Mac 2 into 1 System

[doodsaibot]

I was reading through the forum and other sources online on the matter of 2 into 1 vs. 2 in 2 exhaust systems. From what I understand, 2 pipes into 1 will give you a slightly wider power band, correct? I know my bike is just a 400cc street bike but it seems like an relatively easy, neat conversion not to mention the possibility of wider power range. I like the sound of my stock exhaust, especially in the high end RPMs but I am curious now about the MAC system. Any other DOHC guys or even SOHC riders that have made the switch have an opinion on the matter or notices any difference in their ride? Thanks.

 

[xschris]

Your stock exhaust that has the crossover under it will give you the best overall performance at all rpm's. An aftermarket 2-1 or 2-2 setup will be more at certain rpm's My 2-1 vintage kerker on my 80 likes low and very high rpm's. I would stick to what you have and don't cut it up. If you have the cash get a mac and see what you think. At some point I will switch mine back to the factory setup. It's much better for everyday riding.

 

[Sesty]

I never had a stock set up. When i bough the bike it had chopped headers with emgo slip ons. They were crazy loud. I switched to MAC 2-1 the next year. The 2-1 sounds great, much quieter but I did not notice much difference in performance. If you like the look of the OEM and they are in good order I would keep em. Def dont cut them up or anything like that. Plenty of people looking for stock exhausts.

 

[BBS360]

Performance gains on 2-1 exhausts seem pretty debatable with our 180 degree crank.

 

[LuckyEight]

weight saving...

 

[BBS360]

Ok, "engine performance".

 

[xschris]

Ok there would be a weight savings. I think the stock 80-82 exhaust with all the brackets weighs around 25-30lbs. My kerker weighs about 8lbs. But my 81 and 82 with the same xs360 carbs and K&N RC-130 filters run much smoother and pulls better through out the rpm range than the 2-1. I would like to see dyno numbers, but there is no way for me to do it. I would imagine yamaha would have spend a bit more time and money into developing there systems for there bikes than most aftermarket muffler places. Remember a mac system only costs around $200. Look up a real race exhaust and those go for thousands. The cheap systems are more for the "look" and "sound" rather than tuning.

 

[doodsaibot]

My bike is somewhat of an everyday rider, at least for the weekends. I'll do anything from city to country rides, low speed to max speed, low revs to high revs. I think the MAC looks better but as yall said, the current pipes are better for everyday, versatile riding. I suppose I may experiment with that in the future. I understand re-jetting would be in order as well.

 

[Wolfe_11B]

I can only add that it sounds cool. That's all I got

 

[16VGTIDave]

I did some math a while ago regarding exhaust header design for the DOHC:
For a 7k RPM peak, the primary pipes should be 1" ID and just shy of 23" long before merging into the collector. Then have a 1.6" ID tailpipe about the same length as the primary pipes. After that, as long as the pipe is larger, it doesn't have any tuning effect.
8K would be 1.25" ID and 19.5" long, 1.7" ID tailpipe.
9K would be 1.3" ID and 17" long, 1.8" ID tailpipe.
10k would be 1.4" ID and 15" long, 1.9" tailpipe.

See the pattern? Small ID and long pipes for lower RPM. Larger ID and shorter pipes for higher RPM. This applies to all normally aspirated 4-Stroke engines.

I haven't had my hands on a MAC system in over a year, but they appear to have 1.5" OD pipes that are rather long, easily 20" or more. Based on my calculations, the MAC system isn't actually tuned. It's just a bunch of pipe bent into a fancy shape. The stock header pipes are double walled, so even though they appear to be 1.5" pipe, they are closer to 1" ID, maybe smaller.

 

[Old Mose]

I got the Mac 2 into 1 setup because it was available and cheap and I didn't have a choice as my original pipes were damaged in a wreck. I went up one size on the main jet some time ago which greatly improved performance but I didn't have factory mufflers either. The Mac system isn't really tuned but it does seam to me to have more low end and I like the sound and look!

 

[doodsaibot]

Thanks for all that info guys. After reading the posts, it seems to me that for the most part, the MAC is a good option in the event the stock pipes are in bad shape, you want something lighter or you simply don't have the stock pipes for vintage bikes like these. Or if you'd like a different sound!

Dave, are you running custom made pipes on your Maxim? They look different than stock.

 

[16VGTIDave]

Not really. My exhaust was very rusty, so I cut the pipes just before the cross over, then scuffed and painted the pipes with BBQ paint. It turns a flat dark grey/black once it is heated. The mufflers are from a HD Sportster. Very heavy, but good flow on a 400 at a reasonable volume. It works, so I haven't been rushing to replace it.

 

[doodsaibot]

HD, huh? Not turnin' into a Harley guy on us now are ya? Your bike looks like it's ready to ride down to Mexico and back. Kinda wish I had that lamb skin seat cover and nice suspension for my hill country ride earlier today. After so many miles this stock seat is like riding a wooden board.

 

[16VGTIDave]

LOL! No more than I'm turning into a Kawasaki guy (rear suspension), a Suzuki guy (rear shock), or a Honda guy (seat). If I made it to Mexico, I'd keep going to Costa Rica and visit a buddy down there. No point in turning around early!

The sheepskin seat cover was easy to make! I got the sheepskin for $45 CDN last summer (probably $40 US back then) at a flea market. I then bought a yard of 1/2" nylon strap and a buckle from a local craft store. Probably less than $2. I used CAD (Cardboard Aided Design) and made a template of the top of the seat. Cut the sheepskin to match and sewed a loop of strap at the front of the sheepskin to hook under the nose of the seat. The buckle and strap were sewn onto the back corners to keep the sheepskin from sliding forward. Less than 2 hours to make it. All weather, all day comfort! The leftover sheepskin made a cover for my office chair.

 

[doodsaibot]

Heck yeah! Thanks for the pointers. I am planning a trip to Galveston to see some family and friends this month and I am going to need all the seat comfort I can get. It will be just over 400 miles roundtrip for that weekend. Not doable with just the stock seat! At least not for me. I picked up a spitfire windscreen for those longer, high speed hauls and hopefully it helps quite a bit too.