New Member

[JoshR]

Hi all,

I am back on two wheels! My first bike was a Boulevard so this is a bit of a upgrade for me . Loving the bike so far. I have a few issues I will ask about in the proper forum. Glad to be here and thanks for having me.

Josh

 

[Fire-medic]

Welcome, I am going to offer you a FREE GIFT! just for joining the forum! That's a sharp looking bike you have there. How many miles on it?

Your 'free gift' does come with a catch: you need to change-out your four-into-four Cobra exhausts for almost anything else, even the OEM system, which Yamaha's engineers did a good job of designing.

"Whoa, Nellie-Belle," you might say, "my shiny, gleaming chrome exhaust with its four, count 'em, four exhausts is the apple of my eye, and just listen to that thunderous roar when I open 'er-up!"

Yes, the four-into-four system you have is visually impressive. It has a sound of power. But unfortunately what it doesn't have is the performance of even the OEM exhaust. It doesn't provide the scavenging which the OEM and the well-designed aftermarket exhausts do, when they're a complete cylinder head to exhaust tip full system. If you change-out your four-into-four Cobra for a full system, even the OEM headers with its two chrome (most years) chrome twin megaphones, will give you another probably 15 RWHP due to proper scavenging.

If your system has a Dynojet Stage 1 jet system in the carburetors, it needs to be replaced to OEM jetting if you go with the OEM exhaust. The Stage 1 jet kit is notoriously hard to dial in and it doesn't work as-well as the OEM jetting.



Her are some reference docs to assist you in seeing what's involved. And the factory service manual.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf
You can remove one carb diaphragm cap and remove the slide and its needle, and compare it to this to see which needle you have which should tell you if the jetting was changed.



One of the carburetor diaphragm cap's screws is a security screw. You can use a straight-jaw Vise-Grip to grab the sides of the head of that screw, or you can splurge on a Harbor Freight security screwdriver bit set, which has just what you need. Make a sandwich at home one day to take to work, instead of going to BK, the Golden Arches, or Subway, and buy this:
https://www.harborfreight.com/secur...M9BsJtdMy9Wd-BMCQ-_nkHJiFOrA_UMkaAvp0EALw_wcB
On sale for $7.99 until July 6.



Like Christy Brinkley told Chevy Chase in National Lampoon's Vacation, "Well, are you gonna go for it?"

 

[CaptainKyle]

Welcome ! Congrats on the bike

 

[JoshR]

Welcome, I am going to offer you a FREE GIFT! just for joining the forum! That's a sharp looking bike you have there. How many miles on it?

@Fire-medic Thank you for taking the time to write all that up! That is some incredibly valuable information. I got it with 11,255 miles on it. So it does have a stage 1 kit in the carb with the cobra exhaust. The guy I bought it from did have the paper work that showed the stage 1 kit and exhaust being installed by the dealer by the 1st owner. He did give me the original exhaust so I have that sitting in the garage. I also do have the Harbor Freight security bit kit somewhere in the garage. Do you have a good suggestion on where to get the original jets from? Do I have to change anything else out ie headers or such with the cobra exhaust?

Thanks,

Josh

 

[marsmax85]

Welcome to the forum !!

 

[Dkid]

Welcome to the Classroom Bud.

 

[Fire-medic]

About jets:
Your local Yamaha dealer should have them available.

Sean Morley [email protected] or dannymax [email protected] can get you what you may need for those carburetors. They are also willing to answer questions, a great help in getting things sorted.

Parts houses like Parts Unlimited can get them.