Mac 4x1 pipes on an 82 XJ650J ... yay or nay, what say you?

Been doing some research for the wife's 82 Maxim 650. Lovin' the whole 4 into 1 setups. Both her and I are into the 1978 to 1983 "AMA Superbike Production Class" look and feel .. the whole Wes Cooley GS1000 Suzuki trip ... hence the desire to go to those killah *Yoshimura-looking* 4x1s.

Issues that are non-issues for us:

** Bad chrome or chrome that blues too easily: The pipes will be dechromed immediately for modding purposes.

** Bad or cheapo/crappy-assed exhaust collars: If the Macs are crappy (and from what I've seen they usually are) we'll TIG weld on new ends and use stock or stock type collars. (We're equipped to do so).

** Sorta-kinda poor fitup: I am used to that. I install the pipes, fighting them on all the way. Once installed to my liking I take a torch to them, evenly heating them a good bit until they soften and "settle" in place. Allow to cool overnight while still installed on the bike and the pipes will literally FALL into place when R&R'd. Obviously this is a problem for pipes that are chromed .. but since we're dechroming them right away ....

I am more concerned with decent performance rather than quality issues that I can overcome. Not looking for huge power gains, just some cool pipes with decent stock engine compatability and general ease of tune. The carbs need a total rebuild at this point, so we have to get into those anyhow in the event Macs require rejetting. We intend on shitcanning the Mac muffler and using a fully tuneable 4 inch Supertrapp instead.

So I guess I'm asking if the Macs are generally "usable" pipes. Or are they so horrible that you're just not going to get a decent state of tuning with them? We also plan on using the dreaded pods with the Mac pipes. K&N pods, not Chinese Ebay pods. So then ... pods, Macs, and Supertrapps (here's to hoping!). Jsyk, I think I've read every "HELL NO!" thread and post regarding the use of pods on this forum. So I've been sufficiently warned. Problem is, I'm stupider than that.

Ok .. so I have my helmet on (for the beatings I'm about to take) and I've got my pen and paper out for notes (for useful info tossed my way). So I'm as ready as I can be ... deep breath ... squinting ... and hitting "submit".

Haahaa!!

Thx!!

 

Well, changing the intake or exhaust requires a Rejet. From what I hear, and from what you're asking. It's not going to run like you want it to. You might get lucky. I know chacal has a formula for figuring out jet sizes for modified intake and/or exhaust, but like I said, from what I hear you're going to have a hell of a time getting it to run right, and spend a lifetime trying to get it perfect. with the pods anyway

 

I have a MAC on a 83 750 mine are the black ones
The fit Isn't perfect but close enough, the collars are crap,
Never did get the stock muffler to run right,stumble at 5k
Went with a supertrapp universal with 5 rings and 128 mains and 41 pilot with stock intake
All bets are off with pods, it's going to take some huge jets or a major mod somewhere

 

I have the Mac 4To1 on my 83 XJ750K Maxim and the bike runs perfect! No problem tuning, stock carb parts no issues!

 

Re: Mac 4x1 pipes on an 82 XJ650J ... yay or nay, what say y

According to the specs for a set of MAC 4 to 2 with turnouts, that re-jetting isn't required as long as baffles are used? What about tuning or would this be considered close to stock as well?

 

I have the MAC 4 to 1. Fitment is decent, the PO used a bunch of washers as shims to get the spacing for the back right. I ended up getting it to fit better with less shims, go figure. It adds an extra step to getting the back tire off.
The bike runs ok, lacks a lot of low end power. Unfortunately the PO drilled four holes in the baffle so it pops and backfires (way overkill).

 

Thank you everyone. I was hoping that they'd be able to tune decently with some rejetting. Adding the Supertrapp helps tons with that, at least that's been my experience. The headers look a bit large so I was hoping to hear something about the low end .. and I did! Perhaps using the right jets and carb tweaks wil help, as well as getting the muffler volume set to the bike's liking (using the Supertrapp to adjust the exhaust system volume is helpful sometimes. When I say *volume* I do not mean how loud it is.). As I mentioned the carbs need to be done anyhow, so rejetting and retuning isn't that big an issue. Start fat, right?

As far as making it run *perfect* .. well ... I've never had a bike that ran that way, so I guess I just don't know any better! That's after building sixteen race bikes and owning several brand new off the lot bikes as well. They all seem to need a bit of something.

Just kicking all of this around for now.

Thanks for the advice.