Problems with my new OFNA Ravager

[bacchus]

I just received my new Ravager. This is my first Nitro RC. I am experiencing a lot of problems and I am not able to complete the break-in.

I followed the OFNA instructions for break-in of the Force 28 engine. I have installed the glow plug provided with the Ravager. I called OFNA and the technician told me to use this plug for break-in because it's a "hot" plug. He also told me to use a medium plug after completing the break-in.

- I confirmed that the needles are all setup correctly for break-in. High speed is 3 1/2 turn out and low speed is flush with the sleeve.
- I check the servo trim and it's in a neutral position.
- The batteries in both the emitter and receiver are fully charged.

First tank: run engine rich and let it run at low RPM for the first tank. I was able to start the engine very easily. Everything goes well. After almost 10 minutes, the RPM start to increase rapidly and the buggy is now moving forward. The temp is also raising rapidly. I did stop the engine. When the engine was cool, I restarted it. After 2-3 minutes it does the same thing. When the temp was close to 230 is stopped the engine again. I finally completed the first tank by changing the settings of the idle screw to slow down the engine.

Second tank: It's now time to build a little bit of heat in the engine, but not too much. This time the engine is very hard to start first. When I was able to start the engine it was running pretty well at idle. After 2-3 minutes the RPM start to increase and the temp as well. The RPM varies a lot. It looks like someone is pulling the throttle every second, but I confirmed that the throttle is not moving. I must use the brakes to stop the buggy from going forward. Even when I apply the brakes the engine RPM continues to increase. I tried to slow down the engine with the idle screw but it automatically dies if i do that. I must stop the engine because the temp is reaching 250 (confirmed with the water drop test). During all this time I checked the throttle and it's still in the neutral position. I let it cool and tried again. Same result. I also confirmed that I am running in a rich setting.

At this point I do not know what to do next. Is there anything I do wrong ? I am totally lost.

If someone can help me to fix the problem it would be very appreciated.

Thanks

 

[jetmechG550]

Sounds like it could be an air leak, make sure you carb is secure, you can also pull it off and apply a little high temp RTV to the base. Are these pull starts? regardless you can easily remove the backplate and apply a little high temp RTV to it as well. Not knowing your experience level I'm going to throw it out there that very small increments go a long way. Also slightly richening your LSN may help depending on the conditions of the day (cold, hot, humid, etc). When making adjustments think of the needle as the hand on a clock and only move it in one hour increments and only do one needle at a time. For grins, let the engine warm up (200 or so) blip the throttle to clear it out and then pinch off the fuel line and start to count. you should get to roughly 4-5 seconds and a slight rise in rpm before it dies. If it dies before that, the LSN is too lean, if it runs longer, the LSN is too rich, if it won't die, it's an air leak.

 

[bacchus]

Thanks, this is very useful information. Yes, this is a pull start engine. I ran the test as described. It takes about 4-5 seconds for the engine to die and the RPM is raising just before.

I found why the engine is so difficult to start. It seems like the carb does not "pump" the gaz from the tank. I had to put my finger on the pipe exit, without heating the glow plug, and cranking for about 50-60 times to prime the carb. There was also a noise coming from the carb when I was doing that. Could it be an air leak as you described ?

Anyway, looks like the air coming from the tubing is why whatever I do with the needle screws, it's still running lean. It's probably also explaining the RPM variation.

Do you think that sealing the carb will resolve the problem and is it safe to use Permatex Ultra Copper RTV to seal the carb and backplane.

Thanks again for your help.