OEM exhaust/carb tuning

[bheinz57]

Okay, I have thoroughly gone through the "I drilled out my OEM exhaust" threads. I have done it myself, and like it a lot. What I would like to do here in this thread is to find out at what point in time does someone need to turn to their carbs after modifying the stock exhaust.

Basically, I have not touched the settings on the carbs doing the 1/2 inch drilling of the OEM baffles. However, if I were to drill out the middle section a bit (Long bit, down the middle...) Am I going to run a bit lean until I make a carb adjustment, and where should I start.

I would like to make this thread a compilation of, I did this, then this...

So, no need to adjust carbs with my first step of drilling with the 1/2" holes I am assuming, but any more holes am I prone to running a tad lean and what should I do next?

Thanks guys.

Brian

 

[yankee in texas]

The 1/2 holes didn't flow enough air to require any rejetting only a minor A/F adjustment. When I went larger it did.




Yankee

 

[SpecOps13]

I drilled five 1/2" holes between the rivets and a 1/2" hole in the middle, done with a long screwdriver. I turned it with a wrench after i punched through to make it a round hole. I ran new plugs on a 45 mile ride. Not the perfect test but the bike ran great. The plugs showed a very light tan color after the ride. I did shut it down and coast in at the end so there was no idle time. Speeds ranged from 70 on the highway to 35-40 for a while. Others have said the VMax runs rich from the factory. I feel it's nearly perfect after these mods.

I made end caps with holes just for looks.

I believe that if the holes were much larger, rejetting would be necessary.

Dave

 

[tfisher65]

Drilling out the stock exhaust will make it go rich in the higher rpm's and lean in the lower. I adjusted the a/f and re-jetted the mains to 150 from stock 152.5.

 

[bheinz57]

Any other input? Seems like there maybe an adjustment needed at a certain interval of drilling the stockers. But at what point are you guys needing to do that?

Brian

Just trying to get a compilation of ideas.

 

[richwrench]

FWIW - I have 5 1/2" holes & center baffle untouched. Pilot screws all set at 2 & 1/2 out - bike runs awesome. I've never dyno'ed it , so I can't tell you if it's a little rich here or a little lean there, but it runs great to me. No flat spots, surging, or plug fouling.

 

[bheinz57]

^ Same with me right now. No issues, but I don't take my plugs out and check often to see if there are any underlying issues. But good info. So, you think you punch out the center section and you may have issues? Why did you stop @ the 1/2" holes?

Brian

 

[richwrench]

I like the 1/2" holes because I can change my mind, drill out the rivets & reinstall the endcap & all is stock again. Once I punch out the center baffle, the muffler is forever altered - there's no going back. This was a bigger deal to me a couple of years ago - lately I'm thinking just do it. Cops really don't check noise levels around here. I want a Kerker 4-2-1 some day, but that's a 1000 dollars away...

 

[naughtyG]

I want a Kerker 4-2-1 some day, but that's a 1000 dollars away...

You talked to Kyle lately Rich? I sold him a stock system so that he could sell the Kerker off his Max, and that's way less than a grand..

 

[yankee in texas]

Nothing's going to beat a full aftermarket exhaust for sound and power but you can get 115hp, 38mpg, a sound better than most slip ons and some money left in your pocket.


5 - 3/4 holes enlarged to nearly 7/8 with unibit
K&N Filiter
Tune

Jetting - A/F 2.5 Stage 1 needles,springs,shims
Air jet DJ 150 Main 145.5

Bike jumps from idle to redline !!!


Yankee