GEBE/Tanaka Engine Owners (any 2 stroke) Read This

Discussion in 'Rack Mounted Engines' started by AndyT, Aug 13, 2009.

  1. AndyT

    AndyT Member

    I have had my GEBE Tanaka 32 setup for a few months now. I only have about 175 miles on it. At about 120 miles I started to notice the engine was a little down on power, and seemed a bit sluggish. I had made up a new batch of pre-mix and had run about 2 tanks through, so I thought it was just some bad gas. I pulled the plug and the insulator was barely tan, almost white actually. I got some new gas and used Lucas 2 stroke semi-synthetic oil for the first time. I took a quick run and the plug looked a little better. I took a couple of short trips and the engine felt even worse. I was thinking it may have been running too hot, and had sustained some damage.

    I recently bought a new R/S EH035 someone had for a backup (never run, with the manual for $100!), so I pulled the Tanaka, threw on the Robin and took a nice long ride to compare the engines. The Robin was walking all over the Tanaka.

    I called GEBE and spoke to Julia and Dennis, thinking the engine had developed a problem and would need to be worked on. Julia mentioned that it could be a fuel delivery problem (she was so close!). Dennis wanted me to try running it again, and to let him know if it improved or got worse. He said he I could send him the engine and he would check it out if need be.

    Since I would be sending the engine to Dennis if required, and not taking it to a repair center, I decided to investigate the problem. I pulled the exhaust and inspected the piston. From what I could see of the cylinder and it all looked OK. No signs of a partial seizure or other damage. I pulled off the carb and checked the bolts on the insulator/intake manifold and one screw was just more than finger tight! I could see signs of oil getting on the oversize gasket. I torqued the manifold down to Tanaka spec of almost 5nm (Newton Meters). I put it all back together and mounted it back on the bike.

    I took a quick run around the block at 9:00pm (with lights) and it was running perfectly, probably even better than when I first ran it. It might be just a bit noisier, as I am hearing some "piston slap" or mechanical noise when I let off the gas, but it's not real bad and that could be normal. At this point I'm just happy to have it running like it should again. A 20 mile trip showed that a good running Tanaka 32 running a 13t gear will pretty much mop the floor with the Robin running a 12t gear. On hills they feel about the same, but as soon as it levels out the Tanaka just runs away. The Robin is still a great engine though, with lots of torque, and I'm glad to have it.

    Edit: IF YOUR ENGINE IS RUNNING FINE AND YOU ARE NOT COMFORTABLE DOING REPAIRS, DON'T TOUCH IT! (added at GEBE's request since this is not a common problem)

    If you are comfortable doing repairs, and if you notice this problem (lean condition and bogging), it might be your intake manifold bolts, or even a loose carb. Tanaka didn't put Lock-Tite on the threads, or at least they didn't on mine, so putting a drop on the threads and torquing the bolts to 4.8nm (what Tanaka recommends for the 40 with the same size bolts) will buy you some cheap insurance. Zenaoh/Red MAX engines are very similar and they recommend using thread locker on these bolts. Air leaks can cause the engine to run hot and bog out when you apply the throttle, or even a seizure, resulting in a bigger problems. Any problem can ruin a nice trip and send you pedaling off into the sunset.
    Last edited: Aug 13, 2009

  2. Happy Valley

    Happy Valley Active Member

    An air leak then leading to a lean condition. Nice piece of diagnostic mechanics.
    Thanks, good to keep in mind.