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Discussion Starter #1
I noticed sometimes (quite frequently) if I try to rev match on down shifts at lower RPMs it will cough back through the air box. It is pretty quiet, I can feel it on my leg. It doesn't increase RPM, it definitely slows the motor down.

Anyone else have this, or do I need to bring it to the dealership?

I rarely got pop on decel. Bike is completely stock. 09 Classic with 1500 miles.
 

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The stock 900 doesn't like the throttle being snapped too fast. The secondary throttle plate (removable-2 screws) is slow letting in fresh air compared to the injector. You end up with too much fuel that's waiting for fresh air to ignite. If an intake valve is just a tad too tight it could contribute to burning off the excess fuel fumes in the intake tract. Try adjusting your throttle hand and see if there's any change. Otherwise, I'd take a look at the valves cuz one that's too tight may not be fully sealing in time.
 

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My 900 does it too, and I was just about to post it! Mine seems to have a pretty fierce pop that come back through the airbox. It occurs down shifting from 3rd to 2nd only (so far). It seems to be only if I don't have the RPM's high enough when matching. I twist the throttle, but occasionally my foot it faster then the bike responds, and POP, there it goes again.
 

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Discussion Starter #5
I will just be less ham fisted. Your explanation was great Baitis thanks!

If the RPMs are above I'd guess 2500-3K It does not do it. If I am chugging in 4th @ 30 or so and want to do two quick blips into 3rd and then into 2nd. It will usually cough on the downshift to 3rd.

It really doesn't need to be matched that slow, just trying to minimize drive line lash a tad.

It is a bad habit I carried over from Dirtbikes, Dual Sports and my Sport Bike.
 

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A tach would be nice, I hate toys without tachs. At the higher rpms the velocity of air and fuel is getting sucked in to combustion chamber. Without having to spend a fortune on a new intake and controller you can remove the secondary throttle plate that's just behind the air filter. The purpose of the plate is for smoother throttle response but that sucker is slow to open. The main plate can be open but the secondary is mostly closed so you end up with a bunch of fuel of the air is restricted. Remove two screws and it slides out. The downside is that you need to learn throttle control all over again...but I like it. The 900's run a bit fat and I haven't heard of anyone needing a fuel controller just for removing the secondary throttle plate. Also, if you're doing 30 in 4th you're lugging the engine and it will puke as will any engine. The 900 likes to rev - keep it in 3rd. Chugging the engine will also result in carbon deposits on the pistons and different set of problems.

I had the same problem, dirt and sport bikes spoil us. Adjusting to slow mode takes some practice but the 900 is a capable engine once you figure out it's quirks.
 

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Discussion Starter #7
Yes likely. Ill check the speed more closely. I tend to be more likely to put it in 5th @ and indicated 40 than not.

I feel like I'll break it, I don't know why. I have to say it feels much more likely to break when you mindlessly forget to downshift while slowing for a turning car and get back on it. The primary drive does not sound like it is having fun in those circumstances.

You think coming off a bike that would start making power @ 9K RPM I would stop babying this one. That one was 16 years old so I cared less if the motor ate it.

What is the red line on the 900? Does it have a limiter?
 
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