SE 44 mil carb

[03fxst]

Okay, so far so good. Sort of.
Just took the first test ride. Bike definitely has more power both low end and high. Throttle is much more sensitive as predicted. Lugged it slightly pulling away from a dead stop on a steep hill and no detonation. That is wonderful.
Now for the issues. There is more popping and backfiring through the pipes when I shut the throttle all the way while decelerating at high RPM's. Not excessively high, just cruising RPM range, or down hill using the engine compression. Slight touch of the throttle stops it. Mikuni web site says that is normal for performance engines. Maybe, but the CV didn't do it.
Next, no idle. Zip. Stopped at a red light and closed the throttle and she died. Repeated it a few times. Nothing in the guide speaks to the hanging idle adjuster on the carb side. Just instructions for the idle air adjustment. Can't do that without idle. Also, this carb rattles a lot. Again Mikuni says slide rattle is normal.

I want to resolve these minor issues before getting a dyno check on the AFR.
What are your thoughts?
Did I mention the power increase and loss of detonation.....gotta love it.
03FXST

[03fxst]

Turns out the idle adjuster was shut off. The book said it was set at the factory but on closer reading it is the idle air adjuster that is set there. The main idle adjuster was all the way closed. Adjusted it to a smooth idle and went out again.
Backfiring is reduced back to what it was, Bike feels smoother at the bottom end and runs like scalded cat on the highway. The bottom end throttle response must be felt to be believed. It is like the rear wheel is attached directly to my right hand. It isn't twist and go, it's twist and gone.
Bike also jumps to life when I hit the start button. That is a major improvement over the CV. Can't wait to try it on a long run for fuel consumption and overall ride-ability.
Still rattles like a grand mothers teeth on a cold winter night... I may fall in love with that sound once I get used to it.

Call me a convert.
03FXST

[frisco-rigid]

03

Figured you would be..

OK, you figured out it's the Idle Speed adjuster that is hanging..
The Idle A/F adjuster is the wee brass screw AND IN makes Rich----Out makes Lean..!!!
I take that screw all the way out and grind a Notch at ONE end of the slot..
Then, at my convenience, I can dial in a wee more OR less Idle fuel any time and know exactly how far I re-adjusted by looking at the Notch on the "clock"..

The pop back is still evident in my 127" too,, no matter what I've done..
Try the next size up Idle jet--- you prob have the #25 in there, it's standard..
That took care of ALL pop back with my 93"..

By all means do the throttle tape procedure for final jetting..
Take all slack outa the cable and make your first mark and so on..
It makes it soooo much easier..
The 97 needle is also standard and I bet it's the one you end up with, But those little tiny notches really make a very big diff..

Remember,, you must Re-Tool your brain to think in terms of "throttle position" now rather than Rpm's..
It may take some getting used to,,,, runnin 80 at 3600 R's but only being about 1/8th throttle and knowing you're still No Where near getting close to the Main jet..
I know you've got all this in the very informative book,,, I'm just re-inforcing..

Have a Ball

[03fxst]

Hey Frisco
Looks like the needle may be lean or the Mik doesn't like the advance curve I have set. According to the tuning book detonation at 1/4 throttle low to mid rpm range is a sign of one or the other.
Rolling on to one quarter in third or fourth above the lugging stage but not up at top RPM causes extreme detonation. Book says the 97 needle is in there. Carb came with two main jets to swap out but nothing else so I'll have to experiment with advance curve first and then the jet. Harley offers a race tuning kit for the carb. I will check the dealer Monday to se if one is in stock. I gather it would have a selection of jets. Or should I just order a richer needle and see what that does?
I haven't adjusted the needle position because the book says that is for issues at 1/4 to 3/4 throttle and I'm not there yet.

living and learning..
03FXST

[frisco-rigid]

Hi Buddy

Hmmm, you might be right but I wouldn't think so..
I would suspect timing And Mikuni or whatever carb--- twisting it in too low R's will get deton..
Me, I keep high R's or I drop down before twisting..

A 97 was perfect in the 120" with 10.5-1 for a couple years with Never any deton but about a year ago I installed a 96 and got wee more power and 1 more MPG,, how bout that.. But, of course they are all diff..

You did take up ALL slack in the throttle before marking yes..????? If you didn't 1/8 throt will look like 1/4..

I run a wee rich in the idle A/F adjust..


A kit of jets might be a waste a dough.. Call around for individual units,, I would guess all you'll need is a 27.5 and a 96.. You may Never see your Main,, really.. I been in my main maybe 3 times only while racing..
Before you write off the 97 check that timing and, no matter what the book says, raise the 97 all the way just for comparison..
If timing is correct and the idle A/F & jet is also, then raising it total will likely tell the story cuz if all the way doesn't work then of course you need a 96..

Also--- you must read the Teeeeensy Letters on top of the needle cuz the 42 and the 45 needles look identical but the taper is actually quite diff..

Hey, took me a couple weeks, then I fine tuned for several more..

[03fxst]

Thanks
I'll call around on the jets and buy a couple. I don't think I was low enough in the RPM range to even come close to lugging so it wasn't a gearing issue. It was perfectly smooth in that range at that speed with a roll on before.
I did leave some the free play in the throttle though. I think I compensated for it on my estimates. I want the free play because the throttle response is so touchy now. Until I get a feel for the new reality of how the bike handles out of the blocks I want some grace in my hand so I don't make s stupid mistake in traffic.
I will smooth out the advance curve and back off on the advance itself the way the book suggests and try that. Then I will focus on the needle itself and where it sits. I'll also go a tad richer on the idle circuit since this issue is right off a closed throttle position.

Marbles in the cylinder, marbles in my head...
03FXST

[frisco-rigid]

03

You mis-understand my meaning of taking out the free-play....

I Do Not mean the free-play in the cable.. We want a little bit there..
I mean the free-play in just the throttle barrel itself at the grip..

Just simply twist it that teeensy weensy bit until the play is out and it just starts to wanna move the slide----- THEN mark all the reference marks..

[03fxst]

Sorry about that
Good thing I decided against following what I thought you were telling me to do. Throttle is now marked the way you actually were telling me. Won't get to do much roll on testing on the ignition though. Pouring rain for the next day or so.

Speaking of slippery roads and the main jet. Okay, we weren't but I'll change the subject. Before the Mik a full throttle roll on in first gear would lead to tire spinning just before the top of the gear. She'd pull like crazy and then break loose. With the Mik its like the bike is on ice in first gear. I'm not talking hole shots. Just pulling away and deciding to twist it part way through the gear. Scary at first, but amazing now.

When it's on the cam it's off the charts...
03FXST

[03fxst]

Another thought
Since the only change made is the carb/manifold combination should I stay away from the ignition curves and concentrate on that needle? I don't want to start chasing my own adjustments as I try to tune it. I was thinking of doing a three part Dyno run. 1/4 throttle, 3/4 throttle and full throttle to get AFR numbers and then re-grouping.

Frisco before I raise the 97 I have a question for you. Obviously you've done it with the same carb and it works so that is probably the simply answer. But, in the interest of understanding why and not just how. I am puzzled by the Mik tuning book. It says Needle adjustment will only change the mixture beyond the 1/4 position and not from closed to 1/4 where I am getting this detonation. That just doesn't seem to make sense to me.

Still raining, still thinking..
03FXST

[frisco-rigid]

Hey 03

Um, even though I think the Mik book is one of the best for instructions it can be a wee confusing.. For example it states that the Idle circuit controls from Idle to 1/8..
Then on the next page it states the straight portion of the needle controls from "off idle to 1/4"..
OK, which is it..
I called Mik USA and spoke to Steve.. He told me it's the latter but I got more "change" in that area with Idle jet changes.. Sooo, which is best advice, I dunno,, I just react to what happens to me..

Believe me--- I'm Not trying to convince you that you Must run a 97,,, I'm just trying to sugg a reason or two for the deton and giving my experience..

I sugg'd you total raise needle position only to see if it changed anything,,, for comparison..

Ok,, let's pretend I'm there and I'm taking over ------- I would implore you to increase the idle jet size 1 up..
Then I would encourage a Rich Idle A/F mix.. In-other-words,, instead of the middle of the "range" on the dial as the book advises------the fat end of the Range..
I would keep the 97 for the time being cuz in my experince, right or wrong,, I found that getting the Idle circuit correct is Key to beginning the jetting to My Miks,, once it's right you start the needle fine tune..
The 97 being standard, is a good average needle to begin with..
I Don't know what your advance curve is but I think an aggressive curve is deadly.. My rate of advance on our 80", 93", 120" & 127" are fairly easy and only to 28* max.. And I never use VOES..
Your call on that stuff..
But, I think it's important to settle on timing and lock it down.. Make it final, then continue..

Oh yeah,, and remember,, you can do a plug reading just the same as with any other carb that jets by Rpm's,,, but in your case it'll be by Throttle position,, I've done it ,, works well..

frisco-rigid@mchsi.com
Anytime