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two stroke tuneing - 9/2/2012 10:49 PM   
stevegauth30@comcast.net


 

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From: Bristol, CT, USA
Status: offline 		I have a GMS 76 two stroke, usualy im alright at tuneing them, but this one is a pain in my butt.I got it to idle great, and even transition nicely, it  passes the pinch test alright, but dies at full throttle after about ten seconds. theres no bubbles in the fuel line, the glow plug is brand new,  i just dont get it. any thoughts? cmon, i know theres some real smart guys out there reading this. thanks in advance for the knowledge.

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RE: two stroke tuneing - 9/2/2012 11:59 PM   
speedracerntrixie


 

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quote:

ORIGINAL: stevegauth30@comcast.net

I have a GMS 76 two stroke, usualy im alright at tuneing them, but this one is a pain in my butt.I got it to idle great, and even transition nicely, it  passes the pinch test alright, but dies at full throttle after about ten seconds. theres no bubbles in the fuel line, the glow plug is brand new,  i just dont get it. any thoughts? cmon, i know theres some real smart guys out there reading this. thanks in advance for the knowledge.


It's getting too hot. Causes are:

High speed needle too far in.

Plug too hot a range

too much prop

Fuel has too much nitro

Fuel has too little oil

Fuel is old and has been exposed to air and has water in it.

Please don't come back and tell us how many turns the needle is set at, that really means nothing because it will change some with different setups. If all else checks out you simply need to run the high speed open a little more. I will usually get the high speed set a tad on the rich side before messing with the low. Quite possible you are too rich on the low side and in order to get idle and transition you are over compensating with the high speed needle.



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RE: two stroke tuneing - 9/3/2012 1:03 AM   
larrysogla


 

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Status: offline 		Looks like the muffler pressure nipple is clogged up and when you open the throttle wide open the engine responds but because of the clogged muffler pressure nipple the engine eventually starts to lean out and then dies...............just a guess of course and my 2 cents. 'Nuff said.

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RE: two stroke tuneing - 9/3/2012 2:08 AM   
stevegauth30@comcast.net


 

Posts: 338
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From: Bristol, CT, USA
Status: offline 		 I think speed racer was right, I opened the high speed two more turns and it seems better. I never had to open a high speed that far, but I also never had a GMS either. Huh,learn something new every day. Thanks. Some day I'll know enough not to have to ask dumb questions.



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RE: two stroke tuneing - 9/3/2012 2:52 AM   
speedracerntrixie


 

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Status: online 		Steve, the only dumb question is the one not asked. Glad to be of some help.


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RE: two stroke tuneing - 9/3/2012 3:12 AM   
Gray Beard


 

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Status: offline 		And each engine is it's own animal. Just because you had it doing everything you think it should doesn't mean it is always correct. Lean runs like you described happen all the time with a cowled engine when just a tad lean and not quite enough cooling. Just a bit too lean and even an opened engine will over heat a bit. Lack of pressure could have also been the problem.

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