Modified Carbs and Airbox Mods.

[koko64]

Because price gouging Pussbucket sucks big black dog's balls.

https://www.flickr.com/photos/150482584@N03/shares/i5hjEs

Pics showing "radiused" bellmouths and transition to the throat and a radius to the slides leading edges to promote airflow and reduce turbulence. 3/4 done and requiring final polishing. For details use the search for carb mods. Title is "Carb mods while you save for FCR's".

Since Pussbucket has wrecked so many threads and tutorials, I have rolled a few of my own into this one. Thanks for everyone's help. I still haven't worked out how to display actual pics, just links to pics despite the helpful advice. I'm doing this here because it's just too much time to go back and fix all the threads those greedy pricks have ruined. Imagine the carnage over the whole Web?!

[greenmonster]

 

What tools & machines involved?
How much does this affect jetting?

No luck searching  "Carb mods while you save for FCR's".

[Speeddog]

http://www.ducatimonsterforum.org/index.php?topic=71115.0

[koko64]

Thanks Nick.
Gert, I used an air grinder and dremel with sand mops of various grades. I also used fine finishing pastes and polishes. The carbs require disassembly of course and thorough cleaning and blowing out with compressed air.

Yes I found low speed jetting requirements changed and I tried smaller pilot jets as low as 35's, but settled for  37.5's like CCW used to recommend. Needle and main jet settings are dependent on air box mods. I use 165 mains in open air boxes with our fuel down here. I recently had to lean low speed jetting off a bit as the 98 RON I was using changed.

[ZoomZoomZoom]

sick

[greenmonster]

Thx dp.
  Tony.

[koko64]

They are nothing compared to FCRs, but better than stock. I just hate how some things are built down to a very minimum standard. I like the choke/enrichening circuit though! They are just so unfinished.

I am going to test a set on my 900 today, but  will have to wrap the manifolds in exhaust heat wrap and cover the oil cooler. I have also fitted a Mikuni quick turn single cable throttle. Jetting for smoothness and economy and accepting that there is no accelerator pump, I'm trying 165 mains (175DJ), DJ 730 needles on notch#4, 37.5 pilot jets, DJ springs and Factory Pro needle jets. I will try this with some open airbox and rubber velocity stack mods.

It will work fine as long as I roll on the throttle for the first half turn rather than crank it in a roll on. The last half turn can be pinned once you are going. For outright acceleration you need the cruise muxture too rich to compensate for no accelerator pump, so as long as you accept the carbs basic design and "ride the carb" they work fine.
The carb mods actually help response and economy with less turbulence, less slide flutter, better atomization and better airflow. I know this by looking at the carbs and spray pattern with the airbox lid off and by the better response. I havent dyno tested or measured flow, but you can concretely see the difference revving the motor with the filter off.

Really enjoying this analogue bike.

[koko64]

Tested two sets of CV carbs on the Monster today. First set leaked like a sieve and the slides didn't rise correctly. OK put those aside and pull them apart to transfer the jets to set number two. Set number two required plenty of testing to get the slides to rise and fall together, but no leaks and tight as a drum. Love the choke. Very responsive and I'm quite surprised by that. The quick turn throttle contributes to that, but what must help response is no slide flutter and a nice spray pattern. Even with DJ springs which are very soft there is no slide flutter just snappy response. Thinking about it, I reckon if you just fitted a quick turn throttle to stock carbs it would promote even worse bogging without an accelerator pump and more slide flutter with the square edged slides and steps in the carb throat. I'm theorizing that slide flutter may not just be causing turbulence due to the square edged slide but is evidence of turbulence caused by the steps in the carb throat.  What do you reckon?

 Will do more work tomorrow.

[koko64]

https://www.flickr.com/photos/150482584@N03/shares/SB32U1

20170803_162558 by Tony Kokonis, on Flickr


An idea of how the worked carbs sit in the re arranged airbox.

[koko64]

https://www.flickr.com/photos/150482584@N03/shares/qu35z8

What the rubber stacks look like out of the airbox.

[koko64]

https://www.flickr.com/photos/150482584@N03/shares/a4j6Dw


Here is an attempt to maximize airbox volume. This airbox is now on a hi comp M750 with FCR39s.

[greenmonster]

Filter glued in enlarged box or what?

[koko64]

I used windscreen adhesive/sealant to goop the K&N filter to the airbox lid. The filter is raised and the stacks are dropped, opening up the usable airbox volume in between. I gutted an old oem filter to make a gasket and removed the lethal filter support struts and epoxied them up and under the new filter location. I went into it in great detail in the old thread.

I went to check on my notes and found my pics had been kidnapped. Getting an old Monster again has made me revisit all these mods.

[ducpainter]

You know you can hotlink pics so they appear on the forum...right?

[koko64]

Im still trying to work that stuff out.