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.28 ofna hyper mt top end stall

.28 ofna hyper mt top end stall

Old 03-12-2020, 02:33 PM
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Default .28 ofna hyper mt top end stall

Hey guys top end stall problems...

ofna truck
.28 hyper 7 motor, new, 5th tank, original plug
2 speed

So revs good till about 3/4-full throttle, bogs then dies.

stock carb settings and adjusted to lean out top end like instructions said. Still same.

broke it in 3 tanks idle and two tanks cruzing.

no idea what it could be, someone said maybe glow plug but doesnt seem right.
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Old 03-12-2020, 03:21 PM
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while attempting to tune, the vehicle is warmed up correct?
from the sound of it, it seems like rich on the HSN, and maybe some on the LSN,
when you were leaning it out, where you doing 1/8 turn, then running a WOT pass then leaning again as needed?
if it was the glow plug typically the engine will die as soon as the glow igniter is removed, but its not bad to have spare plugs either way as sometimes faulty plugs do weird things.
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Old 03-12-2020, 05:08 PM
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Yea it warmed. I wasnt even tuning it. I broke it in 3 tanks at idle, 2 tanks at 1/4-1/2 throttle like instructions said. All the sudden it starts dieing on 1/2 to full throttle, bogging heavy and if i keep throttle on it goes off but if i let off it stays on. Also if i keep it under 1/2 throttle its fine, runs like a champ. I turned in the HSN 1/4 and then another 1/4, tried both as the instructions also stated after breaking in to turn it in a 1/4 to 1/2 turn. Its just so bizare.
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Old 03-13-2020, 10:34 AM
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from what you are describing it really sounds like the HSN is still very rich, does it sound kind of blubbery as you are on the throttle? HSN takes over the fuel mixture from 1/2-full throttle. if its really rich it will load up the crankcase and flood out the engine.
im surprised they said 1/2 turn in the manual, that is alot lol.
i would get the truck warmed up, then run it back and forth down the road, then lean the HSN 1/8 turn, then repeat. it will take a bit, but you should start hearing it clean up and really "get on the pipe". once you get decent performance doing that then work on your LSN.
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Old 03-13-2020, 12:15 PM
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Originally Posted by snowman49 View Post
from what you are describing it really sounds like the HSN is still very rich, does it sound kind of blubbery as you are on the throttle? HSN takes over the fuel mixture from 1/2-full throttle. if its really rich it will load up the crankcase and flood out the engine.
im surprised they said 1/2 turn in the manual, that is alot lol.
i would get the truck warmed up, then run it back and forth down the road, then lean the HSN 1/8 turn, then repeat. it will take a bit, but you should start hearing it clean up and really "get on the pipe". once you get decent performance doing that then work on your LSN.
hey so this is crazy. Put in nee plug. Nothing. Put in stocks settings. Started to richen the top end. Im at 4.5 out from close. But it stopped dieing, now tho it was being flooded on startup so i dialed back low end and boom. Starts up, idles bice, hauls ass top end. To be honest it still gets a bit jittery at the cery top, maybe go to 5. But u also have a mid needle so i need mote research on this to tine properly. But man so wierd
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Old 03-13-2020, 02:20 PM
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you had to richen further than factory settings? that is very strange. is the engine sounding crisp? or is it "4-stroking"?
biggest recommendation is to leave the mid speed needle at factory settings, as a basher you will not get enough gains to performance vs how much of a headache tuning it can be.
this is your engine correct?
https://www.cmldistribution.co.uk/di...MacStar_28.pdf
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Old 03-15-2020, 03:46 PM
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yea thats my motor, sounds like and runs like a beast now, turned up top end and lowered bottom, kept middle stock.
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Old 03-15-2020, 07:19 PM
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I saw a T-Maxx with an engine that would die once it warmed-up no matter what was done to the carb settings or what kind of glowplug was installed. The owner gave up and took the truck inside to have the engine replaced by the hobby shop staff. My best guess is it had a massive air leak somewhere that didn't manifest until the crankcase heated up and expanded a bit.
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Old 03-16-2020, 12:41 PM
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Originally Posted by fyrstormer View Post
I saw a T-Maxx with an engine that would die once it warmed-up no matter what was done to the carb settings or what kind of glowplug was installed. The owner gave up and took the truck inside to have the engine replaced by the hobby shop staff. My best guess is it had a massive air leak somewhere that didn't manifest until the crankcase heated up and expanded a bit.
an engine that dies after warmed up and wont re-start until cooled is a worn out engine.
as it warms up the sleeve expands and there is not enough seal in the combustion chamber, so there is not enough compression for the mixture to ignite correctly. ending up in a "stall", then the engine has to cool down and re-shrink and will be able to be re-started because the compression is back while its cold.
it sounds like the thread starter's issue is with the tune as it just stalls when you give throttle, so it is either getting too much fuel, or not enough fuel so its cutting/bogging out.
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Old 03-17-2020, 02:13 AM
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That was my other hypothesis, but I've never personally owned an engine that badly worn-out so I couldn't be sure. The engine in that T-Maxx was in baaaad shape; as soon as the engine warmed up a bit, no matter how much I opened the throttle or messed with the fuel mixture, the engine stalled. Once it warmed up a bit, I couldn't even get it to run at half throttle while continuously cranking the engine with the electric starter. I've never seen anything like it before or since.

Anyway, stalling just as the throttle opens sounds like a rich HSN setting plus a glowplug that isn't hot enough. When idling, the glowplug is barely warm (at least by the standards of hot engine parts), and then a burst of freshly-mixed air and alcohol-vapor chills the combustion chamber even more and retards the ignition timing so much that the engine stalls. It happens to me occasionally when I run a car tuned for hot weather on a chilly early spring day; a hotter glowplug is a nice quick fix for running nitro on those unseasonably cold days. My winter nitro truck has a hot glowplug in it all the time for the same reason, though it's also specifically tuned to run reliably at 0C.
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