RCDad1977

Happy holidays, friends! I appreciate the support in advance!!!

I received my present early this year from my wonderful wife. Very beautiful Dunerunner. Started as easily as any 2 stroke I've ever started. Smokes well and sounds great. However, after a few minutes of running, smoke starts decreasing, engine starts revving higher and then it dies. I can give it throttle (break in level only) after it is started and it accelerates fairly well even with higher oil ratio, but as it gets closer to dying, any throttle kills it immediately. Then it won't restart for about 30 minutes to an hour and pull chord is stiff. After an hour, it restarts like a dream and a few minutes later turns into a nightmare again.

I am trying to work this out logically. I don't see why it won't restart right away. Is it because the piston has expanded due to heat (read on one site)? It seems like a fuel delivery problem, but I don't know where to start. High and Low needles make no difference in the eventual outcome of dying and not restarting. Spark plug comes out dry when it dies. It does not seem like it is flooded, although I first thought that because of the delay in restarting and heavy pull chord, but clearly it is getting lean when it dies. Choke does not help seemingly either. How can it be getting fuel when I start it, but seemingly stop getting fuel after it is running? Maybe I'm pulling in gas with the pull chord, but without my doing that after it is running, it somehow starves?

Any and every thought and suggestion is greatly appreciated. I don't want to kill this engine before I even get to play with it!!! By the way, painting is coming along. I'll post more pics with future entries.

zackS30

Do those have fuel pumps?
Maybe ur battery pack doesn't have a good charge? Especially if it has a fuel pump then its not getting enough energy to pump the fuel? Just I thought.
U said u have a higher oil ratio, maybe the higher amount of oil is messing with the actual fuel that's getting to it??

I'm not that familiar with those engines sorry, just stating some things I would suspect first.

RCDad1977

Thank you. I did check battery. It's at full voltage. There is just a carb and a fuel filter. Remarkably I may have have found the problem. A young guy at my local hobby store suggested that because it would become so hard to start and very hard to pull the pull start, that perhaps there was a compassion problem. Too much compression, which I had never hear of. Didn't make sense to me but I did what he suggested and unscrewed the spark plug a few turns to increase the piston space. Tried it out. Started up great. Pull cord was no longer tight. Then I waited for it to die again ... never happened. It ran for a full tank
So far, so good. So I'm going to put some washers on the spark plug to create the same space. I can't be sure its solved, but it went from not starting and rock hard pull start with 3 minute run times before dying ... to easy start easy pull and ran the whole tank out. Why is a bit of a mystery. Could it be that when the motor warmed up the compression became too high and put back pressure on the fuel delivery so the carb leaned out despite wide open needles? That's the only thing that makes sense, and the hobby kid said he's seen it in nitro cars before. I've never heard of it but I hope this is really it. No one from Redcat suggested it at customer service or the 3 dealers I called.

zackS30

Wow that is weird.
I know that with heat metals swel.
I wouldn't think there would be back pressure since once the piston is in compression stage the valves are all closed.
With my nitro tornado the glow plug came with a washer I had assumed it was for keeping the plug from being struck by the cylinder. But adding a washer would keep it back and also crest a bigger gap while changing the compression but I wouldn't think that only a 1mm gap if that would change the compression ratio that much?? Also with adding the washer u run the risk of creating a leak from the spark plug since its not ssitting flush in the housing making a seal, I could be wrong I suppose. I just know that when ever my lawn mower wouldn't start I took it to my dad and had him fix it lol.

RCDad1977

Ya, Zack I agree with everything you're saying. I wouldn't have expected this to work, but as you said, backing the spark plug out does create more space. And as I thought about it, these engines have very little cylinders. In a car, it seems infinitesimal the difference a mm could make, but in these tiny two strokes, it might be significant. What I can tell you is this ... I ran it for 4 hours yesterday without even dying once after a week of frustration and 3-5 minute runs. As far as the metal swelling, that's what I thought the problem was initially, as well. But it really seems that the problem was too much compression. The second the motor warmed up, the compression would be obviously higher with heat as the gas expands, and then it would rapidly start leaning out until within a couple minutes there would be no more smoke and a dead engine that was too hard to turn over. Again, I'm not positive what the physics are exactly (as you said, shouldn't there be valves affecting back pressure?), but that is definitely what I experienced. It felt like the most abnormal engine I have ever encountered. Now it feels like an engine again. Still breaking it in. Not in great tune, likely. Oil ratio still high, but it runs pretty well that being said. I know there are guys and gals out there with broken 1/5th scale hearts because of running issues - lol. I hope this thread finds its way into someone's hands who can be helped, but perhaps I'm the rare case. Somehow, I don't think so, since there are a number of people having issues with Redcat 1/5th scale it seems. I'll try posting on other active threads if it seems like someone is having a similar issue. And we'll still have to see how my car runs after break in and some tuning. I'm not expecting blazing performance from the stock motor. It's kind of a show car for the kids (I have my 80+ mph brushless Arrma typhon stock motor 6s with upgraded 22t pinion) and anything this big moving around at decent speed is super thrilling. Driving it in laps even is almost zen with the deep motor sound and nice suspension roll. Definitely wanted to recommend the dunerunner but this motor thing definitely has to continue to be fixed. Thank you for your responses, Zack. What are you working on these days? Have a wonderful Christmas!

zackS30

Well glad u got her all figured out and running well!!
If someone has the same problem as u they will probably start a new thread asking the same ? Haha, no big deal though. Glad I could help.

If buy "what are you working on these days" u mean what cars do I have, I have all axial rigs now(my signature says all my cars)
I used to have a tornado s30 and an rs10xt. I sold them and regret it I miss my little nitro. I think I'll save up and get a dune runner they look pretty cool.

zackS30

Well glad u got her all figured out and running well!!
If someone has the same problem as u they will probably start a new thread asking the same ? Haha, no big deal though. Glad I could help.

If buy "what are you working on these days" u mean what cars do I have, I have all axial rigs now(my signature says all my cars)
I used to have a tornado s30 and an rs10xt. I sold them and regret it I miss my little nitro. I think I'll save up and get a dune runner they look pretty cool.