Topic: Yamiya exhaust differences?

[Dunk]

I need a new exhaust for my CB750 K5. It has a 70s Kerker 4-1 that is louder than I'd prefer even after repacking and perhaps the bigger problem is I scrape it on the ground often. It hangs out to the side too far.

I have a CB750 K1 with this Yamiya exhaust and is is definitely quieter and I can't drag it on the ground, pegs hit first. I'm happy with it overall aside from loss of center stand.
https://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_142_88&products_id=671

Yamiya now has listed this other exhaust that appears to have the same baffle but the pipe is slightly longer and attaches to the passenger peg mount. What's the difference? For such a short amount more pipe I would expect the dB to be about the same, but maybe slightly quieter in the saddle since it exits farther back?
https://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_142_88&products_id=4212

I'd prefer not to lose the use of the center stand, but so be it if need be. I need a quieter pipe that won't get me killed by limiting lean angle. I know the shorter Yamiya pipe is reasonably quiet and meets my needs for everything but a center stand. Which should I get, or should I consider something else?

[69cb750]

Do you want a header or original 4 pipe ?

[Dunk]

4-1. Repop pipes are expensive, this bike is my daily rider, and judging by how loud original 4-4 pipes are on a 500/550, 4-1 is probably a bit quieter.

[69cb750]

Headers are louder then original 4 pipes.
Perhaps a quiet header muffler is available now.

[MauiK3]

The Yamiya 4-4 repop isn't very loud and you get to use the center stand.

[Jerry Rxman Griffin aka MuthaF'er]

Dunk, does your Kerker have the street baffle or the competition baffle? Quite a bit difference in size of the baffle tube/opening between the 2. I have both baffles. 

[PeWe]

That Yamiya 4-1 look restrictive. But it look nice. I like that style too.
My K6 had a similar design in the 80's and 2014-15, Alfa 4-1.
 
Hindle 4-2-1 is both silent and have good flow. Long muffler.
If riding in legal speeds less sound level than my K2 with Yamiya no numbers 4-4 with diffusers/baffles in without padding.

Another thing when open throttles much more.

https://www.ripplerockracers.com/product/cb750-hindle-vintage-racing-exhaust-system-fits-1969-78/

But this is another style.
Yamyia 4-1 is very slim and will not be an obstacle for bags.

But it must be possible to make a centerstand stop as other 4-1?
But it will have a long stick out on left side without stock 4-4 partly covering it.

[Dunk]

Dunk, does your Kerker have the street baffle or the competition baffle? Quite a bit difference in size of the baffle tubbe/opening between the 2. I have both baffles. 

My Kerker baffle is about 33.6mm ID. The Yamiya baffle is about 28mm ID. I repacked the Kerker last year which quieted it down a lot as the old packing was worn out and loose. A smaller vaffle with more packing may help quiet it more, though would not address the lack of ground clearance.

[Jerry Rxman Griffin aka MuthaF'er]

I'm not close to my stuff to measure but that sounds like the less restrictive louder competition baffle.

[Dunk]

Measuring again, comparing my Kerker to Yamiya, I get 1.34" ID on the kerker baffle and 1.14" on the Yamiya. Yamiya makes a larger "race" baffle for their pipe, I've never tried it. This seems like the Kerker baffle is the smallest "competition" baffle they advertise as 1.5". If I was to keep this pipe I would want to try the factory baffle which is longer and has a bend but is about the same ID as the baffle I have. This baffle seems to be unobtainium. They don't sell them individually, and most folks probably trashed them.

Found elsewhere:
P/N 100-6351, standard 1.5" (installed during manufacturing)
P/N 100-6387, competition 1.5"
P/N 100-6356, competition 2.0"
P/N 100-6357, competition 2.5"

My current exhaust is actually a Winning Performance, which was some sort of spinoff of Kerker back in the day. Something about a falling out between partners or some such. Picture attached, the baffle before getting new packing which did quiet it down appreciably.

The Hindle looks nice. If it's quieter than what I have, retains the centerstand, and most importantly will not rub before the factory pegs, it may be a better option.

[Dunk]

I got to looking at the Winning performance/Kerker exhaust today. The way the muffler is mounted, with a large spacer, would seem to push it out a bit farther than it needs to be. I don't know how much ground clearance I could gain by shortening that spacer, but it seems plausible since the period Kerker advertisements claim increased clearance from factory exhaust.

This pipe is hanging way out there and I scrape it all the time, whereas the left side I just lift my foot and the peg folds up nicely. It has been sketchy a time or two in right turns. If I can get more ground clearance by changing the mounting it would be serviceable. If I can do that and find an original style baffle to quiet it just a bit it would be great.

[Dunk]

I measured dB on the Kerker with small 1.5" competition baffle tonight (measurements below, not scientific, using a cheap $20 meter). To me it sounds a lot louder than it actually is at idle, maybe because it's so deep. Interestingly the clutch rattle at idle is significantly louder than the exhaust, thought the exhaust sounds louder to me. I have no easy way to measure when riding, but subjectively it sounds quietest (quieter than idle) at 2500-5000 RPM under light or no load at steady speed, under load at higher RPM is when it's louder than I'd like.

   20' behind: 65 dB
   5' behind and to left: 75 dB
   Seat, pointed back, idle: 71 dB (75 w/ clutch rattle)

The factory 100.6351 DBAE baffle is the same ID but it looks like about twice the length of packing as it has a slight bend to fill most of the muffler space. I got to thinking this wouldn't be a terribly difficult part to make if it's genuinely unobtainium. It's probably not much, if any, difference in performance from the small short baffle. I can't imagine an extra few inches of smaller ID and a slight bend would make much difference as compared to the ID differences in the different baffles.

[caluser2000]

There should be an aftermarket baffle the correct or near enough size to do the task. I fit a 6" aftermarket baffle in my CB550F "cafe" style EMGO "muffler". Put house insulation around it then ali mesh to hold the insulation in place and tie it together with 32thou lock wire.

I don't like riding at all with too noisy exhaust note. It just annoys other road users in town as well as frightens live stock and other animals on my favorite twisty roads.

[Jimcg]

... as well as frightens live stock and other animals on my favorite twisty roads.

A good way of thinking and very thoughtful of you! 🙂👍

/Jim

[caluser2000]

... as well as frightens live stock and other animals on my favorite twisty roads.

A good way of thinking and very thoughtful of you! 🙂👍

/Jim

I don't want to hit frightened animals that is all. Could get a bit messy for me and the beasty. Hitting a blind wolfhound following the sound of sheep dog barks was an interesting experience. Luckily I was traveling a walking pace by then because of the sheep flock. Farmer was fine with it.

The country roads can get quite narrow as well. Escape options are- into ditch, into bank, over cliff or into/through fence. Farmers don't like the last one.

here are picks of what I did re cafe muffler baffle.

[Dunk]

Interesting modification. I have a pair of those type of baffles I was going to try on my CB350 to quiet it down when I tried both a Thailand repop exhaust that was obscenely loud and then a set of Emgo chambered mufflers that were still pretty loud under load. I think the twins are just naturally very loud from only a single exhaust pulse per muffler and no crossover. I ended up with a pair of new OEM takeoff Triumph mufflers that have a nice deep sound but are very quiet... $40 off CL. In any event, I've seen perforated tubing for sale in various ID that is intended to make custom exhaust. A length of that, a bend, a few welds, and figuring out the OD for the inner end cap shroud might get me what I want for this Kerker.

Interestingly the Ikon shocks I installed the other day are just a hair taller than factory shocks. The exhaust didn't rub on a spirited ride with the new shocks, though I didn't drag the right peg. I'll have to test further. Shortening the spacer the muffler attached through would probably get me enough clearance. If so, I will probably pursue making a longer baffle for this muffler.

[caluser2000]

I certainly know what you mean by what obnoxiously loUd is all about. I worked around jet aircraft for a large part of my life. Even with Grade 5 ear defenders on it can get to you. I got a shorty reverse cone muffler you can take the end cap off and and remove as needed just for the hell of it it is shorter than the cafe muffler. Swapping mufflers around on my CB550F takes around 10 minutes to do.

I've also got a crappy early '80s SAGA 4 into one.  I cut the drain pipe off the end of it and I had an engineer buddy put an adapter on so I could swap mufflers if I chose to. A few of the headers are a bit dented so I'll do that exhaust wrap thingy folk rave about just for #$%*s and jiggles. I is nice to have choices

[disco]

I don’t know if you have considered the ‘Delkevic’ 4 into 1? It’s stainless steel and far cheaper than a 4-4 system. My repro 4-4 system for CB750 cost me nearly 2,000 AUD, and even though it’s always garaged, it’s rusting from the inside out, after only 4 years. My Delkevic systems on the other hand, cost about $600 AUD and show no signs of corrosion whatsoever.
Btw the short ‘universal’ muffler which I expected to be louder than the larger megaphone muffler (I have both types) is actually quieter and very much road legal. It’s really quiet, yet has the look I wanted. I haven’t been able to touch the muffler onto road. The pegs drag before that happens. Btw Centre stands remains in place. For me, the Delkevic will be on the next 2 bikes I’m building without a doubt.

Pics below are from the Delkevic Australian & US websites.

[caluser2000]

‘Delkevic’ 4 into 1 stainless headers are certainly on my short list if I ever want to replace the OEM headers which aren;t too bad yet after a good clean up. Yes they are quite good value as well. Next up for my CB550 is replacement rims though.Hopefully I'll have that done by the end of this year/early next year.

I bought a new OEM exhaust set in the early '90 for my '76 CB550F. The muffler was rotting out at around 5 years so had a collect to mufler adapter made up for a reverse cone EMGO muffler. That EMGO muffler still is showing no sign of rusting after all these years.

[Dunk]

caluser2000, Jet engines and power tools, inadequate protection, I get it. Delkevic is surprisingly cheap. I think I prefer chrome like on the Winning Performance / Kerker, but stainless has merits for a daily rider that sees rain. I wonder if it would be quieter than the Kerker with 1.5" comp baffle. Might be worth a shot.

Looking at this model is it seems they advertise as being more quiet, "street rumble". Anyone know the ID of the baffle or length that has packing? Is there a baffle or chamber before the perforated tube with packing? They mention baffle in/out or the entire innards entirely removed as options.
https://delkevic.com/full-system-to-fit-cb750k-four-sohc-1969-1976-with-classic-megaphone-muffler-and-stainless-steel-4-1-headers/

[caluser2000]

Why not just ring them up and ask or email them? If there is a contact form on their website use that.

Grade 5 ear defenders were the best ear protect at the time Not sure if that has though unless noise reduction ones are issued these days.