I have a an older MGT 4.6 that I picked up used recently and recently took the engine out, gave it a clean and sealed the backplate as is was not running reliably. Well...I finally got some time today to play with the 4.6 after reinstalling it. I am having some odd results. I took the HS and LS needles to the factory settings and it started on the first pull no problem. I adjusted the idle and just let it run for a bit with no throttle. Maybe 1/4 tank no issues. So I then took it out in the alley and began to tune it. I first started with the high speed needle and got it set just right. Then I adjusted the low speed. Runs pretty good, but it can be leaned a little more I think. For now I will leave it be until I hear back from this post. Funny thing is it runs great for about 1/3 of a tank and then stalls. It is not possible to start it again until it cools down which is weird as it is only 185 degrees at the glow plug after hard driving for a few minutes? Not hot by any means.

I can only assume that as the engine heats up it is developing air leaks. But would this not lead to it getting MUCH hotter than 185? I am a little confused. I am willing to admit the engine needs to be replaced, but I want to be sure this is a good learning experience. No point putting in a new engine every time the one I currently have some issues.

BTW I noticed that after hard full throttle run, the idle has a purr like sound (kinder sputters very rapidly) for a minute or two then returns to a smooth sound. Watching some Youtube Savage tuning videos this same sound happened when it was too lean (follow this link then go to 3 mins 30 seconds to hear the sound I am talking about), though in my case I am pretty sure I am not anywhere near lean. Lots of smoke and good temps.

Thanks as always everyone,
matt

I richened the the LSN and it no longer makes the sputtering sound, but still stalled after 5 mins of driving and will not start again for about 15-20 mins. BTW...I bought a cheap (like 70USD at my local hobby shop) Tactic 2.4Ghz spread spectrum pistol and it is AWESOME! I cannot believe the range. I had it over 1000 feet away tonight and I could still control it (though I could barley see the darn thing). Of course this is when it stalled. LOL...took like 4 seconds to go that far and a few mins to walk it.

Sounds to me like it's worn out.
You could tear it down and check the pinch, then you would know for sure.
If you need pics of good and bad pinch I have some.

Really SLAYERDUDE? You can show pics of the pinch? Please share. I did take the engine out recently and the crank does get much harder to turn when the piston is at the top of the sleeve. Is that pinch?

Thanks

I can also tell you that when the engine was out I could hear air hissing out of the exhaust port (sounds wet and squeeky) when I turned the crank so the piston was at the top of the sleeve It does get rather hard to crank at the top and for sure there is some decent compression, but I also know due to the sound that there is some leakage around the piston. Of course the engine was at room temperature and this problem may not happen at operating temps as I believe the seal get better.

I guess I am just not 100% convinced this engine is done. Where are the engine gurus out there with their opinions?