Coring mufflers

ST Gui

240Robert
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It's your time and money. If it makes you happy...

I modified the exhaust on my 750-4 several times. Watching the plugs after several longish runs at different speeds (and killing the engine quickly to examine them) I found that the engine ran noticeably leaner at the upper midrange and top end and backfired a lot. Cool at first but it got old quickly.

I had to experiment with raising the needles in the carbs and trying various larger high-speed jets. I finally got the bike running well. Dialing in the carbs gave me better performance and full economy (not great just better) as long as I wasn't WFO.

After a little over a year I missed the sound of the pockita-pockita factory exhaust. So I had to reset the mixture and it wasn't as easy as doing a reset.

I'm not crazy about the sound of the STs but at least the 1300's FI would make it a little more forgiving. I haven't heard an aftermarket exhaust that would make me go through the trouble.

If your mod gets you what you want Rock On! Just be careful what you wish for.
 

Blrfl

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2. My goal is to make it a bit louder and maybe find some more throttle response.
You'll get louder, but you're poking at the wrong end for more throttle response. Opening up the exhaust nets you some additional horsepower, but the laws of physics extract a penalty by stealing torque from the low end.

More go-fast when you crack the throttle open comes from torque, and you make more torque by stuffing more fuel and air into the combustion chamber. That means some combination of a freer-flowing intake, larger bores in the carbs and intake manifold and changes to the valve timing to suck it all in. If you've got cash to burn, there's always forced induction. You will, at some point, need to consider the exhaust, but not until you're making more gas than what you have can carry.

--Mark
 

John OoSTerhuis

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Unless you've got BEFORE and after dyno test results, any claim of improved performance DIDN'T happen.

Some ST1100 historical background - over 20 years ago members of the new ST1100 community were trying 'old-timey' 'hop-up' tricks on their STeeds. In the Spring 1994 issue of the ST1100 Newsletter (p.8), Charlie Woods (STOC 2) mentioned drilling a quarter inch hole through the OEM mufflers. On STeinar Fremme's iconic ST1100 website some folks reported drilling one inch holes around the air cleaner case was the quick and easy way to improve performance. IMNSHO, after all these years I think The Wisdom Of The LiST and the rest of the ST community is that the beST way to improve performance somewhat lies in carb jets/needles, supercharging, or losing weight (ST/rider).

Mutilating a perfectly serviceable set of expensive OEM mufflers just seems wrong to me.... and futile.

As to exhaust 'note,' the reports I remember indicated the change was too small to justify it. If you must, get an aftermarket designed and certified for the ST1100.

John
via iPhone 6
 
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OP
OP
bobdog2o02
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Ok, so i got these things yesterday. Unlike other attempts of just drilling a hole through them i think i will take a different approach. I think my best plan of attack is to cut the factory welds that hold them together and take the guts out. Then reassemble with a generic perforated baffle tube and test. I will post pics of what i find.

A few side notes....

How is a muffler that you can see straight through ever tuned to a specific motor?
Why would i spend more money on hollow pipes that need removed every 3,000 miles for tire changes when for $100 i can have essentially the same thing that wont need removed?
 
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Ok, so i got these things yesterday. Unlike other attempts of just drilling a hole through them i think i will take a different approach. I think my best plan of attack is to cut the factory welds that hold them together and take the guts out. Then reassemble with a generic perforated baffle tube and test. I will post pics of what i find.

A few side notes....

How is a muffler that you can see straight through ever tuned to a specific motor?
Why would i spend more money on hollow pipes that need removed every 3,000 miles for tire changes when for $100 i can have essentially the same thing that wont need removed?
Well....to your surpise, what you can 'see thru',( if your referring to a stock exhaust, and not 'holed' rusted thru) is NOT the same as expansion pressures. My friend, with a statement like that....you got a whole lot of learnin' ahead of you as far as exhaust systems back pressures. No offense intended, just the facts as I see them as this thread has progressed and your responses;).
 

Uncle Phil

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BTW, you don't have remove the mufflers for tire changes. Just remove the hanger bolts (takes a few seconds) and the rear axle will wiggle right out under the mufflers which can be raised up now ever so slightly. :D Good luck on your experiment - you only learn by trying!
 
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How is a muffler that you can see straight through ever tuned to a specific motor?
Easy to explain with a few differential equations. It's about the pressure reflection that occur when the exhaust gasses exit the pipe. Some of the various parameters have been mentioned above. Also ; RPM, intake port & ram tube length,

Years ago ( when I was younger and even more foolish than I am now ) , I had a Honda CB750. I decided to pull the baffles. Nice ( ? ) and loud without the baffles, but a pain in the "ears" and annoying to the cage driver's too. But no real performance increase. Two days later, I re-installed the baffles.

Like John has said, if you do some searches, often dyno tests have proved either a decrease in performance, or only a slight marginal increase . So why bother ?

I like the quiet exhaust on my ST1100. If the exhaust was any louder, I wouldn't be able to hear the cool straight-cut camshaft gear whine.
 
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thekaz

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I guess then i have a serviceable set, though pretty rashed up, of mufflers for sale. Who wants em?
NO NO Don't sell them dude. The best way to learn is mess with stuff. I say get rid of the cats & AIR system just to piss off the tree huggers and reduce heat. You may need to fiddle with carbs if doing this creates a flat spot. Post some pics !!! PLUS worry more about how the bike rides when your done. We are not talking about a track bike here LOL
 
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thekaz

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How is a muffler that you can see straight through ever tuned to a specific motor?
Usually its about the diameter and length of the perforated pipe equalling air flow. For most its about obtaining a flat torque curve which is a combo of tuning & opening up the exhaust or intake.
 

John OoSTerhuis

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....
I like the quiet exhaust on my ST1100. If the exhaust was any louder, I wouldn't be able to hear the cool straight-cut camshaft gear whine.
+1 :clap2:

I think it's worth repeating: without BEFORE and after dyno test reports, any improved performance claim is hearsay/anecdotal... didn't happen! OTOH, increased obnoxious sound levels is NOT an ST1100 improvement, IMNSHO.

John
 
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I for one would like to see/hear the results of your mod. The only real complaint is the grandpa mufflers quiet the engine too much. Just don't want to drop the coin on a set of mufflers I've never physically heard or suffer the inconvenience of having to remove them for rear wheel maintenance. If the mod works I would do this to mine.

I had Kerker slip ons on my old VFR with no baffles. Let the V4 roar! Sounds like a hotted up Chevy small block.
 
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I for one would like to see/hear the results of your mod. The only real complaint is the grandpa mufflers quiet the engine too much. Just don't want to drop the coin on a set of mufflers I've never physically heard or suffer the inconvenience of having to remove them for rear wheel maintenance. If the mod works I would do this to mine.

I had Kerker slip ons on my old VFR with no baffles. Let the V4 roar! Sounds like a hotted up Chevy small block.
I bet in 29 years, you may think differently. :) Re-post then , please.
 
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Phil :

That was a test to see if you and others seniors are sharp enough to pick up on that. Congratulations, it looks like you passed. Waiting for other responses from all the other seniors on this Forum.

Personally, I may not be around ( in my present form ) in 29 years , but my ST1100 may still be rolling down the road.
 
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