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Discussion Starter #1
generally speaking no -

an exhaust pipe change on v-twins usually does not require re-jetting the carburator
depending on the pipes some minor adjustment to the air/fuel screw may be needed
on some bikes

fuel injected bikes will compensate automatically without problems in most cases

however if you modify or change the intake system by using a high flow filter element
or opening up the airbox re-jetting will be needed on carbed bikes to add more fuel to
compensate for the increased air flow and correct the lean running condition that will result
jet kits are available for nearly every bike and are not expensive-there are some very small parts involved though in the kit and if you are not good at working with small parts
have it done by a qualified service tech.

fuel injected bikes will require remapping of the bikes computor to add more fuel to
compensate for leaness.there are several units on the market that can be installed
on f/i bikes that will take of this,but the best way is to have the bike put on a dyno
and the air/fuel ratio adjusted through out the entire rpm band and doing each cyclinder
independently for maximum effect-this requires the use of a laptop and tuner who is
familiar with these type of programs-once completed no more adjustment will be required

remember when changing pipes to use new crush gaskets for a proper seal at the exhaust flange-do not try to re-use the old ones,they will most likely not seal properly
causing an exhaust leak
 

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AZ's Official Mechanic
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bikeaholic said:
fuel injected bikes will compensate automatically without problems in most cases
this is only true if its a CLOSED LOOP SYSTEM (has an O2 sensor)

MOST bikes are OPEN LOOPED and will need to be remapped to compensate for the extra air/exhaust
 

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Yeah thank god for technology *rolls eyes*
 

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T-man said:
QKENUF is dead-on, as usual. Open loop systems can ONLY compensate some at low end via vacuum sensing, but at higher speeds will do nothing to compensate for air flow changes.
So.. if I have installed a K&N filter on my Drifter (1500 F/I), and drilled out the baffles in my pipes, do you recommend installing a Power Commander or the equivalent? I've heard it can be expensive to have the dealer adjust it.

Thoughts?

Thanks!
K
 

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Katafer said:
So.. if I have installed a K&N filter on my Drifter (1500 F/I), and drilled out the baffles in my pipes, do you recommend installing a Power Commander or the equivalent? I've heard it can be expensive to have the dealer adjust it.

Thoughts?

Thanks!
K
You can go to the power commander site and see if you can download a map for your bike that has that particuliar pipe and air filter. as well, you can manually set the commander yourself. its very easy and is the next best thing to installing a map. I would recommend that you talk to the power commander tech desk and see what they say. then set it to what they recommend and run it for about 200 km or so and pull a plug and see how lean the bike is running. I had to do that and i found that i ended up resetting the P/C one setting richer than they had recommend in all 3 settings ( low, med and hi ) I then went to a bike dealership in town that was putting on a bike show and was advertising dyno tests for $50.00 and told me they would set the P/C for me for another $30.00. As it turned out, i had the P/C set perfectly and my bike performed at 100% on the dyno. All you really need to do is do some research on the P/C site and read the instructions carefully and you'll find its really not that intimidating. Good luck!
 

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hey QKENUF4U or anyone else that knows...

QKENUF4U said:
this is only true if its a CLOSED LOOP SYSTEM (has an O2 sensor)

MOST bikes are OPEN LOOPED and will need to be remapped to compensate for the extra air/exhaust
You say most bikes are open looped. I have a 2002 VN1500 Meanie that has stock exhaust etc and I want to install aftermarket pipes such as Cobra Slashdowns soon. Is my model of the MS an OPEN LOOPED one? Should I consider further mods as mentioned at beginning of thread or will I be forced to anyway?

Any advice would be appreciated. Thanks.
 

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its all about balance

the intake system and the exhaust systems need to be balance with each other.
when either is changed this cause an uneven system, either the intake does too much and it goes rich running
or the exhaust does more than the intake and the running condition goes lean
so anytime you change one then usually you will have to adjust the other system to keep it balanced
yes the closed loop using an O2 sensor can read the changes an adjust
any other systems, they will be out of balance
 

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any time you change your intake or exaust it's best to retune. you get the most out of the mod that way. at the very least keep an eye on your plugs read them.lean=hole in piston. been there.
 

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vance-hines bigshots on the hog made a big change. for a cruiser i would look at them a1 in my book.air filter and retune it's all about combo.
 

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with carbs - exhaust change only is not enough to cause a need for jet kit.

If you do an intake AND exhaust then you best do a jet kit.

Most bikes are lean from the factory anyway so tweaking the A/F screw a little aint gunna hurt anything with or without an exhaust / intake change.

kenny
 

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Well thanks! I've got a 1993 Vulcan 1500A and have installed K&N elements and am looking to install MAC exhaust? Will I see any issues?

Mike
 

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Make Another Choice

try looking for a better exhaust first.

yes, you should have to rejet with the air and exhaust mod.
 

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Make Another Choice

try looking for a better exhaust first.

yes, you should have to rejet with the air and exhaust mod.
I take it you don't care for MAC?
They make great pipes for model airplanes... was thinking about their 4-1 for the 750.
 
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