Mac 4-2 exhaust rejetting

[OMCC]

I hit a pothole on the highway and managed to snap one of the stock exhausts. Insurance looks like they will cover it but since I do all the work myself I need to submit a parts list to the company. What size jets do I need for these pipes

http://www.ebay.com/itm/Yamaha-XS110...3d31a0&vxp=mtr

Also is there anything else I need when replacing the stock exhaust?


I have also been looking at these http://www.ebay.com/itm/Yamaha-XS110...6b5f45&vxp=mtr

does anyone have experience with xpipes?

[mrhammer2u]

When I installed the Mac 4 to 2 I did not rejet and bike ran perfectly. They do make more noise than stock, but it's a pleasant noise. Nothing like open pipes. It's a direct bolt on. I bought new gaskets though.

That X-pipe looks like it would be in the way of oil changes and restrict ground clearance...right?

[DiverRay]

One or two members have used the X-pipe, and yes, it DOES get in the way of almost everything. They are a good drag pipe, but not a good street pipe.
On the Mac's, I'd go up one size in main jets, and re-tune the carbs. You will loose a little MPG, but that should keep them from turning color so fast.
Oh, and be ready to replace a stud or two, as Murphy is always close by with exhaust systems.....

[OMCC]

One or two members have used the X-pipe, and yes, it DOES get in the way of almost everything. They are a good drag pipe, but not a good street pipe.
On the Mac's, I'd go up one size in main jets, and re-tune the carbs. You will loose a little MPG, but that should keep them from turning color so fast.
Oh, and be ready to replace a stud or two, as Murphy is always close by with exhaust systems.....

How do I find out which size jets are currently in my bike. I assume they are standard from the factory.

[OMCC]

When I installed the Mac 4 to 2 I did not rejet and bike ran perfectly. They do make more noise than stock, but it's a pleasant noise. Nothing like open pipes. It's a direct bolt on. I bought new gaskets though.

That X-pipe looks like it would be in the way of oil changes and restrict ground clearance...right?

did you experience any blueing? Do you have any recording of what they sound like?

[DiverRay]

How do I find out which size jets are currently in my bike. I assume they are standard from the factory.

Jetting tips:http://www.xs11.com/forum/showthread.php?t=382
IF they are factory, they will be 137.5, up one size will be 140. Remember, use ONLY Mikuni jets!!!

[mlew]

Before you install and run the new exhaust paint the inside of the pipes with high temp exhaust paint. It will keep the pipes from turning blue and rusting. Don't be light on the paint, I used a whole can on mine and after two years they still look good. I run my SG with one size up on the mains.

[jetmechmarty]

[mlew]

That stuff will work also Marty. My local auto parts store only has high temp paint.

[madmax-im]

wish this was done to my exhaust as it has turned colors...not blue though

[BA80]

I have a Mac 4 into 2 on my SG with a F engine. I started out with stock jetting and got some serious bluing and a top end pre ignition. Went up 1 size on the pilots because I was having to turn the mixture screws out 4 or 5 turns to get the idle correct. That also helped my low end response.

Went up from the 137.5 stock jets to a 140 in an attempt to get rid of the bluing and the pre ignition. It helped but the pre ignition was still there. Jumped the mains up to 142.5 this last overhaul and the pre ignition seems to be gone now.

That being said my mileage hasn't changed noticeably but overall performance has.

It really depends on your riding style and air filter setup and several other factors. The nice thing about the 79 carbs is with every main jet change you still have 5 jet needle settings to play with. I'm running on the middle groove with this last change but thinking of dropping the needles 1 notch to see how it is.

Also, with the richer mix the engine seems to be running cooler.