Sounds like piston is hitting spark plug...

Rusty_Nail

Active Member
Oct 11, 2019
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Hi everyone. In the last couple days, I've noticed what I can best describe as a "clinking" noise when it idles or when I try to ride. When I try to ride it it struggles and can barely accelerate. Doesn't even have 5 hours run time on it. It's running 40:1. I'm going to check everything I can as I want to break it in properly. I'll post of a short video later today of it idling so it can be heard. Here's a pic of the Plug that's in it now. Not sure if its considered an normal noise with the stock china doll motors?
 

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wrench

Well-Known Member
Aug 20, 2019
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NO that's not a normal noise or symptoms.
Rusty your S/P NGK B-4L has too hot of a heat range (#4) and is causing a pre ignition Knock
The fuel air mix igniting before spark @TDC because of a hot S/P electrode, robbing your engine of power You should be using a NGK S/P with a #6 heat range.

The lower the # of a S/P the hotter it is.
Use NGK B6HS
 
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Rusty_Nail

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Oct 11, 2019
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Ok. If I remember right I had Autozone look up that exact plug but the only result they got was the one I bought. Would I maybe have better luck at like oreilly or carquest auto parts? As for the oil mix, soon as my gas can is empty I'll switch to 32:1 and try that.
 

Rusty_Nail

Active Member
Oct 11, 2019
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Ok I ordered 2 of those plugs on Amazon so I have an extra. When I get them I'll put one in and let ya know if the motors running better. Thanks again.
 
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Corson1183

New Member
Apr 5, 2021
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so I'm getting the same problem and I have the NGK B6HS plug it's been doing it since I got the engine so idk It even does it with the stock plug that comes with the engine. it happens when it's idling and it's causing my engine to smoke like crazy like really thick grey smoke. I thought it was my drive gears but I greased and tightened them so it cant be that.
 

JerryAssburger

Active Member
Mar 11, 2017
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Salem Oregon
Corson1183, spray some soapy water around the head gasket area and see if you can get it to idle while observing the joint. My 2 stroke made a REALLY strange noise when running, (also almost no actual power) and it ended up being the head to cylinder joint leaking. Hope you find the problem.
 
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Larry Trotter

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Nov 26, 2017
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Well there’s a good reason the kits mostly recommend a 16 to one break in mixture. 40 to one for break in is a disaster waiting to happen and it likely happened to you. Sounds like piston slap and the lack of power from rings seized in the grooves. Pull off the top end and do a reality check.