Chris07

I just purchased a Nitro MT RTR and I have a few questions. If you have any insight it would be great appreciated.

What should the normal operating temperature of the 15fe be? I was seeing around 300 degrees when doing some mild-heavy running. Is that to high? Under full throttle I am seeing a nice steam of blue smoke so I don’t think I am running lean…

I also think I am having a slight idle problem. Once the engine gets warm the idle is a little erratic, idle rpms change from lower to higher, but it doesn’t stall. The truck doesn’t move, but the idle rpms constantly change. It idles smooth when engine is cold. I have tried raising idle rpms but it still is not very smooth. It runs smooth under a load during normal running. Is this just a trait of a single adjustment carb??

Thanks!

kyokai2

Yes, 300 is a little too hot, I am not familiar with the engine your refering to but can give you some insight to your problem. First of all, pinch your fuel line close to the carb and see how long it takes for the engine to start revving up, it should take 2 to 3 seconds before revving. If it revs sooner than that your low end needle setting is to lean so try richening it up. Also, you may have a slight air leak somewhere around the carb, backplate or fuel line causing the lean condition so get some airseal from your LHS and seal it up good. Your engine should run between 220-260 running full out, or cooler just putting around.

dagass

I seem to recall reading that anything between 230 and 280 degrees is normal for the 15FE. 300 definitely sounds a little on the high side to me.

As for the erratic idle, it sounds like you may have an air leak somewhere. Check your fuel tubing for any small cracks and make sure that the lid on your gas tank is seated properly. Also check your lines when the motor is running. If you see air bubbles in the feed line to the carb, that could also cause some problems. You may want to remove the tank and put o-rings under the tank where it attaches to the upper deck. This helps to keep the fuel from foaming from all the vibration.

Lastly, check to make sure that there are no air leaks around the base of the carb. I've had issues with my 15FE similar to yours. The seal at the base of my carb had a small tear in it. I replaced the seal and the problem was solved. Good luck!

Chris07

Thanks for the advice. As for a low rpm setting, I only have one adjustment. I'll richen it up to see if I can get the temps down a little. I can't see having a bad seal on this thing already. I am only on my 5-6 tank of fuel, but I guess i could. I don't know much about this, but you would think if I had a bad seal or something along those lines it would run poorly. The motor runs great and it stays running and never have any problems with it stalling. Wouldn't a seal cause poor running?

I am going to a nitro tuning class this tuesday, so maybe they could give me a little insight.

Chris07

Also keep in mind it idles fine when the motor is fairly cool. It could be that I am just running to warm. They have told me if I see a blue stream of smoke I am not running to lean. I'll richen it up and see where that gets me. If I had a bad seal, now that I think about it, it would do it more so when its cold because. Metal expanes when hot, so that means there would be less of a leak when the motor is warm. This sound right to you guys?

dagass

As you know, the 15FE has a single needle, so the low speed needle theory isn't an issue. As far as the seal around the base of the carb, you might just want to make sure that both screws that hold the carb in place are tightened.

As for fluctuating rpm's, thats generally caused by an air leak somewhere.