Engine Trouble Mysterious Starting Issue + Bogs at WOT

[Whitewill1412]

Ok - here are some pics of the carburator.
View attachment 194494
View attachment 194495
Ironically, its brand is "Runwell". I removed the red part.
So, the general consensus is not to consider rejetting the carb, right?

We are assuming that this was all the doing of excessive oil in the fuel, if I understand correctly

Seems like you had way too much oil. Then you said something about running it with no oil. That is even worse.

 

[apsci]

Maybe yes, maybe no. No telling by just dumping oil in the tank and adding fuel.

The plug shows lean, that's fuel to the engine not oil/fuel ratio. Move the c-clip to center and try again.

That's just an NT carb.

I will try that tomorrow - you are more experienced , so I will not take your opinion lightly. But here's a thought from me : The engine also dies when I choke it, meaning when I restrict airflow. So, if it were running lean, would that not mean that choke would actually help it run better, not kill it?

 

[GW's Motorized]

I will try that tomorrow - you are more experienced , so I will not take your opinion lightly. But here's a thought from me : The engine also dies when I choke it, meaning when I restrict airflow. So, if it were running lean, would that not mean that choke would actually help it run better, not kill it?

That's the reason we say it's most likely the excess oil. If you had an air leak or where running lean choke would make it run better

 

[Chainlube]

I will try that tomorrow - you are more experienced , so I will not take your opinion lightly. But here's a thought from me : The engine also dies when I choke it, meaning when I restrict airflow. So, if it were running lean, would that not mean that choke would actually help it run better, not kill it?

With the weather these days, a choke isn't needed. Putting the choke on just compounds the issue.

 

[apsci]

I set the c-clip to the center and cleaned everything related to fuel, emptied the carb bowl etc. I thought I could get away with crudely cleaning the stuff off the spark plug but it did not work, though combustion signs occured much earlier.

Due to the religious holiday here, I was not able to purchase a new spark plug. Also, I will not be able to work on the bike in the near future for unrelated reasons.

I am sorry this thread had to end anticlimactically, I would like to apologize to everyone who took the time to post.

Key takeaways for people like me, who bought cheap Chinese kits:

- Always always mix oil in a separate container and take precise measurements, NO EXCEPTIONS!!!

- Always check in regular intervals to see whether fuel mixture is correct

- no name NT Carburator is not pleasant to work with

 

[GW's Motorized]

No worries, when you do have time to work on your bike just come back and ask any questions you might have.

 

[Flight Risk]

I'm not real familiar with these spark plugs with multi electrodes, but I see very little gap on at least one of those.

 

[Nate82]

Second from the very top

That's where I'm at on my needle setting, 2nd notch down (leaner side). My elevation is about 500 ft to 1,000 ft above sea level and I had to move to that notch to actually get the performance the motor is supposed to give. Before that it was running fairly rich and four stroking a lot as you know all about @GW's Motorized. But I'm still glad I ran it rich like that for a bit as that was the first tank on the brand new motor.

 

[Nate82]

Hello,

I am having some issues with my "70cc" Chinese 2 stroke. So, starting is a pain. I have to pedal with the clutch engaged for at least 200m or 300m total until the engine starts to show signs that combustion is happening, then two attempts later the engine does indeed start. The carburator e-clip i have set to both "low" and "high" positions for rich and lean fueling until 3/4 throttle, but the results are the same. The carburator is the NT Speed, the one with the red back. The spark plug was black and filled with weird fluff when i removed it. It also was black when the c clip was set to lean fueling. I am suspecting i added too much 2 stroke oil to the premix, since i forgot to measure if the gasoline i added really was one liter. The red back I have removed to add airflow, but i get the same issue. Also, the engine begins to die after 20min of operation. At full throttle, it bogs down. At 3/4, it runs best and achieves the highest speed.

To summarize my setup:
- NT Speed Carburator, stock, back removed
- C clip currently one level under leanest setting
- Fuel may have contained too much oil, yet I have also topped it up with fuel without any oil in it, and I have the same issue.
- Running the engine dry, with petcock closed, then turning the petcock on and pedaling leads to the same starting issues, so I don't suspect flooding.

If I kill the engine, it might start again easily without much pedaling, but if I wait 5 minutes, I have to pedal as much as starting with a cold engine.

I would like to thank everyone who took the time to read this, you are all great people.

Where you ran your tank dry check your petcock and make sure there's not a bunch of crap on it if you're affecting the gravity fuel flow at all it will affect things.

If it's a new motor expect it not to run the best on the first couple maybe even a few tanks. When you're through at least one tank if you're still having the same issue try leaning it out a bit by moving the c-clip to the second Notch from the top.

Once again if your motor is a new motor do not push it. On the first tank let it run rich it's good for it, pedal assist up hills give it barely any throttle. Slowly work your way into half throttle. Don't bother going over that for at least two tanks. If you start pushing your motor too soon you will ruin it more than likely.

Always check your head bolt Torque after each run and ensure it cools off before you do so. Make sure you have no intake leaks. That mostly includes, but isn't limited to, checking your intake manifold where it connects to the block. Ensuring that it's tight ( don't over tighten, you'll strip them). as well, ensure your carburetor is pushed all the way onto your intake manifold and that the clamp is very tight. not so tight that you strip it, but tight. You want to make sure no air can get around those little slits that are cut in it.

Get rid of that garbage Chinese spark plug, it'll give you problems anyway in the end,. Go out and get yourself an NGK-BR6HS and Gap it to no bigger than 0.30", however you're probably best at 0.25" - 0.28".

Before attempting to start the motor did you do all the prechecks? Did you deck the head as well as the intake and exhaust ports? Aldo the intake manifold? Did you port match the intake manifold?

Do you notice any oil coming out of your block anywhere such as around the exhaust gasket, around the clutch cover and or around the head/cylinder top. If you see oil coming out of any of those areas you have a problem that needs to be addressed.

That's about the best I can do as far as helping at this point with the information you've given. And this is all stuff that I've learned very recently despite the fact that I am a certified small engine mechanic. I am learning that these are definitely a different Beast and definitely require some TLC and love to keep them going and to even get them going correctly. Good luck and I hope to hear how you make it