Need MK Mod expert opinions

8 replies to this topic
  • Thumpin_426

Posted September 12, 2001 - 01:18 PM


I'm doing the mod this weekend and I live at sea leval. Are these settings a good place to start?
*Main Jet= 165 with after market pipe
*Pilot Jet= Leave stock
*Fuel Screw= Out 1 3/4 turns
*Squirt Duration= .3 - .5 seconds
*Squirt Timming should just miss the slide

I understand how to adjust the duration once the mod is complete but how do you adjust the squirt timming so it misses the slide? I downloaded the pics of the mod and I'm still not sure.

I have been debating on adding a FMF Power Bomb head pipe. I already have the Power Core IV silencer. After this mod is complete, would the head pipe help or harm the overall performance? All replies will be greatly appreciated!!

  • YZThump

Posted September 12, 2001 - 01:49 PM


I'm not an expert on the mod,but I know it works.I'm also in West Palm Beach.The screw that you will drill and set is the adjustment for the squirt,time it and set it as close as possible and fine tune with jetting or fuel screw.I have the DSP pipe and am very happy with the mod.It pulls really hard from bottom to top!!! Let me know if you need some help.It sounds like the settings you are thinking about will be spot-on,exactly what I have.

[This message has been edited by YZThump (edited September 12, 2001).]

  • Boit

Posted September 12, 2001 - 08:42 PM


I agree with YZThump. Since you are at the same altitude and humidity conditions as me, I might be able to help you final jetting. What fuel are you using? This is important. I use 100% race fuel so my jetting probably won't work for you. In my opinion, if you want to realize the highest return from doing this mod, jetting is of the utmost importance. I also highly recommend using a race fuel such as VP C-12..or even C-18, if you can afford it. These fuels are fairly easy to jet. Whatever fuel you choose to use, stick with it and jet accordingly. That includes pump gas, although pump gas is notoriously inconsistent in quality and that throws jetting askew. With the high RPM and fairly high compression ratio of the 426, fuel choice and jetting can make a huge difference in how this machine runs. What I like about this bike is how easy it is to change a jet with the correct tools.

  • Thumpin_426

Posted September 13, 2001 - 03:18 AM


Hey Boit, I've been mixing 50/50 Amaco 92 Octane with what we call CAM 2 down here. It is 110 octane race fuel. It's what everyone uses in their 1/4 mile cars and drag bikes. The bike seems to realy like it. My mix ends up around 102 Octane. What do you think, too little, too much,.......

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  • blaze

Posted September 13, 2001 - 02:48 PM


how do you like that fmf silencer? still as much power as stock?

  • Thumpin_426

Posted September 14, 2001 - 03:15 AM


Yeh, I love it!! The low end torch is better out of the corners and the top end is a little quicker too.

  • blaze

Posted September 14, 2001 - 06:44 AM


one is on its way. thanks

  • Boit

Posted September 14, 2001 - 03:59 PM


You are fine with the octane content of this fuel mix. When choosing a fuel for this machine, the most important factor is the distillation curve. Pump gas is distilled to provide adequate needs for the typical automobile that rarely exceeds 6,000 RPM's. The 426 redlines at 11,200 RPM which doesn't leave much time for the ignition, power, exhaust, and intake cycle to complete. If you look at the specs on the websites of race fuel suppliers, each fuel grade should describe what it is intended for. VP and Sunoco both have fuels that are excellent choices for the 426. There is a general concensus that octane determines the flame speed, which is untrue. Octane provides protection against preignition. To get the maximum benefit from running race fuel in the 426, you must be willing to jet crisp or you will be disappointed. If your engine runs well and throttle response is crisp, you probably are jetted correctly. As easy as it is to swap a main jet, I see no reason why a rider wouldn't want to try a couple of different size main jets to get a feel for how making a change affects the engine. I'm using a #158 during the hot months and the difference between it and a #160 is substantial. When the ambient temperature drops into the 40's F, the #160 is what the engine likes due to the denser cool air. So, my opinion is to continue using your fuel mixture and experiment a little with jetting. Start out by making a written record of your current jetting so you will know exactly where you started. A good starting point would be one step richer on your main jet and see how the bike revs at the top of the RPM range. If it's too rich, it will blubber. The aim here is to actually get the main jet too rich so that the engine blubbers. . . and then start leaning it out by one jet size at a time. Once you get the proper main jet, it usually becomes quite apparent as the engine really comes alive from the mid-high all the way to the rev limiter. When I did this, I started with two sizes richer than stock on the main jet and noticed how the blubbering decreased each time I went one size leaner until I installed the #158. From that point on, the engine took on an attitude of Mike Tyson chomping on Holyfield's ear. It rips!

  • Thumpin_426

Posted September 15, 2001 - 05:31 AM


Hey Boit, Thanks for the info. It helped alot!! I just completed the MK mod and I have everything set up for sea level conditions. I'll make a post when I get back.


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