Jetting advice: CPR air filter on 950

[Sporting Wood]

Originally Posted by randel

Thank you all, a lot of valuable information!
As a conclusion, I thought about following setup going from H2W prefilter setup to CPR filter when it arrives:

Main Jets 175/175 front/rear
Idle Air Jet 50
Mixture Screws 2 turns
Float Level 4mm
install Factory Pro needles (I have FP kit), 3rd clip?

Did I miss anything?

Good starting point imho. I like the 2nt clip on my bike, but they all seem to respond a little differently. If its rich on the bottom end, of if it bogs down when you suddenly open the throttle, drop her down a notch...or turn in the screws a bit...or lean the bowls more... Raising the needle smooths the transition from slow jet to main, but there tends to be a lot of bleed through with the CVRs, soaking the bottom end and I find it easier and better to leave the needle in 2. It is all about creating good throttle response and an even transition from slow to main jet...and there are several ways to do this.

I'll report back once I've got some time with it and we'll compare notes.

Originally Posted by bruceca2002

What would be the optimum jetting for my mostly stock SE950. 2 into 1 pipe with an Acra silencer with spark arrestor. All pollution equipment removed and needles moved up one clip position. I get no popping on deceleration but it only gets about 30 mpg. How many turns out should the fuels screws be set at? The bikes runs very well as is but goes through a lot of gas. Thanks, Bruce

I don't have any experience with the 2-1 pipe but it would seem you are too rich where you run it most. Sort of to reiterate what I said above. If you were stock and only raised the needle, you have smoothed the transition zone, the 4000 rpm range where they like to cough and sputter out lean... but you have done so at the expense of enrichening your bottom end. Either turn in the screws, or lean the floats...or both, or drop the needle back down and attack the tune by first fixing the top end lean condition with bigger mains. This will also flow more fuel to the bottom and the transition. Lean the floats a mm and turn the screws to about 1.5-2 turns out. I'm not a fan of the stock needle but it can work this way.

[Sporting Wood]

Originally Posted by mousitsas

Peace SW, it all is ok!
Point is that cool hard numbers have nothing to do with what we are talking about. For me in jetting, all I want numbers for is when it comes to mains to not run lean (or very rich) on the top end. But KTM did the work for us here, by setting the ballpark. Also you and H2W and K2M did a lot of wideband work, I acknowledge that and gave us a nice running low-midrange. From there on I really don't think I need any numbers, I only rely on my feeling of what a nice running engine should be like. And if the two are in dispute, I would always tune to what feeling is telling me.

[Sporting Wood]

Update, I really like free flowing air. 175 mains, 42 slows, 1 3/4 turns on the screws, leaned float by a mm, 87 octane, fp needle @ 2. Runs great from 800' to 12,000...prolly good under 800', didn't get that low yet. It roars, makes plenty more power.

I can up the mains from this easily, I was worried going to Colorado that it'd be too fat.

Rolled my own filter out of a scrap of 1/8" alloy and some buna grommets that hold it firm to the carb base. Bought the same itg filter as the cpr guys use...best $80 mod ever

[Grinderman]

Thanks so much sporting wood!! I am going from the h2w setup to the CPR. 2 questions for you. We only want the 42 pilots?? Why not the 45's? And second is easy. I want to mimick your FP setup with the needles. 2nd position is from the top down or bottom ( pointy end) up? Thanks in advance for helping out.

[mousitsas]

Originally Posted by Grinderman

Thanks so much sporting wood!! I am going from the h2w setup to the CPR. 2 questions for you. We only want the 42 pilots?? Why not the 45's? And second is easy. I want to mimick your FP setup with the needles. 2nd position is from the top down or bottom ( pointy end) up? Thanks in advance for helping out.

I am not really entitled to answer, as I don't have a CPR box, but I have gone from H2W to a DNA filter + sommers door mods, which flows similarly with the CPR at least for small throttle openings. What I found, is that to eliminate popping on deceleration I had to turn the fuel screws 3 turns out which is more or less the limit of their adjustment range on the rich side and still pops a tad, but goes much better than H2W. I only touched the fuel screws and the mains going from H2W to DNA. So, I would suggest if anything to fatten up the jetting in this area if you change to a free-er flowing setup, but that might not be necessary.

[Sporting Wood]

Mains bleed fuel into the throat, big mains bleed more counteracting some of the need to fatten the low end.
No 45's because I find them too rich at altitude...and I'm on my way back from freaking Colorado! I did get them to work at home well but the climb up to 4-5000' always revealed that the bottom starts to choke. I want it to work everywhere and return good mileage...even at a loss of some power...though 45's absolutely rock at low elevations... 3rd gear wheelies!

2nt leanest clip btw, not from the pointy end. I find the 3rd bleeds more fuel into the low circuit, complicating getting the bottom to run well. Fat mains multiply that problem. I get good throttle response, no hole at needle opening so I see no reason.

[Grinderman]

Awesome!! Exact info needed. Appreciate it guys!

[Sporting Wood]

Originally Posted by Grinderman

Thanks so much sporting wood!! I am going from the h2w setup to the CPR.

Frankly, there's a reason I didn't buy the CPR to do this.

[Grinderman]

O.k. I put in the fp needles at position #2 with the big washer/spacer on top and the skinny little one on the bottom. My float height is right around 3.5mm. 42 pilots. 175f and 178r on the mains. I would have made them the same but I didn't have 2 175's. And the result was.....Crap! Bike was flat as a pancake in the top end. Wasn't snappy at all off the bottom. In all my previous setups I can power wheelie in first and 2nd. This one was dead. I don't think the answer is bigger mains. I ran a 175/180 setup previously with the stack needle in position 3 with the float much higher into the bowl (leaner, correct?). It pulled pretty well at those settings but of course I always WANT MORE! Help me please.....

[Sporting Wood]

Originally Posted by Grinderman

O.k. I put in the fp needles at position #2 with the big washer/spacer on top and the skinny little one on the bottom. My float height is right around 3.5mm. 42 pilots. 175f and 178r on the mains. I would have made them the same but I didn't have 2 175's. And the result was.....Crap! Bike was flat as a pancake in the top end. Wasn't snappy at all off the bottom. In all my previous setups I can power wheelie in first and 2nd. This one was dead. I don't think the answer is bigger mains. I ran a 175/180 setup previously with the stack needle in position 3 with the float much higher into the bowl (leaner, correct?). It pulled pretty well at those settings but of course I always WANT MORE! Help me please.....

Every bike is different, gas varies, altitude, expectations, etc... Sounds like you had it pretty good last setup. I'd go back to that if it was me. Small adjustments from there.

Was it factory needles, factory airjets, airbox, etc? If you had it with the h2w kit, the airjets should be different... and no way would it have run on those big mains.

[Grinderman]

Hey thanks for the quick reply. My last setup was not the h2w setup in any way. When I initially set up my cpr filter I pulled all of the jetting that was set up for the pre filter and put all stock items back on. What I am trying to improve on is..
42 pilots
175f main, 180r main
3 clip stock needle
cpr air filter
I have the remote for the fuel screws, but from what I understand these are more for the air/fuel at idle then anything. Is that right?

It sounds like these fp needles are the way to go in the less restrictive environment, and I am trying to follow your lead because you know what's up. I like the idea of 2nd position on the clip because it can cover a wider range in elevation. I just don't know what direction to head at the moment. I am at sea level and it's hot here in Nor Cal. Maybe I well try 3rd position and see if that makes a difference. If it is still flat in power I well throw the stock needles back in and compare. I screwed up by changing two things instead of just one. I should not have touched the floats until after changing the needle and riding it. Believe it or not this crazy bike that I spend all of my time on is what keeps me sane

[Sporting Wood]

Originally Posted by Grinderman

Hey thanks for the quick reply. My last setup was not the h2w setup in any way. When I initially set up my cpr filter I pulled all of the jetting that was set up for the pre filter and put all stock items back on. What I am trying to improve on is..
42 pilots
175f main, 180r main
3 clip stock needle
cpr air filter
I have the remote for the fuel screws, but from what I understand these are more for the air/fuel at idle then anything. Is that right?

It sounds like these fp needles are the way to go in the less restrictive environment, and I am trying to follow your lead because you know what's up. I like the idea of 2nd position on the clip because it can cover a wider range in elevation. I just don't know what direction to head at the moment. I am at sea level and it's hot here in Nor Cal. Maybe I well try 3rd position and see if that makes a difference. If it is still flat in power I well throw the stock needles back in and compare. I screwed up by changing two things instead of just one. I should not have touched the floats until after changing the needle and riding it. Believe it or not this crazy bike that I spend all of my time on is what keeps me sane

Thanks for the compliment. Anything I know about these things is gleamed from a lot! of practice not getting them right.

FP needles are totally different! I'd say that if its better in the 3rd clip for you on the stock needle, might stick with it...or spring for the fp needles which are totally the way to go imho. Stock needles are fatter/leaner with much less taper... making flatter transition to wfo power. All it changes moving clips down is the transition to main comes slightly earlier and there will be a bit more bleed through into the low circuit...which is likely why you had a leaner float before and probably a bit less on the screws. Shouldn't make so drastic an effect on elevation performance, if any at all. The greatest factor I have found in that regard is the 45 slow jet.

I'm east coast, our air is humid...your's is dry. I have my valves adjusted tight, yours may be loose. I left the plugs in my Akras... Whats working for me might not be so great for you. Esoteric I know, but these carbs are really fickle.

Best thing is to get the other stuff close, especially the float height, then top speed it to dial in the mains. Set those and leave them alone. Then figure out if it runs better in clip 2 or 3, 42 or 45 slows.... Small singular adjustments from there. I know its not that helpful but...

[Goss]

This new run on the CPR set up has many of us becoming carb apprentices to you gurus.

I have installed the CPR with Ken's jet kit for 500 ft elevation. I have a hanging idle issue now but had to leave town and could not finish tweaking to remedy that. Ken thinks I need to check my floats again and if they are both at 3mm then set them to 4mm. The kit did come with FP needles and they were set at the 3 clip. Can't wait to get home and get the thing dialed in.

Looks like a good thread to interact with if one needs advice thanks to Sporting Wood and other experienced tuners.

[Sporting Wood]

I heard sporting wood was considering laser cutting a bunch of these here air filter plates out, saving the perspective buyer a whole bunch of cash...

i mean, wtf? Its only a $75 filter and the plate is an easy thing to make. You guys spending $300 got too much money!


Here is the filter (Ok, so its $90 now, price went up)

You'd also need a couple of Dzus connectors the folks there sell for $2.15 each.

All else you need is a scrap of 1/16 or .080" alloy... I used a 1/8" piece of 6061 but just about any decent quality aluminum sheet would do... old road signs, legal size clip board, etc...

I didn't use the X-ring attachment as CPR. It looks as though it'd create an opportunity for vibration as evidenced by their first version self destructing. Instead I located some large Buna-N Grommets that isolate vibration to the plate and more firmly affix the plate to the carb bodies imho.




Jigsaw and a drill is all a guy needs to make this thing. I can provide a tracing, or even could lend out a 1/4" plexiglass template. I made this one with a Bosch woodworking router with a bearing mounted flush cutting laminate bit... :eek Even cut a bevel on the side that clips to the filter flange with a bevel cutting bit.

The two little holes I put in there were to affix the template to the metal ... and a mistake in placing one so close to the grommet. Welded'em up though so its no biggie now. Next time, it'd be in a better spot, and likely just riveted over once the cutting was done.

Beat the crap out of it traversing some Colorado passes last week and viola, no cracks! No leaks, no cuts to the Grommets... nothing.

Better - Cheaper - Just as Fast!




Also... as an aside... Those dern weirdly sized 1.3mmX6.3mm carb o-rings that like to leak, I sourced a bag of 1000. Anyone who needs some, pm me. SASE and the promise of a beer might get you a fresh set.

[Goss]

Installed CPR filter setup on 04' 950S, elevation 510 ft, Akras with inserts in place.

180 main in front
185 main in rear
65 idle air jet front and rear
45 low speed jet front and rear
4mm float set
FP needle at 3rd clip

Idle hangs slightly so to attempt correcting this my IMS are 3.5 turns out but still having idle hanging.
Going in on the IMS makes the hanging idle worse.

Bike cruises fine with no surging but does not have real crisp throttle response like it did with air box and pre-filter.
Seems down on top end power as no power wheelies are happening. No bogging or stumbling.

Any suggestions on where to go from here ?