I recently bought a set of MAC pipes to replace my existing system which was rusted out on my '82 XJ650 Maxim. I did this in the midst of other things (carb rebuild). The bike is not running right and I'm having trouble getting the carbs to sync. Wondering if anyone else has added a MAC exhaust (2 into 1) system and if so, is jetting required? I checked the macperformance site and others and could not find an answer. I already trashed the old pipes, I'd really hate to have to pick a set up on ebay just to pinpoint the problem.

Thanks

Because you are adding a free-flow exhaust, rejetting or decreasing the baffle size of your new pipes will be necessary to balance out the intake/exhaust parameters.

I added the MAC 2 into 1 pipes to mine last year in conjunction with a Dynojet 1 & 3 jet kit and K&N filter pods. It worked great right away. I was able to synch the carbs easily.

You can also go with just the Dynojet Stage 1 kit and the stock filter and it will flow more air and balance out the exhaust. It's a lot less money to solve the problem. The only difference between stage 1 or 3 is that 3 comes with a larger selection of main jets to accomodate the K&N filter pods.

See if you can safely insert a smaller pipe into the outlet baffle to reduce the diameter and see if this helps. I can't remember what the stock baffle outlet size was, but I think the MAC is 1".

Hope this helps.

Michael

Interesting.... This does help, thanks!

I have the kit on order. Just a few questions. I checked my plugs and they are all a tan color which would seem like a good thing. I would have thought they would be different (black or white)due to the flow issue I suspect. Just hoping I'm not compounding a couple different issues. I am using the stock air box & filter.

I was able to get the carbs to sync or at least that's what I thought. It appeared to be running ok, but after a 30min ride, I noticed the idle was erratic and it was backfiring on one side of the pipes. It would appear that the sync adjustment did not take hold. Sounds like I need to jet the carbs correct?

Did you have to tweek the mixture? How did you go about that since these exhausts don't have the hole to insert a sensor. The instructions for the kit say to open the caps & drive the mixture screw in and back out 3 1/2 turns. I'm hoping that is all I need to do.

Well, I can always hope.

You only need to change your jetting if you change the air flow.

MAC makes a number of exhausts. The 4 into 1 is a higher flowing system than the stock 4 into 2 into the collector into 2.

Now - if you brought the MAC equivalent of the stock exhaust, then I really doubt the air flow will be much different.

I'm not sure how the MAC stock equivalent flows compared to stock. There is a chance that it does indeed flow slightly better... Personally I'd keep a close eye on it. If it's pretty close to stock you might be able to get enough mixture adjustment with the current jets.

If you have dark tan plugs then you're ok. However, if they start going lighter on you that means the engine is running leaner, and that you will need to adjust it for the higher flowing pipes. Keep an eye on it.

75% confident you'll be ok without the kit.

Woot.

I already ordered the kit, but I'm going to try syncing again before proceeding. The plugs are a very light tan color.

I bought the pipes off ebay see the link below, but there is no model number or anything that came with it. It sure seems like there is more flow coming from these pipes. They are LOUD too!

ebay item

Thanks

I just went with the Mac 4->1 but haven't had the bike sufficiently back into rideable shape to test it out. Soon... very soon....

Cheers,
John

Well folks, I'm going to have to conclude that a Mac 2 in 1 exhaust & a stage 1 jet kit just makes this bike RUN LIKE A RAPED APE!

Wheeeeeeeeeeeeeeeeeeeeeeewwwwwwwwwww! HOOOOOOO!

What a difference! The carbs synced to perfection. Throttle responce is dead on, my erratic idle is gone, steady as a clock.

No.... I'm not excited........