MAC/Yoshimura exhaust systems.

Wow, those are sweet! Any idea on pricing? I'm guessing about $2500 for the titanium versions...

I'd like to preface this with I don't know nearly anything about exhaust. I read through this thread though to begin my education. If Otakar would prefer I start my own thread for this, I can do that.

I have an '81 KZ750. As far as I can tell, it has the stock exhaust as it is two 2-1. I know it originally had a cross-over pipe but that pipe is MIA since I purchased the bike. The ports for the crossover look blocked off, with what I am not 100% sure. The bike otherwise is mostly stock as well. The only modification I have made is Dyna coils and cables.

I would like to start looking for a 4-1 system as the lack of crossover pipe is a problem I think? There is a farmer near me who has a barn filled with early-80s bike parts. I'm going to go peruse the exhaust section to see if I can't find something better for my bike.

What am I looking for? How do I tell if something will fit my bike? I understand the basic check is header spacing where it clamps to the engine, but is there other things to keep an eye on? I think I'll be taking my bike out there so I can eyeball some things.

I guess I am just looking for some advice/tips in relation to exhaust for an '81 KZ750 H2.

kz750saskatoon wrote: ...'81 KZ750...stock exhaust...two 2-1...originally had a cross-over pipe but that pipe is MIA...ports for the crossover look blocked off...would like to start looking for a 4-1 system as the lack of crossover pipe is a problem I think?....

Imo, lack of a crossover pipe isn't much of a problem, although it probably has some adverse impact on performance at high rpm and wot.

My recollection is that as motorcycle mufflers became quieter and increasingly restrictive, a cross-over tube was added to allow exhaust through both mufflers, particularly beneficial at higher rpm such as wot with performance enhancment due to a less stifling exhaust flow.

For example, a cross-over pipe was added to British twins sometime in the late 1960's (as I recall), between the header pipes, in close proximity to the exhaust ports. My 1967 BSA 650 A65 Spitfire Mark III did not have the cross-over. And in stock form ran an honest consistent >100 mph with open reverse cone megs. But did vibrate just a little.:lol:

A cross-over pipe likely adds little or nothing to performance at lower rpm or with relatively nonrestrictive cans, such as open unbaffled reverse cone megaphones.

The original KZ900-B1 LTD had no cross-over pipe on its 4>2 Jardine exhaust system.

The 4>4 stock exhaust systems had no cross-over.
However, the muffler pair on each side had a connection between them.
Cylinders #1 and #2 exhausted through the left-side pair of mufflers.
Cylinders #3 and #4 exhausted through the right-side pair of mufflers.

Good Fortune!

otakar wrote: I have two Yoshi pipes with the Aluminum mufflers and one series 1 mini pipe, which is on my 78 Z1R. I want to make a Yoshi stile tail pipe for a Kerker header that I have and get rid of the Kerker tail pipe. The only problem I have ever found with the Yoshi pipes is that you must allways get rid of the centerstand with them. If I use the Kerker header I will be able to retain it. This is one reason I also like the MAC pipes. They perform and sound like the Yoshi and you can also keep the centerstand. The MAC canister pipe sounds like a Yoshi and the Megaphone like the Kerker.

I was working on a "Kerkimura" sytem as well recently. Actually, it's just a piece of 2.5" tubing to match the Kerker collector, one bent, one straight. My project is stalled until the fall due to the usual family/house stuff. Anyway, I like the short piece better, and did find a 2.5" baffle that fits quite well. If there is any interest, I could start a new thread.

EricHa wrote:

otakar wrote: I have two Yoshi pipes with the Aluminum mufflers and one series 1 mini pipe, which is on my 78 Z1R. I want to make a Yoshi stile tail pipe for a Kerker header that I have and get rid of the Kerker tail pipe. The only problem I have ever found with the Yoshi pipes is that you must allways get rid of the centerstand with them. If I use the Kerker header I will be able to retain it. This is one reason I also like the MAC pipes. They perform and sound like the Yoshi and you can also keep the centerstand. The MAC canister pipe sounds like a Yoshi and the Megaphone like the Kerker.

I was working on a "Kerkimura" sytem as well recently. Actually, it's just a piece of 2.5" tubing to match the Kerker collector, one bent, one straight. My project is stalled until the fall due to the usual family/house stuff. Anyway, I like the short piece better, and did find a 2.5" baffle that fits quite well. If there is any interest, I could start a new thread.

Yeah that'd be cool! I personally prefer the Yoshi look over the Kerker look, and I scratched my Kerker in a lowside a few months ago- they want $400 for just the empty megaphone (no Kerker badge or baffle). This is for my daily driver bike, so I'd like to still have easy access to the oil filter.

This good information. I always wondered if missing the cross-over was a performance concern. I do have some thoughts about the bike's high rpm performance (struggles to go much faster than 120-130km/hr). My mileage still isn't where I'd like to see it (between 30 and 35).

Maybe I'll just get some pictures of what I have on there later today and ask a few questions about them in another post.

That is exactly the same thing i want to do. I saved a Kerker header and will install a tail pipe just like that on it.

This a Yosh pipe?

Oddly, none of these systems truly resemble the one on my'83 GPz 1100 and I haven't seens the same long gold-colored tag yet. I would post a photo but the bike is currently 400-miles away. I know for a fact it was purchased when the bike was brand-new and I believe was made to fit the twin-shocker as there is a pretty good dent where the uni-track hits it.

I also remember it being termed the "series 7 competition pipe" (required center-stand removal) as was the one I bought for my 82 GPz 550 in 1988. It has the straight-through all-steel baffle. It was superceded by the aluminum cannister type that I thought to be ugly at the time. It's a shame, but I think I just tossed my late-80's Yosh catalog about 2-years ago.

You can slightly see the long tag. Maybe my memory is out there, but I remember this being "Series-7"

The highest I remember them going back than was a series IV and they already had the aluminum can. But you can be right. I stopped following them in 1981.

Of possible interest:

www.kzrider.com/forum/2-engine/364179-ma...s?limit=20&start=100

kzrider.com/forum/2-engine/251721-vance-...20&font-size=smaller

www.kzrider.com/forum/2-engine/254680-yo...t=20&start=20#255236





Good Fortune!