GLOBAL WAR ON COBRAS, Part Deux

[iraqvet750]

I WOULD FIRST LIKE TO THANK those who responded to my query regarding finding stock mufflers for my '85. The issue raised two minor, potential complications -- i.e. black vs. chrome endcaps, and whether the '85 mufflers were less restrictive than newer iterations.

With these and other factors in mind, I've decided that the best long-term solution is to try to recondition the mufflers the bike was born with, keeping original fitment intact. First and foremost, I understand that the OEM equipment from the factory offers the best-engineered, tested and balanced combination of performance, sound, noise abatement, reliability, and arguably looks the best. Any aftermarket deviation may offer improvement(s) in one or more areas at the expense of others.

That said, while I work on the original mufflers, I can't resist the look and sound of the nefarious, farkle-ly, shiny object, and horsepower-killing Cobra slip-ons. I read up on the Great Cobra Brouhaha of 2020 on this forum, and have been adequately forewarned of the tradeoffs -- e.g. more of a "hot rod" look and sound while sacrificing 10+ horsepower, the original appearance, potential reliability, attracting cops, pissing off my neighbors, and many other things I'm probably not aware of.

I have been slowly replacing parts to return my '85 to as close to stock as possible, but will never get much past 90% original, especially given the (Dark Amethyst) repaint, with the "Von Dutch" style pinstripes on the fenders (which are very subtle and I'm told very well-done, but unoriginal). My bike has >30K miles and will never be of Bring a Trailer or collector quality, so I think I'm just going to ride it (moderately) until the wheels fall off and enjoy it. I'm perfectly happy taking mellow beach cruises on the Max and going to bike nights, Thunder Beach, etc, while saving more spirited riding for its VRod stablemate. (Speaking of Bring a Trailer, I submitted an application package to BaT to auction off its baby brother, the '86 Fazer seen in the photo. It's siphoning time and resources from the others, particularly the Max.)

So I ordered the Cobras on sale, cheap. All drawbacks considered, I think they complete the "drive-in", lake-piped look, and restores some of that V8 sound I had briefly before I fixed my exhaust leak. If I can't handle the diminished performance or neutered VBoost, I'll take some photos for posterity, then revert back to stock and dump the Cobras.

Here's my question (finally): Using the factory intake, does anyone recommend changing the jetting while switching from stock, to Cobra, and back to stock?

Thanks again, and I welcome any additional positive/negative information regarding the Cobras. I promise I won't get bent out of shape and reignite that battle royale.

 

[Parminio]

You will live to regret that decision; not so much for the ridiculous loss of power and very poor gas mileage, but more for the "you will run so rich you will smell like you bathed in gasoline 5 minutes after you get on it" aspect.

What's more, if you ever are unfortunate enough to get stuck in stop and go traffic, you'll probably wind up puking because of it.

And there will be absolutely nothing on this earth you can do about it.

Here's my question (finally): Using the factory intake, does anyone recommend changing the jetting while switching from stock, to Cobra, and back to stock?

No. Reason: you can not tune untuned pipes. It's a waste of time, money and effort. It has been tried many times. It has always failed.

 

[iraqvet750]

You will live to regret that decision; not so much for the ridiculous loss of power and very poor gas mileage, but more for the "you will run so rich you will smell like you bathed in gasoline 5 minutes after you get on it" aspect.

What's more, if you ever are unfortunate enough to get stuck in stop and go traffic, you'll probably wind up puking because of it.

And there will be absolutely nothing on this earth you can do about it.



No. Reason: you can not tune untuned pipes. It's a waste of time, money and effort. It has been tried many times. It has always failed.

Ok, thanks for the warning. I appreciate it.

 

[Fire-medic]

You are already aware of the Cobra looks, four into four/ slash-cut, and the precipitous drop in horsepower, throttle response and carburetor issues. The UFO now Star Rider Performance four into four package is a full exhaust system including header pipes and it will give you an increase in performance properly jetted. If you keep them clean and waxed you will preserve as much as possible the appearance and avoid severe pitting.

Since it's your bike you get to do whatever it is that you wish to and for some people the appearance is paramount more so than the performance that they may never choose to use. Since you've done the research on various posts on here you know that the stage 1 kit is not the jet kit to use; I suggest that going to something like a 150 or a 147.5 main jet may help reduce the hydrocarbon fumes that parminio was speaking of. As you mentioned keep us informed as you work through the installation and usage and report such things as throttle response, noise, perceived levels of power, and anything else that you believe is pertinent to furthering our documentation of the Cobra system on the bike. It would be interesting to see that your involvement with the cobras includes time on a dyno, but don't expect that you are going to break into the triple digits with the Cobra system.

Did you ever find the thread about the use of the the VMax to serve as a baseline for the Dynojet 250 dynamometer calibration? I believe that both Sean Morley and I have posted about that including links to articles about the Dynojet 250 dynamometer during its development. That makes for some interesting reading and understanding of how a dynamometer works.

 

[iraqvet750]

You are already aware of the Cobra looks, four into four/ slash-cut, and the precipitous drop in horsepower, throttle response and carburetor issues. The UFO now Star Rider Performance four into four package is a full exhaust system including header pipes and it will give you an increase in performance properly jetted. If you keep them clean and waxed you will preserve as much as possible the appearance and avoid severe pitting.

Since it's your bike you get to do whatever it is that you wish to and for some people the appearance is paramount more so than the performance that they may never choose to use. Since you've done the research on various posts on here you know that the stage 1 kit is not the jet kit to use; I suggest that going to something like a 150 or a 147.5 main jet may help reduce the hydrocarbon fumes that parminio was speaking of. As you mentioned keep us informed as you work through the installation and usage and report such things as throttle response, noise, perceived levels of power, and anything else that you believe is pertinent to furthering our documentation of the Cobra system on the bike. It would be interesting to see that your involvement with the cobras includes time on a dyno, but don't expect that you are going to break into the triple digits with the Cobra system.

Did you ever find the thread about the use of the the VMax to serve as a baseline for the Dynojet 250 dynamometer calibration? I believe that both Sean Morley and I have posted about that including links to articles about the Dynojet 250 dynamometer during its development. That makes for some interesting reading and understanding of how a dynamometer works.

Thank you for the tips on the main jet. I will keep the group apprised of my likely challenges as I embark on this quixotic quest to make the Cobras work and play well with the carburetors. I'll also check out the thread on the Dynojet, and may put the Max on the dyno if I can get it running halfway decent. And if I can't, then I'll join the legions of fallen warriors who tried the Cobras and were defeated by its inherent design flaws, and will report back as such.

 

[Parminio]

legions of fallen warriors who tried the Cobras and were defeated by its inherent design flaws,

Again, that is the problem: there is NO design. They are literally just straight, large pipes. Absolutely ZERO thought was put into making them tuned. That's how exhaust works: it is made to precise specifications based on the amount of flow the engine produces and how much back pressure is needed for it to run at maximum performance.

When you suddenly put huge, long pipes that are far too large for the engine in question (which is exactly what Cobras are) there is only one way on this planet you're ever going to make them work: Put them on a much, much larger engine.

The Cobras would be far better suited to a 2.5 liter inline 4 cylinder turbo engine than they are an engine half that size sans turbo.

 

[davfuzzell]

Good morning. I have quite a bit of experience with the Cobra slash cut slip ons on my various Gen 1s over the years. Please feel free to call me at 405-210-3311.
Fuzzy in Oklahoma City

 

[TheFleshRocket]

My first Vmax was a ‘98 that I overpaid for on EBay back in the early 2000s (pictures were fuzzy and the bike was in far worse condition than expected), and it had Cobras on it with the baffles punched out. I eventually low-sided it and replaced the scuffed Cobras with a set of Kerker slip ons. (The Cobras got Ebayed to a buyer in Russia.). I had a local shop rejet the Vmax while rebuilding the carbs. I don’t remember it being gas-stinky with the Cobras, and I don’t remember it making a noticeable difference in power when switching to the Kerkers. Not that I’m trying to give anyone false hope about Cobras not costing power or having any of the other drawbacks.

 

[iraqvet750]

My first Vmax was a ‘98 that I overpaid for on EBay back in the early 2000s (pictures were fuzzy and the bike was in far worse condition than expected), and it had Cobras on it with the baffles punched out. I eventually low-sided it and replaced the scuffed Cobras with a set of Kerker slip ons. (The Cobras got Ebayed to a buyer in Russia.). I had a local shop rejet the Vmax while rebuilding the carbs. I don’t remember it being gas-stinky with the Cobras, and I don’t remember it making a noticeable difference in power when switching to the Kerkers. Not that I’m trying to give anyone false hope about Cobras not costing power or having any of the other drawbacks.

Thanks for sharing your experience. Was the Kerker a 4 into 1?

 

[TheFleshRocket]

Thanks for sharing your experience. Was the Kerker a 4 into 1?

Actually, now that I think about it, it wasn't Kerkers, it was Jardine slip-ons. I remember finding them on Ebay and they were brand new but like half price so I contacted the seller to make sure the listing included both sides, which it did. I installed them in place of the Cobras with no other changes, and I remember them being a lot quieter (than unbaffled Cobras, at least), but not really feeling much different as far as engine performance went.

 

[Davelaf]

I can't help it if I like the sound the cobras put out. I just got a sonic cleaner and I figured if I have a couple sets of spark plugs I can put in and out when they get fouled and clean them. Can I run some seafoam or kerosene to clean the valves up? It seems faster too. Could be because front shocks need rebuilt and they move up and down a lot, or maybe because I didn't ride it for 4-5 months. But yes, FASTER!!!

 

[Davelaf]

Good morning. I have quite a bit of experience with the Cobra slash cut slip ons on my various Gen 1s over the years. Please feel free to call me at 405-210-3311.
Fuzzy in Oklahoma City

So are you for or against?? Any solution to the rich gas mix? I have a stage 7 in and they tuned it with the factory exhaust, which I like too. Maybe I should text you. Thanks. I've been to Ponca City.

 

[iraqvet750]

Actually, now that I think about it, it wasn't Kerkers, it was Jardine slip-ons. I remember finding them on Ebay and they were brand new but like half price so I contacted the seller to make sure the listing included both sides, which it did. I installed them in place of the Cobras with no other changes, and I remember them being a lot quieter (than unbaffled Cobras, at least), but not really feeling much different as far as engine performance went.

Thanks, and I'm glad to hear it's working out for you.

 

[iraqvet750]

You will live to regret that decision; not so much for the ridiculous loss of power and very poor gas mileage, but more for the "you will run so rich you will smell like you bathed in gasoline 5 minutes after you get on it" aspect.

What's more, if you ever are unfortunate enough to get stuck in stop and go traffic, you'll probably wind up puking because of it.

And there will be absolutely nothing on this earth you can do about it.



No. Reason: you can not tune untuned pipes. It's a waste of time, money and effort. It has been tried many times. It has always failed.

Parminio: I respect your broad range of experience, depth of knowledge, and overall VMax expertise. I am prepared to eat crow if this experiment fails miserably, and will keep a sense of humor about it. Here's a possible Gen X corollary (below); may turn out to be 100% relevant. In any event, I do value your input.

 

[Fire-medic]

The oldest Gen. X would have been 13 y.o. at the release of that album. The youngest Gen. X wouldn't yet have been conceived.



More power to you for undertaking something that no one on here has been able to do: get Cobra 4/4 slip-ons to make even the same power as an OEM exhaust. Watch the first 2:30 of a great movie with Robin Williams, Awakenings. See if you can find the analogy to what you're trying to do.





In the approval of new drugs or medical treatments, the drug or the treatment being considered for acceptance into medical use needs to undergo 'double-blind' experimentation. Some people get the drug or the treatment being considered, while others get something which doesn't have any known medical benefit for which the new drug or treatment is being considered. The one not-having any known practical use for that disease or affliction is the placebo. The 'double-blind' factor means that the people administering things do not know which is the active ingredient or treatment and which one is the placebo.

The placebo may in some instances, seem to have a beneficial effect on the patient, but its success is nowhere-near the level of success for the drug or the treatment which actually does have a beneficial effect. A drug or a treatment need only demonstrate that it is equal to other currently-used drugs or treatments, in its effectiveness, that it has less reactivity to other drugs, or fewer side-effects to be considered for acceptance as an approved drug or treatment by the Food and Drug Administration.

A trick that stereo shop salesmen would use is when demonstrating speakers, they would turn-up the volume on the one pair of speakers they would make more $ on, compared to another pair. The human ear tends to perceive louder sounds as 'better,' so gullible customers would buy the speakers set-to a slightly higher volume/SPL (sound pressure level).



Efficiency in sound reproduction (speakers) is a 'thing,' where for a delivered voltage of energy one speaker may produce a higher SPL than a less-efficient speaker. Different designs of audio speakers have different power consumption requirements. Loudspeaker Efficiency is the ratio of total acoustical output power to electrical input power, measured in watts, expressed as a percentage.

So why are we talking about loudspeakers and efficiency? Because when we're looking-at/listening-to exhausts, we tend to equate sound with power. Obviously, the power produced on a dynamometer or on a 1/8 or 1/4-mile dragstrip or a top speed reached in a measured half-mile or a mile is a better way to measure net horsepower. But for many people, there is a positive correlation between sound and horsepower: more sound, more horsepower. The Cobras may produce more sound/SPL, but they don't produce more horsepower than an OEM Gen. 1 VMax exhaust, with its sound resonator box and tuned megaphones. It seems like you're willing to try to challenge that, but I think you're going to end-up like Robin Williams, with a lot of Annelida, unable to prove your hypothesis.

"I'd rather eat Annelida than ride with Cobras"​

 

[one2dmax]

Plus side:
To me the Cobra's look cool and that's about it. Pretty bleak on the plus side of the Cobra's.

Downsides:
You have to take off the centerstand in order maintain some semblance of cornering clearance (or it holds the stand too far down so that it hits on the left side when cornering that direction).
Sound is way too uneven and weird. No "tuned" or V8 sound to me. That is in part due to the unique skip cylinder sequencing that our system does.
Of course the loss in hp (about 10%) which is about all I really care about lol. Otherwise why bother buying this bike. It doesn't handle great or stop great so why give up one of the other things it does well (for a cruiser).

Jetting can be swapped leaner (as it needs with even stock or other systems).

Did I see someone mention they have a stage seven with the stock mufflers (or any brand of slipon for that matter)? That's about as ******** as you can get lol. About the same as Joe Redneck putting on a 750 "double pumper" on his 350 sbc with **** heads and a performer intake. You're going to get much more intake then you can get out the exhaust.

The Star 4 tip setup isn't a 4-4. It still ties cylinders together to keep the scavening and just throws some extra tips on it to keep the look. Sort of like the tips pontiac put on the Transams and Fiero GT's.

As I said. I love the Cobra's for the hot rod look and that's about the extent of it.