Hi, and Greetings from Finland!
I have a problem with Thundermax with bigbore kit and I'm hoping that you could help me out.
Just finished Fuel Moto 107 build (10.5 comp) with Wood 777 cams, SE throttle body and level B headwork on my 2007 Road King. I already had Thundermax with Autotune and I used basemap from FuelMoto. Engine started up fine but after running a while I got code that said "rear cylinder running lean". I Used Thundermax monitor mode and the rear cylinder was showing AFR values between 15 and 19. I suspected intake leak and tried to locate it with WD40 and propane, but couldn't find any. I also checked cracks from the exhaust pipe, couldn't find any and re-torqued exhaust flanges => still running lean.

I remembered reading somewhere that Thundermax doesn't like Platinum spark plugs and changed them => still running lean. I still have the performance spark plug wires from Fuel Moto.

Then I removed the rear O2 sensor, cleaned it, put it into the front cylinder, (and front sensor to back) => rear cylinder still running lean.
I'm not that familiar with Thundermax and running out of ideas, so I was wondering if someone else has experienced similar problems. Any help is appreciated!

Br Sami

 

If you switched around the O2 sensors from front to back and the rear cylinder is still running lean, I think it's safe to say your sensors are good and the Thunder Max is getting and accurate reading. What about a problem with the rear fuel injector. Just a thought. Trying pulling off the electrical connector to it and apply some dielectric grease.

 

Thanks for the suggestion. Throttle body and injectors were new from the box, and connectors looked good. Also checked that injector wires were in a correct injectors.

Br Sami

 

Try removing the ECM connector from the Thunder Max and use a light coating of dielectric grease on the connections and reinstall it. I think they advise doing this in the install directions to help avoid some drivability issues. It can't hurt, I did it to both Thunder Maxes on our bikes. I would think if you had an intake leak it would idle eratically.

 

I will check the connectors and put some grease to them tomorrow. There's some fluxuation on idle, but not much, I was thinking there could be some because of cams. like said, I have sprayed all kind of chemicals on top of throttle body and couldn't get any change on idle speed.

Br Sami

 

Pull the tank and swap the injectors. That will tell you right away what the injectors are doing.

 

What are you using for an exhaust system?

 

I have 07-stock head pipe with actuator motor (Europe model) removed. V&H turndown slip-ons with modified baffles. Baffle diameter is little over 2".

If my timing is off by one tooth, that would also cause symptoms like this, right? I'm 99% sure that the timing is correct but I guess I have to pull the cam cover and check it today to be 100% sure.

Br Sami

 

the rear typically runs "leaner" due to less airflow- hotter.

in response we might richen the mixture slightly ( although this can screw up what he front is doing if you don;t have independent control) or retard the ignition timing by about 3 degrees to the rear cylinder only ( if you can)

I would suggest adjusting the spark timing before opening the cam chest.

as for dielectric grease...it can be a double edged sword- it can seal moisture out...or it can trap moisture in...and corrode causing resistance in the circuit

our electronics run less than 5 volts DC and often milliamps, even slight resistance in a connection can cause problems.


another thing to check is that you have proper fuel pressure and volume


one of these days I want to get one of those acuators and try to use it for a 2/1 at low rpms and 2/1/2 at higher speed...transition about 3200 rpms

mike

 

I'm not that familiar with Thundermax but I thought that with Autotune it adjusts both cylinders separately? And even if spark timing is off, the AFR's should be ok?

Bike has 16k miles and the fuel filter has never been changed. How can I check fuel pressure/ volume? Can I see those values from Thundermax?

Mike, you can get my actuator, you just have to come and get it from Finland

Br Sami