Engine sounds different...

[LaKraven]

So I've changed my air filter, engine coolant and spark plugs (the oil was changed < 1000 miles ago along with the filter so I'm leaving that for now) and the engine sounds... different!

It doesn't sound "bad", but "more aggressive"... a bit louder and more "throaty".

Am I right in thinking this is because of the super clean filter? The old one was a year overdue for changing and really clogged up with crap (spark plugs were also overdue for changing and had heavy carbon deposits on them all), so I'm thinking what I'm hearing now is "an engine with better airflow and better combustion".

I mean, if it were (hypothetically speaking) a spark plug not firing at all or not firing quite properly, would the sound be "obvious" in that case? Like a backfire noise or something? Also, in that event would I not get a warning light on the "dash" and FI failure codes in maintenance mode? Would it even turn over if one of the spark plugs wasn't working properly? I don't know how "smart" the EMS is on this bike!

If necessary I can record a short sample of my engine sound when turning it over and revving her up.

Note: I haven't yet test-ridden the bike. I'm going to do that in the morning (with the Mrs trailing in the car with my tools in case anything goes wrong). The bike fires up and idles beautifully, there's no "smoke" or any visible "crap" coming out of the exhaust, and the engine is taking a fair while longer to get its first bar on the temp guage - which you'd expect with a clean rad and fresh coolant). It revs up smoothly and seems to  "drop off" abruptly when I close the throttle (probably normal, never really paid much attention to the "drop off" before).

Anyway, I've been as descriptive as I can so I'll wrap this up, but if anyone has any thoughts or ideas (and especially answers to the questions) that's appeciated

[greywolf]

There was once a problem with filters coming without gaskets. The gasket was supposed to be taken off the old filter edge and put on the new filter. If your filter was on the shelf for years it could have come without a gasket. If the airbox wasn't completely seated, you'd also get more intake noise. A new filter shouldn't be any noisier than the old one unless the old one was completely stuffed with dirt. Also make sure a boot hasn't come off a throttle body intake. It could be your imagination though. Most people don't remember sound volume or quality that well, a fact often used to trade money for unneeded audio equipment.

[mr_diver]

I went from a factory fitted filter used through crap UK winter weather for 14k miles. black a very clogged. to K&N and she whistles with the new one (under load) and shes done it after every service. noticed it and check every time before taking apart the airbox.

[LaKraven]

The new filter does have a gasket (I was surprised to find having removed the gasket from the original before chucking it)... and it is sealed up.
The old filter really was completely caked with shit, dead bugs and 16,000 miles worth of sand, and even grit from the last two winters!

[greywolf]

That sounds bad enough the new filter could be noisier.

[mr_diver]

OEM filters are supposed to be changed at every other service I believe- so that 7k to an OEM filter.

K&N cost me £32 and I never need another, it gets banged on the floor and thrown back in the bike.

so after 16k I'm not surprised it sounds different. O2 starvation with the old one!

[greywolf]

14,500 miles is the interval for checking the air filter. It goes well with the timing for a valve clearance check and plug replacement. 7500 miles is too soon for plugs. Or just put in NGK CR8EIX plugs and forget about them.

[Sven]

14,500 miles is the interval for checking the air filter.

According to my Suzuki handbook, 11,000 miles is the interval for changing the air filter

[greywolf]

According to my Suzuki handbook, 11,000 miles is the interval for changing the air filter

Another look indicates that's correct for replacement. It also says to inspect it every oil change/3500 miles. If ridden on dirt and dust, that's probably a good idea. If not, as is my case, I'm waiting for the valve clearance inspection.

[patropsley]

According to my Suzuki handbook, 11,000 miles is the interval for changing the air filter

Another look indicates that's correct for replacement. It also says to inspect it every oil change/3500 miles. If ridden on dirt and dust, that's probably a good idea. If not, as is my case, I'm waiting for the valve clearance inspection.

pat that makes sense now I changed at 11k service and was disappointed to see it wasn't that dirty I will inspect instead of replace at next change point
regards
pat

[Strommer]

I change my paper one every third service - that's about 11k.  Gets some hoover action at the intermediate services.

[LaKraven]

Well, I test-rode the bike today for a good few hours (remembering to stop after about 5 miles to check and top-up the coolant levels with the air flushed from the cooling system) and it rode like a dream.
Yes, the engine is a little louder but it's also shifting better and already I can tell my fuel enecomy is better (like it used to be when I first got the bike rather than the way it's been for the last ~5000 miles).

Next major service (24k miles if I'm not mistaken) I'll be putting in a K&N filter (at present I just did a direct replacement for the OEM filter).

I've gone with the NKG (or whatever they're called) plugs as mentioned in an earlier reply, so hopefully they'll last longer than those crappy ones fitted by the dealership when the bike was built (which were basically missing the inner electrodes and I don't quite get how they were still working at all to be honest).

just want to thank everyone for their help! Last thing to do (tomorrow) is a full brake pad replacement (these are aftermarket... can't remember the brand but they're highly-regarded with copper-colour plates and what I think is galvanized steel pad? Anyway, they're going in tomorrow (even though the brakes work fine at the moment, the existing pads look a bit thin for my tastes).