Topic: 4-2 Exhaust

[VitaminCB550]

I see that almost no one sells the 4-2 exhaust anymore... Why could this be? Is there a disadvantage to having this exhaust versus 4-4 or 4-1?

[ProTeal55]

I have a 4 into 2 on my bike, was on their when I bought it.
I have heard that some people who switched from a 4 into 2 to a 4 into 1 went back, becasue they said they lost bottom end power. Prob. harder to set as well..I am sure a 4 into 1 makes great top end power, but what about down low, for the stoplight races ?

I am happy with my 4 into 2, for the momment   

[Dave Wyatt]

I installed a NOS Jardine 4-2 on my Hondamatic in place of the factory 4-1.  It really woke the old girl up!  It's got torque that I did not know was available.  I now have very long primary tubes that merge behind my foot pegs.  That, I believe, is the key to the torque.  A 4-1 with long primaries could be as effective, but space prohibits 4 single tubes from going too far.  I have seen some Honda drag bikes with long primary 4-1 systems, but the hang too low for a street bike.  I like to lean both directions.

[Cowboy48]

I would love to have a 4-2.  The 4-1 that was on my bike when I bought it has a big dent.  I like the balanced look of a 4-2 without the bulkiness of a 4-4 (forgive me vintage gods).  I haven't seriously looked into replacing mine yet but if you find a good deal on 4-2 please post it because I can be easily convinced to make it a priority.   

[ProTeal55]

Like in 1/4 mile dragracing.

Open Headers = Good Top End/High RPM power
Full Exhaust = Good stoplight racing toqure down low - possibile "choke"up high (in rpms)

The key is to get a exhaust that gives you the best of both worlds outta one system. For these bikes I would think a 4 into 2 would be "THE" system. If the bike is a track only / high rpm bike, then a 4 into 1 would work best..

[VitaminCB550]

Like in 1/4 mile dragracing.

Open Headers = Good Top End/High RPM power
Full Exhaust = Good stoplight racing toqure down low - possibile "choke"up high (in rpms)

The key is to get a exhaust that gives you the best of both worlds outta one system. For these bikes I would think a 4 into 2 would be "THE" system. If the bike is a track only / high rpm bike, then a 4 into 1 would work best..

Then why do so many people run a 4-1? I'm sure 95% of the people using this system dont need the top end as much as the low end. Also, my bike turns "on" from 5-9000 rpm and I have a 2-2... Reason?

[Dave Wyatt]

I would love to have a 4-2.  The 4-1 that was on my bike when I bought it has a big dent.  I like the balanced look of a 4-2 without the bulkiness of a 4-4 (forgive me vintage gods).  I haven't seriously looked into replacing mine yet but if you find a good deal on 4-2 please post it because I can be easily convinced to make it a priority.   

I found mine on ebay.  They were not made for the Hondamatic, but a regular CB750.  They went on with a few minor changes to the bike.

[ProTeal55]

I am guessing that allot of people run a 4 into 1 for the sound/look of the pipe, more than anything.
I remember when I first bought my bike, all my friends said the first thing I needed to buy was a 4 into 1, and half of them arent even into bikes  Most "cafe" style bikes you see will run a 4 into 1 , becasue it "fits" the cafe/racer look.

I am keeping my 4 into 2 thats on the bike, and when the mufflers rot off (which will be soon), I plan to replace them with automotive dragracing bullet mufflers...

To each their own, thats my 4 cents on the topic....

[volthause]

I'd love to run a 4 into 2 with some high side pipes with modern cans on 'em... but I fear it would look a bit silly on a '74 bike. :/

[Andrew Foss]

MAC sells 4-2 systems, i hate the look of their mufflers though. i want to try to just buy the headers and get new mufflers for them. i forget the site, but you will find it easily if you google it.
-andrew

[HondaMan]

4-2 only works if the pipes tangle up with each other and get quite a bit longer. The pulse timing that works best is the 2 center together with the 2 outer together so the "hot" waste spark cycle imparts flow pressure into the junction. These are hard to make and even harder to tune, because the length works out to be about 12" longer than the 750 pipes we all know (similar for the 500).

BMW fixed it this way: flow straight to the end of the pipe, turn 180 degrees and go back to the front of the muffler portion, then go back again along the outside shell to the exhaust, exiting in a reverse cone. This causes a large low-pressure moment at the last 180 bend at lower engine speeds, at the first one in mid-range, and at both  together at both bends at higher engine RPM. These are the most efficient pipes I've seen, but don't fit a CBnnn.   

[Green550F]

I think yhe 4-2 on mine would look so much better upswept a bit.  Love the growl though! Verry distinct, no other bike in town sounds like it!

When I was a kid, my dad's Suzuki 185 could be heard 1/2 mile away.  When we heard him coming home, all my freinds started making excuses to leave.  Now that leaves a formidable impression!

[ProTeal55]

I'd love to run a 4 into 2 with some high side pipes with modern cans on 'em... but I fear it would look a bit silly on a '74 bike. :/

Their is a pic here---->http://www.sohc4.us/forums/index.php?topic=9212.0 of a 70's yamaha with a newer sportbike "can" on it. I think the muffler looks too new for the bike myself, but maybe you could get it to look good with some trial and error....

[volthause]

wow, that's a huge can. i'd try to run something a little smaller. maybe not carbon either. it's just a silly pipe dream (pun intended) at the moment. much larger fish need to be fried on my 550 before i worry with a custom exhaust.

thanks for the pic though!

[ProTeal55]

Ya , that muffler is huge. I am sure you could run a smaller Ducati Monster sized "can" to get the look you are going after.

I right their with ya, I have allot of other things to deal with first, before the exhaust gets addressed.