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Uh oh, got myself into some trouble here.

Uh oh, got myself into some trouble here.

Old 04-29-2012, 05:09 PM
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Default Uh oh, got myself into some trouble here.

I have no clue if I'm posting this in the right place, but here's the deal. Long time rc enthusiast, newby rc owner. Ive had my truck about 3 months now, and generally speaking I love it. I've got an HPI Trophy truggy f4.6, pullstart. Everything on the truck is stock other than the pullstart, the first one melted on me. The truck has about 12-15 tanks run threw it at this point.

So today I was out running my truck, and I had a bit of a mishap. Apparently one of the wire leads on the battery pack in my truck broke off (No idea how), and the truck floored its self and I lost complete control of the steering and throttle.

The truck hit one tree, did a backflip off of it and landed on its side and kept going, high a second tree, another flip and landed on its side. Finally flipped its self over and after about 4 seconds it died. Took about 15 minutes to figure out the broken wire lead issue, got that fixed and now have full control again.

Next issue was the engine was locked. Pulled it off and took it apart, obvious issue.

I tried to post a picture, but Im not allowed. So the damage is piston connecting rod shredded, slight damage to the bottom of the piston shirt, full of metal shavings, no noticeable damage to the crank.

Now my questions are, do I need a new crank/piston? How do I get the sleeve out? Do they make upgraded pistons/rods/sleeves, possibly out of better material? Best prices? Can I get an upgraded heatsink?

As mentioned before this is a F4.6 on a trophy truck.

Thanks for any help!
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Old 05-01-2012, 02:27 PM
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Originally Posted by Hpi_Noob View Post
I have no clue if I'm posting this in the right place, but here's the deal. Long time rc enthusiast, newby rc owner. Ive had my truck about 3 months now, and generally speaking I love it. I've got an HPI Trophy truggy f4.6, pullstart. Everything on the truck is stock other than the pullstart, the first one melted on me. The truck has about 12-15 tanks run threw it at this point.

So today I was out running my truck, and I had a bit of a mishap. Apparently one of the wire leads on the battery pack in my truck broke off (No idea how), and the truck floored its self and I lost complete control of the steering and throttle.

The truck hit one tree, did a backflip off of it and landed on its side and kept going, high a second tree, another flip and landed on its side. Finally flipped its self over and after about 4 seconds it died. Took about 15 minutes to figure out the broken wire lead issue, got that fixed and now have full control again.

Next issue was the engine was locked. Pulled it off and took it apart, obvious issue.

I tried to post a picture, but Im not allowed. So the damage is piston connecting rod shredded, slight damage to the bottom of the piston shirt, full of metal shavings, no noticeable damage to the crank.

Now my questions are, do I need a new crank/piston? How do I get the sleeve out? Do they make upgraded pistons/rods/sleeves, possibly out of better material? Best prices? Can I get an upgraded heatsink?

As mentioned before this is a F4.6 on a trophy truck.

Thanks for any help!

Simple solution, Buy a new motor.

And If you dont have one, Pick up a Failsafe of sorts from your LHS.
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Old 05-01-2012, 02:31 PM
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Runaways are like cats, they ALWAYS land on their feet lol.
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Old 05-01-2012, 02:45 PM
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Originally Posted by gameholic2 View Post
Runaways are like cats, they ALWAYS land on their feet lol.
Bahahahahaha, thats just funny!!
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Old 05-01-2012, 02:50 PM
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What are you guys using to prevent a nitro runaway? Do failsafes work if your RX battery dies?
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Old 05-01-2012, 02:53 PM
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Originally Posted by Integra View Post
Simple solution, Buy a new motor.

And If you dont have one, Pick up a Failsafe of sorts from your LHS.
a FAILSAFE would not help you when the power shuts off due to a breakage.

The best thing is to get a throttle return spring and a fast but weak (torque wise) servo for the throttle

If the power shuts off, the throttle will be puled back buy the spring and atleast idle the motor

I have seen a few runaways 99% are due to battery issues and not radio communication errors since the move to 2.4GHz

If the motor screamed when it went upside down it's time for a re-build or a new motor

rebuild - new piston, sleeve and rod is a cheaper method than a new mill
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Old 05-01-2012, 02:54 PM
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I always run a throttle return spring in the form of a woman's hair band ;-) It works, as long as the result of the runaway isn't a bent linkage....and assuming it's strong enough to close your carb slide.
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Old 05-01-2012, 07:40 PM
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Not sure what a rebuild kit costs for that engine, but you are probably better served by just buying a new engine. If you have metal shavings all over, chances are the engine bearings got messed up in the process of it blowing up. Get a new engine and a throttle return spring/failsafe.

Then you can use this screwed up one to learn about the engines, how they work, how to tear one down, etc, etc. If you do decide to rebuild it, be advised that it is easy to mess something up and have a more expensive pile of parts sitting on your workbench. There are plenty of youtube videos to check out to see how to do it. It isn't exactly rocket science, but can be a little intimidating the first time you do it. After-run oil and lint-free microfiber rags will become your best friends when you start the rebuild process.
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Old 05-02-2012, 06:13 PM
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Cool Cost to Repair

Cost to repair the 4.6 you have parts your looking at around $130-150 for parts and $50.00 in labor to pull it down, clean it, prep it, reuild it and break it in. I usually charge $225. total for parts, labor, and shipping cost. Add on an additional $30.00 and i include polish, porting, and balancing
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Old 05-03-2012, 09:41 AM
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HPI motor's are NOT worth rebuilding.


Nova, RB Different story.
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Old 05-05-2012, 12:22 PM
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Buy any budget engines that fit your truck and install a throttle return spring + fail safe
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