Cobra 6 into 6; help!

[deepbluediver]

Can anyone tell me the definitive answer on whether carb re-jetting is required if I swap my stock pipes out for a set of Cobra 6 into 6? I've heard so many different opinions, I don't know what to believe. I understand these pipes result in a different backpressure situation, which will result in a loss of horsepower. But will it cause any damage to the engine in addition?  How much HP can I expect to lose? The local Honda dealership wants to charge me 6 hours labor to re-jet the carbs at $100 an hour, and this seems like a lot of dough. Is this reasonable? The problem is I've already bought the pipes, and don't want to install them if I'm going to see a marked reduction in power (or possible engine damage). Any assisitance from a voice of knowledge would be greatly appreciated! If anyone has swapped to Cobra's without re-jetting, please let me know your experience to date with these pipes. Thanks very much in advance.......

[FLAVALK]

Some do and some don't. It is not required in that you will have problems if you don't. I once had a valk with Cobra 6x6 and rode it many miles with no change to carbs and no problem. Some say you loose performance, but I could get off my Valk with the 6x6's and get on my second Valk that was totally stock and could tell no difference in performance. The Valk with the Cobra's just sounded better, IMHO.

[Hellcat]

http://www.valkyrieriders.com/shoptalk/jetting.htm

Some info in this link about doing it yourself, and whether it's necessary. Also says you lose 6 HP with the 6x6s and might get it back with rejetting.

[Foozle]

If memory serves, the Cobra "jet" kit that accompanies these pipes is a needles-only kit.  I ran the Cobras with these adjustable needles without ever touching the factory jets - and had nice tan plugs the entire time.  I would certainly try this first before digging into the carbs.  Just my .02.  Terry

[cutter]

Have 6x6 Cobras on my I/S and no rejetting done. Installed around 25000 mi now have over 164000 mi and not one problem with them or the motor. Have never touched the carbs for anything either.  

[Old Geezer Richard]

Hey DeepBueDiver , I 've had my cobra pipes on my 98 Fat Lady since I bought the bike and she purrrs and I have not monkeyed with the carbs at all ..... all I have done to my Fat Lady is the 6 degree wheel , K&N filter , I/S springs and sea foam and she is getting 40 mpg as long as I stay at 3000 rpm's constant ..... my question is this , how are going to notice a 6 hp drop anyway , I don't ....... put them on there and enjoy the sound and the looks you'll get from all the wanta-be's ..... ride safe

[Redline +]

I'm new to the Valk, but I will give you my opinion as an old hot rodder. Installing the Cobra pipes will flow more air, more air needs more fuel. The reports of less power I'm guessing is from running too lean. I have the Cobra pipes on my 2002 Standard. They were installed and the bike rejetted by Honda at the expense of the original owner.

When I purchased the bike, about 10 weeks ago, I put it on my buddies dyno to check air/fuel ratio and verify that the jetting is correct. We made two runs with the baffles in, then as an old hot rodder, the next two runs were with the baffles out. You should have seen all those Harley guys running out of the building hands over thier ears. A fat lady, open pipes, full throttle, 6000 rpm under load in high gear, inside a steel building is quite an experience. Air fuel ratio was right on, gained 5 hp and 5 ft lbs of torque without the baffles.

I have very little blueing on the pipes, I have seen some that are very blue, jetting perhaps. My .02, install the Cobras and tune as required for proper air/fuel ratio. Mine sounds sweet and goes like a bat out of hell, but I guess all Valks do!

[Airetime]

Can anyone tell me the definitive answer on whether carb re-jetting is required if I swap my stock pipes out for a set of Cobra 6 into 6? I've heard so many different opinions, I don't know what to believe. I understand these pipes result in a different backpressure situation, which will result in a loss of horsepower. But will it cause any damage to the engine in addition?  How much HP can I expect to lose? The local Honda dealership wants to charge me 6 hours labor to re-jet the carbs at $100 an hour, and this seems like a lot of dough. Is this reasonable? The problem is I've already bought the pipes, and don't want to install them if I'm going to see a marked reduction in power (or possible engine damage). Any assisitance from a voice of knowledge would be greatly appreciated! If anyone has swapped to Cobra's without re-jetting, please let me know your experience to date with these pipes. Thanks very much in advance.......

The reports of reduced power are because of the unequal length pipes which result in unequal back-pressure. The pipes will blue. The Cobra pipes are simply not "tuned" pipes and therefore will reduce overall HP. As such, some of the plugs will appear to be burning properly and some not. HP loss? Depends, but most who have posted here and have had them on the dynos report 5 – 10 HP loss. Remember that to compare dyno results, each bike would have to be run at the same altitude, same air density and within the same short period and on the same dyno. Some lean, some not. If you want to experiment by using various baffle sizes to fine tune each pipe, that might result in having tuned pipes. Then you can see exactly how all the plugs are burning and adjust or replace (or not) the needles.