Mikuni Tuning, Detonation
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Joined: May 2009
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From: The South
Mikuni Tuning, Detonation
I'm having trouble getting the bike to run just right so I'm looking some help. It's got a 96" Ultima, Mikuni HSR 42, Thunderheader 2 into 1, Dynatek 2ki with the lowest advance curve and no VOES.
Under heavy throttle, I get serious pinging/ detonation in the high RPMS. It also takes a while to warm up and I need the choke a lot before it runs right. Everything points to it running lean, correct?
Here's where I need some tuning help.
I bought the carb used so I don't have any spare jets. The slow jet is 22.5, main jet is 175, probably the stock needle in the middle position.
The idle air mixture screw will choke off the engine around 2.5-3 turns out, which is expected. However, it will only make the engine rev faster if you turn it all the way in. Is this also looking like it's lean? Many of y'all are not running as rich as I am, which has me stumped.
If I buy a master jet kit for the HSR 42, it doesn't come with the fat main jets, so I think I'd have to buy the kit for the larger carb. I believe their jets are interchangeable.
http://www.power-barn.com/servlet/th...tor-Jet/Detail
Under heavy throttle, I get serious pinging/ detonation in the high RPMS. It also takes a while to warm up and I need the choke a lot before it runs right. Everything points to it running lean, correct?
Here's where I need some tuning help.
I bought the carb used so I don't have any spare jets. The slow jet is 22.5, main jet is 175, probably the stock needle in the middle position.
The idle air mixture screw will choke off the engine around 2.5-3 turns out, which is expected. However, it will only make the engine rev faster if you turn it all the way in. Is this also looking like it's lean? Many of y'all are not running as rich as I am, which has me stumped.
If I buy a master jet kit for the HSR 42, it doesn't come with the fat main jets, so I think I'd have to buy the kit for the larger carb. I believe their jets are interchangeable.
http://www.power-barn.com/servlet/th...tor-Jet/Detail
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From: The South
My understanding is the VOES adds advance at higher RPMS. I'm getting detonation at high RPMS already after backing the timing off as much as possible.
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From: la la land jerzey
with the lowest advance curve and no VOES. < U wrote
WHY no voes < it does not take power away ???????
the stock low speed from Mikuni is 25 - they come 17.5 to 30 in 2.5 numbers
stock high speed jet is 160 - they come 150 - 210 in 2.5 numbers
std needle is a 97 - they make a 96 and a 95 richest one we found -
you need to down load mikunis book on the carb and read all of it - it tells you just how to jet it, when you get it as close as you think than dyno it -- the A/F does not lie -- johnjzjz
WHY no voes < it does not take power away ???????
the stock low speed from Mikuni is 25 - they come 17.5 to 30 in 2.5 numbers
stock high speed jet is 160 - they come 150 - 210 in 2.5 numbers
std needle is a 97 - they make a 96 and a 95 richest one we found -
you need to down load mikunis book on the carb and read all of it - it tells you just how to jet it, when you get it as close as you think than dyno it -- the A/F does not lie -- johnjzjz
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From: la la land jerzey
Ok i just read the latest post if your timing is to late the combustion chamber is not finished with the last charge / this will also cause issues < not enough time for the flame front to complete it burn - the plug fires too late in the cycle
whats in the motor its not a secret - every combo has been tryed many times ---
i am off for now will look again at lunch -- jz
whats in the motor its not a secret - every combo has been tryed many times ---
i am off for now will look again at lunch -- jz
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Joined: May 2009
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From: The South
with the lowest advance curve and no VOES. < U wrote
WHY no voes < it does not take power away ???????
the stock low speed from Mikuni is 25 - they come 17.5 to 30 in 2.5 numbers
stock high speed jet is 160 - they come 150 - 210 in 2.5 numbers
std needle is a 97 - they make a 96 and a 95 richest one we found -
you need to down load mikunis book on the carb and read all of it - it tells you just how to jet it, when you get it as close as you think than dyno it -- the A/F does not lie -- johnjzjz
WHY no voes < it does not take power away ???????
the stock low speed from Mikuni is 25 - they come 17.5 to 30 in 2.5 numbers
stock high speed jet is 160 - they come 150 - 210 in 2.5 numbers
std needle is a 97 - they make a 96 and a 95 richest one we found -
you need to down load mikunis book on the carb and read all of it - it tells you just how to jet it, when you get it as close as you think than dyno it -- the A/F does not lie -- johnjzjz
Dirt don't hurt
Joined: Jan 2011
Posts: 21,062
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From: Haslet Texas
The Dynatek ignition and Ultima recommend not running a VOES. With those jet ranges, it looks like if I buy the 42 kit, I can get enough pilot jets and needles to tune properly, but if I need a richer main jet I'll have to buy them individually since the needles are different part numbers for each carb.
It is my thought that all such recommendations were written before the EPA gave us this crappy gas.
The VOES is supposed to stop detonation.
Personally I would try one and see what happens.
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Road Warrior
Joined: Aug 2007
Posts: 1,560
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From: Oakdale Ca.
I have some extra. Large mikuni jets ,free you pay shipping. (i am running s&s now) what sizes do you need ?
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From: SE Louisiana
If the wire is grounded, your always on the high timing map, and if disconnected, your always on the low timing map.
Check your static timing to make sure it is set up correct per instructions.
(you could also get in between the advance curves by setting the 35* mark slightly foward of center in the timing hole window, which will retard all advace curves by one or two degrees compared to maps in the timing map picture below)
http://www.dynaonline.com/skins/down...ct/D2Ki-1P.pdf
The function of the VOES is to let you have more advanced timing at low load situations(cruising and slow acceleration), and then switch to a lower timing map under high loads, to avoid detonation.
You could also vary where the switch takes place by adujusting the VOES.
Your timing may not be the culprit, but cant see not taking advantage of the VOES for street use.
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Joined: Jan 2008
Posts: 84
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From: Cleveland, Ohio
I have a S&S 124 C.I, engine bored and I'm running the Dynatek ignition - see signature. I am running the super G carb though. Compression is 11.3 to 1. Originally I ran the Dynatek ignition with no VOES. I ran the lowest advance curve and under heavy throttle I got pinging/ detonation that I could not tune out with carburetor jetting. Added the VOES and this solved my problem.
The VOES does not advance the timing at high RPM. The VOES senses manifold vacuum pressure. At heavy throttle the manifold pressure is reduced and the VOES retards timing to eliminate pinging/ detonation. The Dynatek ignition will follow the timing curve you have it set for, only on heavy throttle will the VOES reduce timing to eliminate pinging/ detonation.
Follow this link to a great article on how the VOES works. http://www.wildwestcycle.com/f_voes.html
Can't see running with out a VOES - It worked for me.
The VOES does not advance the timing at high RPM. The VOES senses manifold vacuum pressure. At heavy throttle the manifold pressure is reduced and the VOES retards timing to eliminate pinging/ detonation. The Dynatek ignition will follow the timing curve you have it set for, only on heavy throttle will the VOES reduce timing to eliminate pinging/ detonation.
Follow this link to a great article on how the VOES works. http://www.wildwestcycle.com/f_voes.html
Can't see running with out a VOES - It worked for me.