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Discussion Starter #1
My googlefu seems to be inoperative tonight and I'm getting nowhere with Search.

I've just bought me a 96 748 to keep me occuped during the long cold winter. Needs a good overhaul which I've begun planning. I pulled out the standard airfilters which look grotty and are the original foam type. Not particularly keen on them and they look a bit small. Anybody got any suggestion on which ones to use? The bike 'has been chipped' already which sounds like it could cause lots of fun.
 

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Standard is the best for performance. Get OEM or Uni replacements, oil them, and spray the runners behind them with some sticky chain lube to catch excess dust. Check and replace/clean regularly.

MWR makes good over-trumpet filters. Avoid other brands, most have a tendency to either dampen performance or fall apart and get sucked into the intakes.

BMC makes nice filters that slot into the airbox apertures with some minor modding. But they are STUPID expensive.
 

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+1 for MWR. Will be running them on my 748R and plan to pick up a second for my 748.

The MWR will allow you to run carbon runners or hollow out and smooth the inside of the stock ones. Easy job with a dremel.

Good luck on the rebuild, post up picks as you go. Everyone loves s good tear down.
 

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Discussion Starter #5

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Come in Spinner :)
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definitely stock, here's why from the hall of wisdom

http://www.ducati.ms/forums/80-hall...rs-stock-vs-aftermarket-airbox-resonance.html

good luck with the bike post up lots of pics

The stock air filters did nothing for the motor in my 748R when it sucked in a loose airbox bolt that chewed up the intake port and valves on the lower head.

Resonance and reflective frequencies aside, the stock filters are crap. Nothing but an oily chunk of loose fitting foam. If I lose 1 or 2hp and gain a wide safety margin again foreign debris entering my engine with an over-stack filter, I'm perfectly ok with that.

Unless you're REALLY trying to eek out that 10/th of a second at the track, it's likely not going to negatively affect the engine in any real way running an over the stack style filter. There's always a better way to make more power than the factory set up. If there wasn't...then the entire aftermarket automotive performance industry would cease to exist.
 

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Air filters aren't there to stop loose bolts wrecking engines... that's what good maintanance and locktite are for.
 

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Air filters aren't there to stop loose bolts wrecking engines... that's what good maintanance and locktite are for.
No they aren't......unless they can, in which case they will.

A) The motor was like that when I got it.

B)The bolt appeared to have snapped at the base of the threaded portion. Loctite would not have helped here.


If the bike had an over the stack air filter like the MWR, it never would have gotten sucked into the front stack. Also, the airbox seal isn't exactly.....air tight shall we say? Especially after a few years on it, it's not going to seal like it used too once the tank's been off a few times. So that's more dust and dirt getting past the stock style filters.


We've all heard stories of people getting something sucked in there. If I recall, in that (I'm a tool and crashed my bike thread) someone had mentioned their throttle sticking when something fell in the stack and jammed the butterfly.


The point isn't that it's there specifically to stop foreign debris like loose or broken nuts and bolts or whatever from entering the engine. We all know it's an air filter and that it's primary purpose is to filter the air lol. The point here simply put is that it can. Even with the best maintenance, sh*t still happens and when it does I'd rather not have to deal with excess collateral damage if I can.



All just one man's opinion though. :D
 

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If the bolt snapped it was overtightened... bad maintanance.
Plenty of threads on here about the dangers of that bolt coming loose.

.
 

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If the bolt snapped it was overtightened... bad maintanance.
Plenty of threads on here about the dangers of that bolt coming loose.

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Just to be certain here as I just searched 748R airbox bolt and didn't find much, we are both talking about the four goofy bolts that secure the lower half of the two piece airbox to the intake valve inspection covers right?


Murphy's Law. It's a bitch, and when it strikes I'd rather have some level of safe guard than nothing. The MWR filter is there, it's available, and for those who want a little more peace of mind it's a nice choice to have. Maybe some like you aren't concerned, and for them there's plenty of other filters out there.
 

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Regarding inbox filter.

Its unfortunate that text is in the hall of wisdom, as it is merely a theoretical guess and testing will prove it wrong.
(Easy to fall for a long text, it doesnt mean its valid though)

The claimed powerloss is from the foam collapsing on the stacks, not from foam taking up volume.
Using a filter with a cage inside, keeping it from collapsing, there is NO LOSS with the filter in the box.

I have done the actual testing on several bikes over several years and it comes out the same, no loss with a filter inside the box (that do not collapse).
I can also confirm that a collapsing inbox filter robs power in the region of 5-7 hp on a 996, in one test I had widemouthed black nylon stacks on and it was real easy to see where the filter had hit the stacks.

Correct filter in the box -> identical power as of no filter at all.
 

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I believe TomTom when he says that tests that he ran show that peak power was unaffected, but keep in mind that the airbox resonance is assisting air flow into the engine at a number of points in the rpm range. It has an overall positive effect on smoothing dips and raising power levels throughout the engine rpm range, after proper tuning and testing at the factory,
 

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Its not just peak power, the whole rpm range is identical no filter to inbox airfilter.
Put the two dyno runs on top of each other and theyre identical from bottom to top.

I agree with you that resonance will affect the output, but its just the airfilter doesnt affect resonance in this application.

Lifting the tank will change resonance and it subsequently affects the form of the curve, same goes for no airbox, if you put the filter in the box and it doesnt affect the form of the curve at all (not better, not worse but identical), its safe to say it doesnt affect resonance, 2c.
If you beleive in that resonance changes the output there is no other logical conclusion.

Edit: Im guessing the information you had available was that someone tried inbox airfilter and it killed power period, if you knew the testresults I mentioned and why their test of inbox filters failed I guess it would turn things around, no?
 

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Discussion Starter #15
Looks like an in-box filter then. My 900SS had swallowed a nut before I got it and I am now allergic to that kind of experience. I like the idea of spraying a little chainlube on the inner surface of the ram pipes. Not impressed by the seal round the box. This needs to be good and solid for any resonance effect to work. I'll probably re-enforce the lip by doublesided tape under it.

I've seen a suggestion that smoothing the internal surface of the ram pipes. Anybody tried this and wants to tell? Also the mesh at the entrance to the runners has got to go. The signs are that the fairing came from China. I've got a background from the aircraft industry and have played with wind tunnels in my past. The mesh on the fairing WILL restrict airflow.

Thanks for all your help gentlemen.
 

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If you're worried about the airbox seal, you could run a strip of high density insulation (like for a door seal) around the bottom of the tank. Will create a better seal and make the tank more stable.

The seal on my 748 was absolutely trashed when I bought it. I didn't feel like spending crazy money on a new one. My airbox seal is two layers of of this high density foam. Has worked flawlessly for almost 3000 miles since the rebuild. It's cheap, and has a wider seal area than the stock rubber seal too.


Just a thought. Should be able to find that stuff at a hardware store out there in Norway I'd think.
 

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Discussion Starter #18
Thanks for that. I will use a cage to support the filter. The doos seal sounds a better idea than mine so I'll nick that idea. I'm still at the 'what the hell have I actually got' stage. As is the normal case with older sports bikes, it has been modified. See my wee thread on that!
 
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