Airbox or separate Filters? An age old question.

I did this to my 1997 M750 - don't know how it runs yet, still sorting wiring out!!

https://www.flickr.com/gp/152408274@N08/5d4FkP

First time use of Flickr and I could only manage to insert the link, not the image - any tips?

Cheers folks

And also has Dynojet Stage 2 and "straight through" pipes

[Darren69]

Nasher - Stick with the K&N pods and get a set of flat slide Keihins, that would be the way to go.

[Nasher]

Originally Posted by Darren69

Nasher - Stick with the K&N pods and get a set of flat slide Keihins, that would be the way to go.

Oh yes, don't worry I understand that, and would love to, but the 39's or 41's are both well out of my budget for either of the bikes.

Nasher

[Dukedesmo]

Originally Posted by utopia

I thought those meshes on the bellmouths of Guzzi carbs were to stop them sucking your nuts in while you were getting your knee down ....?
You know, in the Italian style .. shorts and trainers.

Nutmesh...

[Darren69]

Originally Posted by Dukedesmo

Something like this;



EVR large airbox with TPO 'Beast' velocity stacks on my 916, shame you can't see it when the tank's on because it's automotive porn...

I have the TPO Beast stacks on my S4, they are huge and only just fit but do give a little bit more midrange torque.

I have read many times in various places that the best setup for the 748/916 bikes is either the standard airtube filters or those BMC ones that you have; any over the stack filters mess up the airflow and also reduce the airbox volume. I have gone for the standard DP carbon airbox and DP airtubes which will take a flat panel Powercross filter. Would probably get another set of TPO beasts for that too eventually.

[Zimbo]

It generally is quite difficult to get the carbs to balance and run perfectly with the individual K&N filters, airbox with chopped lid and K&N filters, plus dynojet stage 2 kit, is the way to go. The FCR41s seem to work best with the airbox as well, should you ever fit a set!

[Darren69]

If I were you I'd take it and get it dyno'd before you change anything. My guess would be that you may be losing a bit of mid-range at the expense of top end that a stage 3 would give you against a more real world riding stage 2. It certainly looks like a very neat job though.

I fitted the same pods to my M900 with FactoryPro kit - couldn't get it to run right. Had it dyno'd and ended up with a massive main jet. It was fine wide open, but on partial throttle (like trying to cruise at 75 a 80) it stuttered. Same deal feeding throttle back in gently (yes, sometimes....) through corners. I tried all sorts for a very long time - float levels, jet and needle changes, checking everything again and again. I finally went to Rosso Corse to ask for help and was told "I can check it, but only when you take those off and put the air box back on. If it ran better with pod filters, Ducati would have used them." I got another airbox and it runs fine now - I just took the rubber trumpets off and made a few extra holes. I bought some plugs to fill the holes in case they messed things up, but didn't need them....
Just need to use it now......

[Nickj]

Originally Posted by Dukedesmo

Something like this;



EVR large airbox with TPO 'Beast' velocity stacks on my 916, shame you can't see it when the tank's on because it's automotive porn...

Similar to mine but shorter stacks, that would go with the higher rev capability and of course more bits to blob in the fuel.



Not a pic of mine, I'm still reading through the Ducati workshop manual to get the hang of how it's stuck together and comes apart.

[utopia]

Originally Posted by PaulR

.....I bought some plugs to fill the holes in case they messed things up, but didn't need them....

Funny how the simplest thing can make such a difference.
I've occasionally pondered cutting a few holes in my airbox, but have always chickened out for fear of wrecking a perfectly good lid.
But now that I have been enlightened I shall drill a few carefully positioned and sized holes to match some of Halfords' finest blanking grommets.
Thanks for the nudge.

I was lucky enough to nab the last pair of FCR39s on ebay before the post-brexit price hike.
Added to a fortuitous 15% discount code from my eldest son, I paid just half of the current, slightly incredible £1.4k asking price.
Note though, I believe there is a Mikuni flatslide option which global economics now renders less salty.

For me, an airbox does two things.
1) It provides a relatively pressure-stable, turbulence free supply of air.
2) It keeps the wet and crap off the air filter.
Mine will be staying, even though I like the simplicity and ease of access that pod filters give.
Though I've just junked the airbox and fitted a pod filter on my single cyl Dommie.
In its case, the simplicity thing was just too strong.

[Nasher]

Thanks Gents

I have sourced an airbox now, and fitting it to the M900 is one of my many project stacking up to keep me busy over the winter months.

It does have a mint lid, which I'm reluctant to cut, so I plan to make a replica of the lid edge in Aluminium to clamp the filter in place with a splash guard at the front.

Alternatively I might try and source an already cut lid and stash the good one away for when it's worth enough to supplement my pension.

It will be a while, but I'll obviously post some pics when it's done.

Nasher

[Nasher]

So I finally got around to fitting the airbox to my M900 today.

To recap, sometime between Albie owning it, and me buying it from Blah Blah 4yrs ago, somebody had cut through the airbox just in front of the Coil mounting bracket and left just the battery holder in place. Replacing the panel air filter with two large K&Ns.
The bike is also fitted with a Dynojet stage 2 kit, early bigger valve heads, and Remus DP exhausts.

Dynojet don’t even list a Stage 3 kit for the M900 or 900SS for use with separate filters, saying it’s better with a std airbox and cut down lid.

I recently made a clamp ring for the filter instead of cutting the lid of the airbox I purchased:

http://www.ukmonster.co.uk/monster/s...ad.php?t=56618



So have now gone from this:



To this:



I had a good ride round this afternoon on everything from local 20mph roads to a blast up the motorway, and can’t believe the difference in the bike.
As far as I can tell it feels better in all areas of the rev-range, and under different states of load, and that’s without any adjustments to needle height or jets.

It feels stronger and smoother lower down, picks up less erratically right through the rev range, and is happier bumbling along at lower revs when not under load.

But the big difference is when coming off the throttle. I can now actually slow down progressively by shutting the throttle slowly, whereas before I was always anticipating the sudden large amount of engine braking, as if I’d shut the throttle quickly, that seemed to happen suddenly on it’s own.
The throttle was far more like a on-off switch than it is now.

It also used to pop and bang quite a bit if shut down suddenly, but today I only had one small instance of that whilst trying to provoke it into doing so.

I’m sure it could probably be made even better with a trip to a rolling road, but those with Carb experience, or simply the willingness to be bothered with carbs are few and far between.

There is also the small matter of how difficult it is to get to the needles and jets on a monster each time a change needs to be tried.
Because of that I might even cut this new airbox in half, in a different place to the one originally fitted, adding a bracket which uses the coil mounting screws to bolt the two halves together.
The aim of which will be to enable just the airbox to be removed quickly without disturbing the battery, starter solenoid, and coils.

Nasher.

[Nasher]

Had the caps and float bowls off the carbs today so I could finally see exactly how they are set up.

The Needles are definitely Dynojet, and have the clip in the 4th slot from the top(or 3rd up).
Exactly how Dynojet stage 2 instructions suggest.

The springs I do not think are Dynojet, they feel/look heavier, more like std ones.
Dynojet do suggest std springs can be used to slow throttle response.

The main jets are marked 17C.
I thought the first one was a mis-stamped 170, but they are both the same, and looking at them under a scope they are definitely 170C, there is a definite end to the top and bottom of the 'C' it doesn't fade out.

The stage 2 kit comes with Dynojet YJ144 and YJ150 jets(equivalent to Mikuni 135 and 140) dependant on your exhaust, so I'm assuming the jets are @170 and have gone in it because of the separate filters.

I'm tempted to try and get some Dynojet 150 jets and try them, but really do need to find a rolling road that can be bothered with carbs within a reasonable distance of the South coast.

Nasher.

[Flip]

Alf's Motorcycles in Worthing have a dyno but it's not overly advertised as it's in Alf's den at the back of the main shop which is all Kawasaki these days.

Alf himself is a Ducati man though and usually found rebuilding bevel twins - he may be worth a chat with as he certainly knows his way around carbs.

http://www.alfsmotorcycles.co.uk/