Yep, a DJ150 main jet.. Last dyno session further confirmed a .5 lean spike in the 8-9k range.. Since I now have data showing fairly precisely how much "fatter" an AFR you get per jet size (.1 per size increase), I calculated 5 sizes bigger - from the DJ140 in the bike - would get 13:1 down to 12.5:1 with a the spike going from 13.5:1 to 13:1.. I can live with the spike raising AFR to 13:1 but I hope the low and midrange aren't going too fat...

Having ridden the bike some, I think I've got it - It is once again sounding different, hard to describe, kind of a mean growl like it wants to kill something and eat it, when you snap WOT.. it pulls cleanly and hard from any starting RPM with any measure of throttle increase..

I'll dyno again Tuesday.. With any luck at all, it'll show an AFR range of 12 to 13:1 and that'll be a "wrap" on the dyno tuning..

 

This is just crazy, as in interesting and cool. Was this with 3N? How many turns on the screw? Are CV carbs really this tolerant? Not trying to contradict, on the contrary this is interesting to me as I want to get the best jetting I can so I want to understand this carb. Your dyno tests are priceless data.

I read that with time the main jets that the needle moves in and out of get worn and let more fuel pass so that could explain, but that doesn't account for main jet at high rpm wot.

The largest main I have is 132, I'll have to try that tomorrow. It is about the same as a 139 at sea level.

cheers

 

Yes, 3N.. Turns out it's really a no brainer - you just have to follow the "CVK Setup Procedure" link on my signature line. Take your perfectly functioning setup and get the main jet size optimized first.. Problem is/was that without dyno testing you never know exactly what your getting with a particular main jet. The damned bike runs great with a wide variance of main jet sizes - even with the lid off.. What it takes to get under 13:1 @ WOT without the lid is/was uncharted waters.. And for you, at your altitude, it still is..

My carb is new so there should be no wear in the Needle Jet yet. My research indicates some versions of the CV carb do wear out the Needle Jet but, so far, I haven't found where our CVK is known to do so..
A lower needle clip position uncovers more of the main jet sooner. Giving a fatter AFR within the needles' range of influence. But shortly after 6.5K @ WOT the needle is done and it's all main jet+main air jet (MJ+MAJ) mixing fuel and air in the needle jet which then flows it into the carb barrel.. You'll never get the prize (extra 3 HP) until the main jet is correct. And for near sea level with slip-on and lidless, that may be a DJ150 !

With a proper main jet, the clip position needs to come up in order to not over-fuel the low and mid RPM range..

So if/when you get your leaky butterfly shaft fixed and everything is back to normal using the setup you've found (we are not troubleshooting, we are performance tuning) you might try the 132, 3N with fuel screw set to midway between idle drops.. If you sense stronger power from 7k to 10k, your on the right track. Then if the pilot + needle clip position gives smooth powerful transitions when snapping to WOT, you're well on your way to "Holy Sh$t" power..

 

Oh, I just read that your leaky shaft is fixed. YooHoo!

 

haha, yeah crossing my fingers I confirm the fix again today. Do you have a dyno run with the DGR running 140 and 3N? I can only find the one for that setup and FMF.

cheers

 

No I don't.. But if you'll print off and study the FMF and DGR charts, you'll see that the DGR needs more fuel below 6.5K than the FMF. Using any given carb setup, the DGR will always show leaner below 6.5K than the FMF.. But remember that using larger and larger main jets will also "fatten" up any given clip position.. If your calculations indicate the 132 @ 5K is similar to a 139 @ SL, then you'll have a really good main jet size for the stock header+PC4, in my opinion.. I'm thinking all you gotta do is set 3N, pilot to middle of idle drops and HANG ON!

 

I think you're right. I had another ride today and I could only feel correct jetting. Feels better than before actually.

I'm going to try 132 with 4N tomorrow and see how that goes. Thanks for your feedback it's really helpful.

cheers

 

Well, I just hope I'm helping..LOL

It really hinges on your calculations of jet size vs altitude as to whether the 132 is a viable option at 5K. With the 132 in, its all about how it runs and feels above 7K from current baseline. Under 7k, (AFR's during the transitions from pilot to needle and needle to main) is needle and then pilot tuning..

 

So did a Dyno run on DJ150 3N today and added it to the post.. Too rich almost everywhere.. So I'm thinking I'll try a DJ144 and 2N. 2N because the Dyno tuner said the clip notches are usually good for 1 point on the AFR. A DJ144 will probably send the low and mid range into the high 11:1's (at 3N) and the top end to 12.5:1... Since there is no gain from over-fueling the low to mid RPM range, perhaps 144/2n will get a mid to high 12:1 throughout the RPM range..?

 

So are you adjusting your float height everytime you change the needle notch position?

When I tried the 5N it was too rich and bogged down and died.
I just tried 3N today and it was so lean I'd have to pull throttle + keep choke on just to get it to idle.

So... 4N is the only option I can even test on my bike unless I mess with float height.
Is this the case for you as well?