did before.