Cobra Exhaust HP Loss Explained, Please?

[Fire-medic]

Supertrapp is usually a slip-on replacement for the stock resonator can & megaphone unit. No increase in performance, just a lighter weight package. You need a full header/canister set, properly-designed, to increase performance, and part of that is a mandatory re-jet, and other mods to the carbs, such-as different length springs, & drilling bigger holes into the carb slide bottoms. Just installing the full system will make your bike worse than stock, you have to make the intake complement the exhaust.

The Marvings, if you just got slip-ons, are the same story, no increase in performance.

 

[Bongo]

Ok I've heard enough bashing on the Cobra exhaust system. I bought a 1995 orande Vmax last year with 13,000 and some change on it from the original owner. It rates a 8 out of 10 on the scale. It came off the floor with the Cobras on it he doesnt know if the they jetted it it or what. He liked it bought it rode it home. 22 years later i buy the bike from him. He buys a 2017 gen 2 max. Ok my best freind has a 1985 killer red max kept in immaculant condition. He put super traps on it and had it dyno tuned. He got a 123 hp out of it I've seen the paper work. Its freaking fast!!
We have road together for 3,000 plus miles now. Yes he can beat me not like you guys exaggerate. From a rolling start to 100-120 hes no more than 2-3 bike lenght a head of me and sometimes i stay with him pretty good. Just depends on who gets the best jump on each other. So enough of the over the top BS on Cobras. Lol.

 

[El Canadiense]

Supertrapp is usually a slip-on replacement for the stock resonator can & megaphone unit. No increase in performance, just a lighter weight package. You need a full header/canister set, properly-designed, to increase performance, and part of that is a mandatory re-jet, and other mods to the carbs, such-as different length springs, & drilling bigger holes into the carb slide bottoms. Just installing the full system will make your bike worse than stock, you have to make the intake complement the exhaust.

The Marvings, if you just got slip-ons, are the same story, no increase in performance.

Thanks for the info. Have an FJ1200 with the full SperTrapps ... haven't driven it yet.

 

[one2dmax]

The Supertrapps are pretty easy to ID most of the time. They slip on in place of the stock mufflers and keep the stock pipe work. You can get better results from changing the jets one or two sizes smaller. You will have similar power to stock with less weight.

 

[lipripper]

I’ve got Kerker slipons. Seems pretty close to the factory ride, sounds better. What kind of jetting would I be looking for? I ride in Tn; 400-1000’ elevation

Thanks for any help
I’m a newb , had the bike (99 model) for 3 years now, and am finally getting around to fine tuning it. I’ve got the factory exhaust(minus headers) if anyone is interested in helping me out/ swapping jetting advice for these factory exhaust (they’re gathering dust in my barn) . Lemme know

Lipripper
[email protected]

 

[Fire-medic]

Sean mentioned it, going one or two main jet sizes smaller from the stock 152.5 should crisp it up a bit.

 

[G max]

I’ve got Kerker slipons. Seems pretty close to the factory ride, sounds better. What kind of jetting would I be looking for? I ride in Tn; 400-1000’ elevation

Thanks for any help
I’m a newb , had the bike (99 model) for 3 years now, and am finally getting around to fine tuning it. I’ve got the factory exhaust(minus headers) if anyone is interested in helping me out/ swapping jetting advice for these factory exhaust (they’re gathering dust in my barn) . Lemme know

Lipripper
[email protected]

I've got 147.5 mains in my vmax1200 all the other jets are factory and the max runs like a raped ape.

 

[G max]

I've got 147.5 mains in my vmax1200 all the other jets are factory and the max runs like a raped ape.

I'm also looking for a muffler for my vmax were are you living? I'm in Florida.

 

[lipripper]

I'm also looking for a muffler for my vmax were are you living? I'm in Florida.

I’m in Nashville Tn, if you’re asking me? I’ve got Kerker Series K slip ons, and shimming the air box helped it out tremendously. I reckon I’m gunna leave that as is and work on the suspension now.
Off to another thread
Thanks all

 

[G max]

I'm interested in your exhaust if you still have them.

 

[lipripper]

I'm interested in your exhaust if you still have them.

GMax- hit me up on my email and we work something out.
[email protected]

 

[lilredrooster]

Ok I've heard enough bashing on the Cobra exhaust system. I bought a 1995 orande Vmax last year with 13,000 and some change on it from the original owner. It rates a 8 out of 10 on the scale. It came off the floor with the Cobras on it he doesnt know if the they jetted it it or what. He liked it bought it rode it home. 22 years later i buy the bike from him. He buys a 2017 gen 2 max. Ok my best freind has a 1985 killer red max kept in immaculant condition. He put super traps on it and had it dyno tuned. He got a 123 hp out of it I've seen the paper work. Its freaking fast!!
We have road together for 3,000 plus miles now. Yes he can beat me not like you guys exaggerate. From a rolling start to 100-120 hes no more than 2-3 bike lenght a head of me and sometimes i stay with him pretty good. Just depends on who gets the best jump on each other. So enough of the over the top BS on Cobras. Lol.

Fantastic Post Bongo..... Good to see some accurate, honest, unbiased, sensible, current, real world, comments coming from a Cobra exhaust owner sharing their actual personal experiences.....

Many Thanks for sharing....

 

[lilredrooster]

For anyone seriously interested in the Cobras, owners, buyers, enthusiasts, etc....

Have a look at the below thread for some further alternative views and comments.....

https://www.vmaxforum.net/threads/cobra-exhaust-tuning-recommendation.46778/page-6#post-477609

 

[lilredrooster]

I know of two guys from way back that were both VMax Racers, VMax Tuners, VMax Builders, VMax Fabricators/Mechanics, both had VMax Speed Shops and both had their sole, individual, dedicated Dynos.

One owned and tuned his personal bike over many years and recorded the data & history from his Dyno, as follows: Stock motor, stock carbs & exhausts, set up: Max = 108 RWHP. Added Kerker 4/1 Full Exhaust, Jet Kit inc KN Filters, set up: Max = 121.4 RWHP. (Plus 13.4HP). Added 4 x Flat Slide Carbs, set up: Max = 128.5 RWHP (Plus 7.1 RWHP).

The other quoted the very best stone stock Vmax bikes he had ever seen on his dyno was 104-108 RWHP (Avg 106RWHP). He also owned an immaculate stone stock VMax that pulled 99 RWHP, same Dyno.

The above suggests that both guys Dynos were similar in their BHP measurements, it also suggests that around 107/108 RWHP is right up there for an all stock VMax and that 99 RWHP is good/average.....

Typical/Realistic Gen1 VMax Qtr Mile Times/Speed is 11.5 Secs at 116 MPH. (Terminal Speed = Power).

A common Internet performance calculator converts the above Terminal Speed at 102.5 RWHP, this also seems to broadly correspond in line with the Dyno numbers from the two separate Speed shops above.

My VMax (Original Stock Motor) is now around 22 years old, I am very pleased with my Cobras and have no plans to change them, my experience so far tells me with my personal bike it is between 2 BHP and 7.5 BHP (5 BHP AVG Loss) below a very good/top notch performing all stock VMax.

The data I am using with my VMax is based on less than a handful of runs at night at the Dragstrip, in very average conditions with some clutch slip. I am very confident of closing that gap now that upgraded clutch springs have been installed.

To be continued……

 

[one2dmax]

How about I send you a header and you try it at the strip and get your real world experience for yourself. I have tried it personally on multiple bikes and will stand behind my comment that the Cobra's are the worst performing exhaust you can install on your bike. That doesn't mean it's the worst cosmetically looking set (I think the standard Marks are ranked close to the least cosmetically attractive to me).

 

[lilredrooster]

Many Thanks Sean, very kind of you to offer but No Thanks on the exhaust....
It would be very expensive to ship to Australia and I am so close to matching the stock exhaust performance now, that it really does not matter one little bit to me if I find the final couple of HP or not....
My VMax version is just about where I want it now including the Cobras, it ticks all my Muscle/Cruiser boxes including budget and has more than enough performance to meet my needs as it is....
Ride Safe..... Enjoy the Ride......

 

[lilredrooster]

 

[user 16790]

for what it's worth, my bike has laser pro-stock silencers that make a nice sound but no idea of hp figure and not bothered as I can hardly use full throttle anyway due to a knackered wrist (can't turn it enough), bike is plenty fast enough as it is and not bothered by pub talk numbers, nice bike, enjoy

 

[lilredrooster]

Many Thanks Julian, glad you enjoyed my VMax version, hardly any two Dynos are the same and very expensive to hire also just to get a "number", had much more fun testing it out at the Dragstrip for one night, I know now it is very close to stock performance even with the clutch slipping slightly at the top end, funny thing is, riding on the street I didn`t know I had a problem with the clutch at the top end, anyhow clutch is upgraded now so hopefully will make a little difference down the track......
Ride Safe...... Enjoy your Ride......

 

[lilredrooster]