KZ440B factory 2-into-1 - any good?

I picked up a pile of KZ440B parts which included an OEM 2-into-1 that looks like this:



It's quite heavy and apparently not meant for performance, but the things that jump out at me are 1) the weird angle that the left header joins the right and 2) the excessive length of the left header. I'm not an engineer and assume this exhaust was a "good enough" sort of solution.

Do we know if this was an effort to save some weight (one muffler vs two)? Any idea how well it works?

I would guess it was done more out of an effort to save cost than anything else. Primary length mostly effects what RPM peak torque occurs at. When two primaries are different lengths this creates two different peak torque point for each cylinder, maybe 500 rpm difference here. This creates a flatter, but lower, torque curve by essentially offsetting the two peaks. Sometimes this is done intentionally to provide better traction, it is not uncommon on rally cars.

In addition to cost savings, it might have been a shot at looking more sporty.

I can not tell from the pic if the down pipes are close to the same length or not. You would need to measure both to where they join to see how much difference there is. I did enlarge the pic and used string to compare them and they appear to be close to each other in length.

If you have not as of yet, you may want to read the post on the subject. kzrider.com/forum/2-engine/595632-kz440-single-muffler-exhaust

They work ok. It's definitely a cost saving thing. They first showed up on the Kz400S models which were budget models (no electric start, drum brake in front, no tach). But I had no problem getting a jetting solution to work well with that exhaust and pods with stock carbs (different jets, though).

DoctoRot wrote: I would guess it was done more out of an effort to save cost than anything else. Primary length mostly effects what RPM peak torque occurs at. When two primaries are different lengths this creates two different peak torque point for each cylinder, maybe 500 rpm difference here. This creates a flatter, but lower, torque curve by essentially offsetting the two peaks. Sometimes this is done intentionally to provide better traction, it is not uncommon on rally cars.

That makes sense: the 440B was designed to be a commuter/ride-to-work bike, so a wide[r] and flat[ter] torque curve would be desirable.

TexasKZ wrote: In addition to cost savings, it might have been a shot at looking more sporty.

I was thinking that might have been part of the motivation, but to my eye it's not terribly sporty.

gd4now wrote: I can not tell from the pic if the down pipes are close to the same length or not. You would need to measure both to where they join to see how much difference there is. I did enlarge the pic and used string to compare them and they appear to be close to each other in length.

I haven't measured them yet, but in person the difference is pretty noticeable.

loudhvx wrote: They work ok. It's definitely a cost saving thing. They first showed up on the Kz400S models which were budget models (no electric start, drum brake in front, no tach). But I had no problem getting a jetting solution to work well with that exhaust and pods with stock carbs (different jets, though).

I appreciate the info. The 440B project bike has the dual-leading-shoe drum brake because I want the retro look. I wish it had a kickstarter but I'll trade that for the electronic ignition.

Engine-wise it has VM30s and the plan is to use stock headers with aftermarket mufflers. The 2-into-1 was sort of an unintended bonus - I'm not sure what (if anything) to do with it.

My buddy considered putting a disk brake on the front, but I convinced him the drum looked way better and we actually got it working good enough that I didn't feel he was missing any braking power.