Dying off throttle symptom?

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Amoeba

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Hey gang,

This is a new one to me. I've got a HPI G3.0 w/rotostart that is showing an odd symptom I've not run in to before and was looking for some input.

I got this used along with the MT2 from charliejp and am trying to get it dialed in. It fires up super easily but when giving it throttle it climbs rpm well but when letting off the gas anywhere between 1/2-WOT instead of climbing back down it dies and coasts. I'm not sure if that indicates weak compression, an air leak, or a failing glow plug... the usual suspects.

Compression isn't super tight (it *is* a used mill) but resistance feels good manually rotating and the mill fires up almost immediately with no problems. I can maintain a high idle just fine but the symptom occurred both at the settings I got it at and when set back to factory defaults. Getting a consistent normal idle has been problematic.

I've taken the G3.0 out and put in an Outlaw 18 SS w/pullstart in the meantime but would like to see if I can get the G3.0 issue fixed.
 

charliejp

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Glad you got her going! That mill has been through hell and back. It did seem to have decent compression but it's been falling for awhile.
 

Amoeba

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Wait, which one, the G3.0 or the outlaw 18? :)

The 18 fired up and tuned in under 5 minutes and is currently powering one of my original HPI MT's. The G3.0 has been the one leaving me scratching my head. Was it showing the same symptom for you?

No worries charlie, at the price for the whole kit even if I have to replace the mill through HPI's engine exchange it was still a good deal.
 

charliejp

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The 3.0 is the one I was referring to. The outlaw is barely broke in. I think I only ran about 2-3 tanks after break in before I put on the OS. The 3.0 was gettiing harder and harder to keep running and I could'nt get a happy idle anymore. I figured it was pretty well done. I was running Odonnel 99s in it and that seemed to help. I think the plug I shipped it with was an older one.
 
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Amoeba

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Thanks for the additional info charlie. So, anyone got some clues where I should start looking? If it's a failing compression problem due to sleeve/piston I might as well just engine exchange it since a new engine through exchange is cheaper than the parts... and I have 2 other original HPI MT mills that are dead as well. Freak em out and do 3 at once.
 

Scrogg

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Sounds like a faulty mill to me, it could have a bad bearing or bushings or simply not enough compression at running temp.
 

olds97_lss

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Yep, she sounds worn out a bit. I had a similar issue with a couple engines of mine. I had them re-pinched and they were like new again.

Not sure if it's worth it to you to try, but if the engine is still mechanically sound, a $25 may get you another season or two out of it.
 

Amoeba

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Yep, she sounds worn out a bit. I had a similar issue with a couple engines of mine. I had them re-pinched and they were like new again.

Not sure if it's worth it to you to try, but if the engine is still mechanically sound, a $25 may get you another season or two out of it.

I checked the prices for new sleeve etc for better pinch but I might as well spend the extra $40-ish to do an exchange for new mills.
 

Amoeba

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What I meant was, you can get it re-pinched for $25. I had 3 done last spring by Ray at www.rayaracing.com.

I agree with you though. Spending $60+ for a piston/sleeve in a $100 engine just doesn't make sense.

I'll keep that in mind when my more expensive mills need some TLC. Since I can get NIB G3.0 replacement for $65 though.... a rebuild just doesn't make sense. Gotta love companies with exchange programs :)
 

olds97_lss

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Oh, wow! Didn't realize it was that reasonable!

Figured it was like traxxas "ERP" where they take your old engine and charge you $20 less so you can't have any spare parts. lol what a crock!
 
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