alltimeqb,i also have an 07 with cobra pipes and i can cruise in 5th gear at 50 no problem..i do know after tweaking the pms that even a slight adjustment leaner makes my exhaust sound change and it wont cruise like it does at low rpm's..the carb adjustment on my bike is really touchy..i rejetted with the cobra kit when i put the pipes on it..i spent many hours getting my carb adjusted..and it was worth it.. Mike

Thanks for the input Mike. I've got an '08 which means FI.

I just pulled all plugs and here's the result.

This thing is running too rich... how the heck do you lean-out a FI bike????

Oops, file size too big.

Here are the plugs:

With the O2 sensors unhooked the computer reverts to what is called failure mode or limp home mode or whatever you want to call it. I don't know how the engineers designed the fuel map but I would guess that in that mode it's a little on the rich side to prevent overheating.

Whatever the case it's probably not going to run like it should until you reinstall the O2 sensors. They're the only feedback the computer has for determining fuel mixture.

Scott B.

texasscott1 wrote:
With the O2 sensors unhooked the computer reverts to what is called failure mode or limp home mode or whatever you want to call it. I don't know how the engineers designed the fuel map but I would guess that in that mode it's a little on the rich side to prevent overheating.

Whatever the case it's probably not going to run like it should until you reinstall the O2 sensors. They're the only feedback the computer has for determining fuel mixture.

Scott B.

Exactly on the money,the 02 sensors give critical feedback to ECU to set injector pulse rate that in ecense controls the fuel mixutre and without that cirtiacal data from the 02 sensors as already stated the ECU/EFI system stays in limp mode that's generally a bit rich to prevent over lean cond/over heating/etc.

Whoever removed the 02 sensors from your bike when they installed the aftermarket pipes didnt know what they were doing when it came to EFI.

Your plugs are likely fuel fouled but replacing them will only get it running better for a short while untill they get fuel fouled again from over rich fuel cond.

If the TPS/throttle position sensor was also removed it will make matters even worse so chk that out too.

But also keep in mind that even when you reinstall the 02 sensors etc doing that doesnt garentee the stock fuel curve map in stock EFI ECU will be rich enough to handle the mild aftermarket pipes/perf mods you made to your bike.

You still may need to move up to an afermarket ECU/IGN box or use some sort of prgm with stand alone pc/laptop to remap your stock ECU/EFI system for a richer fuel curve that the stock fuel injectors will hopefully handle as far as having the ability to provide the required fuel enrichemnt your motor needs.

Good luck

Scott

You may be right Texas, although oneperfectrun says that his are hooked up and he still has the sputtering issue.

I have one of the O2 sensors, guess I could buy another and tie 'em back into the Cobras.

Other than that not sure what to do...

BTW here's a picture of my plugs just before I replaced 'em with Iridiums:

alltimeqb wrote:
You may be right Texas, although oneperfectrun says that his are hooked up and he still has the sputtering issue.

I have one of the O2 sensors, guess I could buy another and tie 'em back into the Cobras.

Other than that not sure what to do...

Hooking up the O2 sensors is going to help a lot. Also, disabling the AIS could effect how the FI bike performs. The AIS reignites unburned fuel in the exhaust and the engineers who designed everything have taken this into consideration and instead of controlling it by vacuum have incorporated management of the AIS in the computer.

When the computer is signaling for the AIS to allow air to flow to the exhaust and it doesn't the performance of the engine could be affected. Something to think about. The AIS is a good thing - it reduces emissions without any effect on power or performance.

If you ever get a chance to watch a display of the O2 sensor working it's something to see. A normal sensor works in a range up to 1.0 volt. As it's working you see a constant switching above and below 0.5 volt. The computer looks at the last combustion result, changes the pulse width of the injector slightly to compensate looks at the next one, etc. etc. all very fast.

Scott B.

The latest: I had only one of the O2 sensors from the PO but hooked it up and voila!

Bike is running 95% compared to before situation. I get a slight sputter but very infrequently. In fact it seems as though it's completely gone.

I'll let you all know how the second O2 sensor works once I get one.

Thanks.

Spoke too early...

Sputtering is back... I'm going to Yamaha now.

alltimeqb wrote:
Spoke too early...
Sputtering is back... I'm going to Yamaha now.

Yamaha will probably want to see if it runs okay with the stock pipes and air cleaner. The type of fuel injection system the Road Star has is geared to a certain volumetric efficiency. Change that enough and the programming may not be able to handle the increased airflow especially with one O2 sensor missing.

The same was true with early cars that used the speed density system. Changing exhaust flow for instance would make them run badly. Those systems could be fooled by adding larger capacity injectors that with the same pulse width delivered a little more fuel.

Scott B.