coopjim

So it's a 2 cylinder ..... or more!

May I ask what brand spark plugs you guys are using?

May I ask what brand spark plugs you guys are using?

Thought I'd post an update. A lot has happened but not much result. We replaced the plugs and ignition wires, caps and rotors. Adjusted the valves and we sent the carb to Jabiru for inspection. They found the carb float level low and adjusted it as well as cleaning and inspecting the entire carb. We installed it and still had the same power drop at 2500 rpm. The engine is now in a crate headed to Jabiru USA for evaluation and repair. Fingers crossed it's not a big problem.

I'll let you all know when it comes back.

Check that your dashpot is installed correctly and is closing fully. Nev

There has been lots written and read about possible cause. We're convinced it's a lean mixture problem too. Run-up is fine. The problem comes with the increase to full throttle for T/O. We've increased carb jet sizes, checked carb float levels, tried running it with carb heat on, partial choke, looked for intake leaks, etc. The Folks at Jabiru USA thought it might be turbulent air in the intake side of the carb so they sent us a device to "stabilize" the air flow. Nothing has worked so far. The Iridium plugs are a new angle and we're happy to try it out. It ran fine last Fall but this problem developed with the colder temperatures. We're about to the point where there are no larger jets that's why the partial interest in the AeroJector TBI.

Thanks for the thoughts.

MarkI have a 3300 that had a similar thing happen after I had a service done. It was winter and luckily for us the temps rarely get below 10 Degrees C. The motor ran perfectly the day before with the same OAT. We had changed the spark plugs from the Irridium back to standard plugs and every morning after start up the motor used to give a cough when trying to advance the throttle quickly. This would continue for about 5 mins until the engine warmed up. After a week of this I changed the plugs back to Irridium ones and the problem dissappeared. Since then i have found that by monitoring each cylinder head temp and exhaust temp my fuel mixtures were on the lean side. I have richened both the needle jet and the main jet by one size. Motor now starts first time every time no matter what the outside temp and has never given any sign of hesitation. Just something to think about with the spark plugs. I would firstly try carby heat as others have suggested and then look at the carby jetting.

Wags

Thanks,

Jim

Anyone have experience with the Aerojector (AeroCarb http://www.aeroconversions.com/products/aerocarb/) as a replacement for Bing carby on Jabiru 3300?

I don't know that we'll do this but just in case the Bing continues to be difficult to figure out. Still waiting on the "stabilizer" coming from Lightning USA.

Off topic I know but should be of interest to jab owners, after experiencing difficult starting I installed a cold start kit in August last year in my 3300 Jab (pictured at left) and it has not failed to start on the first attempt since that time. Have not needed to drill the choke jet. Coopjim - I'd be upping those jet sizes to current Jab recommendations and checking float levels and fuel flow. Cheers.

Float level was fine. We've now turned our attention toward the air turbulence through the SCAT tube from the air box and are going to install a "stabilizer" at the entrance of the carb, for trial from Jabiru USA. At the same time, we are replacing the small pressure equalizer tube (altitude compensating pressure equalizer) from the air box to be sure it's not part of the problem. For now, we are leaving in the large jets recommended by Bing (265 main jet and 285 needle) to minimize the number of changes. Should have some results in a few days.

Will be discussing suggestions with USA Jabiru and Bing folks this week. Thanks for suggestions and the Service Bulletin.

Gregv,

I'm very interested in your lessons learned from this. I have a 2005 Esqual (Lightning) with the Jabiru 3300 in it and have very similar problems. We have been following Bing's suggestions and have been putting in larger and larger main jets. We're now up to a 265 main jet. It is running a little better but still has a loss of power when takeoff power is applied and higher than expected EGTs. We are going to put in a new metering needle from Jabiru USA since the Bing rep says they need replacing every 200-300 hours.

Any thoughts?