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Discussion Starter #1
Looking for input on if I just should break down and buy an fi tuner or if I should do the marble intake mod? Only issue I am having is a slight popping on deceleration. Someone also suggested if I set my idle and completly release throttle during deceleration this will go away as well. Does this work and if so how do I set the idle. VN900 Custom
 

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Do you have pipes and intake? If you don't, don't wast money on the Fi tuner and just do the MOD. The idle should be fine as long as it has been messed with. And how bad is the popping? I like the popping personally, it sounds like how a bike should sound. Ever heard a race bike, they pop like crazy on decel.
 

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If you have pipes and stock intake you might not need a tuner, but every bike is different.

If the idle is set correctly, and you're running 87 octane fuel, you probably won't get popping. Most folks who get popping (most, not all) are getting it because they've bottomed out the idle because it 'sounds cool' and are running 93 octane or something.

There's plenty of discussion on the octane debate, won't get into it here. But- bottom line is, your bike calls for 87 (91RON, which is 87 R+M/2 like we have in the states), and using it tends to eliminate popping.

As far as how to adjust? Get the bike warm, then find a small black thumb screw in the front part of the intake. Clockwise rev's faster, conter-clockwise rev's slower.

I did this video a while back. (A LONG while back, that poor thing is nearly stock in that video!) I set the idle with a sunpro automotive tach. That's probably right at about 1050 or the 'top end' of the idle spectrum. 950 is the low end. Below that and you'll likely get popping, and perhaps even too low of oil pressure at idle.

https://www.youtube.com/watch?v=0wxO_MrqVCE

My theory is (and it's just a theory) that since the idle screw adjusts the position of the throttle when it's released, having the idle set too low creates a 'rich' idle, because there's not enough air (but to your mapped fuel injection system, it's dumping in the amount of fuel it expects is needed for 1000 rpm's, even though you're only turning 800!). The rich condition causes some mild popping and backfiring as it runs really rich in those couple of seconds of deceleration (until the motor idles and smooths out)
 

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Thanks for your help and yes I have been running 94 octane fuel in the bike. I will change to the cheap stuff next tank. So I guess I need to some how track down a tach so that I can adjust. I have never adjusted it but the previous owner might have. Just wondering the hose that you put the marble in what is that hose for?
 
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