Octane and idle screws

[mavgrab302]

First of I usually use the mid grade gasoline, with the idle screws pretty much all set at or around 5 turns out. Over the weekend not paying attention I had put in high grade gas. Going in stop and go traffic I started having a really hard time taking off and keeping the bike idling, it was stumbled big time. got to the house and started fooling with it, tried leaning and that didn't work at the end I had to turn all the idle screws out to about 6.5 tuens out and it ran just like before, perfect. My question is is the vmax really that picky on fuel grades, and what grade do most of you guys use?

I have the stage one kit with the dj needle 3rd slot if memory is right, drilled slides, and 170 mains, 150 pilot jet, 240 sea level.

 

[2fear]

Mine runs the same on 87 or 93 octane so I just use the 89 midgrade.

 

[tugla]

wow 6.5 turns out id say thats way too far. 2.5-3.5 seems to be the norm and i have never had to adjust my screws pending on fuel grades from the pumps. are those 170 DJ or mikuni jets?
might need idle circuit cleaned out, shot gun/peeshooter something like that to start.
what kind of mileage you getting. have you had them apart lately for cleaning and also a sync job?

 

[4gasem]

Octane won't make it stumble unless it's VERY low... 87 on a stock motor equates to the most HP and it lessens as the octane increases. Higher octane=less volatile for high comp engines.

Sounds like you have water in your fuel. Try putting some seafoam in it and drive it for about 20-30 minutes. It should clear up over time.

Mine does the same thing when I let it sit with ethanol fuel and no startron mixed in.

Chris

 

[SpecOps13]

I'm running non ethanol gas in mine. If I have to put ethanol in because I got too far from home, where I keep a gas supply, it runs like ****. My adjustment is 3 turns out. Sounds like you have another problem as mentioned being 6-1/2 turns out.

Good Luck, I'd try running some good carb cleaner through it and you may have just gotten some bad gas when you filled up last.

 

[gamorg02]

my screws are up near 6 on certain carbs they still adjust up to about 8/9 turns..

 

[tugla]

my screws are up near 6 on certain carbs they still adjust up to about 8/9 turns..

on the vmax garrett? wow didnt realise that, does it pop if you turn them in??? think i counted 10 on turns but dont think you want to be right at the end anyways, might fall out hahaha might aswell take them out and put a rubber plug in there with a tiny hole, be the sale thing hahahaha

 

[gamorg02]

yea it kept adjusting so we kept unscrewing it. i have covers on them so if they ever came loose it'll catch them.

 

[mavgrab302]

yeah I realize lower octane burns quicker prone to detonation and th opposite from higher octanes, but this has happened twice and the only remedy has been to turn out the idle screws.
heres my set up again: "Y" removed, 170 DJ main, 150 dj pilot jet " with the stock 120 mikuni pj it stumbled bad, reguardless of screw settings", drilled slides, and i think it's the 3rd slot on the DJ needle..and the floats are all correct. I also have the marks 4-2 exhaust with pipe sleeves overlaying the reso tubes so it's wicked loud..lol
once at at a stop at long red lights it just gradually gets worse, keep having to rev it to keep it going and then nurse it to move with out dying. I know when it's running good I'm still rich but it's the dj #1 kit since theres not alot of play in the kit so there little tweaking. I know cold starting requires no choke, ever...lol
replies:
I get about 130 miles that being with the warn light already on.Synnc and cleaned about 8 monthes ago.
no water in the tank and my bike moves if not everyday everyother day.....

 

[2fear]

Stock Vmax calls for 86 octane minimum.....
Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause autoignition.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, an uncontrolled ignition is not desired in a spark ignition engine.
A fuel with a higher octane rating can be run at a higher compression ratio without causing detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require higher octane usually deliver more motive power and do more work for a given BTU or calorie of fuel. Engine power is a function of the fuel, as well as the engine design, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.
Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.
However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate, that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.
Most fuel stations have two storage tanks (even those offering 3 or 4 octane levels), and you are given a mixture of the higher and lower octane fuel. Purchasing premium simply means more fuel from the higher octane tank; the detergents in the fuel are often the same.

 

[RagingMain]

my screws are up near 6 on certain carbs they still adjust up to about 8/9 turns..

I have verified using an A/F meter that anything past 5 turns doesnt really affect your mixture. The screw is as far out as it is going to be to uncover the holes leading to the carb throat

 

[gamorg02]

I have verified using an A/F meter that anything past 5 turns doesnt really affect your mixture. The screw is as far out as it is going to be to uncover the holes leading to the carb throat

i respectfully disagree as I watched the a/f change on a dyno with a sniffer. maybe its vboost being wide open? not sure but we went too rich at like 7 screws and had to back it down to 6ish.

 

[wildman98]

disagree pull fake tank cover off read fine print MIN OCTANE 91

 

[2fear]

disagree pull fake tank cover off read fine print MIN OCTANE 91

Haynes manual = USA min octane is 86
Haynes manual = UK min octane is 91
Bill, remember you have the California model that could be the reason it states 91 octane, for polution.

 

[MaxMidnight]

I think you will find the difference is a classic example of two nation separated by a common language.

Here is what Wikipedia has to say on the topic:

'Generally, octane ratings are higher in Europe than they are in North America and most other parts of the world. This is especially true when comparing the lowest available octane level in each country. In many parts of Europe, 95 RON (90-91 AKI) is the minimum available standard, with 97/98 RON being higher specification (being called Super Unleaded). The higher rating seen in Europe is an artifact of a different underlying measuring procedure. In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in Canada, the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in Canada and the US, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90–91 US AKI=(R+M)/2, and deliver 98, 99 or 100 (RON) (93-94 AKI) labeled as Super Unleaded - thus regular petrol sold in much of Europe corresponds to premium sold in the United States.'

So now we know!

 

[wildman98]

hey chuck pull fake cover tell me what it reads.i pulled cover on:ummm:cant remember his name the guy that syk my carbs.his reads 91 octane:confused2:also dont think his is cal bike.let me no what youres reads use youre glasses:clapping:lol.

 

[mavgrab302]

I disagree as well, haven't used an air fuel sensor but the motor reacts screwing them in to 5.5 turns and 7.5 turns. I'm sure my problem stems from using the stage 1 kit with the pj150 jet , where they are set now using mid grade is between 5 3/4 to 6 1/2 to get the smoothest idle and response.
Being the screws are mechanical, meaning the stay shape only move in and out from an orfice, you would think turning past lets say 5 it would be useless to turn out to 6 because the holes are uncovered the same as 5 turns but for what ever reason the bike does react. It's weird cause the holes don't let anymore fuel etc through after some point of turning out screws. Turning out to 8 to I think 10 is where the screws will fall out, I have noticed the bike really stops changing attitude and stays the same.
As I said before I think it has to do with the low compression of the motor, fuel octane, and the pj 150 jet from DJ. but without the larger pj jet the bike was very hard nail down at idle and and popped and lagged no matter where the crews were set.

 

[allisontech]

My 2004 is a non Cali Max, and it does say Min 91 under the cover. I have to agree with Wildman. I've been running 93.

Bill

 

[sdt354]

Stock engine, regular gas. 3 to 3 1/2 turns on the mixture screws. Runs ok, and exhaust valves are CLEAN. Running high test in a stock engine? Take a look sometime.

 

[Rhoy Carter]

When mine started acting up like that at long red lights i found the problem was in the charging system