Re: same old jetting questions :(

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Buster Hymen

Administrator
Staff member
Admin
Joined
Mar 28, 2006
Messages
4,217
Reaction score
45
Tips for Pilot and needle settings

Excellent carb tuning tips courtesy of Mark (maleko89)!!

maleko89 said:
You should probably be able to accept WOT in any gear above 2K w/o any bucking or complaint.

Do the following tests.

1) Cruise at 4K in 5th gear .. hold RPM steady (count to 5) and then whack it WOT as quickly as you can. You shouldn't feel the slightest delay or hesitation. If you do, too rich. This does not work at 3.5K or 4.5K, only at 4K because the slides will start to retract at 4.5K even at the lightest throttle angle. 4K sets us up on the threshold and gives us a big jump when we whack it. there is no other RPM to do this where you will get as big a slide jump when rapidly moving to WOT.
This tests for too rich of needle.

2) Verify that starting cold .. that the engine is weak .. and will complain if you try to hold the RPM at 1800 rpms. Within 1-2 min or no later than when the temp needle touches the first mark you should be able to hold the engine between 1500 and 2K w/o complaint or popping back through the carbs. At the least you should be able to do this by the time the engine is fully warmed up but if you are more than 1/2 way between the dot and cold on the temp gauge your pilots are plugged or too lean... (clean or reduce the PAJ2). If you can hold 1.5-2K as soon as you start cold then your pilots are set too rich and you will suffer rich symptoms when it comes to operating temp (clean or enlarge the PAJ2). Only change PAJ2 bigger/smaller if you mixture screws are out or in too far already.
This is how you set your pilot mixture.

3) Do a hard WOT pull in 2nd or 3rd gear from below 3K. Look for a smooth pull all the way up. If it seems to lag in the 4-5K range then too much needle. If we sputter going past 4.5K you don't have enough needle.
This tests for needle richness and leanness.

4) Verify you can cruise "nice and deliberate" at 5K .. if you stumble around and are OK everywhere else you don't have enough pilot.
Another pilot mixture test.

As for your mains, I'd at least go to 147.5's. General rule is to subtract main jet size by 1% for every 1000 feet above sea level. So, need to decrease main jet size of 152.5 by 4.5%. 95.5% times 152.5 = 145.6. I'm thinking 145's would work best at 4500 feet above sea level.
Excellent info and has now become a sticky in the Carb section! :thumbs up:

Here's how you set your mixture screws:

Do one carb at a time. Turn the mixture screw in all the way until seated. The engine tone should stumble/change. Now, slowly turn out the screw until the idle recovers. Once there, turn the screw an additional 1/4 to 1/2 turn. Now, do the other 3 carbs the same way. Once you set your mixture screws do the mixture test as noted above.
 
Last edited by a moderator:
Re: Tips for Pilot and needle settings

Thanks Buster, not originally from me though. Collection of notes in my Library from Steve Detamore, Paul Czernics, Terry Campbell and Eric Harnish.
 
im confused on the jetting size i guess. anything ive ever delt w/ except the max if you want richer jets(mains) you go up in sizes,meaning numbers) but it seems the oppisit for this. or am i reading this wrong? this is excellent info though. thanks again.
 
Bigger is richer.

How do the new pipes sound?Major improvement over stock.The stock jets are rich enough for the HMF's.Stage one dynojet kits are basically a waste of money.I would do the Stage 7 kit or Morley kit or nothing at all.

Are you just wanting more performance or are you worried about being lean with the new exhaust?
 
im confused on the jetting size i guess. anything ive ever delt w/ except the max if you want richer jets(mains) you go up in sizes,meaning numbers) but it seems the oppisit for this. or am i reading this wrong? this is excellent info though. thanks again.

It depends on which jets. If you increase size of fuel jets, get richer. If you increase size of pilot air jets, main air jet....you get more air thus lean.

Mark
#1098
 
it's been raining pretty much since i put them on so i havent much time to ride it. i only had it out once and it was improvement over the supertrapps in the performance. i havent figured out how to put the clamps on with the washers so i left them off. i'll most likely get longer stainless ones. im a little disappointed in that they leak at the joints. i knew i shouldnt have put sealant on. they sound strange when idling vs the trapps, less of a rumble. but oh man man you get on the throttle a whole differnt tough sound. overall i like them. i havent had a chance to do the lean testing yet as i went out and did 130 mph speed test.
 
I hope that you do not lose a can riding without the straps.Mine does not leak without sealant.I have heard they are almost impossible to get off with it on there.I have had my system on and off several times.Maybe you'll get better the next couple times.Could you post a few pics back by the cans?
 
Just went thru this the other day with my HMF system. I put the the clamp on, washer between the two taps and used the original mounting bolt. Left side went on easily...had to fiddle a bit with the right but eventually got it on. Took my centerstand off as it just touched the can. No sealant....looks like no leaks but I'll check again in a couple days.
Sounds great!!

Dale #2592
 
I also tighten mine again 3 or 4 times after warming it up and test riding it.Give it time to seat and expand.
 
shawn im running it w/ the clamps on, just w/ no washers using the stock bolts. i havent even had a chane to get it out since the first ride because of rain, but ill snap a veiw shots and video the sound like i did on my s.trapps to have you listen and look.
 
Re: same old Vgas jetting questions :(

I have 260 mains and it is running like crap, I was told I should go down to 258s but I can't find them anywhere, My local shop only goes to 225s and online I can not find any larger than 230s.
Anyone else have any input ? Mains, needle clip positions ?
 
160 and 158 maybe if you're talking dynojet
160 dynojet would put you around a 150 Mukini, Likewise a 158 would put you around a 148 Mukini. (close, but not accurate)

They're rated differently, but a 260 is way too big for anything short of a Dodge Tomahawk!
 
I pulled all four last night, I have three 160s and one 260, No wonder it was running like crap huh ?

From what I have found so far, I have been told that one is running a 158 and Kloker has 130s so I think I will buy a set of 145s and see how it runs.

From what I was told 41mm Vgas carbs normally have 160s, is there a visual way to tell indeed I was shipped 39mm and not 41mm ?
 
If you have Vgas they are 39mm.He does not offer any bigger.Pcw offers 39 &41mm.

The thing that really sucks about the flatslides is that everytime that you try a jetting change its about $30 whether it works well or not. $7-8 apiece.Nobody local to me has any.
 
OK, I am now at 125 main's and still can't use the last 1/4 of the throttle, will not pull past 125. It falls on it's face when you twist past 3/4, even at lower speeds. I doesn't seem to make quite as much power down low either.

Any ideas, anyone ? :bang head:
 
How many turns out are the idle mixture screws? What clip are your needles on?

Did you put new plugs in?I'll bet you definately fouled that one with the 260 main jet in it.That and check the sync real good so all the cylinders are working equally together.

I actually know these carbs real good after months of working with them.I can also see how some people are going to lose power by not keeping them correctly tuned.

The bad thing is that I do not know the Vgas setup like I do the PCW one.They are the smae carbs though,can't be different on tuning them.

How does Vgas link the 4 carbs together or are there 2 cables(one for each set)?
I just switched back to the stock throttle tonight with push-pull cables.I decided that I did not want to have the throttle stick who knows when with only a pull cable and a quick throttle.
 
I have new plugs, and all four seem to be chattering nicely ( idleing 1500rpm on the dot.
I have yet to look at the clip position or idle screws, I was just trying to get the mains right first since they affect the needles too.

there are one set of push pull cables per bank of two.
 

Latest posts

Back
Top