Marks 4-2 made my A/F ratio rich?

[06Vmaxfan]

I added a Marks 4-2 exhaust with the 14" cans and had my bike dyno'ed to see what adjustments need to be made. The dyno chart shows me very lean at idle then rich from about 2K all the way to red line. My A/F ratio from 2K up is around 12-1

I would have thought a better breathing exhaust would have gone in the other direction and made the bike lean.

When I am riding I get a backfire sound out of the cans. Some I can barely hear and others are louder but not real loud. This happens as I am just cruising down the road at a steady speed and happens more when it is cooler outside.

 

[maleko89]

No, increasing exhaust flow richens. Basically, opening up the system after the carbs richens...opening up intake side leans.

 

[gamorg02]

opening the intake makes it lean, opening the exhaust makes it richer.

 

[SpecOps13]

Welcome to the VMF. Shim your "Air Box Y" to lean it some. You need to fatten the Air/Fuel at the bottom. You have a dip at 4500 that puzzles me a little.

 

[gamorg02]

mine did the same thing, may need stage 7 needles or a larger paj2

 

[Rusty McNeil]

Do it the Factory Pro way (there is a guide on their website) and start at the top, one size smaller on the main, I think 12:1 is too rich in my opinion, even at WOT under power...

Make sure your float levels are right first tho' ............nothings gonna be right if that's not right.

You work from there down to idle until it's right....

Shimming the airbox is a worth a try too.


I wouldn't worry too much about what it is under 3000 rpm unless they were doing a steady throttle/rpm roll to see exactly what it is. The way they do Dyno runs the guy could have whacked the throttle and made it look lean down low until the carbs slides catch up, you could do 10 dyno runs and play with the throttle slightly differently and get a different a/f down low every time.

I like to see the dyno operator roll into the throttle MUCH slower than they usually do, it gives you a more diagnosable a/f graph that ties into a given rpm better. Usually all they do is whack it till redline and hand you your HP number. A little longer time at a given RPM and you have a much better a/f graph to work with.

What specifically is your current set up?

 

[06Vmaxfan]

Not sure what a paj2 is. Is see the logic in the richening of the A/F ratio, I had it backwards. I don't suppose adding a K&N air filter will ballance it back out, that seems to easy to actualy work..

I guess that popping I hear in my mufflers is un burned fuel.

 

[06Vmaxfan]

My current set up is bone stock other than the Marks pipes. I have been spending all my hot rod money on my other project (2007 mustang gt/cs) and am at a stopping point on that one so I want to get back to the Vmax. I considered buying a gen 2 Vmax but this bike it paid for and I only have 5200 miles on it.

I like the Vgas carbs that UFO offers but I cant get over the 2K cost for a set of carbs.

 

[Rusty McNeil]

Not sure what a paj2 is. Is see the logic in the richening of the A/F ratio, I had it backwards. I don't suppose adding a K&N air filter will ballance it back out, that seems to easy to actualy work..

I guess that popping I hear in my mufflers is un burned fuel.

Your coasting enricheners might have been gummed up too, and adding an exhaust just made it obvious????

 

[Heretic]

My current set up is bone stock other than the Marks pipes. I have been spending all my hot rod money on my other project (2007 mustang gt/cs) and am at a stopping point on that one so I want to get back to the Vmax. I considered buying a gen 2 Vmax but this bike it paid for and I only have 5200 miles on it.

I like the Vgas carbs that UFO offers but I cant get over the 2K cost for a set of carbs.

Don't bother with the Stage 1 jet kit, it will only make it run richer in the middle and top end. I ended up going back to stock needles to lean up the mid section. In my opinion Vgas carbs aren't worth the cash unless you are going for the looks or have a 1500cc + engine. If you run air filters on them they will net you maybe 5hp. You can get that with the Morley Muscle jet kit or Stage 7. There was a guy from Omaha that went to Topeka a few years back with flat slides on an otherwise stock bike (besides exhaust) and even w/o filters didn't do any better than those with Morley's kit. I would never run my bike w/o air filters on the street.

 

[06Vmaxfan]

I went to Morley's web sight and requested a price on his jet kit. I told him what I was working with and what I am looking for so maybe he will recomend the correct jet kit and air filter.

I am going to have a local shop do the install and tune the bike on the dyno. I was told by the 2 local shops with dyno's that it is going to cost around $750 in labor to do the work. I spent $800 for the exhaust and not sure what the jet kit is going to cost.

I just spent $2600 on the long tube headers, mid pipe and Borla stingers for my Mustang GT. That includes parts, labor and tune. I am going broke with exhaust systems and tuning on my projects.

 

[dmax1]

Would elavation make a difference? I was thinking about a Marks 4 into 2 with the 14 inch cans and wondered how that would affect my performance at 4500 feet. My Max is a stock 85. :ummm:

 

[06Vmaxfan]

Yes elevation makes a difference. I live 20 miles west of Atlanta right now and did live in Colorado Springs Colorado a while back. When I lived in Colorado I had to advance the timing on my car to get it to make power in the upper elevations. My bike I had at the time seamed to do better dealing with the thin air.

 

[gamorg02]

$750???? fuck man find a new shop. never heard it over $400

 

[06Vmaxfan]

All the shops around here are expensive. There are 2 performance shops within 30 miles and they were both $750 to install and tune the bike.

If you think that is high I just paid $640 to have my long tube headers installed and $300 for the dyno tune. The other shops were $750 for the install and $500 for the tune. This was for my Mustang.

 

[maleko89]

It takes less than an hour to install a jet kit. Dyno's aren't needed to tune. I recommend doing it yourself.

 

[Redbone]

I went to Morley's web sight and requested a price on his jet kit. I told him what I was working with and what I am looking for so maybe he will recommend the correct jet kit and air filter.

I am going to have a local shop do the install and tune the bike on the dyno. I was told by the 2 local shops with dyno's that it is going to cost around $750 in labor to do the work. I spent $800 for the exhaust and not sure what the jet kit is going to cost.

I just spent $2600 on the long tube headers, mid pipe and Borla stingers for my Mustang GT. That includes parts, labor and tune. I am going broke with exhaust systems and tuning on my projects.

I think there is a better way to do this that will benefit you and one of our members.
Raginmain has offered to ultrasonically clean, repair and install Morley's jet kit for a generous donation to one of the charities he supports. You have to pay for shipping, any parts needed and Morley's jet kit. Here is the link to the thread for you read about what he does, how to contact, etc. I'm sure you will come out ahead and know the carbs have been work on by a mechanic that knows the Vmax carbs inside out.unk:
http://www.vmaxforum.net/showthread.php?t=10537

 

[KJShover]

it takes less than an hour to install a jet kit. Dyno's aren't needed to tune. I recommend doing it yourself.

+1

 

[overzat]

get seans jet kit and do the work your self. You will be pleased with the end result

 

[Rollie]

All the shops around here are expensive. There are 2 performance shops within 30 miles and they were both $750 to install and tune the bike.

If you think that is high I just paid $640 to have my long tube headers installed and $300 for the dyno tune. The other shops were $750 for the install and $500 for the tune. This was for my Mustang.

Where is Douglasville ? Sorry didn't read all the thread . Give me a p.m. , there are cheaper shops around Atl. if you don't want to do it yourself.