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I think i blew the motor

Old 02-28-2008, 07:12 PM
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1fastredsc
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Default I think i blew the motor

So i went round 2 with tuning the truck today. I had removed the carb, cleaned it out (wasn't dirty just did it to make sure), and reinstalled it using silicone sealant. Then i put the needles back to there stock settings. Fired up the truck, ran slowly for a few minutes to warm it up. Then i started going WOT to tune the HSN. This time around i looked to see if it would go fast at the top end and only tune the HSN based on that. Once it sounded like it was going full blast but still had plenty of exhaust smoke (wanted to keep it on the rich side), then i started messing with the LSN. At first i would flick the throttle, RPM's would rise, then fall, then climb up to normal idle. I figured based on what i read that was lean, so i started richening the LSN till it idled correctly after having the throttle flicked. Then i finished out the tank on those settings, which made the low to mid throttle kind of rich and would bog the motor slightly, but at WOT it would clear out and go balls to the wall with plenty of smoke. Then i filled it up with another tank of fuel, restarted the motor and kept running it. Then half way through the tank it just shut off mid throttle with no warning. I figured well i guess i have more tuning to do. So i went over there with the glow igniter to restart, went to pull and the starter wouldn't move, at all. So i took it to my bench, emptied out the tank of fuel to store it for the day. I decided to take out the glow plug and have a look down the hole. The glow plug looks new, wet and kind of shiny. Normally this is supposed to be a sign of a rich running engine. But then i looked through the hole at the top of the piston and the piston looks like it's pitted. The pitted piston is supposed to be the sign of a lean running engine, but the new and wet looking glow plug tells me it's rich. ***? Anyhow i'm going to take the top of the motor off and have a look at what i broke this weekend. I'll post back after i've done this.........
Old 02-28-2008, 07:18 PM
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Vigilante212
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Default RE: I think i blew the motor

sounds like something might have gotten into the motor.
Old 02-28-2008, 08:07 PM
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Sniper.308
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Default RE: I think i blew the motor

A couple grains of heavy sand at 20,000+ rpm will pit the hell out of an piston. my .02
Old 02-28-2008, 08:11 PM
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burnchassis3
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Default RE: I think i blew the motor

This is why everyone NEEDS a tempurature gun.
CS
Old 02-28-2008, 08:29 PM
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1fastredsc
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Default RE: I think i blew the motor

Actually i have a digital laser IR temperature gun. Motor stayed under 200 degrees the whole time, measured roughly at the glow plug. BTW, how would dirt get into the motor if the air filter was on?
Old 02-28-2008, 10:02 PM
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C-Fraser..::HPI::..
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Default RE: I think i blew the motor

your running it pretty cold usally i run at 250 at least
also maybe you had to much silicon sealent and some got lose and went into the engine..
Old 02-29-2008, 01:59 AM
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savaged_dude
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Default RE: I think i blew the motor

Have you changed the head shims at all? What GP are you useing long/short? Also what nitro %? Sounds like detonation to me.
Old 02-29-2008, 02:08 AM
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1fastredsc
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Default RE: I think i blew the motor

Totally stock engine dude. The glow plug is the one that came with the engine. 20% nitro O'Donnels fuel.
Old 03-01-2008, 04:35 PM
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1fastredsc
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Default RE: I think i blew the motor

Ok, i think i know what happened, but i took the motor apart anyway. Judging by the stripped section of the flywheel i think a rock got lodged between the frame at the flywheel and while i was trying to turn over the motor it was still jammed in there. Basically i took the motor out and the minute it came off the frame i was able to turn the flywheel by hand, but then i saw the stripped edge of the flywheel and a scratched section of that aluminum frame it sits on right where the flywheel normally is. But i figured it'd take it apart and have a look at the piston to inspect that pitting i saw through the glow plug hole. The head looks perfect but it does look like the piston was just slightly pitted, maybe that came from running it too lean the first time i tried tuning it. But the good news is that the sleeve's walls look excellent, you can see the cross hatching on the cylinder wall still so it's definitely in good shape. So i put it back together and took the opportunity to take my dog bones out, clean, and re grease them. I'll see if i can run the truck a little later on but for now it's all back together.
Old 03-01-2008, 04:48 PM
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1fastredsc
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Default RE: I think i blew the motor

Let's see if those pictures work this time.
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