We don't know jabara. Plug reading with ethanol'd fuel is difficult - read about that yourself - this plug looks like it went through break-in.

It certainly does not look "rich".. Which means that it seems you could certainly go richer on the main jet - likely improving power levels everywhere.. If I were ordering jets, I'd get a DJ148, DJ150, DJ152 - this is in addition to the jets you already have. I think you already have up to DJ146..?

Having DJ144-DJ152 will surely cover the bases with whatever we eventually find out about BB fueling with a lidless airbox and CVK..

 

What are you using for fuel? Ethanol or Non.? Plug looks good. Ethanol fuel doesn't color well. Tough to explain but ethanol will tend to look leanish when correct. If you tune for tanish brown with ethanol you will be rich. Many write ups on this out there. I just know from 20+ years of performance engine building experience.

I would leave it right there till you can get a wideband on it at a dyno. Your on the right track.

 

Just to add to the mix of carb set-ups....
I finally had the time to change jets on my 351. Previously I had a DJ128 main and 35 pilot with the 2206 needle on 3rd groove. Snorkel removed with FMF Q4. I'm at about 1100 Ft ASL.
Today I put in a DJ142 and 38 pilot and removed the filter lid. No other changes as I wanted to see how it ran with those changes alone.
Low speed throttle response is much stronger. Just blipping the throttle breaks the tire loose and lifting the front wheel is much easier.
Riding at WOT it pulls strong but my butt dyno thinks it does not pull as strong as it did with the previous set-up.
Any recommendations as to what I can try to make it pull stronger at higher RPM?

 

Using ethanol 93 octane for break in. I guess since I got two responses saying it doesn't look terrible I will leave it at 144 for now since it's running like a champ (I have zero complaints, it runs strong at all rpms, throttle response is great, no pinging or surging) I put a new iridium plug in it (this one may have been original) so I'll see how the new one looks in a week or so.

I have up to a 146, I'll order up to 150, I need a 40 pilot anyway, the only thing i haven't cured is my backfiring on deceleration, but I just put a kuoba screw in it to experiment and hi temp rtv'd the crap out of my air injection stuff(tapped and blocked with a jb welded bolt)

Thanks

 

My money is on a bad DynoButt. The increase in the low-mid range has rendered your dynobutt useless for assessing the top end. While your current fueling has increased your top end, it has also not increased it anywhere near as much as it did the low-mid..

We have no data for 351 lidless fueling with the various exhaust mods at this point - so my opinion is next -
Change the clip setting to 1N, Put back in the stock slide spring, be sure the slide lift hole is standard (and not drilled to 7/64 or larger). Since you seem to be running the stock header, put in a DJ146 main jet.
If your slide is drilled and your spring is stock (as per your 2206 kit instructions) then just reset the clip to 1N. Your needle is leaner than the 2152 kit, so maybe 1N will be enough - we should know more soon...


The idea is that you'd have the same biggy increase in the low-mid but with a top end that is more enhanced than you've ever felt..

Keep in mind that a fully uncorked 250 with the stock header runs out of breath at 9k - stands to reason a 351 blowing thru the same will run outta breath sooner..
I would expect that power levels start tapering off somewhere around 8k-8.5k on your bike.. Biggy top end would need a Pbomb or Mbomb, to go with your Q4..

If doing this tweaking/tuning is fun for you - have at it. Otherwise, we are hoping for some dyno data soon to help us "home in" on the fueling needs of a lidless 351 and the CVK setup that does the "trick" ..

 

I just re-read your post here.. Now we don't know if a BB responds the same as a stockbore to a full FMF exhaust - it is still sucking and blowing thru stock valves and ports - but tailing off after 8500 indicates a "too small" main jet on a "similarly modded" stockbore. Properly fueled stockbores, setup as yours, pull hard to 10.5k rpm..

 

I concur, mine did also. I had the good luck to run most of these setups almost back to back to feel the difference. 144/1N on the 250 pulls very linear and strong all the way to redline whereas on my 330 it definitely tapers off a bit, could definitely be main jet, but could also just be port/valve breathing ability. I may throw the 146 I have in there since the carb is out anyway, doubt I'll be able to tell any difference in that small of a change but you never know.

I am concerned about going to rich also as the top of my piston already looks very dark... I dunno if that's normal or not

 

Well burning some oil during break-in is normal - hence the darkening..?

I'd put the 146 in it.. You may or may not be able to tell any difference as doing so is dependent on how well you are testing top end power.. I certainly hope a BB can make big power on top when given 12.5:1 to 13:1 AFR and a full exhaust system..

 

Thanks for your input.
I won't be adding a P or M bomb header and I prefer getting the most power in the mid range so things may be pretty good as it is now. But, I have a 146 main so I will be trying that out.

 

just ordered my bb 351 kit, now I need to order some carb jets. I already have a dynojet mq2152 kit, but the biggest main jet is a dj132. after reading this thread,(and thank you for all the info) I would like to start off with a dj146 , a 38 pilot and a dn0228 needle 1n with stock spring. the question I have is where to get the jets from? jets r us have the main jets, but I am lost on witch pilot jet to order, ANY advice would on this kit install would be appreciated.