CV40 Idle: 12.9 Cruise 13.9 WOT 13.2 - Slow Roll on Throttle 15.2????

[Yo J]

Bike Runs Great
06 RK
1.9 /1.6 Heads
.030 HG
203 SE Cam
CV40

I have a digital AFR meter in the FRONT header pipe

Idle: ~12.9
Cruise: ~13.9
WOT: ~13.2

However when cruising 50+ and give it a slight slow roll on the throttle AFR goes to ~15.2 then settles out at ~13.9 is this normal?

Thanks....

[FLTRI]

What exhaust system?

[Yo J]

Bub 7 TD

[mayor]

yoj, what needle are you running in that bike?

btw..how was the trip?

[Yo J]

yoj, what needle are you running in that bike?

I will be taking the CV off tonight in order to determine what the jets and needle size are..

Trip was great..to Cape Hatteras...

Going to BFHD Sat for another Dyno Shootout.... See You There?

[mayor]

it sounds like the issue you are having with Becky's bike is the transition point on the needle.  Sonny had a similar problem on his dresser when he was running the N65C needle. Is she getting any ping when it dips lean? 

Going to BFHD Sat for another Dyno Shootout.... See You There?

no not this time....got to work this week end.  Heading to the left coast (San Diego) on Saturday.  good luck on your dyno run, and I'll be expecting an e-mail with the runs files.   

glad to hear the trip went well.  BTW I finally got the T-max hooked up on my RK.  I have to say so far I really like that system. 

[Jeffd]

seems like if it was only occuring during a  slow roll non load type situation and the afr went right back to 13.9 it would be no big deal.  lots of people like the lean afr at cruise, you see them in the 14.5 range.

[Yo J]

Is she getting any ping when it dips lean? 

No pinging.. does get popping on decel...

[mayor]

if no pinging,  as Jeff mentioned probably nothing to really worry about.  decel popping, has the slide been modified?

[ederdelyi]

Accel pump or the mix going overly rich can fool the sensor into thinking the mix is lean ... sounds like that is what is happening. I often disable accel enrichment with EFI for tuning purposes just for that reason. Remember, the O2 sensors read O2 content, not fuel or other exhaust gases ... only 4 or 5 gas analyzers can't be fooled like that.

[Yo J]

I will be taking the CV off tonight in order to determine what the jets and needle size are..

50
195
N8EA + 1 Shim

[blackhillsken]

Ed, are you saying that too rich of mix can make the O2 sensor read lean?  Is the theory that the sensor over-cools for a fraction of a second?

[ederdelyi]

Ken,
As you know, two main the two main causes for false lean readings for both wide and narrow band sensors are air intrusion and/or  a lean or rich misfire. Both of the misfire conditions can result in incomplete combustion and give a false lean reading. I believe that in some cases the accel enrichment or accel pump action on a slow roll on actually results in increased incomplete combustion and until a steady state condition is reached the readings will be off. The pump circuit is not usually a problem, although I have seen some weird things happen with either restricted pump inlets or pump inlets exposed to a "forced air" stream.

I ran some tests with both O2 and 5 gas meters reading the same pipe and this is how I arrived at my conclusion ... I may be FOS, but it's the only thing that made sense to me.

[blackhillsken]

Right you are about a misfire causing a lean reading.  I've even purposely shorted a cylinder just to verify my dyno sniffer found it's way into the right pipe.

Just not sure I go with a misfire under the conditions in the original post (slight roll-on while cruising) though.
My opinion is, since it's very short term, it's just a temporary lag of the fuel coming up the emulsion tube.  Especially at the low intake velocity of a 50 mph cruise.

[FLTRI]

Right you are about a misfire causing a lean reading.  I've even purposely shorted a cylinder just to verify my dyno sniffer found it's way into the right pipe.

Just not sure I go with a misfire under the conditions in the original post (slight roll-on while cruising) though.
My opinion is, since it's very short term, it's just a temporary lag of the fuel coming up the emulsion tube.  Especially at the low intake velocity of a 50 mph cruise.

[ederdelyi]

What I saw pointed to incomplete combustion, not a complete misfire. With an elevated O2 from any source be it internal or external the O2 sensor will read lean whereas a 4 or 5 gas will show the combustion inefficiency and an accurate AFR under the same conditions. Response time is also a factor for both, with the better widebands usually the winner in that regard. The pump and heater circuit has a pretty quick response time, but it also has a fairly wide temp range and the cooling would have to be pretty drastic to exhibit that behavior. I've seen the same behavior from narrow bands that have no pump or heater.

Bottom line is that I believe it to be a false lean reading, exactly what the cause may be is open to discussion ... I'm not learned enough to say but I do believe what the muti gas analyzer tells me.

[ORork]

Great thread. I was told when opening the throttle the air mass moves (in) very fast as compared to the liquid fuel, hence a lean moment in a properly jetted system. One could tweak the squirter/orifice/plunger spring pressure to get the "fuel lag" as mute as possable.....but could you get it linear?

I mean, put a different weight on the bike and the engine rev up speed is not going to be the same, but the squirter is going to operate as you set it.

[Yo J]

Ok more help pls...

50
195
N8EA + 1 Shim

I noticed that the idle screw was only < 1/2 turn out (~12.9) so I figure it was running rich down low and was adjusted to ~12.9... so I removed the shim (OK I was bored) now the bike has 12.9 @ 1.5 turns and runs ~13.2-13.4 WOT....

Buuuuuutttttttt

at cruise its at 14.7 - 15.2 

So wut do I do .. ??

Put the shim back?
Change the slow ?

Go to a different needle??

Much Thanks!

[ORork]

I'd put the shim back in. Up the main to a 200 and put in a smaller pilot. Maybe a 46.

[FLTRI]

No need to fret. You just changed the wrong jetting.
Put the needle shim back in. That will return proper AFR @ cruise.
Put a #46 or #48 pilot in to replace the excessively rich #50 pilot.
Leave the main jet as it is producing proper AFR @ WOT.
Readjust idle mixture. Should end up about 1 1/2 turns out.
There ya have it,
Bob

[mayor]

No need to fret. You just changed the wrong jetting.
Put the needle shim back in. That will return proper AFR @ cruise.
Put a #46 or #48 pilot in to replace the excessively rich #50 pilot.
Leave the main jet as it is producing proper AFR @ WOT.
Readjust idle mixture. Should end up about 1 1/2 turns out.
There ya have it,
Bob

although the targeted 12.9 idle seems like a rich setting to me.  my guess is 13.6-13.8 is probably about as rich as you would need at idle. 

[Yo J]

Put a #46 or #48 pilot in to replace the excessively rich #50 pilot.
Bob

Hey Bob,

OK I did put a 48 in last night to test and believe it or not I could not get the AFR below 17... yes I turned the screw out 3+ turns until I got scared of it falling out..

I am thinking from other reading that maybe I have a bad jet... because 48 is so popular for other builds...

Is it bad to run with the idle screw only 1/2 turns out?

Funny with Rineharts and the same jetting I got (ok GF got) 10% better fuel mileage...

In a scale of 1-10with 10 being metdown... how bad is 14.7 - 15.2 at cruise?

tnx

Sporty Needle?

[mayor]

Sonny had good luck with the NOKK needle (27241-95).  I have one you can try, but you have to wait till I get back from the west coast before I can get it to you.     

why such a rich target for idle?

[Yo J]

the NOKK needle (27241-95).  

I have one thanks... I woke up n the middle of the night with "Sand the shim/washer" so I will try that next...

I always heard that 12.9 was a good target for idle to keep things cool???

EDIT: I have one thanks...

[ORork]

OK you put the smaller pilot in and now your cruise is lean. How is the idle mix? If the idle reacted favorably, now on to the needle. Seems the over lap effect between pilot and needle showed just how much sharing is going on. You're on track.

[Yo J]

OK you put the smaller pilot i

I tried the 48 with N8EA + 1 Shim and it was way lean and I could not adjust via idle screw... so I went back to 50 with no shim and I am rich down low at 1 turn and way lean at cruise 16+... if I go two turns out my idle afr is ~12.3 and the cruise goes to > ~14.9 with NO shim....

SO for today I will just sand the shim or look for a thinner one... then I will have to do more reading... thanks for the advice

[ORork]

shimming the needle less isn't going to enrichen any where. When you're at cruise speed your on the fat shank of the needle. put in a skinnier needle. Or, if they're available, get a larger needle jet (not the needle, the hole/jet the needle passes through).

[Jeffd]

are you sure of the accuracy of your afr meter?  try an N72S needle. 

[Yo J]

are you sure of the accuracy of your afr meter?  try an N72S needle. 

Good question going to BattleField HD for the Dyno shoot out... stay tuned... I reckon..

[FLTRI]

Something is simply not right here.
Idle AFR is fine between 13.5-14.2 AFR. No need to run excessively rich (<13.5) @ idle.
If good idle is attained w/#50 @ 1/2 turn but you say w/#48 it is way lean w/screw almost falling out, something's wrong. There just isn't that much difference between the 2 jets to cause 1 to be way rich and the other way lean.
Cruise AFR is controlled by the needle. Raising the needle will make the cruise richer and lowering it makes the cruise leaner.
So again:
With the #48 pilot adjust the idle AFR to 13.5-14.0 reading whichever cylinder reads the leanest @ idle.
Idle screw adjustment will only make a very small change to the cruise AFR.....very small, if measurable at all.
The needle shimmed to produce 13.5-14.5 reading the leaner of the 2 cylinders is ideal.
The main jet that produced the 13.2-13.7 AFR @ WOT is ideal.
Not rocket science just understanding what does what.
HTH,
Bob

[Admiral Akbar]

Intake leak?  Max

[FLTRI]

Intake leak?  Max

Should be lean @idle w/intake leak right? It's way rich @ idle.

[Yo J]

are you sure of the accuracy of your afr meter?  try an N72S needle. 

Good question going to BattleField HD for the Dyno shoot out... stay tuned... I reckon..

OK got back from BFHD... Travis compared the digital meter I have on the RK with the DynoJet and the was a .7 diff (DynoJet read leaner).  He said my meter ran richer ....  RK hit  101TQ/90HP ... will post in Dyno section tomorrow night when I can scan charts in...

It has been suggested that I go 2 shims on needle and 48...

If I wanted to start over what would be a good baseline for jets & needle?


Mayor.... talked to Wayne & Travis @ BFHD - they said they had a 5-7% error reading low in Apr Dyno Shoot out..  Ultra was 98TQ/90HP (1.8/1.5 valves)

Thanks everyone for your suggestions/help/comments...

[FLTRI]

It has been suggested that I go 2 shims on needle and 48...

If it needs more fuel @ cruise that is perfectly acceptable to do.

If I wanted to start over what would be a good baseline for jets & needle?

Same as above, but why start over since you are so close to getting it right?
Bob

[Overcamber]

geez I love reading about all this fine tweaking..makes me want to go and buy a afr meter 

[Overcamber]

what would be a decent brand of afr meter to shop for for my carbed 2003? do people sell them used once they tune their bike or just keep them installed forever? thanks