OEM Carbs? Post your setup

[BDenmark92]

First post in a forum ever but here goes

2006 with 18,000mi.

Previous owner had Cobras installed and carb work done but all stock other than that
All I know is the carbs have 170 main jets (took a peak while I was taking care of an over flow issue)


As far as more power out of the cobras, I removed the center plugs and now the rear tire spins much easier

 

[huw s]

Some oh so good info there - a bit refreshing after spending time on the xj forum, with everyone preaching not to remove the awfull airbox and fit pods, don't mod anything etc.
Nice to see folks not afraid to use engineering to solve problems - on the list to do - break down the carbs, clean and set up. The only mods I know I have is a k&n and filter box top removed.

 

[one2dmax]

Some oh so good info there - a bit refreshing after spending time on the xj forum, with everyone preaching not to remove the awfull airbox and fit pods, don't mod anything etc.
Nice to see folks not afraid to use engineering to solve problems - on the list to do - break down the carbs, clean and set up. The only mods I know I have is a k&n and filter box top removed.

You may want to reconsider the complete removal of the "y" section from the top of the airbox. Try shimming it to where it has a little engagement along it's edges with some washers. Around 1/8-3/16" or so. This will still allow for the directed airflow that works best with the stock box.

 

[huw s]

You may want to reconsider the complete removal of the "y" section from the top of the airbox. Try shimming it to where it has a little engagement along it's edges with some washers. Around 1/8-3/16" or so. This will still allow for the directed airflow that works best with the stock box.

Thanks, you misunderstand me - the y is missing, I didn't remove it! But, it sounds like that wasn't such a wise move by the PO, can I make one out of ally? Maybe shim it up a bit?

 

[one2dmax]

You can make one or email me and i'll sell you one for $10 shipped (basically covering postage) if in the US. A little more postage if going out of county.

 

[Bailey28]

All stock 2006 Vmax, 15k miles. Stock exhaust.

40 Mikuni brand pilot jets,
1.5 turns out on all fuel screws

147.5 Mikuni brand mains

Stock needles, no shims under them
Stock slide springs full length

Slides NOT drilled.

Float dry measurement 1.075" toe to flat on carb body. Wet came to 16.60mm from "center mark" to liquid.

Sea level 87 Octane

Good carb sync.

Very crisp and smooth, no complaints.

 

[thunder]

40 feet above sea level 2003 Vmax
Holeshot exhaust 4 into 2
Stock air box and filter
147.5 mains
Stock needles shimmed .028"
PAJ2 160 mikuni
2 1/2 - 3 turns out on fuel screws
Slides not drilled
Vacuum equalization mod
Stock V boost
44 mpg
Air box resonance is a thing, used to have Dynojet 1 and 7 but switched back; I could never get the flat spot out at 6000 rpm and the bike was way too rich with either Dynojet needels after numerous dynamometer tests.
It seems the engineers that worked on the Vmax had it dialled in quite well so not much tweaking is needed for a stock engine. The Holeshot exhaust allowed the engine to draw more air and fuel and made a big difference in the performance and fuel mileage.

 

[Sniffbooger]

Thought this was a good thread to keep alive...

My current setup is (SUBJECT TO CHANGE ) :
-2000 Vmax, stock engine, 20k miles, probably needs valve adjustment soon...
-Less than 100 feet above sea level
-Dale Walker Holeshot exhaust 4- 2
-Stock air box with "Y" (thanks Sean)
-K&N stock type air filter
-Vent bowl hoses under top cover (thanks Sean)
-Stock needles shimmed from prior owner, haven't measured washer thickness yet
-Float level set by casting mark on jet blocks, need to measure wet level again
-Main jets 147.5 Mikuni (thanks Sean)
-PAJ2 170 Mikuni (thanks Sean)
-PAJ1 90 Mikuni
-Pilot jets 37.5 Mikuni
-K & L (Taiwan) rubber jet block gaskets (thanks Fire-Medic)
-Lightly worn OEM emulsion tubes, will be installing new Factory Pro HDJ emulsion tubes soon
-3 to 3 1/2 turns out on fuel screws
-Stock diaphragm slides, not drilled
-Vacuum equalization mod (not really necessary with my good Carbtune synch)
-Stock V boost 6k
-Rotella T4 (15w40) oil
-CA 87 octane pump gas
-35 mpg avg city/hwy, 40+MPG on hwy only

Runs smooth, idles fine, heats up pretty good at stop lights, fans come on more than before....it also seems a little soft through the midrange since I installed the 147.5 mains compared to the prior 150s but I just blew a Dodge Charger off the road from the green light to the 405 South high speed on-ramp... but the MPG with these smaller mains has improved and saves me a couple stops at the gas station each month... Will update post as changes are made.

 

[Vinmax]

Current setup at 5280' Broomfield, Colorado:

(Setup has flawless carburetion going from the Denver Metro area all the way up to Mt. Evans at 14,000'+ altitude)

I get about 145-150 miles before low fuel light comes on.
Stock box with stock air filter. Modified with half-moon piece cut out of box top for better breathing at high end. 'Y' piece is on box top.
Stock 2001 Vmax exhaust (non-modified).

main jets = 142.5 Mikuni
pilot fuel jets = 42.5
pilot air jets number 1 (PAJ1) = 95
pilot air jets number 2 (PAJ2) = 180
(I tried running 160's on PAJ2's but lost my crisp midrange throttle response; stock 170's where better, and then settled on the 180's which are perfect)
Stock needles (no shims)
Stock (non-drilled) slides
Dynojet springs from a Stage I kit (stocks leave my midrange a bit 'laggy.' The Dynojets are really keep the midrange response 'alive' is what I found out on my bike)
Idle fuel screws out about 1.5 turns each

All the sync ports are tied together on all 4 carbs with vacuum hose for a smooth idle.
*changed back to stock and now all carbs are fully independent except when Vboost kicks in.

I run Denso COP's with a stock 2001 ignitor box.

Perfect starting in all weather and temps. I use the choke/idle enrichment for about a minute on cold starts. Great midrange throttle response. I can consistently pull 135mph with no low, mid, or high end hiccups. I've hit 142.7mph with this setup at about a 7000' altitude. 5th gear pulls from as low as 1500 rpm are scrisp, smooth, and pulls great.

KJShover asked years ago if I'm running a Venture rear......​

*No, I'm not running a Venture rear on this setup. Bike has 47,000+ miles on it now. Still running strong. I generally use 85 or 87 octane Colorado pump fuel.

Vinnie

 

[TK3333]

Mark's 4-2-2 exhaust
Morley Muscle jet kit in oem carbs.

 

[Jack Hammer]

Vacuum equalization mod interests me. Anybody, please tell me the differences you saw when you did the mod.

I understand that this might help idle on a heavily tuned bike. I've got lots of mods too. If I turn the knob to increase idle speed past 1000 rpms, it gets intermittent lopey, if I keep it under one grand, usually around 975, it is very smooth. I'm wondering if this mod might allow me to adjust a bit more idle.

Then again, I just synced my carbs and they are dead on so I'm thinking this mod will not do anything. My brain tells me this would help a bike that is out of sync and out of precise tune.

I also run European 98 grade gas, lower grade is 95 which contains 10-15% ethanol, 98 has only 5%.

Give me your opinions please.

 

[marsmax85]

Vacuum equalization mod interests me. Anybody, please tell me the differences you saw when you did the mod.

I understand that this might help idle on a heavily tuned bike. I've got lots of mods too. If I turn the knob to increase idle speed past 1000 rpms, it gets intermittent lopey, if I keep it under one grand, usually around 975, it is very smooth. I'm wondering if this mod might allow me to adjust a bit more idle.

Then again, I just synced my carbs and they are dead on so I'm thinking this mod will not do anything. My brain tells me this would help a bike that is out of sync and out of precise tune.

I also run European 98 grade gas, lower grade is 95 which contains 10-15% ethanol, 98 has only 5%.

Give me your opinions please.

your electrical system likes it at 1000 to 1100 rpms especially the cdi

 

[Jack Hammer]

I haven't seen any difference at all whether idle is 950 or 1050. Works all day long. My charging system is working very well.

I'm wondering about the turbulence this mod could generate to make a difference. It could also be so that you might see a better turbulent benefit by hooking the cylinders furthest away from each other based on firing order, like #1 to #3 and #2 to #4.

 

[Jack Hammer]

Ended up doing the vacuum equalization mod. Lopey idle turned into a steady hot cam V8 idle. Better throttle response and pull in lower rpm range. I was also able to up the idle speed to 1050 rpms. My engine clearly liked it.

 

[Sniffbooger]

Can't believe it would make that much difference...I've changed mine back and forth a few times and no noticeable difference in how my bike runs or idles...its a bit weird really...that your bike would be so drastically affected by the vacuum mod hack...personally I just like my bike super synchronized and the idle mixture jets set good...thats the best my bike ever ran...vacuum mod or not.

 

[Jack Hammer]

I didn't believe it would either. I did a full tune prior so I was thinking to myself that this mod would be a waste of time. It wasn't. I have been pondering about why. I've got few ideas to throw around and try.

 

[thunder]

I ran as lean as 147.5 mikuni's at sea level. Woke the bike up a lot.

I made that decision after leaning it out for Utah-Wyoming altitude, installing 145's
When I got it home (Houston, elev. 15-25') from that project and unloaded from the trailer and took it for a spin it was was unbelievable how great it ran with the 145's in it. So I bumped it up to 147.5's in light of the new low altitude and never looked back.

That was with the stock airbox, K&N filter, and stage 1 needles on what clip I don't remember any longer.

Its pretty difficult to go too lean with the commonly available jets in my opinion.

I am running the 147.5 Mikuni main jets as well; with an elevation close to sea level. Tried the stage 1 and 7 kits, but was rich always. Confirmed with dyno so went back to stock needles. Runs much better. It truly did wake up the beast with more pulling power in all gears, lol.